一、异常
org.apache.ibatis.binding.BindingException: Type interface com.tjcu.dao.UserDao is not known to the MapperRegistry. at org.apache.ibatis.binding.MapperRegistry.getMapper(MapperRegistry.java:36) at org.apache.ibatis.session.Configuration.getMapper(Configuration.java:536) at org.apache.ibatis.session.defaults.DefaultSqlSession.getMapper(DefaultSqlSession.java:215) at com.tjcu.util.MybatisUtil.getMapper(MybatisUtil.java:57) at com.tjcu.test.UserTest.testSelectAll(UserTest.java:22) 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.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$2.evaluate(ParentRunner.java:222) at org.junit.runners.ParentRunner.run(ParentRunner.java:300) at org.junit.runner.JUnitCore.run(JUnitCore.java:157) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:221) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
二、解决方案分为两种情况:
1.在mybatis核心配置文件中(mybatis-config.xml)配置mappers
<!-- 每个mappers.xml文件都需要在mybatis-config.xml核心配置文件中注册--> <mappers> <mapper resource="com/tjcu/dao/UserDaoImpl.xml"></mapper> </mappers>
2.就是namespace编写出错(就是namespace的位置与实际文件位置不同)
注意报错中提示的:is not known to the MapperRegistry.这个表示没有这个映射地址,也就是说虽然配置文件中配置了,又能是SQL配置文件Mapper.xml中配置错误了,也有可能namespace中编写时出了错误,看下面一个实例:
namespace的设置与文件实际的位置不同
将上面的namespace修改为正确位置后问题就解决了,如果不是这里出错那么就可能是xml中的mappers节点配置错误啦。
完成后这个问题就解决了,如果以上步骤完成后运行时还报错那么说明,那么xml配置文件错误了,查找方向为优先SQL映射文件(Mapper结尾的文件),然后再看mybatis-config.xml的错误,不过虽然MyBatis框架一般都是xml配置文件的编写错误,还是需要注意自己的Java代码是否有写正确!