java - 当整个 Maven 项目在 junit 测试下运行时，logger.info 抛出空指针异常

Question

这是示例代码

class Temp
{
    public static int someMethod()
    {
        Logger logger = LoggerFactory.getLogger(Temp.class);
        logger.info("Some information");//NullPointerException
        return 0;
    }
}

class ClassToTest
{
    public int methodToTest()
    {
        Temp tempInstance = new Temp();
        int i = temp.someMethod();
        return i;
    }
}

class TestAClass
{
    ClassToTest classToTestInstance;
    @Before
    public void setUp()
    {
        classToTestInstance = new ClassToTest();
    }
    @Test
    public void testMethodToTest()
    {
        int i = classToTest.methodToTest();
    }
}

这是一个场景。这个测试用例可能会通过。但是在实际代码中，当我运行单个测试用例或运行整个测试类时，测试用例通过但是当我在 junit 测试下运行 maven 项目时它失败并出现 NullPointerException。我无法发布实际代码，因为它是专有代码。如果有人遇到过此类问题，请指导我。

运行实际代码时得到的堆栈跟踪:

java.lang.NullPointerException
    at org.slf4j.impl.Log4jLoggerAdapter.info(Log4jLoggerAdapter.java:304)
    at Temp
    at ClassToTest
    at TestAClass
    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:483)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at mockit.integration.junit4.internal.JUnit4TestRunnerDecorator.executeTestMethod(JUnit4TestRunnerDecorator.java:142)
    at mockit.integration.junit4.internal.JUnit4TestRunnerDecorator.invokeExplosively(JUnit4TestRunnerDecorator.java:71)
    at mockit.integration.junit4.internal.MockFrameworkMethod.invokeExplosively(MockFrameworkMethod.java:40)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:70)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:50)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)

Answer 1

这个问题是因为 logger 在 Temp 类中是 static。如果 Temp 类的实例之前在另一个测试类中创建，则它无法加载临时类的 logger，因为它已经加载。因此，当我们在 junit 测试下运行整个项目时，它会失败。因为 Temp 类的 logger 位于已加载的其他测试类中。通过使用 JMockit mocking logger 解决了这个问题。 @SubOptimal 感谢您抽出时间。