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的技术博客,深入 Java 运行时与生产诊断、低成本大模型推理和 Agent 工程实践。" itemprop=description></span><span hidden itemprop=post itemscope itemtype=http://schema.org/CreativeWork><meta content="mybatis系列-foreach 解析 | Nicksxs's Blog" itemprop=name><meta content="在 org.apache.ibatis.builder.xml.XMLConfigBuilder#parseConfiguration 中进行配置解析,其中这一行就是解析 mappers" itemprop=description></span><header class=post-header><h1 itemprop="name headline" class=post-title>mybatis系列-foreach 解析</h1><div class=post-meta-container><div class=post-meta><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-calendar"></i> </span><span class=post-meta-item-text>发表于</span> <time itemprop="dateCreated datePublished" title="创建时间:2023-06-11 23:20:31" datetime=2023-06-11T23:20:31+08:00>2023-06-11</time> </span><span class=post-meta-item><span class=post-meta-item-icon><i class="far fa-folder"></i> </span><span class=post-meta-item-text>分类于</span> <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/ itemprop=url rel=index><span itemprop=name>Java</span></a> </span>, <span itemprop=about itemscope itemtype=http://schema.org/Thing><a href=/categories/Java/Mybatis/ itemprop=url rel=index><span itemprop=name>Mybatis</span></a> </span></span><span class="post-meta-item cloudflare-page-counter" data-title="mybatis系列-foreach 解析" data-increment=true data-path=/2023/06/11/mybatis%E7%B3%BB%E5%88%97-foreach-%E8%A7%A3%E6%9E%90/ title=阅读次数><span class=post-meta-item-icon><i class="far fa-eye"></i> </span><span class=post-meta-item-text>阅读次数:</span> <span class=cloudflare-page-counter-count></span></span></div><div class=post-description>在 org.apache.ibatis.builder.xml.XMLConfigBuilder#parseConfiguration 中进行配置解析,其中这一行就是解析 mappers</div></div></header><div class=post-body itemprop=articleBody><p>在 org.apache.ibatis.builder.xml.XMLConfigBuilder#parseConfiguration 中进行配置解析,其中这一行就是解析 mappers<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br></pre><td class=code><pre><span class=line>mapperElement(root.evalNode(<span class=string>"mappers"</span>));</span><br></pre></table></figure><p>具体的代码会执行到这<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br></pre><td class=code><pre><span class=line><span class=keyword>private</span> <span class=keyword>void</span> <span class="title function_">mapperElement</span><span class=params>(XNode parent)</span> <span class=keyword>throws</span> Exception {</span><br><span class=line> <span class=keyword>if</span> (parent != <span class=literal>null</span>) {</span><br><span class=line> <span class=keyword>for</span> (XNode child : parent.getChildren()) {</span><br><span class=line> <span class=keyword>if</span> (<span class=string>"package"</span>.equals(child.getName())) {</span><br><span class=line> <span class=comment>// 这里解析的不是 package</span></span><br><span class=line> <span class=type>String</span> <span class=variable>mapperPackage</span> <span class=operator>=</span> child.getStringAttribute(<span class=string>"name"</span>);</span><br><span class=line> configuration.addMappers(mapperPackage);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// 根据 resource 和 url 还有 mapperClass 判断</span></span><br><span class=line> <span class=type>String</span> <span class=variable>resource</span> <span class=operator>=</span> child.getStringAttribute(<span class=string>"resource"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>url</span> <span class=operator>=</span> child.getStringAttribute(<span class=string>"url"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>mapperClass</span> <span class=operator>=</span> child.getStringAttribute(<span class=string>"class"</span>);</span><br><span class=line> <span class=comment>// resource 不为空其他为空的情况,就开始将 resource 读成输入流</span></span><br><span class=line> <span class=keyword>if</span> (resource != <span class=literal>null</span> && url == <span class=literal>null</span> && mapperClass == <span class=literal>null</span>) {</span><br><span class=line> ErrorContext.instance().resource(resource);</span><br><span class=line> <span class=keyword>try</span>(<span class=type>InputStream</span> <span class=variable>inputStream</span> <span class=operator>=</span> Resources.getResourceAsStream(resource)) {</span><br><span class=line> <span class=comment>// 初始化 XMLMapperBuilder 来解析 mapper</span></span><br><span class=line> <span class=type>XMLMapperBuilder</span> <span class=variable>mapperParser</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">XMLMapperBuilder</span>(inputStream, configuration, resource, configuration.getSqlFragments());</span><br><span class=line> mapperParser.parse();</span><br><span class=line> }</span><br></pre></table></figure><p>然后再是 parse 过程<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br></pre><td class=code><pre><span class=line><span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">parse</span><span class=params>()</span> {</span><br><span class=line> <span class=keyword>if</span> (!configuration.isResourceLoaded(resource)) {</span><br><span class=line> <span class=comment>// 解析 mapper 节点,也就是下图中的mapper</span></span><br><span class=line> configurationElement(parser.evalNode(<span class=string>"/mapper"</span>));</span><br><span class=line> configuration.addLoadedResource(resource);</span><br><span class=line> bindMapperForNamespace();</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> parsePendingResultMaps();</span><br><span class=line> parsePendingCacheRefs();</span><br><span class=line> parsePendingStatements();</span><br><span class=line>}</span><br></pre></table></figure><p><img alt=image loading=lazy src=https://img.nicksxs.me/blog/6wAWb4.png><p>继续往下走<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br></pre><td class=code><pre><span class=line><span class=keyword>private</span> <span class=keyword>void</span> <span class="title function_">configurationElement</span><span class=params>(XNode context)</span> {</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=type>String</span> <span class=variable>namespace</span> <span class=operator>=</span> context.getStringAttribute(<span class=string>"namespace"</span>);</span><br><span class=line> <span class=keyword>if</span> (namespace == <span class=literal>null</span> || namespace.isEmpty()) {</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">BuilderException</span>(<span