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content="先补充两个点, 第一是前面我们说了 使用org.apache.ibatis.builder.xml.XMLConfigBuilder 创建了parser解析器,那么解析的结果是什么 看这个方法的返回值" itemprop=description></span><header class=post-header><h1 itemprop="name headline" class=post-title>mybatis系列-第一条sql的细节</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:2022-12-11 20:50:29" datetime=2022-12-11T20:50:29+08:00>2022-12-11</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-increment=true data-path=/2022/12/11/mybatis%E7%B3%BB%E5%88%97-%E7%AC%AC%E4%B8%80%E6%9D%A1sql%E7%9A%84%E7%BB%86%E8%8A%82/ data-title=mybatis系列-第一条sql的细节 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>先补充两个点, 第一是前面我们说了 使用org.apache.ibatis.builder.xml.XMLConfigBuilder 创建了parser解析器,那么解析的结果是什么 看这个方法的返回值</div></div></header><div class=post-body itemprop=articleBody><p>先补充两个点,<br>第一是前面我们说了<br>使用<code>org.apache.ibatis.builder.xml.XMLConfigBuilder</code> 创建了<code>parser</code>解析器,那么解析的结果是什么<br>看这个方法的返回值<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></pre><td class=code><pre><span class=line><span class=keyword>public</span> Configuration <span class="title function_">parse</span><span class=params>()</span> {</span><br><span class=line> <span class=keyword>if</span> (parsed) {</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">BuilderException</span>(<span class=string>"Each XMLConfigBuilder can only be used once."</span>);</span><br><span class=line> }</span><br><span class=line> parsed = <span class=literal>true</span>;</span><br><span class=line> parseConfiguration(parser.evalNode(<span class=string>"/configuration"</span>));</span><br><span class=line> <span class=keyword>return</span> configuration;</span><br><span class=line>}</span><br></pre></table></figure><p>返回的是 <code>org.apache.ibatis.session.Configuration</code> , 而这个 <code>Configuration</code> 也是 <code>mybatis</code> 中特别重要的配置核心类,贴一下里面的成员变量,<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></pre><td class=code><pre><span class=line><span class=keyword>public</span> <span class=keyword>class</span> <span class="title class_">Configuration</span> {</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> Environment environment;</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> safeRowBoundsEnabled;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> <span class=variable>safeResultHandlerEnabled</span> <span class=operator>=</span> <span class=literal>true</span>;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> mapUnderscoreToCamelCase;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> aggressiveLazyLoading;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> <span class=variable>multipleResultSetsEnabled</span> <span class=operator>=</span> <span class=literal>true</span>;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> useGeneratedKeys;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> <span class=variable>useColumnLabel</span> <span class=operator>=</span> <span class=literal>true</span>;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> <span class=variable>cacheEnabled</span> <span class=operator>=</span> <span class=literal>true</span>;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> callSettersOnNulls;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> <span class=variable>useActualParamName</span> <span class=operator>=</span> <span class=literal>true</span>;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> returnInstanceForEmptyRow;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> shrinkWhitespacesInSql;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> nullableOnForEach;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> argNameBasedConstructorAutoMapping;</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> String logPrefix;</span><br><span class=line> <span class=keyword>protected</span> Class<? <span class=keyword>extends</span> <span class="title class_">Log</span>> logImpl;</span><br><span class=line> <span class=keyword>protected</span> Class<? <span class=keyword>extends</span> <span class="title class_">VFS</span>> vfsImpl;</span><br><span class=line> <span class=keyword>protected</span> Class<?