Mybatis源码之Statement处理器BaseStatementHandler（二）

╰半橙微兮° 2022-03-02 08:40 190阅读 0赞

BaseStatementHandler是一个抽象类，并没有实现和CURD相关的类，只是更多的设置了一些参数相关。

源码如下：

/**
     * @author Clinton Begin
     */
    public abstract class BaseStatementHandler implements StatementHandler {
     
      protected final Configuration configuration;
      protected final ObjectFactory objectFactory;
      protected final TypeHandlerRegistry typeHandlerRegistry;
      protected final ResultSetHandler resultSetHandler;
      protected final ParameterHandler parameterHandler;
     
      protected final Executor executor;
      protected final MappedStatement mappedStatement;
      protected final RowBounds rowBounds;
     
      protected BoundSql boundSql;
     
      protected BaseStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
        this.configuration = mappedStatement.getConfiguration();
        this.executor = executor;
        this.mappedStatement = mappedStatement;
        this.rowBounds = rowBounds;
     
        this.typeHandlerRegistry = configuration.getTypeHandlerRegistry();
        this.objectFactory = configuration.getObjectFactory();
     
        if (boundSql == null) { // issue #435, get the key before calculating the statement
          generateKeys(parameterObject);
          boundSql = mappedStatement.getBoundSql(parameterObject);
        }
     
        this.boundSql = boundSql;
     
        this.parameterHandler = configuration.newParameterHandler(mappedStatement, parameterObject, boundSql);
        this.resultSetHandler = configuration.newResultSetHandler(executor, mappedStatement, rowBounds, parameterHandler, resultHandler, boundSql);
      }
      //获取BoundSql
      public BoundSql getBoundSql() {
        return boundSql;
      }
      //获取ParameterHandler
      public ParameterHandler getParameterHandler() {
        return parameterHandler;
      }
     
      //准备语句
      public Statement prepare(Connection connection) throws SQLException {
        ErrorContext.instance().sql(boundSql.getSql());
        Statement statement = null;
        try {
    	  //实例化Statement
          statement = instantiateStatement(connection);
    	  //设置超时
          setStatementTimeout(statement);
    	  //设置读取条数
          setFetchSize(statement);
          return statement;
        } catch (SQLException e) {
          closeStatement(statement);
          throw e;
        } catch (Exception e) {
          closeStatement(statement);
          throw new ExecutorException("Error preparing statement.  Cause: " + e, e);
        }
      }
      //如何实例化Statement，交给子类去做
      protected abstract Statement instantiateStatement(Connection connection) throws SQLException;
     
      //设置超时，实际就是调用Statement.setQueryTimeout
      protected void setStatementTimeout(Statement stmt) throws SQLException {
        Integer timeout = mappedStatement.getTimeout();
        Integer defaultTimeout = configuration.getDefaultStatementTimeout();
        if (timeout != null) {
          stmt.setQueryTimeout(timeout);
        } else if (defaultTimeout != null) {
          stmt.setQueryTimeout(defaultTimeout);
        }
      }
      //设置读取条数，其实就是调用Statement.setFetchSize
      protected void setFetchSize(Statement stmt) throws SQLException {
        Integer fetchSize = mappedStatement.getFetchSize();
        if (fetchSize != null) {
          stmt.setFetchSize(fetchSize);
        }
      }
      //关闭Statement
      protected void closeStatement(Statement statement) {
        try {
          if (statement != null) {
            statement.close();
          }
        } catch (SQLException e) {
          //ignore
        }
      }
       
      protected void generateKeys(Object parameter) {
        KeyGenerator keyGenerator = mappedStatement.getKeyGenerator();
        ErrorContext.instance().store();
        keyGenerator.processBefore(executor, mappedStatement, null, parameter);
        ErrorContext.instance().recall();
      }
     
    }

本文原文地址：[https://blog.csdn.net/qq924862077/article/details/52653683][https_blog.csdn.net_qq924862077_article_details_52653683]

[https_blog.csdn.net_qq924862077_article_details_52653683]: https://blog.csdn.net/qq924862077/article/details/52653683