mybatis中的的处理方法

       在每一次调用的时候是调用Statement.addBatch()方法，最终所有的参数都传递完了，没有更多的参数时调用Statement.executeBatch()方法进行批量操作。在上一篇博文中我们查看了BatchExecutor的源码，它的核心代码doUpdate()方法，每次被调用的时候都是以handler.batch()结束，而handler.batch()对应的底层代码是调用对应的Statement的addBatch()方法。那它是在什么时候执行executeBatch()呢？

  @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;

    if (sql.equals(currentSql) && ms.equals(currentStatement)) {

      intlast = statementList.size() - 1;

      stmt = statementList.get(last);

     handler.parameterize(stmt);//fix Issues 322

      BatchResult batchResult = batchResultList.get(last);

      batchResult.addParameterObject(parameterObject);

    } else {

      Connection connection = getConnection(ms.getStatementLog());

      stmt = handler.prepare(connection);

      handler.parameterize(stmt);    //fix Issues 322

      currentSql = sql;

      currentStatement = ms;

      statementList.add(stmt);

      batchResultList.add(new BatchResult(ms, sql, parameterObject));

    }

  // handler.parameterize(stmt);

    handler.batch(stmt);

    return BATCH_UPDATE_RETURN_VALUE;

  }

 

       它的executeBatch()是在doFlushStatements()方法调用中调用的，它会在当前Executor进行commit时调用，也会在当前Executor第一次执行doQuery()时调用，在这个时候都会调用Executor的flushStatements()方法，而BaseExecutor在执行flushStatements()时最终会调用其doFlushStatements()方法。当然，我们也可以手动的调用SqlSession的flushStatements()方法，其底层实现也会调用对应的BaseExecutor的flushStatements()方法。

  @Override

  public List<BatchResult> doFlushStatements(boolean isRollback) throws SQLException {

    try {

      List<BatchResult> results = new ArrayList<BatchResult>();

      if (isRollback) {

        return Collections.emptyList();

      }

      for (int i = 0, n = statementList.size(); i < n; i++) {

        Statement stmt = statementList.get(i);

        BatchResult batchResult = batchResultList.get(i);

        try {

          batchResult.setUpdateCounts(stmt.executeBatch());

          MappedStatement ms = batchResult.getMappedStatement();

          List<Object> parameterObjects = batchResult.getParameterObjects();

          KeyGenerator keyGenerator = ms.getKeyGenerator();

          if (Jdbc3KeyGenerator.class.equals(keyGenerator.getClass())) {

            Jdbc3KeyGenerator jdbc3KeyGenerator = (Jdbc3KeyGenerator) keyGenerator;

            jdbc3KeyGenerator.processBatch(ms, stmt, parameterObjects);

          } else if (!NoKeyGenerator.class.equals(keyGenerator.getClass())) { //issue #141

            for (Object parameter : parameterObjects) {

              keyGenerator.processAfter(this, ms, stmt, parameter);

            }

          }

        } catch (BatchUpdateException e) {

          StringBuilder message = new StringBuilder();

          message.append(batchResult.getMappedStatement().getId())

              .append(" (batch index #")

              .append(i + 1)

              .append(")")

              .append(" failed.");

          if (i > 0) {

            message.append(" ")

                .append(i)

                .append(" prior sub executor(s) completed successfully, but will be rolled back.");

          }

          throw new BatchExecutorException(message.toString(), e, results, batchResult);

        }

        results.add(batchResult);

      }

      return results;

    } finally {

      for (Statement stmt : statementList) {

        closeStatement(stmt);

      }

      currentSql = null;

      statementList.clear();

      batchResultList.clear();

    }

  }

 

       下面是一个使用Mybatis的BatchExecutor进行批量操作的示例。在示例中我们创建了一个使用BatchExecutor的SqlSession，也可以是SqlSessionTemplate，其实现了SqlSession接口，底层通过一个SqlSession代理进行相应的操作。然后在循环中一次调用对应Mapper的新增操作，相当于调用BatchExecutor的doUpdate()，最后调用SqlSession的commit()方法提交事务，在SqlSession的commit()中会调用Executor的commit()，从而导致了executeBatch()的发生。