class=string>"Mapper's namespace cannot be empty"</span>);</span><br><span class=line> }</span><br><span class=line> builderAssistant.setCurrentNamespace(namespace);</span><br><span class=line> <span class=comment>// 处理cache 和 cache 应用</span></span><br><span class=line> cacheRefElement(context.evalNode(<span class=string>"cache-ref"</span>));</span><br><span class=line> cacheElement(context.evalNode(<span class=string>"cache"</span>));</span><br><span class=line> parameterMapElement(context.evalNodes(<span class=string>"/mapper/parameterMap"</span>));</span><br><span class=line> resultMapElements(context.evalNodes(<span class=string>"/mapper/resultMap"</span>));</span><br><span class=line> sqlElement(context.evalNodes(<span class=string>"/mapper/sql"</span>));</span><br><span class=line> <span class=comment>// 因为我们是个 sql 查询,所以具体逻辑是在这里面</span></span><br><span class=line> buildStatementFromContext(context.evalNodes(<span class=string>"select|insert|update|delete"</span>));</span><br><span class=line> } <span class=keyword>catch</span> (Exception e) {</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">BuilderException</span>(<span class=string>"Error parsing Mapper XML. The XML location is '"</span> + resource + <span class=string>"'. Cause: "</span> + e, e);</span><br><span class=line> }</span><br><span class=line> }</span><br></pre></table></figure><p>然后是<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br></pre><td class=code><pre><span class=line><span class=keyword>private</span> <span class=keyword>void</span> <span class="title function_">buildStatementFromContext</span><span class=params>(List<XNode> list)</span> {</span><br><span class=line> <span class=keyword>if</span> (configuration.getDatabaseId() != <span class=literal>null</span>) {</span><br><span class=line> buildStatementFromContext(list, configuration.getDatabaseId());</span><br><span class=line> }</span><br><span class=line> <span class=comment>// 然后没有 databaseId 就走到这</span></span><br><span class=line> buildStatementFromContext(list, <span class=literal>null</span>);</span><br><span class=line>}</span><br></pre></table></figure><p>继续<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br></pre><td class=code><pre><span class=line><span class=keyword>private</span> <span class=keyword>void</span> <span class="title function_">buildStatementFromContext</span><span class=params>(List<XNode> list, String requiredDatabaseId)</span> {</span><br><span class=line> <span class=keyword>for</span> (XNode context : list) {</span><br><span class=line> <span class=comment>// 创建语句解析器</span></span><br><span class=line> <span class=keyword>final</span> <span class=type>XMLStatementBuilder</span> <span class=variable>statementParser</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">XMLStatementBuilder</span>(configuration, builderAssistant, context, requiredDatabaseId);</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=comment>// 解析节点</span></span><br><span class=line> statementParser.parseStatementNode();</span><br><span class=line> } <span class=keyword>catch</span> (IncompleteElementException e) {</span><br><span class=line> configuration.addIncompleteStatement(statementParser);</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line>}</span><br></pre></table></figure><p>这个代码比较长,做下简略,只保留相关代码<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br></pre><td class=code><pre><span class=line><span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">parseStatementNode</span><span class=params>()</span> {</span><br><span class=line> <span class=type>String</span> <span class=variable>id</span> <span class=operator>=</span> context.getStringAttribute(<span class=string>"id"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>databaseId</span> <span class=operator>=</span> context.getStringAttribute(<span class=string>"databaseId"</span>);</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (!databaseIdMatchesCurrent(id, databaseId, <span class=built_in>this</span>.requiredDatabaseId)) {</span><br><span class=line> <span class=keyword>return</span>;</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=type>String</span> <span class=variable>nodeName</span> <span class=operator>=</span> context.getNode().getNodeName();</span><br><span class=line> <span class=type>SqlCommandType</span> <span class=variable>sqlCommandType</span> <span class=operator>=</span> SqlCommandType.valueOf(nodeName.toUpperCase(Locale.ENGLISH));</span><br><span class=line> <span class=type>boolean</span> <span class=variable>isSelect</span> <span class=operator>=</span> sqlCommandType == SqlCommandType.SELECT;</span><br><span class=line> <span class=type>boolean</span> <span class=variable>flushCache</span> <span class=operator>=</span> context.getBooleanAttribute(<span class=string>"flushCache"</span>, !isSelect);</span><br><span class=line> <span class=type>boolean</span> <span class=variable>useCache</span> <span class=operator>=</span> context.getBooleanAttribute(<span class=string>"useCache"</span>, isSelect);</span><br><span class=line> <span class=type>boolean</span> <span class=variable>resultOrdered</span> <span class=operator>=</span> context.getBooleanAttribute(<span class=string>"resultOrdered"</span>, <span class=literal>false</span>);</span><br><span class=line></span><br><span class=line></span><br><span class=line> <span class=comment>// 简略前后代码,主要看这里,创建 sqlSource</span></span><br><span class=line></span><br><span class=line> <span class=type>SqlSource</span> <span class=variable>sqlSource</span> <span class=operator>=</span> langDriver.createSqlSource(configuration, context, parameterTypeClass);</span><br><span class=line> </span><br><span class=line></span><br></pre></table></figure><p>然后根据 LanguageDriver,我们这用的 XMLLanguageDriver,先是初始化<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br></pre><td class=code><pre><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> SqlSource <span class="title function_">createSqlSource</span><span class=params>(Configuration configuration, XNode script, Class<?