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class=post-content itemscope itemtype=http://schema.org/Article lang=zh-CN><link href=https://nicksxs.me/2023/01/08/mybatis%E7%B3%BB%E5%88%97-dataSource%E8%A7%A3%E6%9E%90/ itemprop=mainEntityOfPage><span hidden itemprop=author itemscope itemtype=http://schema.org/Person><meta content=/uploads/avatar.jpg itemprop=image><meta content=Nicksxs itemprop=name></span><span hidden itemprop=publisher itemscope itemtype=http://schema.org/Organization><meta content="Nicksxs's Blog" itemprop=name><meta content="Nicksxs 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-dataSource解析 | Nicksxs's Blog" itemprop=name><meta content="DataSource 作为数据库查询的最重要的数据源,在 mybatis 中也展开来说下 首先是解析的过程" itemprop=description></span><header class=post-header><h1 itemprop="name headline" class=post-title>mybatis系列-dataSource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:2023-01-08 20:35:14" datetime=2023-01-08T20:35:14+08:00>2023-01-08</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=/2023/01/08/mybatis%E7%B3%BB%E5%88%97-dataSource%E8%A7%A3%E6%9E%90/ data-title=mybatis系列-dataSource解析 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>DataSource 作为数据库查询的最重要的数据源,在 mybatis 中也展开来说下 首先是解析的过程</div></div></header><div class=post-body itemprop=articleBody><p>DataSource 作为数据库查询的最重要的数据源,在 mybatis 中也展开来说下<br>首先是解析的过程<figure class="highlight java"><table><tr><td class=gutter><pre><span class=line>1</span><br></pre><td class=code><pre><span class=line><span class=type>SqlSessionFactory</span> <span class=variable>sqlSessionFactory</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">SqlSessionFactoryBuilder</span>().build(inputStream);</span><br></pre></table></figure><p>在构建 SqlSessionFactory 也就是 DefaultSqlSessionFactory 的时候,<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>public</span> SqlSessionFactory <span class="title function_">build</span><span class=params>(InputStream inputStream)</span> {</span><br><span class=line> <span class=keyword>return</span> build(inputStream, <span class=literal>null</span>, <span class=literal>null</span>);</span><br><span class=line> }</span><br><span class=line><span class=keyword>public</span> SqlSessionFactory <span class="title function_">build</span><span class=params>(InputStream inputStream, String environment, Properties properties)</span> {</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=type>XMLConfigBuilder</span> <span class=variable>parser</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">XMLConfigBuilder</span>(inputStream, environment, properties);</span><br><span class=line> <span class=keyword>return</span> build(parser.parse());</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 building SqlSession."</span>, 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 class=keyword>try</span> {</span><br><span class=line> <span class=keyword>if</span> (inputStream != <span class=literal>null</span>) {</span><br><span class=line> inputStream.close();</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>catch</span> (IOException e) {</span><br><span class=line> <span class=comment>// Intentionally ignore. Prefer previous error.</span></span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br></pre></table></figure><p>前面也说过,就是解析 <code>mybatis-config.xml</code> 成 <code>Configuration</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></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><span class=line><span class=keyword>private</span> <span class=keyword>void</span> <span class="title function_">parseConfiguration</span><span class=params>(XNode root)</span> {</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=comment>// issue #117 read properties first</span></span><br><span class=line> propertiesElement(root.evalNode(<span class=string>"properties"</span>));</span><br><span class=line> <span class=type>Properties</span> <span class=variable>settings</span> <span class=operator>=</span> settingsAsProperties(root.evalNode(<span class=string>"settings"</span>));</span><br><span class=line> loadCustomVfs(settings);</span><br><span class=line> loadCustomLogImpl(settings);</span><br><span class=line> typeAliasesElement(root.evalNode(<span class=string>"typeAliases"</span>));</span><br><span class=line> pluginElement(root.evalNode(<span class=string>"plugins"</span>));</span><br><span class=line> objectFactoryElement(root.evalNode(<span class=string>"objectFactory"</span>));</span><br><span class=line> objectWrapperFactoryElement(root.evalNode(<span class=string>"objectWrapperFactory"</span>));</span><br><span class=line> reflectorFactoryElement(root.evalNode(<span class=string>"reflectorFactory"</span>));</span><br><span