> defaultSqlProviderType;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>LocalCacheScope</span> <span class=variable>localCacheScope</span> <span class=operator>=</span> LocalCacheScope.SESSION;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>JdbcType</span> <span class=variable>jdbcTypeForNull</span> <span class=operator>=</span> JdbcType.OTHER;</span><br><span class=line> <span class=keyword>protected</span> Set<String> lazyLoadTriggerMethods = <span class=keyword>new</span> <span class="title class_">HashSet</span><>(Arrays.asList(<span class=string>"equals"</span>, <span class=string>"clone"</span>, <span class=string>"hashCode"</span>, <span class=string>"toString"</span>));</span><br><span class=line> <span class=keyword>protected</span> Integer defaultStatementTimeout;</span><br><span class=line> <span class=keyword>protected</span> Integer defaultFetchSize;</span><br><span class=line> <span class=keyword>protected</span> ResultSetType defaultResultSetType;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>ExecutorType</span> <span class=variable>defaultExecutorType</span> <span class=operator>=</span> ExecutorType.SIMPLE;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>AutoMappingBehavior</span> <span class=variable>autoMappingBehavior</span> <span class=operator>=</span> AutoMappingBehavior.PARTIAL;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>AutoMappingUnknownColumnBehavior</span> <span class=variable>autoMappingUnknownColumnBehavior</span> <span class=operator>=</span> AutoMappingUnknownColumnBehavior.NONE;</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> <span class=type>Properties</span> <span class=variable>variables</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">Properties</span>();</span><br><span class=line> <span class=keyword>protected</span> <span class=type>ReflectorFactory</span> <span class=variable>reflectorFactory</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">DefaultReflectorFactory</span>();</span><br><span class=line> <span class=keyword>protected</span> <span class=type>ObjectFactory</span> <span class=variable>objectFactory</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">DefaultObjectFactory</span>();</span><br><span class=line> <span class=keyword>protected</span> <span class=type>ObjectWrapperFactory</span> <span class=variable>objectWrapperFactory</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">DefaultObjectWrapperFactory</span>();</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> <span class=type>boolean</span> <span class=variable>lazyLoadingEnabled</span> <span class=operator>=</span> <span class=literal>false</span>;</span><br><span class=line> <span class=keyword>protected</span> <span class=type>ProxyFactory</span> <span class=variable>proxyFactory</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">JavassistProxyFactory</span>(); <span class=comment>// #224 Using internal Javassist instead of OGNL</span></span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> String databaseId;</span><br><span class=line> <span class=comment>/**</span></span><br><span class=line><span class=comment> * Configuration factory class.</span></span><br><span class=line><span class=comment> * Used to create Configuration for loading deserialized unread properties.</span></span><br><span class=line><span class=comment> *</span></span><br><span class=line><span class=comment> * <span class=doctag>@see</span> <a href='https://github.com/mybatis/old-google-code-issues/issues/300'>Issue 300 (google code)</a></span></span><br><span class=line><span class=comment> */</span></span><br><span class=line> <span class=keyword>protected</span> Class<?> configurationFactory;</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> <span class=type>MapperRegistry</span> <span class=variable>mapperRegistry</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">MapperRegistry</span>(<span class=built_in>this</span>);</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> <span class=type>InterceptorChain</span> <span class=variable>interceptorChain</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">InterceptorChain</span>();</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> <span class=type>TypeHandlerRegistry</span> <span class=variable>typeHandlerRegistry</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">TypeHandlerRegistry</span>(<span class=built_in>this</span>);</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> <span class=type>TypeAliasRegistry</span> <span class=variable>typeAliasRegistry</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">TypeAliasRegistry</span>();</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> <span class=type>LanguageDriverRegistry</span> <span class=variable>languageRegistry</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">LanguageDriverRegistry</span>();</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Map<String, MappedStatement> mappedStatements = <span class=keyword>new</span> <span class="title class_">StrictMap</span><MappedStatement>(<span class=string>"Mapped Statements collection"</span>)</span><br><span class=line> .conflictMessageProducer((savedValue, targetValue) -></span><br><span class=line> <span class=string>". please check "</span> + savedValue.getResource() + <span class=string>" and "</span> + targetValue.getResource());</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Map<String, Cache> caches = <span class=keyword>new</span> <span class="title class_">StrictMap</span><>(<span class=string>"Caches collection"</span>);</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Map<String, ResultMap> resultMaps = <span class=keyword>new</span> <span class="title class_">StrictMap</span><>(<span class=string>"Result Maps collection"</span>);</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Map<String, ParameterMap> parameterMaps = <span class=keyword>new</span> <span class="title class_">StrictMap</span><>(<span class=string>"Parameter Maps collection"</span>);</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Map<String, KeyGenerator> keyGenerators = <span class=keyword>new</span> <span class="title class_">StrictMap</span><>(<span class=string>"Key Generators collection"</span>);</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Set<String> loadedResources = <span class=keyword>new</span> <span class="title class_">HashSet</span><>();</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Map<String, XNode> sqlFragments = <span class=keyword>new</span> <span class="title class_">StrictMap</span><>(<span class=string>"XML fragments parsed from previous mappers"</span>);</span><br><span class=line></span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Collection<XMLStatementBuilder> incompleteStatements = <span class=keyword>new</span> <span class="title class_">LinkedList</span><>();</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Collection<CacheRefResolver> incompleteCacheRefs = <span class=keyword>new</span> <span class="title class_">LinkedList</span><>();</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Collection<ResultMapResolver> incompleteResultMaps = <span class=keyword>new</span> <span class="title class_">LinkedList</span><>();</span><br><span class=line> <span class=keyword>protected</span> <span class=keyword>final</span> Collection<MethodResolver> incompleteMethods = <span class=keyword>new</span> <span class="title class_">LinkedList</span><>();</span><br></pre></table></figure><p>这么多成员变量,先不一一解释作用,但是其中的几个参数我们应该是已经知道了的,第一个就是 <code>mappedStatements</code> ,上一篇我们知道被解析的mapper就是放在这里,后面的 <code>resultMaps</code> ,<code>parameterMaps</code> 也比较常用的就是我们参数和结果的映射<code>map</code>,这里跟我之前有一篇解释为啥我们一些变量的使用会比较特殊,比如<code>list</code>,可以<a href=https://nicksxs.me/2022/07/09/mybatis-%E7%9A%84-foreach-%E4%BD%BF%E7%94%A8%E7%9A%84%E6%B3%A8%E6%84%8F%E7%82%B9/>参考这篇</a>,<code>keyGenerators</code>是在我们需要定义主键生成器的时候使用。<br>然后第二点是我们创建的 <code>org.apache.ibatis.session.SqlSessionFactory</code> 是哪个,<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></pre><td class=code><pre><span class=line><span class=keyword>public</span> SqlSessionFactory <span class="title function_">build</span><span class=params>(Configuration config)</span> {</span><br><span class=line> <span class=keyword>return</span> <span class=keyword>new</span> <span class="title class_">DefaultSqlSessionFactory</span>(config);</span><br><span class=line>}</span><br></pre></table></figure><p>是这个 <code>DefaultSqlSessionFactory</code> ,这是其中一个 <code>SqlSessionFactory</code> 的实现<br>接下来我们看看 <code>openSession</code> 里干了啥<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></pre><td class=code><pre><span class=line><span class=keyword>public</span> SqlSession <span class="title function_">openSession</span><span class=params>()</span> {</span><br><span class=line> <span class=keyword>return</span> openSessionFromDataSource(configuration.getDefaultExecutorType(), <span class=literal>null</span>, <span class=literal>false</span>);</span><br><span class=line>}</span><br></pre></table></figure><p>这边有几个参数,第一个是默认的执行器类型,往上找找上面贴着的 <code>Configuration</code> 的成员变量里可以看到默认是<br><code>protected ExecutorType defaultExecutorType = ExecutorType.SIMPLE;</code><p>因为没有指明特殊的执行逻辑,所以默认我们也就用简单类型的,第二个参数是是事务级别,第三个是是否自动提交<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></pre><td class=code><pre><span class=line><span class=keyword>private</span> SqlSession <span class="title function_">openSessionFromDataSource</span><span class=params>(ExecutorType