> parameterType)</span> {</span><br><span class=line> <span class=type>XMLScriptBuilder</span> <span class=variable>builder</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">XMLScriptBuilder</span>(configuration, script, parameterType);</span><br><span class=line> <span class=keyword>return</span> builder.parseScriptNode();</span><br><span class=line> }</span><br><span class=line><span class=comment>// 初始化有一些逻辑</span></span><br><span class=line> <span class=keyword>public</span> <span class="title function_">XMLScriptBuilder</span><span class=params>(Configuration configuration, XNode context, Class<?> parameterType)</span> {</span><br><span class=line> <span class=built_in>super</span>(configuration);</span><br><span class=line> <span class=built_in>this</span>.context = context;</span><br><span class=line> <span class=built_in>this</span>.parameterType = parameterType;</span><br><span class=line> <span class=comment>// 特别是这,我这次特意在 mapper 中加了 foreach,就是为了说下这一块的解析</span></span><br><span class=line> initNodeHandlerMap();</span><br><span class=line> }</span><br><span class=line><span class=comment>// 设置各种类型的处理器</span></span><br><span class=line> <span class=keyword>private</span> <span class=keyword>void</span> <span class="title function_">initNodeHandlerMap</span><span class=params>()</span> {</span><br><span class=line> nodeHandlerMap.put(<span class=string>"trim"</span>, <span class=keyword>new</span> <span class="title class_">TrimHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"where"</span>, <span class=keyword>new</span> <span class="title class_">WhereHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"set"</span>, <span class=keyword>new</span> <span class="title class_">SetHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"foreach"</span>, <span class=keyword>new</span> <span class="title class_">ForEachHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"if"</span>, <span class=keyword>new</span> <span class="title class_">IfHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"choose"</span>, <span class=keyword>new</span> <span class="title class_">ChooseHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"when"</span>, <span class=keyword>new</span> <span class="title class_">IfHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"otherwise"</span>, <span class=keyword>new</span> <span class="title class_">OtherwiseHandler</span>());</span><br><span class=line> nodeHandlerMap.put(<span class=string>"bind"</span>, <span class=keyword>new</span> <span class="title class_">BindHandler</span>());</span><br><span class=line> }</span><br></pre></table></figure><p>初始化解析器以后就开始解析了<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br></pre><td class=code><pre><span class=line><span class=keyword>public</span> SqlSource <span class="title function_">parseScriptNode</span><span class=params>()</span> {</span><br><span class=line> <span class=comment>// 先是解析 parseDynamicTags</span></span><br><span class=line> <span class=type>MixedSqlNode</span> <span class=variable>rootSqlNode</span> <span class=operator>=</span> parseDynamicTags(context);</span><br><span class=line> SqlSource sqlSource;</span><br><span class=line> <span class=keyword>if</span> (isDynamic) {</span><br><span class=line> sqlSource = <span class=keyword>new</span> <span class="title class_">DynamicSqlSource</span>(configuration, rootSqlNode);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> sqlSource = <span class=keyword>new</span> <span class="title class_">RawSqlSource</span>(configuration, rootSqlNode, parameterType);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> sqlSource;</span><br><span class=line>}</span><br></pre></table></figure><p>但是这里可能做的事情比较多<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br><span class=line>26</span><br><span class=line>27</span><br><span class=line>28</span><br><span class=line>29</span><br><span class=line>30</span><br><span class=line>31</span><br><span class=line>32</span><br><span class=line>33</span><br></pre><td class=code><pre><span class=line><span class=keyword>protected</span> MixedSqlNode <span class="title function_">parseDynamicTags</span><span class=params>(XNode node)</span> {</span><br><span class=line> List<SqlNode> contents = <span class=keyword>new</span> <span class="title class_">ArrayList</span><>();</span><br><span class=line> <span class=comment>// 获取子节点,这里可以把我 xml 中的 SELECT 语句分成三部分,第一部分是 select 到 in,然后是 foreach 部分,最后是\n结束符</span></span><br><span class=line> <span class=type>NodeList</span> <span class=variable>children</span> <span class=operator>=</span> node.getNode().getChildNodes();</span><br><span class=line> <span class=keyword>for</span> (<span class=type>int</span> <span class=variable>i</span> <span class=operator>=</span> <span class=number>0</span>; i < children.getLength(); i++) {</span><br><span class=line> <span class=type>XNode</span> <span class=variable>child</span> <span class=operator>=</span> node.newXNode(children.item(i));</span><br><span class=line> <span class=comment>// 第一个节点是个纯 text 节点就会走到这</span></span><br><span class=line> <span class=keyword>if</span> (child.getNode().getNodeType() == Node.CDATA_SECTION_NODE || child.getNode().getNodeType() == Node.TEXT_NODE) {</span><br><span class=line> <span class=type>String</span> <span class=variable>data</span> <span class=operator>=</span> child.getStringBody(<span class=string>""</span>);</span><br><span class=line> <span class=type>TextSqlNode</span> <span class=variable>textSqlNode</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">TextSqlNode</span>(data);</span><br><span class=line> <span class=keyword>if</span> (textSqlNode.isDynamic()) {</span><br><span class=line> contents.add(textSqlNode);</span><br><span class=line> isDynamic = <span class=literal>true</span>;</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// 在 content 中添加这个 node</span></span><br><span class=line> contents.add(<span class=keyword>new</span> <span class="title class_">StaticTextSqlNode</span>(data));</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (child.getNode().getNodeType() == Node.ELEMENT_NODE) { <span class=comment>// issue #628</span></span><br><span class=line> <span class=comment>// 第二个节点是个带 foreach 的,是个内部元素节点</span></span><br><span class=line> <span class=type>String</span> <span class=variable>nodeName</span> <span class=operator>=</span> child.getNode().getNodeName();</span><br><span class=line> <span class=comment>// 通过 nodeName 获取处理器</span></span><br><span class=line> <span class=type>NodeHandler</span> <span class=variable>handler</span> <span class=operator>=</span> nodeHandlerMap.get(nodeName);</span><br><span class=line> <span class=keyword>if</span> (handler == <span class=literal>null</span>) {</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">BuilderException</span>(<span class=string>"Unknown element <"</span> + nodeName + <span class=string>"> in SQL statement."