class=line> settingsElement(settings);</span><br><span class=line> <span class=comment>// read it after objectFactory and objectWrapperFactory issue #631</span></span><br><span class=line> <span class=comment>// -------------> 是在这里解析了DataSource</span></span><br><span class=line> environmentsElement(root.evalNode(<span class=string>"environments"</span>));</span><br><span class=line> databaseIdProviderElement(root.evalNode(<span class=string>"databaseIdProvider"</span>));</span><br><span class=line> typeHandlerElement(root.evalNode(<span class=string>"typeHandlers"</span>));</span><br><span class=line> mapperElement(root.evalNode(<span class=string>"mappers"</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 SQL Mapper Configuration. Cause: "</span> + e, e);</span><br><span class=line> }</span><br><span class=line>}</span><br></pre></table></figure><p>环境解析了这一块的内容<figure class="highlight xml"><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=tag><<span class=name>environments</span> <span class=attr>default</span>=<span class=string>"development"</span>></span></span><br><span class=line> <span class=tag><<span class=name>environment</span> <span class=attr>id</span>=<span class=string>"development"</span>></span></span><br><span class=line> <span class=tag><<span class=name>transactionManager</span> <span class=attr>type</span>=<span class=string>"JDBC"</span>/></span></span><br><span class=line> <span class=tag><<span class=name>dataSource</span> <span class=attr>type</span>=<span class=string>"POOLED"</span>></span></span><br><span class=line> <span class=tag><<span class=name>property</span> <span class=attr>name</span>=<span class=string>"driver"</span> <span class=attr>value</span>=<span class=string>"${driver}"</span>/></span></span><br><span class=line> <span class=tag><<span class=name>property</span> <span class=attr>name</span>=<span class=string>"url"</span> <span class=attr>value</span>=<span class=string>"${url}"</span>/></span></span><br><span class=line> <span class=tag><<span class=name>property</span> <span class=attr>name</span>=<span class=string>"username"</span> <span class=attr>value</span>=<span class=string>"${username}"</span>/></span></span><br><span class=line> <span class=tag><<span class=name>property</span> <span class=attr>name</span>=<span class=string>"password"</span> <span class=attr>value</span>=<span class=string>"${password}"</span>/></span></span><br><span class=line> <span class=tag>&LT/<span class=name>dataSource</span>></span></span><br><span class=line> <span class=tag>&LT/<span class=name>environment</span>></span></span><br><span class=line> <span class=tag>&LT/<span class=name>environments</span>></span></span><br></pre></table></figure><p>解析也是自上而下的,<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_">environmentsElement</span><span class=params>(XNode context)</span> <span class=keyword>throws</span> Exception {</span><br><span class=line> <span class=keyword>if</span> (context != <span class=literal>null</span>) {</span><br><span class=line> <span class=keyword>if</span> (environment == <span class=literal>null</span>) {</span><br><span class=line> environment = context.getStringAttribute(<span class=string>"default"</span>);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>for</span> (XNode child : context.getChildren()) {</span><br><span class=line> <span class=type>String</span> <span class=variable>id</span> <span class=operator>=</span> child.getStringAttribute(<span class=string>"id"</span>);</span><br><span class=line> <span class=keyword>if</span> (isSpecifiedEnvironment(id)) {</span><br><span class=line> <span class=type>TransactionFactory</span> <span class=variable>txFactory</span> <span class=operator>=</span> transactionManagerElement(child.evalNode(<span class=string>"transactionManager"</span>));</span><br><span class=line> <span class=type>DataSourceFactory</span> <span class=variable>dsFactory</span> <span class=operator>=</span> dataSourceElement(child.evalNode(<span class=string>"dataSource"</span>));</span><br><span class=line> <span class=type>DataSource</span> <span class=variable>dataSource</span> <span class=operator>=</span> dsFactory.getDataSource();</span><br><span class=line> Environment.