Mybatis执行ReuseExecutor（五）

一时失言乱红尘 2022-03-06 05:14 161阅读 0赞

ReuseExecutor顾名思义就是重复使用执行，其定义了一个Map<String, Statement>，将执行的sql作为key，将执行的Statement作为value保存，这样执行相同的sql时就可以使用已经存在的Statement，就不需要新创建了，源码及分析如下：

/**
     * @author Clinton Begin
     */
    public class ReuseExecutor extends BaseExecutor {
     
      private final Map<String, Statement> statementMap = new HashMap<String, Statement>();
     
      public ReuseExecutor(Configuration configuration, Transaction transaction) {
        super(configuration, transaction);
      }
     
      @Override
      public int doUpdate(MappedStatement ms, Object parameter) throws SQLException {
    	//获得配置文件
        Configuration configuration = ms.getConfiguration();
    	//获得statementHandler 包括插件内容
        StatementHandler handler = configuration.newStatementHandler(this, ms, parameter, RowBounds.DEFAULT, null, null);
    	//转换为PrepareStatement
        Statement stmt = prepareStatement(handler, ms.getStatementLog());
        return handler.update(stmt);
      }
     
      @Override
      public <E> List<E> doQuery(MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
        Configuration configuration = ms.getConfiguration();
        StatementHandler handler = configuration.newStatementHandler(wrapper, ms, parameter, rowBounds, resultHandler, boundSql);
        Statement stmt = prepareStatement(handler, ms.getStatementLog());
        return handler.<E>query(stmt, resultHandler);
      }
     
      @Override
      public List<BatchResult> doFlushStatements(boolean isRollback) throws SQLException {
        for (Statement stmt : statementMap.values()) {
    	  //关闭Statement
          closeStatement(stmt);
        }
    	//清空sql
        statementMap.clear();
        return Collections.emptyList();
      }
     
      private Statement prepareStatement(StatementHandler handler, Log statementLog) throws SQLException {
        Statement stmt;
        BoundSql boundSql = handler.getBoundSql();
    	//获得sql语句
        String sql = boundSql.getSql();
    	//查看是否存在Statement
        if (hasStatementFor(sql)) {
    	  //如果存在就获取Statement
          stmt = getStatement(sql);
        } else {
          Connection connection = getConnection(statementLog);
    	  //否则通过连接创建一个Statement
          stmt = handler.prepare(connection);
    	  //将sql语句及对应的Statement 保存到map中
          putStatement(sql, stmt);
        }
        handler.parameterize(stmt);
        return stmt;
      }
     
      private boolean hasStatementFor(String sql) {
        try {
    	  //查看map中是否含有sql语句对应的Statement
          return statementMap.keySet().contains(sql) && !statementMap.get(sql).getConnection().isClosed();
        } catch (SQLException e) {
          return false;
        }
      }
     
      private Statement getStatement(String s) {
    	//获得Sql语句对应的Statement
        return statementMap.get(s);
      }
     
      private void putStatement(String sql, Statement stmt) {
    	//将sql语句及对应的Statement保存到map中
        statementMap.put(sql, stmt);
      }
     
    }

本文原文地址：[https://blog.csdn.net/qq924862077/article/details/52641902][https_blog.csdn.net_qq924862077_article_details_52641902]

[https_blog.csdn.net_qq924862077_article_details_52641902]: https://blog.csdn.net/qq924862077/article/details/52641902