</span>);</span><br><span class=line> }</span><br><span class=line> <span class=comment>// 调用处理器来处理</span></span><br><span class=line> handler.handleNode(child, contents);</span><br><span class=line> isDynamic = <span class=literal>true</span>;</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> <span class=comment>// 然后返回这个混合 sql 节点</span></span><br><span class=line> <span class=keyword>return</span> <span class=keyword>new</span> <span class="title class_">MixedSqlNode</span>(contents);</span><br><span class=line> }</span><br></pre></table></figure><p>再看下 handleNode 的逻辑<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br><span class=line>26</span><br><span class=line>27</span><br><span class=line>28</span><br><span class=line>29</span><br><span class=line>30</span><br><span class=line>31</span><br><span class=line>32</span><br><span class=line>33</span><br><span class=line>34</span><br><span class=line>35</span><br><span class=line>36</span><br><span class=line>37</span><br><span class=line>38</span><br><span class=line>39</span><br><span class=line>40</span><br><span class=line>41</span><br><span class=line>42</span><br><span class=line>43</span><br><span class=line>44</span><br><span class=line>45</span><br><span class=line>46</span><br><span class=line>47</span><br><span class=line>48</span><br><span class=line>49</span><br><span class=line>50</span><br></pre><td class=code><pre><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">handleNode</span><span class=params>(XNode nodeToHandle, List<SqlNode> targetContents)</span> {</span><br><span class=line> <span class=comment>// 又会套娃执行这里的 parseDynamicTags</span></span><br><span class=line> <span class=type>MixedSqlNode</span> <span class=variable>mixedSqlNode</span> <span class=operator>=</span> parseDynamicTags(nodeToHandle);</span><br><span class=line> <span class=type>String</span> <span class=variable>collection</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"collection"</span>);</span><br><span class=line> <span class=type>Boolean</span> <span class=variable>nullable</span> <span class=operator>=</span> nodeToHandle.getBooleanAttribute(<span class=string>"nullable"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>item</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"item"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>index</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"index"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>open</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"open"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>close</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"close"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>separator</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"separator"</span>);</span><br><span class=line> <span class=type>ForEachSqlNode</span> <span class=variable>forEachSqlNode</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">ForEachSqlNode</span>(configuration, mixedSqlNode, collection, nullable, index, item, open, close, separator);</span><br><span class=line> targetContents.add(forEachSqlNode);</span><br><span class=line> }</span><br><span class=line><span class=comment>// 这里走的逻辑不一样了</span></span><br><span class=line><span class=keyword>protected</span> MixedSqlNode <span class="title function_">parseDynamicTags</span><span class=params>(XNode node)</span> {</span><br><span class=line> List<SqlNode> contents = <span class=keyword>new</span> <span class="title class_">ArrayList</span><>();</span><br><span class=line> <span class=comment>// 这里是 foreach 内部的,所以是个 text_node</span></span><br><span class=line> <span class=type>NodeList</span> <span class=variable>children</span> <span class=operator>=</span> node.getNode().getChildNodes();</span><br><span class=line> <span class=keyword>for</span> (<span class=type>int</span> <span class=variable>i</span> <span class=operator>=</span> <span class=number>0</span>; i < children.getLength(); i++) {</span><br><span class=line> <span class=type>XNode</span> <span class=variable>child</span> <span class=operator>=</span> node.newXNode(children.item(i));</span><br><span class=line> <span class=comment>// 第一个节点是个纯 text 节点就会走到这</span></span><br><span class=line> <span class=keyword>if</span> (child.getNode().getNodeType() == Node.CDATA_SECTION_NODE || child.getNode().getNodeType() == Node.TEXT_NODE) {</span><br><span class=line> <span class=type>String</span> <span class=variable>data</span> <span class=operator>=</span> child.getStringBody(<span class=string>""</span>);</span><br><span class=line> <span class=type>TextSqlNode</span> <span class=variable>textSqlNode</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">TextSqlNode</span>(data);</span><br><span class=line> <span class=comment>// 判断是否动态是根据代码里是否有 ${}</span></span><br><span class=line> <span class=keyword>if</span> (textSqlNode.isDynamic()) {</span><br><span class=line> contents.add(textSqlNode);</span><br><span class=line> isDynamic = <span class=literal>true</span>;</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// 所以还是会走到这</span></span><br><span class=line> <span class=comment>// 在 content 中添加这个 node</span></span><br><span class=line> contents.add(<span class=keyword>new</span> <span class="title class_">StaticTextSqlNode</span>(data));</span><br><span class=line> }</span><br><span class=line><span class=comment>// 最后继续包装成 MixedSqlNode</span></span><br><span class=line><span class=comment>// 再回到这里</span></span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">handleNode</span><span class=params>(XNode nodeToHandle, List<SqlNode> targetContents)</span> {</span><br><span class=line> <span class=type>MixedSqlNode</span> <span class=variable>mixedSqlNode</span> <span class=operator>=</span> parseDynamicTags(nodeToHandle);</span><br><span class=line> <span class=comment>// 处理 foreach 内部的各个变量</span></span><br><span