execType, TransactionIsolationLevel level, <span class=type>boolean</span> autoCommit)</span> {</span><br><span class=line> <span class=type>Transaction</span> <span class=variable>tx</span> <span class=operator>=</span> <span class=literal>null</span>;</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=keyword>final</span> <span class=type>Environment</span> <span class=variable>environment</span> <span class=operator>=</span> configuration.getEnvironment();</span><br><span class=line> <span class=keyword>final</span> <span class=type>TransactionFactory</span> <span class=variable>transactionFactory</span> <span class=operator>=</span> getTransactionFactoryFromEnvironment(environment);</span><br><span class=line> tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit);</span><br><span class=line> <span class=comment>// --------> 先关注这里</span></span><br><span class=line> <span class=keyword>final</span> <span class=type>Executor</span> <span class=variable>executor</span> <span class=operator>=</span> configuration.newExecutor(tx, execType);</span><br><span class=line> <span class=keyword>return</span> <span class=keyword>new</span> <span class="title class_">DefaultSqlSession</span>(configuration, executor, autoCommit);</span><br><span class=line> } <span class=keyword>catch</span> (Exception e) {</span><br><span class=line> closeTransaction(tx); <span class=comment>// may have fetched a connection so lets call close()</span></span><br><span class=line> <span class=keyword>throw</span> ExceptionFactory.wrapException(<span class=string>"Error opening session. 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></pre></table></figure><p>具体是调用了 <code>Configuration</code> 的这个方法<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></pre><td class=code><pre><span class=line><span class=keyword>public</span> Executor <span class="title function_">newExecutor</span><span class=params>(Transaction transaction, ExecutorType executorType)</span> {</span><br><span class=line> executorType = executorType == <span class=literal>null</span> ? defaultExecutorType : executorType;</span><br><span class=line> Executor executor;</span><br><span class=line> <span class=keyword>if</span> (ExecutorType.BATCH == executorType) {</span><br><span class=line> executor = <span class=keyword>new</span> <span class="title class_">BatchExecutor</span>(<span class=built_in>this</span>, transaction);</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (ExecutorType.REUSE == executorType) {</span><br><span class=line> executor = <span class=keyword>new</span> <span class="title class_">ReuseExecutor</span>(<span class=built_in>this</span>, transaction);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// ---------> 会走到这个分支</span></span><br><span class=line> executor = <span class=keyword>new</span> <span class="title class_">SimpleExecutor</span>(<span class=built_in>this</span>, transaction);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>if</span> (cacheEnabled) {</span><br><span class=line> executor = <span class=keyword>new</span> <span class="title class_">CachingExecutor</span>(executor);</span><br><span class=line> }</span><br><span class=line> executor = (Executor) interceptorChain.pluginAll(executor);</span><br><span class=line> <span class=keyword>return</span> executor;</span><br><span class=line>}</span><br></pre></table></figure><p>上面传入的 <code>executorType</code> 是 <code>Configuration</code> 的默认类型,也就是 <code>simple</code> 类型,并且 <code>cacheEnabled</code> 在 <code>Configuration</code> 默认为 <code>true</code>,所以会包装成<code>CachingExecutor</code> ,然后后面就是插件了,这块我们先不展开<br>然后我们的openSession返回的就是创建了<code>DefaultSqlSession</code><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></pre><td class=code><pre><span class=line><span class=keyword>public</span> <span class="title function_">DefaultSqlSession</span><span class=params>(Configuration configuration, Executor executor, <span class=type>boolean</span> autoCommit)</span> {</span><br><span class=line> <span class=built_in>this</span>.configuration = configuration;</span><br><span class=line> <span class=built_in>this</span>.executor = executor;</span><br><span class=line> <span class=built_in>this</span>.dirty = <span class=literal>false</span>;</span><br><span class=line> <span class=built_in>this</span>.autoCommit = autoCommit;</span><br><span class=line> }</span><br></pre></table></figure><p>然后就是调用 <code>selectOne</code>, 因为前面已经把这部分代码说过了,就直接跳转过来<br><code>org.apache.ibatis.session.defaults.DefaultSqlSession#selectList(java.lang.String, java.lang.Object, org.apache.ibatis.session.RowBounds, org.apache.ibatis.session.ResultHandler)</code><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></pre><td