A query was run and no Result Maps were found for...原來是mapper.xml文件出了問題,是使用MyBatis最常見的一種錯誤

今天遇到一個問題，原來是mapper.xml文件出了問題,是使用MyBatis最常見的一種錯誤

 

報錯的結果是這樣的：

 A query was run and no Result Maps were found for the Mapped Statement 'cn.zrgk.dao.RoleMapper.getRoleList'.  

　　It's likely that neither a Result Type nor a Result Map was specified.
	

org.apache.ibatis.executor.ExecutorException: A query was run and no Result Maps were found for the Mapped Statement 'cn.zrgk.dao.RoleMapper.getRoleList'. 
　　 It's likely that neither a Result Type nor a Result Map was specified.
    org.apache.ibatis.executor.resultset.FastResultSetHandler.validateResultMapsCount(FastResultSetHandler.java:177)
    org.apache.ibatis.executor.resultset.FastResultSetHandler.handleResultSets(FastResultSetHandler.java:150)
    org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:57)
    org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:70)
    org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:57)
    org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:259)
    org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:132)
    org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:105)
    org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:81)
    sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    java.lang.reflect.Method.invoke(Method.java:606)

我的mapper.xml文件中有個查詢語句是這樣寫的：

 　　大家看看圖一，好像根本沒有錯誤，對嗎？再看看

 

　　是的，沒錯，我沒有指定這個方法的返回類型，系統無法識別，於是就這樣改了一下，發現不報錯了

 

 

所以平時啊，我們要多多注意這些細節，更要去多加理解