<span class=type>Builder</span> <span class=variable>environmentBuilder</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">Environment</span>.Builder(id)</span><br><span class=line> .transactionFactory(txFactory)</span><br><span class=line> .dataSource(dataSource);</span><br><span class=line> configuration.setEnvironment(environmentBuilder.build());</span><br><span class=line> <span class=keyword>break</span>;</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><p>前面第一步是解析事务管理器元素<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> TransactionFactory <span class="title function_">transactionManagerElement</span><span class=params>(XNode context)</span> <span class=keyword>throws</span> Exception {</span><br><span class=line> <span class=keyword>if</span> (context != <span class=literal>null</span>) {</span><br><span class=line> <span class=type>String</span> <span class=variable>type</span> <span class=operator>=</span> context.getStringAttribute(<span class=string>"type"</span>);</span><br><span class=line> <span class=type>Properties</span> <span class=variable>props</span> <span class=operator>=</span> context.getChildrenAsProperties();</span><br><span class=line> <span class=type>TransactionFactory</span> <span class=variable>factory</span> <span class=operator>=</span> (TransactionFactory) resolveClass(type).getDeclaredConstructor().newInstance();</span><br><span class=line> factory.setProperties(props);</span><br><span class=line> <span class=keyword>return</span> factory;</span><br><span class=line> }</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">BuilderException</span>(<span class=string>"Environment declaration requires a TransactionFactory."</span>);</span><br><span class=line>}</span><br></pre></table></figure><p>而这里的 <code>resolveClass</code> 其实就使用了上一篇的 <code>typeAliases</code> 系统,这里是使用了 <code>JdbcTransactionFactory</code> 作为事务管理器,<br>后面的就是 <code>DataSourceFactory</code> 的创建也是 <code>DataSource</code> 的创建<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> DataSourceFactory <span class="title function_">dataSourceElement</span><span class=params>(XNode context)</span> <span class=keyword>throws</span> Exception {</span><br><span class=line> <span class=keyword>if</span> (context != <span class=literal>null</span>) {</span><br><span class=line> <span class=type>String</span> <span class=variable>type</span> <span class=operator>=</span> context.getStringAttribute(<span class=string>"type"</span>);</span><br><span class=line> <span class=type>Properties</span> <span class=variable>props</span> <span class=operator>=</span> context.getChildrenAsProperties();</span><br><span class=line> <span class=type>DataSourceFactory</span> <span class=variable>factory</span> <span class=operator>=</span> (DataSourceFactory) resolveClass(type).getDeclaredConstructor().newInstance();</span><br><span class=line> factory.setProperties(props);</span><br><span class=line> <span class=keyword>return</span> factory;</span><br><span class=line> }</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">BuilderException</span>(<span class=string>"Environment declaration requires a DataSourceFactory."</span>);</span><br><span class=line>}</span><br></pre></table></figure><p>因为在config文件中设置了Pooled,所以对应创建的就是 <code>PooledDataSourceFactory</code><br>但是这里其实有个比较需要注意的,mybatis 这里的其实是继承了 <code>UnpooledDataSourceFactory</code><br>将基础方法都放在了 <code>UnpooledDataSourceFactory</code> 中<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>public</span> <span class=keyword>class</span> <span class="title class_">PooledDataSourceFactory</span> <span class=keyword>extends</span> <span class="title class_">UnpooledDataSourceFactory</span> {</span><br><span class=line></span><br><span class=line> <span class=keyword>public</span> <span class="title function_">PooledDataSourceFactory</span><span class=params>()</span> {</span><br><span class=line> <span class=built_in>this</span>.dataSource = <span class=keyword>new</span> <span class="title class_">PooledDataSource</span>();</span><br><span class=line> }</span><br><span class=line></span><br><span class=line>}</span><br></pre></table></figure><p>这里只保留了在构造方法里创建 <code>DataSource</code><br>而这个 <code>PooledDataSource</code> 虽然没有直接继承 <code>UnpooledDataSource</code>,但其实<br>在构造方法里也是<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></pre><td class=code><pre><span class=line><span class=keyword>public</span> <span class="title function_">PooledDataSource</span><span class=params>()</span> {</span><br><span class=line> dataSource = <span class=keyword>new</span> <span class="title class_">UnpooledDataSource</span>();</span><br><span class=line>}</span><br></pre></table></figure><p>至于为什么这么做呢应该也是考虑到能比较多的复用代码,因为 <code>Pooled</code> 其实跟 <code>Unpooled</code> 最重要的差别就在于是不是每次都重开连接<br>使用连接池能够让应用在有大量查询的时候不用反复创建连接,省去了建联的网络等开销,<code>Unpooled</code>就是完成与数据库的连接,并可以获取该连接<br>主要的代码<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><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></pre><td class=code><pre><span class=line><span class=meta>@Override</span></span><br><span