class=line> <span class=type>String</span> <span class=variable>collection</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"collection"</span>);</span><br><span class=line> <span class=type>Boolean</span> <span class=variable>nullable</span> <span class=operator>=</span> nodeToHandle.getBooleanAttribute(<span class=string>"nullable"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>item</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"item"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>index</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"index"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>open</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"open"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>close</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"close"</span>);</span><br><span class=line> <span class=type>String</span> <span class=variable>separator</span> <span class=operator>=</span> nodeToHandle.getStringAttribute(<span class=string>"separator"</span>);</span><br><span class=line> <span class=type>ForEachSqlNode</span> <span class=variable>forEachSqlNode</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">ForEachSqlNode</span>(configuration, mixedSqlNode, collection, nullable, index, item, open, close, separator);</span><br><span class=line> targetContents.add(forEachSqlNode);</span><br><span class=line> }</span><br></pre></table></figure><p>再回过来<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br></pre><td class=code><pre><span class=line><span class=keyword>public</span> SqlSource <span class="title function_">parseScriptNode</span><span class=params>()</span> {</span><br><span class=line> <span class=type>MixedSqlNode</span> <span class=variable>rootSqlNode</span> <span class=operator>=</span> parseDynamicTags(context);</span><br><span class=line> SqlSource sqlSource;</span><br><span class=line> <span class=comment>// 因为在 foreach 节点处理时直接是把 isDynamic 置成了 true</span></span><br><span class=line> <span class=keyword>if</span> (isDynamic) {</span><br><span class=line> <span class=comment>// 所以是个 DynamicSqlSource</span></span><br><span class=line> sqlSource = <span class=keyword>new</span> <span class="title class_">DynamicSqlSource</span>(configuration, rootSqlNode);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> sqlSource = <span class=keyword>new</span> <span class="title class_">RawSqlSource</span>(configuration, rootSqlNode, parameterType);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> sqlSource;</span><br><span class=line>}</span><br></pre></table></figure><p>这里就做完了预处理工作,真正在执行的执行的时候还需要进一步解析<p>因为前面讲过很多了,所以直接跳到这里<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br><span class=line>26</span><br><span class=line>27</span><br><span class=line>28</span><br><span class=line>29</span><br><span class=line>30</span><br><span class=line>31</span><br><span class=line>32</span><br><span class=line>33</span><br><span class=line>34</span><br><span class=line>35</span><br><span class=line>36</span><br><span class=line>37</span><br><span class=line>38</span><br><span class=line>39</span><br><span class=line>40</span><br><span class=line>41</span><br><span class=line>42</span><br><span class=line>43</span><br><span class=line>44</span><br><span class=line>45</span><br><span class=line>46</span><br><span class=line>47</span><br><span class=line>48</span><br><span class=line>49</span><br><span class=line>50</span><br><span class=line>51</span><br><span class=line>52</span><br><span class=line>53</span><br><span class=line>54</span><br><span class=line>55</span><br><span class=line>56</span><br><span class=line>57</span><br><span class=line>58</span><br><span class=line>59</span><br><span class=line>60</span><br><span class=line>61</span><br><span class=line>62</span><br><span class=line>63</span><br><span class=line>64</span><br><span class=line>65</span><br><span class=line>66</span><br><span class=line>67</span><br><span class=line>68</span><br><span class=line>69</span><br><span class=line>70</span><br><span class=line>71</span><br><span class=line>72</span><br><span class=line>73</span><br><span class=line>74</span><br><span class=line>75</span><br><span class=line>76</span><br><span class=line>77</span><br><span class=line>78</span><br><span class=line>79</span><br><span class=line>80</span><br></pre><td class=code><pre><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <T> T <span class="title function_">selectOne</span><span class=params>(String statement, Object parameter)</span> {</span><br><span class=line> <span class=comment>// Popular vote was to return null on 0 results and throw exception on too many.</span></span><br><span class=line> <span class=comment>// 都知道是在这进去</span></span><br><span class=line> List<T> list = <span class=built_in>this</span>.selectList(statement, parameter);</span><br><span class=line> <span class=keyword>if</span> (list.size() == <span class=number>1</span>) {</span><br><span class=line> <span class=keyword>return</span> list.get(<span class=number>0</span>);</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (list.size() > <span class=number>1</span>) {</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">TooManyResultsException</span>(<span class=string>"Expected one result (or null) to be returned by selectOne(), but found: "</span> + list.size());</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=keyword>return</span> <span class=literal>null</span>;</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <E> List<E> <span class="title function_">selectList</span><span class=params>(String statement, Object parameter)</span> {</span><br><span class=line> <span class=keyword>return</span> <span class=built_in>this</span>.selectList(statement, parameter, RowBounds.DEFAULT);</span><br><span class=line> }</span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <E> List<E> <span class="title function_">selectList</span><span class=params>(String statement, Object parameter, RowBounds rowBounds)</span> {</span><br><span class=line> <span class=keyword>return</span> selectList(statement, parameter, rowBounds, Executor.NO_RESULT_HANDLER);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>private</span> <E> List<E> <span class="title function_">selectList</span><span