class=code><pre><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=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></pre></table></figure><p>因为前面说了 <code>executor</code> 包装了 <code>CachingExecutor</code> ,所以会先调用<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></pre><td class=code><pre><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></pre></table></figure><p>然后是调用的真实的query方法<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=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, CacheKey key, BoundSql boundSql)</span></span><br><span class=line> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=type>Cache</span> <span class=variable>cache</span> <span class=operator>=</span> ms.getCache();</span><br><span class=line> <span class=keyword>if</span> (cache != <span class=literal>null</span>) {</span><br><span class=line> flushCacheIfRequired(ms);</span><br><span class=line> <span class=keyword>if</span> (ms.isUseCache() && resultHandler == <span class=literal>null</span>) {</span><br><span class=line> ensureNoOutParams(ms, boundSql);</span><br><span class=line> <span class=meta>@SuppressWarnings("unchecked")</span></span><br><span class=line> List<E> list = (List<E>) tcm.getObject(cache, key);</span><br><span class=line> <span class=keyword>if</span> (list == <span class=literal>null</span>) {</span><br><span class=line> list = delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);</span><br><span class=line> tcm.putObject(cache, key, list); <span class=comment>// issue #578 and #116</span></span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> list;</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> delegate.query(ms, parameterObject, rowBounds, resultHandler, key, boundSql);</span><br><span class=line>}</span><br></pre></table></figure><p>这里是第一次查询,没有缓存就先到最后一行,继续是调用到 <code>org.apache.ibatis.executor.BaseExecutor#queryFromDatabase</code><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></pre><td class=code><pre><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 parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> ErrorContext.instance().resource(ms.getResource()).activity(<span class=string>"executing a query"</span>).object(ms.getId());</span><br><span class=line> <span class=keyword>if</span> (closed) {</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">ExecutorException</span>(<span class=string>"Executor was closed."</span>);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>if</span> (queryStack == <span class=number>0</span> && ms.isFlushCacheRequired()) {</span><br><span class=line> clearLocalCache();</span><br><span class=line> }</span><br><span class=line> List<E> list;</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> queryStack++;</span><br><span class=line> list = resultHandler == <span class=literal>null</span> ? (List<E>) localCache.getObject(key) : <span class=literal>null</span>;</span><br><span class=line> <span class=keyword>if</span> (list != <span class=literal>null</span>) {</span><br><span class=line> handleLocallyCachedOutputParameters(ms, key, parameter, boundSql);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// ----------->会走到这里</span></span><br><span class=line> list = queryFromDatabase(ms, parameter, rowBounds, resultHandler, key, boundSql);</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>finally</span> {</span><br><span class=line> queryStack--;</span><br><span class=line> }</span><br><span class=line> <span class=keyword>if</span> (queryStack == <span class=number>0</span>) {</span><br><span class=line> <span class=keyword>for</span> (DeferredLoad deferredLoad : deferredLoads) {</span><br><span class=line> deferredLoad.load();</span><br><span class=line> }</span><br><span class=line> <span class=comment>// issue #601</span></span><br><span class=line> deferredLoads.clear();</span><br><span class=line> <span class=keyword>if</span> (configuration.getLocalCacheScope() == LocalCacheScope.STATEMENT) {</span><br><span class=line> <span class=comment>// issue #482</span></span><br><span class=line> clearLocalCache();</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> list;</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><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></pre><td class=code><pre><span class=line><span class=keyword>private</span> <E> List<E> <span class="title function_">queryFromDatabase</span><span