class=line><span class=keyword>public</span> Connection <span class="title function_">getConnection</span><span class=params>()</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=keyword>return</span> doGetConnection(username, password);</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> Connection <span class="title function_">getConnection</span><span class=params>(String username, String password)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=keyword>return</span> doGetConnection(username, password);</span><br><span class=line>}</span><br><span class=line><span class=keyword>private</span> Connection <span class="title function_">doGetConnection</span><span class=params>(String username, String password)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=type>Properties</span> <span class=variable>props</span> <span class=operator>=</span> <span class=keyword>new</span> <span class="title class_">Properties</span>();</span><br><span class=line> <span class=keyword>if</span> (driverProperties != <span class=literal>null</span>) {</span><br><span class=line> props.putAll(driverProperties);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>if</span> (username != <span class=literal>null</span>) {</span><br><span class=line> props.setProperty(<span class=string>"user"</span>, username);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>if</span> (password != <span class=literal>null</span>) {</span><br><span class=line> props.setProperty(<span class=string>"password"</span>, password);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>return</span> doGetConnection(props);</span><br><span class=line>}</span><br><span class=line><span class=keyword>private</span> Connection <span class="title function_">doGetConnection</span><span class=params>(Properties properties)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> initializeDriver();</span><br><span class=line> <span class=type>Connection</span> <span class=variable>connection</span> <span class=operator>=</span> DriverManager.getConnection(url, properties);</span><br><span class=line> configureConnection(connection);</span><br><span class=line> <span class=keyword>return</span> connection;</span><br><span class=line>}</span><br></pre></table></figure><p>而对于Pooled就会处理池化的逻辑<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><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><span class=line>81</span><br><span class=line>82</span><br><span class=line>83</span><br><span class=line>84</span><br><span class=line>85</span><br><span class=line>86</span><br><span class=line>87</span><br><span class=line>88</span><br><span class=line>89</span><br><span class=line>90</span><br><span class=line>91</span><br><span class=line>92</span><br><span class=line>93</span><br><span class=line>94</span><br><span class=line>95</span><br><span class=line>96</span><br><span class=line>97</span><br><span class=line>98</span><br><span class=line>99</span><br><span class=line>100</span><br><span class=line>101</span><br><span class=line>102</span><br><span class=line>103</span><br><span class=line>104</span><br><span class=line>105</span><br><span class=line>106</span><br><span class=line>107</span><br><span class=line>108</span><br><span class=line>109</span><br><span class=line>110</span><br><span class=line>111</span><br><span class=line>112</span><br><span class=line>113</span><br><span class=line>114</span><br><span class=line>115</span><br><span class=line>116</span><br><span class=line>117</span><br><span class=line>118</span><br></pre><td class=code><pre><span class=line><span class=keyword>private</span> PooledConnection <span class="title function_">popConnection</span><span class=params>(String username, String password)</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=type>boolean</span> <span class=variable>countedWait</span> <span class=operator>=</span> <span class=literal>false</span>;</span><br><span class=line> <span class=type>PooledConnection</span> <span class=variable>conn</span> <span class=operator>=</span> <span class=literal>null</span>;</span><br><span class=line> <span class=type>long</span> <span class=variable>t</span> <span class=operator>=</span> System.currentTimeMillis();</span><br><span class=line> <span class=type>int</span> <span class=variable>localBadConnectionCount</span> <span class=operator>=</span> <span class=number>0</span>;</span><br><span class=line></span><br><span class=line> <span class=keyword>while</span> (conn == <span class=literal>null</span>) {</span><br><span class=line> lock.lock();</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=keyword>if</span> (!state.idleConnections.isEmpty()) {</span><br><span class=line> <span class=comment>// Pool has available connection</span></span><br><span class=line> conn = state.idleConnections.remove(<span class=number>0</span>);</span><br><span class=line> <span class=keyword>if</span> (log.isDebugEnabled()) {</span><br><span class=line> log.debug(<span class=string>"Checked out connection "</span> + conn.getRealHashCode() + <span class=string>" from pool."