Mybatis执行ReuseExecutor（五）

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);  }}