Duplicate entry 'javajavajav' for key 'username'

org.apache.ibatis.exceptions.PersistenceException:
### Error updating database.  Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'javajavajav' for key 'username'
### The error may involve cn.itcast.mybatis.mapper.NewUserMapper.updateByExampleSelective-Inline
### The error occurred while setting parameters
### SQL: UPDATE tb_user SET USER_NAME = ?, PASSWORD = ? WHERE (  NAME  like ? )
### Cause: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'javajavajav' for key 'username'
    at org.apache.ibatis.exceptions.ExceptionFactory.wrapException(ExceptionFactory.java:26)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:154)
    at org.apache.ibatis.binding.MapperMethod.execute(MapperMethod.java:54)
    at org.apache.ibatis.binding.MapperProxy.invoke(MapperProxy.java:52)
    at com.sun.proxy.$Proxy11.updateByExampleSelective(Unknown Source)
    at cn.itcast.mybatis.mapper.NewUserMapperTest.testUpdateByExampleSelective(NewUserMapperTest.java:184)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    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.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.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:678)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLIntegrityConstraintViolationException: Duplicate entry 'javajavajav' for key 'username'
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:57)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:526)
    at com.mysql.jdbc.Util.handleNewInstance(Util.java:408)
    at com.mysql.jdbc.Util.getInstance(Util.java:383)
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:1049)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4208)
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:4140)
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2597)
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2758)
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2826)
    at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:2082)
    at com.mysql.jdbc.PreparedStatement.execute(PreparedStatement.java:1302)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.ibatis.logging.jdbc.PreparedStatementLogger.invoke(PreparedStatementLogger.java:62)
    at com.sun.proxy.$Proxy16.execute(Unknown Source)
    at org.apache.ibatis.executor.statement.PreparedStatementHandler.update(PreparedStatementHandler.java:44)
    at org.apache.ibatis.executor.statement.RoutingStatementHandler.update(RoutingStatementHandler.java:69)
    at org.apache.ibatis.executor.SimpleExecutor.doUpdate(SimpleExecutor.java:48)
    at org.apache.ibatis.executor.BaseExecutor.update(BaseExecutor.java:105)
    at org.apache.ibatis.executor.CachingExecutor.update(CachingExecutor.java:71)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.ibatis.plugin.Invocation.proceed(Invocation.java:49)
    at com.github.abel533.mapperhelper.MapperInterceptor.intercept(MapperInterceptor.java:61)
    at org.apache.ibatis.plugin.Plugin.invoke(Plugin.java:60)
    at com.sun.proxy.$Proxy10.update(Unknown Source)
    at org.apache.ibatis.session.defaults.DefaultSqlSession.update(DefaultSqlSession.java:152)
    ... 28 more

唯一键  UserName     不可重复