MyBatisPlus使用SpringBootTest测试出现java.lang.NullPoint Cannot invoke***because “this.userMapper“ is null

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问题描述：

使用 MyBatis-Plus 用 SpringBootTest 进行注入 mapper 进行测试出现如下问题：java.lang.NullPointerException: Cannot invoke "com.liam.mapper.UserMapper.selectList(com.baomidou.mybatisplus.core.conditions.Wrapper)" because "this.userMapper" is null

java.lang.NullPointerException: Cannot invoke "com.liam.mapper.UserMapper.selectList(com.baomidou.mybatisplus.core.conditions.Wrapper)" because "this.userMapper" is null

	at com.liam.MapperTest.testUserMapper(MapperTest.java:29)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:568)
	at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:63)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
	at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
	at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
	at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
	at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)

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原因分析：

我的测试代码如下：

@SpringBootTest
public class MapperTest {
    
    

    @Resource
    private UserMapper userMapper;

    @Test
    public void testUserMapper(){
    
    
        //查询所有用户
        List<User> users = userMapper.selectList(null);
        System.out.println(users);
    }

}

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解决方案：

添加注解 @RunWith(SpringRunner.class)

@SpringBootTest
@RunWith(SpringRunner.class)
public class MapperTest {
    
    

    @Resource
    private UserMapper userMapper;

    @Test
    public void testUserMapper(){
    
    
        //查询所有用户
        List<User> users = userMapper.selectList(null);
        System.out.println(users);
    }

}