class=params>(String statement, Object parameter, RowBounds rowBounds, ResultHandler handler)</span> {</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=comment>// 前面也讲过这个,</span></span><br><span class=line> <span class=type>MappedStatement</span> <span class=variable>ms</span> <span class=operator>=</span> configuration.getMappedStatement(statement);</span><br><span class=line> <span class=keyword>return</span> executor.query(ms, wrapCollection(parameter), rowBounds, handler);</span><br><span class=line> } <span class=keyword>catch</span> (Exception e) {</span><br><span class=line> <span class=keyword>throw</span> ExceptionFactory.wrapException(<span class=string>"Error querying database. Cause: "</span> + e, e);</span><br><span class=line> } <span class=keyword>finally</span> {</span><br><span class=line> ErrorContext.instance().reset();</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> <span class=comment>// 包括这里,是调用的org.apache.ibatis.executor.CachingExecutor#query(org.apache.ibatis.mapping.MappedStatement, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler)</span></span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <E> List<E> <span class="title function_">query</span><span class=params>(MappedStatement ms, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=type>BoundSql</span> <span class=variable>boundSql</span> <span class=operator>=</span> ms.getBoundSql(parameterObject);</span><br><span class=line> <span class=type>CacheKey</span> <span class=variable>key</span> <span class=operator>=</span> createCacheKey(ms, parameterObject, rowBounds, boundSql);</span><br><span class=line> <span class=keyword>return</span> query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);</span><br><span class=line> }</span><br><span class=line><span class=comment>// 然后是获取 BoundSql</span></span><br><span class=line> <span class=keyword>public</span> BoundSql <span class="title function_">getBoundSql</span><span class=params>(Object parameterObject)</span> {</span><br><span class=line> <span class=type>BoundSql</span> <span class=variable>boundSql</span> <span class=operator>=</span> sqlSource.getBoundSql(parameterObject);</span><br><span class=line> List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();</span><br><span class=line> <span class=keyword>if</span> (parameterMappings == <span class=literal>null</span> || parameterMappings.isEmpty()) {</span><br><span class=line> boundSql = <span class=keyword>new</span> <span class="title class_">BoundSql</span>(configuration, boundSql.getSql(), parameterMap.getParameterMappings(), parameterObject);</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=comment>// check for nested result maps in parameter mappings (issue #30)</span></span><br><span class=line> <span class=keyword>for</span> (ParameterMapping pm : boundSql.getParameterMappings()) {</span><br><span class=line> <span class=type>String</span> <span class=variable>rmId</span> <span class=operator>=</span> pm.getResultMapId();</span><br><span class=line> <span class=keyword>if</span> (rmId != <span class=literal>null</span>) {</span><br><span class=line> <span class=type>ResultMap</span> <span class=variable>rm</span> <span class=operator>=</span> configuration.getResultMap(rmId);</span><br><span class=line> <span class=keyword>if</span> (rm != <span class=literal>null</span>) {</span><br><span class=line> hasNestedResultMaps |= rm.hasNestedResultMaps();</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>return</span> boundSql;</span><br><span class=line> }</span><br><span class=line><span class=comment>// 因为前面讲了是生成的 DynamicSqlSource,所以也是调用这个的 getBoundSql</span></span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> BoundSql <span class="title function_">getBoundSql</span><span class=params>(Object parameterObject)</span> {</span><br><span class=line> <span class=type>DynamicContext</span> <span class=variable>context</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">DynamicContext</span>(configuration, parameterObject);</span><br><span class=line> <span class=comment>// 重点关注着</span></span><br><span class=line> rootSqlNode.apply(context);</span><br><span class=line> <span class=type>SqlSourceBuilder</span> <span class=variable>sqlSourceParser</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">SqlSourceBuilder</span>(configuration);</span><br><span class=line> Class<?> parameterType = parameterObject == <span class=literal>null</span> ? Object.class : parameterObject.getClass();</span><br><span class=line> <span class=type>SqlSource</span> <span class=variable>sqlSource</span> <span class=operator>=</span> sqlSourceParser.parse(context.getSql(), parameterType, context.getBindings());</span><br><span class=line> <span class=type>BoundSql</span> <span class=variable>boundSql</span> <span class=operator>=</span> sqlSource.getBoundSql(parameterObject);</span><br><span class=line> context.getBindings().forEach(boundSql::setAdditionalParameter);</span><br><span class=line> <span class=keyword>return</span> boundSql;</span><br><span class=line> }</span><br><span class=line><span class=comment>// 继续是这个 DynamicSqlNode 的 apply</span></span><br><span class=line> <span class=keyword>public</span> <span class=type>boolean</span> <span class="title function_">apply</span><span class=params>(DynamicContext context)</span> {</span><br><span class=line> contents.forEach(node -> node.apply(context));</span><br><span class=line> <span class=keyword>return</span> <span class=literal>true</span>;</span><br><span class=line> }</span><br><span class=line><span class=comment>// 看下面的图</span></span><br></pre></table></figure><p><img alt=image loading=lazy src=https://img.nicksxs.me/blog/BFlyxu.png><p>我们重点看 foreach 的逻辑<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br><span class=line>26</span><br><span class=line>27</span><br><span class=line>28</span><br><span class=line>29</span><br><span class=line>30</span><br><span class=line>31</span><br><span class=line>32</span><br><span class=line>33</span><br><span class=line>34</span><br><span class=line>35</span><br><span class=line>36</span><br><span class=line>37</span><br><span class=line>38</span><br><span class=line>39</span><br><span class=line>40</span><br><span class=line>41</span><br><span class=line>42</span><br><span class=line>43</span><br><span class=line>44</span><br><span class=line>45</span><br><span class=line>46</span><br><span class=line>47</span><br><span class=line>48</span><br><span class=line>49</span><br><span class=line>50</span><br><span class=line>51</span><br><span class=line>52</span><br><span class=line>53</span><br><span class=line>54</span><br><span class=line>55</span><br><span class=line>56</span><br><span class=line>57</span><br><span class=line>58</span><br></pre><td class=code><pre><span class=line><span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <span class=type>boolean</span> <span class="title function_">apply</span><span class=params>(DynamicContext context)</span> {</span><br><span class=line> Map<String, Object> bindings = context.getBindings();</span><br><span class=line> <span class=keyword>final</span> Iterable<?