Mybatis源码之Statement处理器SimpleStatementHandler（四）

骑猪看日落 2022-03-06 15:22 173阅读 0赞

SimpleStatementHandler就是使用基本的Statement来执行query、batch、update等操作，其实现还是比较简单的，当然在执行过程中会涉及keyGenerator和ResultHandler操作，这些我们会在接下来的博客中进行详解。SimpleStatementHandler用于执行简单的sql语句，这里简单的sql语句是指sql语句中没有变量，不会通过外部进行参数传入的sql语句。

源码如下：

/**
     * @author Clinton Begin
     */
    public class SimpleStatementHandler extends BaseStatementHandler {
     
      public SimpleStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
        super(executor, mappedStatement, parameter, rowBounds, resultHandler, boundSql);
      }
     
      @Override
      public int update(Statement statement) throws SQLException {
    	//获得sql语句 
        String sql = boundSql.getSql();
    	//获得参数
        Object parameterObject = boundSql.getParameterObject();
        KeyGenerator keyGenerator = mappedStatement.getKeyGenerator();
        int rows;
    	//statement执行sql语句返回更新数目
        if (keyGenerator instanceof Jdbc3KeyGenerator) {
          statement.execute(sql, Statement.RETURN_GENERATED_KEYS);
          rows = statement.getUpdateCount();
          keyGenerator.processAfter(executor, mappedStatement, statement, parameterObject);
        } else if (keyGenerator instanceof SelectKeyGenerator) {
          statement.execute(sql);
          rows = statement.getUpdateCount();
          keyGenerator.processAfter(executor, mappedStatement, statement, parameterObject);
        } else {
    	  //如果没有keyGenerator，直接调用Statement.execute和Statement.getUpdateCount
          statement.execute(sql);
          rows = statement.getUpdateCount();
        }
        return rows;
      }
     
      @Override
      public void batch(Statement statement) throws SQLException {
    	//批处理
        String sql = boundSql.getSql();
        statement.addBatch(sql);
      }
     
      //ResultHandler resultHandler这个参数好像没用啊
      @Override
      public <E> List<E> query(Statement statement, ResultHandler resultHandler) throws SQLException {
        String sql = boundSql.getSql();
    	//statement执行sql语句
        statement.execute(sql);
        return resultSetHandler.<E>handleResultSets(statement);
      }
     
      //实例化Statement
      @Override
      protected Statement instantiateStatement(Connection connection) throws SQLException {
        if (mappedStatement.getResultSetType() != null) {
          return connection.createStatement(mappedStatement.getResultSetType().getValue(), ResultSet.CONCUR_READ_ONLY);
        } else {
          return connection.createStatement();
        }
      }
     
      @Override
      public void parameterize(Statement statement) throws SQLException {
        // N/A
      }
     
    }

本文原文地址：[https://blog.csdn.net/qq924862077/article/details/52653788][https_blog.csdn.net_qq924862077_article_details_52653788]

[https_blog.csdn.net_qq924862077_article_details_52653788]: https://blog.csdn.net/qq924862077/article/details/52653788