MyBatis源码-解读Executor的三个实现类之BatchExecutor(批处理执行器)

た入场券 2023-02-17 14:54 12阅读 0赞

### 文章目录 ###

*  Pre
 *  Executor 执行器
 *  接口继承关系
 *  BatchExecutor(重用执行器)
 *   *  入门小demo
     *  源码
     *  BatchExecutor VS ReuseExecutor

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# Pre #

[MyBatis源码-深入理解MyBatis Executor的设计思想][MyBatis_-_MyBatis Executor]

工程部分见  
[MyBatis源码- SqlSession门面模式 & selectList 源码解析][MyBatis_- SqlSession_ _ selectList]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 1]

实际中，我们都是面向SqlSession编程的，不会直接调用Executor来执行业务逻辑，这里我们仅仅是为了深入了解下Executor体系架构才这么搞的，切记。

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# Executor 执行器 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 2]

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# 接口继承关系 #

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 3]

这里我们重点看下Executor的 三个实现子类。

分别是：SimpleExecutor(简单执行器)、ReuseExecutor(重用执行器)、BatchExecutor(批处理执行器)。

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# BatchExecutor(重用执行器) #

BatchExecutor 仅对修改操作（包括删除）有效哈 ，对 select操作是不起作用。

BatchExecutor 主要是用于做批量更新操作的 ,底层会调用Statement的 executeBatch()方法实现批量操作

## 入门小demo ##

@Test
        public void testBatchExecutor() throws SQLException { 
            // 通过factory.openSession().getConnection()实例化JdbcTransaction ，用于构建BatchExecutor
            jdbcTransaction = new JdbcTransaction(factory.openSession().getConnection());
    
            // 实例化BatchExecutor
            BatchExecutor executor = new BatchExecutor(configuration, jdbcTransaction);
    
            // 映射SQL
            ms = configuration.getMappedStatement("com.artisan.UserMapper.updateById");
    
            Map map = new HashMap();
            map.put("arg0",1);
            map.put("arg1","222");
    
            // 调用doUpdate
            executor.doUpdate(ms,map);
            executor.doUpdate(ms,map);
    
            // 刷新
            executor.doFlushStatements(false);
            // 提交 否则不生效
            executor.commit(true);
         
        }

![在这里插入图片描述][20200614231920904.png]

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## 源码 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 4]

currentSql 全局变量， 非线程安全

statementList 缓存 statement  
batchResultList 缓存 返回结果

@Override
      public int doUpdate(MappedStatement ms, Object parameterObject) throws SQLException { 
        final Configuration configuration = ms.getConfiguration();
        final StatementHandler handler = configuration.newStatementHandler(this, ms, parameterObject, RowBounds.DEFAULT, null, null);
        final BoundSql boundSql = handler.getBoundSql();
        final String sql = boundSql.getSql();
        final Statement stmt; 
        
       // 当前sql , 并且是当前statement
        if (sql.equals(currentSql) && ms.equals(currentStatement)) { 
          int last = statementList.size() - 1;
          stmt = statementList.get(last);
          applyTransactionTimeout(stmt);
          handler.parameterize(stmt);//fix Issues 322
          BatchResult batchResult = batchResultList.get(last);
          batchResult.addParameterObject(parameterObject);
        } else { 
          Connection connection = getConnection(ms.getStatementLog());
          stmt = handler.prepare(connection, transaction.getTimeout());
          handler.parameterize(stmt);    //fix Issues 322
          currentSql = sql;
          currentStatement = ms;
          statementList.add(stmt);
          batchResultList.add(new BatchResult(ms, sql, parameterObject));
        }
        handler.batch(stmt);
        return BATCH_UPDATE_RETURN_VALUE;
      }

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 5]

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3lhbmdzaGFuZ3dlaQ_size_16_color_FFFFFF_t_70 6]

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## BatchExecutor VS ReuseExecutor ##

看输出 和 ReuseExecutor 感觉差不多，其实是有区别的

*  ReuseExecutor ： 设置参数，执行，获取返回结果，然后在设置参数，执行，获取返回结果
 *  BatchExecutor： 批量设置参数 ， 执行 ，获取返回结果。

BatchExecutor仅执行一次，ReuseExecutor 执行多次

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[MyBatis_-_MyBatis Executor]: https://artisan.blog.csdn.net/article/details/106560762
[MyBatis_- SqlSession_ _ selectList]: https://artisan.blog.csdn.net/article/details/106740995
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[20200614231920904.png]: https://img-blog.csdnimg.cn/20200614231920904.png
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