读mybatis源码之八：声明处理器StatementHandler
在执行器中，都会获取声明处理器：
public StatementHandler newStatementHandler(Executor executor, MappedStatement mappedStatement, Object parameterObject, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) {
StatementHandler statementHandler = new RoutingStatementHandler(executor, mappedStatement, parameterObject, rowBounds, resultHandler, boundSql);
statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
return statementHandler;
}
statementHandler = (StatementHandler) interceptorChain.pluginAll(statementHandler);
使用拦截器，声明处理可以定义插件
使用路由声明处理器，可以获取SimpleStatementHandler、PreparedStatementHandler、CallableStatementHandler三大处理器。
到底使用哪个处理器，是由ms.getStatementType参数决定，默认是
mappedStatement.statementType = StatementType.PREPARED; 到底使用哪个处理器，是由ms.getStatementType参数决定，默认是 mappedStatement.statementType = StatementType.PREPARED;
在mapper里面的执行语句 xml标签中可以配置statementType属性： 在mapper里面的执行语句 xml标签中可以配置statementType属性：
Any one of STATEMENT, PREPARED or CALLABLE.
This causes MyBatis to use Statement,
PreparedStatement or CallableStatement Any one of STATEMENT, PREPARED or CALLABLE. This causes MyBatis to use Statement, PreparedStatement or CallableStatement
respectively.
Default: PREPARED. respectively. Default: PREPARED.
BaseStatementHandler BaseStatementHandler
声明处理器基类，主要是产生 : 声明处理器基类，主要是产生 :
protected final TypeHandlerRegistry typeHandlerRegistry; //类型处理注册 protected final TypeHandlerRegistry typeHandlerRegistry; //类型处理注册
protected final ResultSetHandler resultSetHandler; //结果处理 protected final ResultSetHandler resultSetHandler; //结果处理
protected final ParameterHandler parameterHandler; //参数处理 protected final ParameterHandler parameterHandler; //参数处理
另外还准备Statement，具体由各个处理器生成instantiateStatement 另外还准备Statement，具体由各个处理器生成instantiateStatement