java - 使用 @TestPropertySource 属性中的属性会导致 NullPointerException

Question

我有以下测试:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest

@TestPropertySource(value = "classpath:testApplication.properties")
public class ESJavaAPITests {

    @Resource
    private Environment environment;

    private final String    CLUSTER_NAME    = environment.getProperty("ES.cluster.name");
}

属性位于 test/java/resources/testApplication.properties 中，看起来是这样的:

ES.host = localhost
ES.port = 9300
ES.cluster.name = 2m3d

然而，我不断收到 NullPointerException 第 25 行，这正是 CLUSTER_NAME 初始化的行:

java.lang.NullPointerException at com.example.estrans.ESJavaAPITests.(ESJavaAPITests.java:25) at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) at java.lang.reflect.Constructor.newInstance(Constructor.java:423) at org.junit.runners.BlockJUnit4ClassRunner.createTest(BlockJUnit4ClassRunner.java:217) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:227) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:287) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:289) at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:247) 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:117) at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:234) at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:74) 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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)

为什么是 NPE？

Answer 1

你得到一个 NPE 是因为此时你的 CLUSTER_NAME 字段被初始化环境是 null 因为 Spring 还没有时间 Autowiring 类 - CLUSTER_NAME 在创建测试类实例时被初始化。您应该使用 @Value("${ES.cluster.name}") 代替:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringBootTest
@TestPropertySource(value = "classpath:testApplication.properties")
public class ESJavaAPITests {

    @Value("${ES.cluster.name}")
    private String CLUSTER_NAME;
}