class=params>(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, CacheKey key, BoundSql boundSql)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> List<E> list;</span><br><span class=line> localCache.putObject(key, EXECUTION_PLACEHOLDER);</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> list = doQuery(ms, parameter, rowBounds, resultHandler, boundSql);</span><br><span class=line> } <span class=keyword>finally</span> {</span><br><span class=line> localCache.removeObject(key);</span><br><span class=line> }</span><br><span class=line> localCache.putObject(key, list);</span><br><span class=line> <span class=keyword>if</span> (ms.getStatementType() == StatementType.CALLABLE) {</span><br><span class=line> localOutputParameterCache.putObject(key, parameter);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> list;</span><br><span class=line>}</span><br></pre></table></figure><p>然后就是 <code>simpleExecutor</code> 的执行过程<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=meta>@Override</span></span><br><span class=line><span class=keyword>public</span> <E> List<E> <span class="title function_">doQuery</span><span class=params>(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=type>Statement</span> <span class=variable>stmt</span> <span class=operator>=</span> <span class=literal>null</span>;</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=type>Configuration</span> <span class=variable>configuration</span> <span class=operator>=</span> ms.getConfiguration();</span><br><span class=line> <span class=type>StatementHandler</span> <span class=variable>handler</span> <span class=operator>=</span> configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);</span><br><span class=line> stmt = prepareStatement(handler, ms.getStatementLog());</span><br><span class=line> <span class=keyword>return</span> handler.query(stmt, resultHandler);</span><br><span class=line> } <span class=keyword>finally</span> {</span><br><span class=line> closeStatement(stmt);</span><br><span class=line> }</span><br><span class=line>}</span><br></pre></table></figure><p>接下去其实就是跟jdbc交互了<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></pre><td class=code><pre><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>(Statement statement, ResultHandler resultHandler)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=type>PreparedStatement</span> <span class=variable>ps</span> <span class=operator>=</span> (PreparedStatement) statement;</span><br><span class=line> ps.execute();</span><br><span class=line> <span class=keyword>return</span> resultSetHandler.handleResultSets(ps);</span><br><span class=line>}</span><br></pre></table></figure><p><code>com.mysql.cj.jdbc.ClientPreparedStatement#execute</code><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></pre><td class=code><pre><span class=line><span class=keyword>public</span> <span class=type>boolean</span> <span class="title function_">execute</span><span class=params>()</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=keyword>synchronized</span>(<span class=built_in>this</span>.checkClosed().getConnectionMutex()) {</span><br><span class=line> <span class=type>JdbcConnection</span> <span class=variable>locallyScopedConn</span> <span class=operator>=</span> <span class=built_in>this</span>.connection;</span><br><span class=line> <span class=keyword>if</span> (!<span class=built_in>this</span>.doPingInstead && !<span class=built_in>this</span>.checkReadOnlySafeStatement()) {</span><br><span class=line> <span class=keyword>throw</span> SQLError.createSQLException(Messages.getString(<span class=string>"PreparedStatement.20"</span>) + Messages.getString(<span class=string>"PreparedStatement.21"</span>), <span class=string>"S1009"</span>, <span class=built_in>this</span>.exceptionInterceptor);</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=type>ResultSetInternalMethods</span> <span class=variable>rs</span> <span class=operator>=</span> <span class=literal>null</span>;</span><br><span class=line> <span class=built_in>this</span>.lastQueryIsOnDupKeyUpdate = <span class=literal>false</span>;</span><br><span class=line> <span class=keyword>if</span> (<span class=built_in>this</span>.retrieveGeneratedKeys) {</span><br><span class=line> <span class=built_in>this</span>.lastQueryIsOnDupKeyUpdate = <span class=built_in>this</span>.containsOnDuplicateKeyUpdate();</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=built_in>this</span>.batchedGeneratedKeys = <span class=literal>null</span>;</span><br><span class=line> <span class=built_in>this</span>.resetCancelledState();</span><br><span