resultMap 和association collection的一些问题 ReflectionException: Could not set property ‘users‘

错误

org.apache.ibatis.exceptions.PersistenceException: 
### Error querying database.  Cause: org.apache.ibatis.reflection.ReflectionException: Could not set property 'users' of 'class com.itheima.domain.Role' with value 'User{id=41, username='老王', address='北京', sex='男', birthday=Tue Feb 27 17:47:08 CST 2018, roles=null}' Cause: java.lang.IllegalArgumentException: argument type mismatch
### The error may exist in com/itheima/dao/IRoleDao.xml
### The error may involve com.itheima.dao.IRoleDao.findAll
### The error occurred while handling results
### SQL: select u.*,r.* from role r left outer join user_role ur on r.id=ur.rid left outer join user u on ur.uid=u.id
### Cause: org.apache.ibatis.reflection.ReflectionException: Could not set property 'users' of 'class com.itheima.domain.Role' with value 'User{id=41, username='老王', address='北京', sex='男', birthday=Tue Feb 27 17:47:08 CST 2018, roles=null}' Cause: java.lang.IllegalArgumentException: argument type mismatch

	at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:30)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:150)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:141)
	at org.apache.ibatis.binding.MapperMethod.executeForMany(MapperMethod.java:137)
	at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:75)
	at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:59)
	at com.sun.proxy.$Proxy5.findAll(Unknown Source)
	at com.itheima.test.RoleTest.testFindAll(RoleTest.java:53)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:28)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:30)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:300)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:157)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:230)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:58)
Caused by: org.apache.ibatis.reflection.ReflectionException: Could not set property 'users' of 'class com.itheima.domain.Role' with value 'User{id=41, username='老王', address='北京', sex='男', birthday=Tue Feb 27 17:47:08 CST 2018, roles=null}' Cause: java.lang.IllegalArgumentException: argument type mismatch
	at org.apache.ibatis.reflection.wrapper.BeanWrapper.setBeanProperty(BeanWrapper.java:185)
	at org.apache.ibatis.reflection.wrapper.BeanWrapper.set(BeanWrapper.java:59)
	at org.apache.ibatis.reflection.MetaObject.setValue(MetaObject.java:140)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.linkObjects(DefaultResultSetHandler.java:1119)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.applyNestedResultMappings(DefaultResultSetHandler.java:961)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.getRowValue(DefaultResultSetHandler.java:914)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValuesForNestedResultMap(DefaultResultSetHandler.java:877)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleRowValues(DefaultResultSetHandler.java:324)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSet(DefaultResultSetHandler.java:299)
	at org.apache.ibatis.executor.resultset.DefaultResultSetHandler.handleResultSets(DefaultResultSetHandler.java:192)
	at org.apache.ibatis.executor.statement.PreparedStatementHandler.query(PreparedStatementHandler.java:64)
	at org.apache.ibatis.executor.statement.RoutingStatementHandler.query(RoutingStatementHandler.java:79)
	at org.apache.ibatis.executor.SimpleExecutor.doQuery(SimpleExecutor.java:63)
	at org.apache.ibatis.executor.BaseExecutor.queryFromDatabase(BaseExecutor.java:324)
	at org.apache.ibatis.executor.BaseExecutor.query(BaseExecutor.java:156)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:109)
	at org.apache.ibatis.executor.CachingExecutor.query(CachingExecutor.java:83)
	at org.apache.ibatis.session.defaults.DefaultSqlSession.selectList(DefaultSqlSession.java:148)
	... 30 more
Caused by: java.lang.IllegalArgumentException: argument type mismatch
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.ibatis.reflection.invoker.MethodInvoker.invoke(MethodInvoker.java:41)
	at org.apache.ibatis.reflection.wrapper.BeanWrapper.setBeanProperty(BeanWrapper.java:180)
	... 47 more


Process finished with exit code -1

原因

association 适用于 多对一和一对一的情况 ，实体类对应的字段应该是User 而不是原来的List users

 <resultMap id="roleMap2" type="role">
        <id property="roleId" column="rid"></id>
        <result property="roleName" column="rname"></result>
        <result property="roleDesc" column="rdesc"></result>
        <association property="users" javaType="User"  >
            <result property="username" column="username" />
            <result property="id" column="id" />
            <result property="address" column="address" />
            <result property="birthday" column="birthday" />
            <result property="sex"  column="sex" />
        </association>
    </resultMap>

解决

添加一个字段

private User user;
get 
set

 <association property="users" javaType="User"  >
 修改为
  <association property="user" javaType="User"  >

灵感来自

https://blog.csdn.net/soonfly/article/details/63688288

心得

resultMap中的association 标签应该是适用于一对一，而不适用于一对多

 Could not set property 'users' of 'class com.itheima.domain.Role' with value 'User{id=41, username='老王', address='北京', sex='男', birthday=Tue Feb 27 17:47:08 CST 2018, roles=null}' Cause: java.lang.IllegalArgumentException: argument type mismatch

发现这个错误说得挺清楚了。返回的值User与List users 没对应上。

resultMap

resultMap2

roleMap2 以下sql均可
select u.*,r.* from role r left outer join user_role ur on r.id=ur.rid left outer join user u on ur.uid=u.id
select * from role r,user_role ur , user u where r.ID = ur.RID and ur.UID = u.id

<resultMap id="roleMap2" type="role">
        <id property="roleId" column="rid"></id>
        <result property="roleName" column="rname"></result>
        <result property="roleDesc" column="rdesc"></result>
        <association property="user" javaType="User"  >
            <result property="username" column="username" />
            <result property="id" column="id" />
            <result property="address" column="address" />
            <result property="birthday" column="birthday" />
            <result property="sex"  column="sex" />
        </association>
    </resultMap>

roleMap3

<select id="findAll" resultMap="roleMap3">
select r.id,r.ROLE_NAME,r.ROLE_DESC,ur.UID uid from role r, user_role ur where ur.RID = r.ID ;
</select>

写roleMap3 时需要配置findUserById

<select id="findUserById" parameterType="int" resultType="user">
        select * from user where id = #{id}
</select>

    <resultMap id="roleMap3" type="role">
    	<!--association的"id" 此处是与查询user对应上的-->
    	<!--result 里的column 没对应上则为null-->
        <id property="roleId" column="id"></id>
        <result property="roleName" column="ROLE_NAME"></result>
        <result property="roleDesc" column="ROLE_DESC"></result>
        <association property="user" column="uid" javaType="User" select="findUserById" ></association>
    </resultMap>

resultMap & collection

一对多，多对多的使用

<select id="findAll" resultMap="userMap">
        select
         u.*,r.id rid,r.ROLE_NAME rname,r.ROLE_DESC rdesc 
        from user u 
        left outer join user_role ur on u.id=ur.uid 
        left outer join role r on ur.rid=r.id
</select>
<resultMap id="userMap" type="user">
        <id property="id" column="id"></id>
        <result property="username" column="username"></result>
        <result property="address" column="address"></result>
        <result property="sex" column="sex"></result>
        <result property="birthday" column="birthday"></result>
        <!--如果property是集合，那么要用ofType,而不是javaType-->
        <collection property="roles" ofType="role">
            <id property="roleId" column="rid"></id>
            <result property="roleName" column="rname"></result>
            <result property="roleDesc" column="rdesc"></result>
        </collection>
    </resultMap>