   @Test

   public void testExecutor() {

      SqlSession session = this.sessionFactory.openSession(ExecutorType.BATCH);

      UserMapper mapper = session.getMapper(UserMapper.class);

      User user = null;

      for (inti = 0; i < 10; i++) {

        user = new User();

        user.setName("Name_" + i);

        user.setEmail("email");

        mapper.insert(user);

      }

      // 批量插入User

      session.commit();// 提交事务时批量操作才会写入数据库

      session.close();

   }

<dependency>
    <groupId>com.baomidou</groupId>
    <artifactId>mybatis-plus-boot-starter</artifactId>
    <version>3.1.2</version>
</dependency>

<dependency>
    <groupId>org.apache.velocity</groupId>
    <artifactId>velocity-engine-core</artifactId>
    <version>2.1</version>
</dependency>

<dependency>
    <groupId>org.freemarker</groupId>
    <artifactId>freemarker</artifactId>
    <version>2.3.29</version>
</dependency>

<dependency>
    <groupId>com.ibeetl</groupId>
    <artifactId>beetl</artifactId>
    <version>3.0.11.RELEASE</version>
</dependency>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.oracle.mapper.AccountInfoMapper"><!--  接口的全类名 -->
    <!-- type:实体类的全类名 -->
    <resultMap id="BaseResultMap" type="com.oracle.entity.AccountInfo">
        <id column="ID" property="id" jdbcType="DECIMAL" />
        <result column="USERNAME" property="userName" jdbcType="VARCHAR" />
        <result column="PASSWORD" property="password" jdbcType="VARCHAR" />
        <result column="GENDER" property="gender" jdbcType="CHAR" />
        <result column="EMAIL" property="email" jdbcType="VARCHAR" />
        <result column="CREATE_DATE" property="createDate" jdbcType="DATE" />
    </resultMap>
    <!-- id 跟接口中的方法名称保持一致 -->
    <select id="queryAllAccountInfo" resultMap="BaseResultMap">
        select ID,
        USERNAME,PASSWORD,
        GENDER, EMAIL, CREATE_DATE from ACCOUNT_INFO
    </select>
    <insert id="batchInsertAccountInfo" parameterType="java.util.List">
        INSERT INTO ACCOUNT_INFO(ID, USERNAME,PASSWORD,GENDER, EMAIL,CREATE_DATE)
        (
        <foreach collection="list" index="" item="accountInfo"
            separator="union all">
            select
            #{accountInfo.id},
            #{accountInfo.userName},
            #{accountInfo.password},
            #{accountInfo.gender},
            #{accountInfo.email},
            #{accountInfo.createDate}
            from dual
        </foreach>
        )
    </insert>
    
    <insert id="batchInsertAccountInfoUseSeq" parameterType="java.util.List">
        <selectKey resultType="long" keyProperty="id" order="BEFORE"> 
            SELECT ACCOUNT_SEQ.NEXTVAL FROM dual
        </selectKey> 
        INSERT INTO ACCOUNT_INFO(ID, USERNAME,PASSWORD,GENDER, EMAIL,CREATE_DATE)
        SELECT ACCOUNT_SEQ.NEXTVAL, m.* FROM(
        <foreach collection="list" index="" item="accountInfo"
            separator="union all">
            select
            #{accountInfo.userName},
            #{accountInfo.password},
            #{accountInfo.gender},
            #{accountInfo.email},
            sysdate
            from dual
        </foreach>
        ) m
    </insert>
    
    <insert id="insertOne" parameterType="com.oracle.entity.AccountInfo">
        <selectKey resultType="long" keyProperty="id" order="BEFORE"> 
            SELECT ACCOUNT_SEQ.NEXTVAL FROM dual
        </selectKey> 
        INSERT INTO ACCOUNT_INFO(ID, USERNAME,PASSWORD,GENDER, EMAIL,CREATE_DATE)
        values(
            #{id},
            #{userName},
            #{password},
            #{gender},
            #{email},
            sysdate
        )
    </insert>
</mapper>