> iterable = evaluator.evaluateIterable(collectionExpression, bindings,</span><br><span class=line> Optional.ofNullable(nullable).orElseGet(configuration::isNullableOnForEach));</span><br><span class=line> <span class=keyword>if</span> (iterable == <span class=literal>null</span> || !iterable.iterator().hasNext()) {</span><br><span class=line> <span class=keyword>return</span> <span class=literal>true</span>;</span><br><span class=line> }</span><br><span class=line> <span class=type>boolean</span> <span class=variable>first</span> <span class=operator>=</span> <span class=literal>true</span>;</span><br><span class=line> <span class=comment>// 开始符号</span></span><br><span class=line> applyOpen(context);</span><br><span class=line> <span class=type>int</span> <span class=variable>i</span> <span class=operator>=</span> <span class=number>0</span>;</span><br><span class=line> <span class=keyword>for</span> (Object o : iterable) {</span><br><span class=line> <span class=type>DynamicContext</span> <span class=variable>oldContext</span> <span class=operator>=</span> context;</span><br><span class=line> <span class=keyword>if</span> (first || separator == <span class=literal>null</span>) {</span><br><span class=line> context = <span class=keyword>new</span> <span class="title class_">PrefixedContext</span>(context, <span class=string>""</span>);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> context = <span class=keyword>new</span> <span class="title class_">PrefixedContext</span>(context, separator);</span><br><span class=line> }</span><br><span class=line> <span class=type>int</span> <span class=variable>uniqueNumber</span> <span class=operator>=</span> context.getUniqueNumber();</span><br><span class=line> <span class=comment>// Issue #709</span></span><br><span class=line> <span class=keyword>if</span> (o <span class=keyword>instanceof</span> Map.Entry) {</span><br><span class=line> <span class=meta>@SuppressWarnings("unchecked")</span></span><br><span class=line> Map.Entry<Object, Object> mapEntry = (Map.Entry<Object, Object>) o;</span><br><span class=line> applyIndex(context, mapEntry.getKey(), uniqueNumber);</span><br><span class=line> applyItem(context, mapEntry.getValue(), uniqueNumber);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> applyIndex(context, i, uniqueNumber);</span><br><span class=line> applyItem(context, o, uniqueNumber);</span><br><span class=line> }</span><br><span class=line> <span class=comment>// 转换变量名,变成这种形式 select * from student where id in</span></span><br><span class=line> <span class=comment>// ( </span></span><br><span class=line> <span class=comment>// #{__frch_id_0}</span></span><br><span class=line> <span class=comment>// )</span></span><br><span class=line> contents.apply(<span class=keyword>new</span> <span class="title class_">FilteredDynamicContext</span>(configuration, context, index, item, uniqueNumber));</span><br><span class=line> <span class=keyword>if</span> (first) {</span><br><span class=line> first = !((PrefixedContext) context).isPrefixApplied();</span><br><span class=line> }</span><br><span class=line> context = oldContext;</span><br><span class=line> i++;</span><br><span class=line> }</span><br><span class=line> applyClose(context);</span><br><span class=line> context.getBindings().remove(item);</span><br><span class=line> context.getBindings().remove(index);</span><br><span class=line> <span class=keyword>return</span> <span class=literal>true</span>;</span><br><span class=line> }</span><br><span class=line><span class=comment>// 回到外层就会调用 parse 方法, 把#{} 这段替换成 ?</span></span><br><span class=line><span class=keyword>public</span> SqlSource <span class="title function_">parse</span><span class=params>(String originalSql, Class<?> parameterType, Map<String, Object> additionalParameters)</span> {</span><br><span class=line> <span class=type>ParameterMappingTokenHandler</span> <span class=variable>handler</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">ParameterMappingTokenHandler</span>(configuration, parameterType, additionalParameters);</span><br><span class=line> <span class=type>GenericTokenParser</span> <span class=variable>parser</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">GenericTokenParser</span>(<span class=string>"#{"</span>, <span class=string>"}"</span>, handler);</span><br><span class=line> String sql;</span><br><span class=line> <span class=keyword>if</span> (configuration.isShrinkWhitespacesInSql()) {</span><br><span class=line> sql = parser.parse(removeExtraWhitespaces(originalSql));</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> sql = parser.parse(originalSql);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> <span class=keyword>new</span> <span class="title class_">StaticSqlSource</span>(configuration, sql, handler.getParameterMappings());</span><br><span class=line> }</span><br></pre></table></figure><p><img alt=image loading=lazy src=https://img.nicksxs.me/blog/nE19Uv.png><p>可以看到这里,然后再进行替换<p><img alt=image loading=lazy src=https://img.nicksxs.me/blog/la6tMs.png><p>真实的从 <code>?