class=line> <span class=built_in>this</span>.implicitlyCloseAllOpenResults();</span><br><span class=line> <span class=built_in>this</span>.clearWarnings();</span><br><span class=line> <span class=keyword>if</span> (<span class=built_in>this</span>.doPingInstead) {</span><br><span class=line> <span class=built_in>this</span>.doPingInstead();</span><br><span class=line> <span class=keyword>return</span> <span class=literal>true</span>;</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=built_in>this</span>.setupStreamingTimeout(locallyScopedConn);</span><br><span class=line> <span class=type>Message</span> <span class=variable>sendPacket</span> <span class=operator>=</span> ((PreparedQuery)<span class=built_in>this</span>.query).fillSendPacket(((PreparedQuery)<span class=built_in>this</span>.query).getQueryBindings());</span><br><span class=line> <span class=type>String</span> <span class=variable>oldDb</span> <span class=operator>=</span> <span class=literal>null</span>;</span><br><span class=line> <span class=keyword>if</span> (!locallyScopedConn.getDatabase().equals(<span class=built_in>this</span>.getCurrentDatabase())) {</span><br><span class=line> oldDb = locallyScopedConn.getDatabase();</span><br><span class=line> locallyScopedConn.setDatabase(<span class=built_in>this</span>.getCurrentDatabase());</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=type>CachedResultSetMetaData</span> <span class=variable>cachedMetadata</span> <span class=operator>=</span> <span class=literal>null</span>;</span><br><span class=line> <span class=type>boolean</span> <span class=variable>cacheResultSetMetadata</span> <span class=operator>=</span> (Boolean)locallyScopedConn.getPropertySet().getBooleanProperty(PropertyKey.cacheResultSetMetadata).getValue();</span><br><span class=line> <span class=keyword>if</span> (cacheResultSetMetadata) {</span><br><span class=line> cachedMetadata = locallyScopedConn.getCachedMetaData(((PreparedQuery)<span class=built_in>this</span>.query).getOriginalSql());</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> locallyScopedConn.setSessionMaxRows(<span class=built_in>this</span>.getQueryInfo().getFirstStmtChar() == <span class=string>'S'</span> ? <span class=built_in>this</span>.maxRows : -<span class=number>1</span>);</span><br><span class=line> rs = <span class=built_in>this</span>.executeInternal(<span class=built_in>this</span>.maxRows, sendPacket, <span class=built_in>this</span>.createStreamingResultSet(), <span class=built_in>this</span>.getQueryInfo().getFirstStmtChar() == <span class=string>'S'</span>, cachedMetadata, <span class=literal>false</span>);</span><br><span class=line> <span class=keyword>if</span> (cachedMetadata != <span class=literal>null</span>) {</span><br><span class=line> locallyScopedConn.initializeResultsMetadataFromCache(((PreparedQuery)<span class=built_in>this</span>.query).getOriginalSql(), cachedMetadata, rs);</span><br><span class=line> } <span class=keyword>else</span> <span class=keyword>if</span> (rs.hasRows() && cacheResultSetMetadata) {</span><br><span class=line> locallyScopedConn.initializeResultsMetadataFromCache(((PreparedQuery)<span class=built_in>this</span>.query).getOriginalSql(), (CachedResultSetMetaData)<span class=literal>null</span>, rs);</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (<span class=built_in>this</span>.retrieveGeneratedKeys) {</span><br><span class=line> rs.setFirstCharOfQuery(<span class=built_in>this</span>.getQueryInfo().getFirstStmtChar());</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (oldDb != <span class=literal>null</span>) {</span><br><span class=line> locallyScopedConn.setDatabase(oldDb);</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>if</span> (rs != <span class=literal>null</span>) {</span><br><span class=line> <span class=built_in>this</span>.lastInsertId = rs.getUpdateID();</span><br><span class=line> <span class=built_in>this</span>.results = rs;</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>return</span> rs != <span class=literal>null</span> && rs.hasRows();</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>catch</span> (CJException var11) {</span><br><span class=line> <span class=keyword>throw</span> SQLExceptionsMapping.translateException(var11, <span class=built_in>this</span>.getExceptionInterceptor());</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" src=https://ooo.0o0.ooo/2016/08/17/57b421e773057.jpg><span>支付宝</span></div></div></div><div class=post-copyright><ul><li 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