</span>);</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// Pool does not have available connection</span></span><br><span class=line> <span class=keyword>if</span> (state.activeConnections.size() < poolMaximumActiveConnections) {</span><br><span class=line> <span class=comment>// Can create new connection</span></span><br><span class=line> conn = <span class=keyword>new</span> <span class="title class_">PooledConnection</span>(dataSource.getConnection(), <span class=built_in>this</span>);</span><br><span class=line> <span class=keyword>if</span> (log.isDebugEnabled()) {</span><br><span class=line> log.debug(<span class=string>"Created connection "</span> + conn.getRealHashCode() + <span class=string>"."</span>);</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// Cannot create new connection</span></span><br><span class=line> <span class=type>PooledConnection</span> <span class=variable>oldestActiveConnection</span> <span class=operator>=</span> state.activeConnections.get(<span class=number>0</span>);</span><br><span class=line> <span class=type>long</span> <span class=variable>longestCheckoutTime</span> <span class=operator>=</span> oldestActiveConnection.getCheckoutTime();</span><br><span class=line> <span class=keyword>if</span> (longestCheckoutTime > poolMaximumCheckoutTime) {</span><br><span class=line> <span class=comment>// Can claim overdue connection</span></span><br><span class=line> state.claimedOverdueConnectionCount++;</span><br><span class=line> state.accumulatedCheckoutTimeOfOverdueConnections += longestCheckoutTime;</span><br><span class=line> state.accumulatedCheckoutTime += longestCheckoutTime;</span><br><span class=line> state.activeConnections.remove(oldestActiveConnection);</span><br><span class=line> <span class=keyword>if</span> (!oldestActiveConnection.getRealConnection().getAutoCommit()) {</span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> oldestActiveConnection.getRealConnection().rollback();</span><br><span class=line> } <span class=keyword>catch</span> (SQLException e) {</span><br><span class=line> <span class=comment>/*</span></span><br><span class=line><span class=comment> Just log a message for debug and continue to execute the following</span></span><br><span class=line><span class=comment> statement like nothing happened.</span></span><br><span class=line><span class=comment> Wrap the bad connection with a new PooledConnection, this will help</span></span><br><span class=line><span class=comment> to not interrupt current executing thread and give current thread a</span></span><br><span class=line><span class=comment> chance to join the next competition for another valid/good database</span></span><br><span class=line><span class=comment> connection. At the end of this loop, bad {@link @conn} will be set as null.</span></span><br><span class=line><span class=comment> */</span></span><br><span class=line> log.debug(<span class=string>"Bad connection. Could not roll back"</span>);</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> conn = <span class=keyword>new</span> <span class="title class_">PooledConnection</span>(oldestActiveConnection.getRealConnection(), <span class=built_in>this</span>);</span><br><span class=line> conn.setCreatedTimestamp(oldestActiveConnection.getCreatedTimestamp());</span><br><span class=line> conn.setLastUsedTimestamp(oldestActiveConnection.getLastUsedTimestamp());</span><br><span class=line> oldestActiveConnection.invalidate();</span><br><span class=line> <span class=keyword>if</span> (log.isDebugEnabled()) {</span><br><span class=line> log.debug(<span class=string>"Claimed overdue connection "</span> + conn.getRealHashCode() + <span class=string>"."</span>);</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=comment>// Must wait</span></span><br><span class=line> <span class=keyword>try</span> {</span><br><span class=line> <span class=keyword>if</span> (!countedWait) {</span><br><span class=line> state.hadToWaitCount++;</span><br><span class=line> countedWait = <span class=literal>true</span>;</span><br><span class=line> }</span><br><span class=line> <span class=keyword>if</span> (log.isDebugEnabled()) {</span><br><span class=line> log.debug(<span class=string>"Waiting as long as "</span> + poolTimeToWait + <span class=string>" milliseconds for connection."