When I use JUnit, occur this error. How to solve this error?

Question

When I use JUnit, I run into this error:

java.lang.NullPointerException at com.mpdidb.mapper.TbUserServiceTest.selectByPrimaryKeyTest(TbUserServiceTest.java:27) 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:50) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75) at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86) at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:252) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:94) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61) at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:191) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68) at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

And this is my JUnit code:

@WebAppConfiguration
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {RootConfig.class})
public class TbUserServiceTest
{
    @Autowired
    private static TbUserService tbUserService;

    @Test
    public void selectByPrimaryKeyTest()
    {
        String userId = "wusuodai";
        TbUser tbUser = tbUserService.selectByPrimaryKey(userId);
        System.out.println(tbUser.getUserName());
    }
}

How to solve this error?

Possible duplicate of [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — GhostCat, Aug 02 '17 at 08:09
Looks like your @Autowired isnt working in this setup and tbUserService is null. Honestly: if you do not know what a NPE is and how to deal with it, than spring and spring-mvc are *not* something you might deal with right now. Rather focus on reading a good book on java **basics**. — GhostCat, Aug 02 '17 at 08:10
thank you very much. When I run the web application, TbUserService can run normally. But when I junit test will encounter this error, why is this? — Streamer Lee, Aug 02 '17 at 08:19
I told you: that field is null; and the logical consequence is that the @Autowired isnt doing its job - most likely because the *framework* that normally "processes" these annotations isnt up. In that sense: do some research how to do unit testing in a spring context. Or do as I said: step back and learn the basics. Learn to crawl before going for **hurdle racing**. — GhostCat, Aug 02 '17 at 08:20
Hint: you probably want to read https://stackoverflow.com/questions/21878714/how-to-write-junit-test-with-spring-autowire ... https://stackoverflow.com/questions/26462926/autowired-with-junit-tests ... as said: you are **not** the first person trying to do this. — GhostCat, Aug 02 '17 at 09:22

score 0 · Answer 1 · answered Aug 02 '17 at 10:42

0

Static fields can not be autowired by field injection. Consider using setter injection.

private static TbUserService tbUserService;

@Autowired
public void setTbUserService(TbUserService tbUserService){
  this.tbUserService = tbUserService;
}

answered Aug 02 '17 at 10:42

rohanagarwal

771
9
30

When I use JUnit, occur this error. How to solve this error?

1 Answers1