</code> 替换成具体的变量值,是在这里<br><code>org.apache.ibatis.executor.SimpleExecutor#doQuery</code><br>调用了<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br><span class=line>2</span><br><span class=line>3</span><br><span class=line>4</span><br><span class=line>5</span><br><span class=line>6</span><br><span class=line>7</span><br><span class=line>8</span><br><span class=line>9</span><br><span class=line>10</span><br><span class=line>11</span><br><span class=line>12</span><br><span class=line>13</span><br><span class=line>14</span><br><span class=line>15</span><br><span class=line>16</span><br><span class=line>17</span><br><span class=line>18</span><br><span class=line>19</span><br><span class=line>20</span><br><span class=line>21</span><br><span class=line>22</span><br><span class=line>23</span><br><span class=line>24</span><br><span class=line>25</span><br><span class=line>26</span><br><span class=line>27</span><br><span class=line>28</span><br><span class=line>29</span><br><span class=line>30</span><br><span class=line>31</span><br><span class=line>32</span><br><span class=line>33</span><br><span class=line>34</span><br><span class=line>35</span><br><span class=line>36</span><br><span class=line>37</span><br><span class=line>38</span><br><span class=line>39</span><br><span class=line>40</span><br><span class=line>41</span><br><span class=line>42</span><br><span class=line>43</span><br><span class=line>44</span><br><span class=line>45</span><br><span class=line>46</span><br><span class=line>47</span><br></pre><td class=code><pre><span class=line><span class=keyword>private</span> Statement <span class="title function_">prepareStatement</span><span class=params>(StatementHandler handler, Log statementLog)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> Statement stmt;</span><br><span class=line> <span class=type>Connection</span> <span class=variable>connection</span> <span class=operator>=</span> getConnection(statementLog);</span><br><span class=line> stmt = handler.prepare(connection, transaction.getTimeout());</span><br><span class=line> handler.parameterize(stmt);</span><br><span class=line> <span class=keyword>return</span> stmt;</span><br><span class=line> }</span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">parameterize</span><span class=params>(Statement statement)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> parameterHandler.setParameters((PreparedStatement) statement);</span><br><span class=line> }</span><br><span class=line> <span class=meta>@Override</span></span><br><span class=line> <span class=keyword>public</span> <span class=keyword>void</span> <span class="title function_">setParameters</span><span class=params>(PreparedStatement ps)</span> {</span><br><span class=line> ErrorContext.instance().activity(<span class=string>"setting parameters"</span>).object(mappedStatement.getParameterMap().getId());</span><br><span class=line> List<ParameterMapping> parameterMappings = boundSql.getParameterMappings();</span><br><span class=line> <span class=keyword>if</span> (parameterMappings != <span class=literal>null</span>) {</span><br><span class=line> <span class=keyword>for</span> (<span class=type>int</span> <span class=variable>i</span> <span class=operator>=</span> <span class=number>0</span>; i < parameterMappings.size(); i++) {</span><br><span class=line> <span class=type>ParameterMapping</span> <span class=variable>parameterMapping</span> <span class=operator>=</span> parameterMappings.get(i);</span><br><span class=line> <span class=keyword>if</span> (parameterMapping.getMode() != ParameterMode.OUT) {</span><br><span class=line> Object value;</span><br><span class=line> <span class=type>String</span> <span class=variable>propertyName</span> <span class=operator>=</span> parameterMapping.getProperty();</span><br><span class=line> <span class=keyword>if</span> (boundSql.hasAdditionalParameter(propertyName)) { <span class=comment>// issue #448 ask first for additional params</span></span><br><span class=line> value = boundSql.getAdditionalParameter(propertyName);</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (parameterObject == <span class=literal>null</span>) {</span><br><span class=line> value = <span class=literal>null</span>;</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (typeHandlerRegistry.hasTypeHandler(parameterObject.getClass())) {</span><br><span class=line> value = parameterObject;</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=type>MetaObject</span> <span class=variable>metaObject</span> <span class=operator>=</span> configuration.newMetaObject(parameterObject);</span><br><span class=line> value = metaObject.getValue(propertyName);</span><br><span class=line> }</span><br><span class=line> <span class=type>TypeHandler</span> <span class=variable>typeHandler</span> <span class=operator>=</span> parameterMapping.getTypeHandler();</span><br><span class=line> <span class=type>JdbcType</span> <span class=variable>jdbcType</span> <span class=operator>=</span> parameterMapping.getJdbcType();</span><br><span class=line> <span class=keyword>if</span> (value == <span class=literal>null</span> && jdbcType == <span class=literal>null</span>) {</span><br><span class=line> jdbcType = configuration.getJdbcTypeForNull();</span><br><span class=line> }</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=comment>// --------------------------> </span></span><br><span class=line> <span class=comment>// 替换变量</span></span><br><span class=line> typeHandler.setParameter(ps, i + <span class=number>1</span>, value, jdbcType);</span><br><span class=line> } <span class=keyword>catch</span> (TypeException | SQLException e) {</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">TypeException</span>(<span class=string>"Could not set parameters for mapping: "</span> + parameterMapping + <span class=string>". Cause: "</span> + e, e);</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br></pre></table></figure></div><footer class=post-footer><div class="affiliate-creative affiliate-creative--post-end" data-affiliate-id=tencent-cloud-general><a rel="sponsored noopener" aria-label=腾讯云产品优惠 href=https://cloud.tencent.com/act/cps/redirect?redirect=2446&cps_key=2e33a1eedb380997d03618b4a5ba6ca7&from=console target=_blank><img alt=腾讯云服务器、数据库和云产品优惠 decoding=async height=419 loading=lazy src=/uploads/affiliate/tencent-cloud-general.webp width=690> </a><span class=affiliate-disclosure>推广</span></div><div class=reward-container><div>请我一杯咖啡吧!</div><button>赞赏</button><div class=post-reward><div><img alt="Nicksxs 微信" src=https://i.loli.net/2020/01/12/NUlWanT31E8LQGx.png><span>微信</span></div><div><img alt="Nicksxs 支付宝" 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