</span>);</span><br><span class=line> }</span><br><span class=line> <span class=type>long</span> <span class=variable>wt</span> <span class=operator>=</span> System.currentTimeMillis();</span><br><span class=line> condition.await(poolTimeToWait, TimeUnit.MILLISECONDS);</span><br><span class=line> state.accumulatedWaitTime += System.currentTimeMillis() - wt;</span><br><span class=line> } <span class=keyword>catch</span> (InterruptedException e) {</span><br><span class=line> <span class=comment>// set interrupt flag</span></span><br><span class=line> Thread.currentThread().interrupt();</span><br><span class=line> <span class=keyword>break</span>;</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>if</span> (conn != <span class=literal>null</span>) {</span><br><span class=line> <span class=comment>// ping to server and check the connection is valid or not</span></span><br><span class=line> <span class=keyword>if</span> (conn.isValid()) {</span><br><span class=line> <span class=keyword>if</span> (!conn.getRealConnection().getAutoCommit()) {</span><br><span class=line> conn.getRealConnection().rollback();</span><br><span class=line> }</span><br><span class=line> conn.setConnectionTypeCode(assembleConnectionTypeCode(dataSource.getUrl(), username, password));</span><br><span class=line> conn.setCheckoutTimestamp(System.currentTimeMillis());</span><br><span class=line> conn.setLastUsedTimestamp(System.currentTimeMillis());</span><br><span class=line> state.activeConnections.add(conn);</span><br><span class=line> state.requestCount++;</span><br><span class=line> state.accumulatedRequestTime += System.currentTimeMillis() - t;</span><br><span class=line> } <span class=keyword>else</span> {</span><br><span class=line> <span class=keyword>if</span> (log.isDebugEnabled()) {</span><br><span class=line> log.debug(<span class=string>"A bad connection ("</span> + conn.getRealHashCode() + <span class=string>") was returned from the pool, getting another connection."</span>);</span><br><span class=line> }</span><br><span class=line> state.badConnectionCount++;</span><br><span class=line> localBadConnectionCount++;</span><br><span class=line> conn = <span class=literal>null</span>;</span><br><span class=line> <span class=keyword>if</span> (localBadConnectionCount > (poolMaximumIdleConnections + poolMaximumLocalBadConnectionTolerance)) {</span><br><span class=line> <span class=keyword>if</span> (log.isDebugEnabled()) {</span><br><span class=line> log.debug(<span class=string>"PooledDataSource: Could not get a good connection to the database."</span>);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">SQLException</span>(<span class=string>"PooledDataSource: Could not get a good connection to the database."</span>);</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> }</span><br><span class=line> } <span class=keyword>finally</span> {</span><br><span class=line> lock.unlock();</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>if</span> (conn == <span class=literal>null</span>) {</span><br><span class=line> <span class=keyword>if</span> (log.isDebugEnabled()) {</span><br><span class=line> log.debug(<span class=string>"PooledDataSource: Unknown severe error condition. The connection pool returned a null connection."</span>);</span><br><span class=line> }</span><br><span class=line> <span class=keyword>throw</span> <span class=keyword>new</span> <span class="title class_">SQLException</span>(<span class=string>"PooledDataSource: Unknown severe error condition. The connection pool returned a null connection."</span>);</span><br><span class=line> }</span><br><span class=line></span><br><span class=line> <span class=keyword>return</span> conn;</span><br><span class=line> }</span><br></pre></table></figure><p>它的入口不是个get方法,而是pop,从含义来来讲就不一样<br><code>org.apache.ibatis.datasource.pooled.PooledDataSource#getConnection()</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></pre><td class=code><pre><span class=line><span class=meta>@Override</span></span><br><span class=line><span class=keyword>public</span> Connection <span class="title function_">getConnection</span><span class=params>()</span> <span class=keyword>throws</span> SQLException {</span><br><span class=line> <span class=keyword>return</span> popConnection(dataSource.getUsername(), dataSource.getPassword()).getProxyConnection();</span><br><span class=line>}</span><br></pre></table></figure><p>对于具体怎么获取连接我们可以下一篇具体讲下</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 class=post-copyright-author><strong>本文作者: </strong>Nicksxs<li 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