java.lang.IollegalStateException:临时文件夹尚未创建

Question

我正在为我的用例创建一个新的@Rule，看起来像

public class ActiveDirectoryConfigurationRule extends ExternalResource {
  @Rule
  public TemporaryFolder temporaryFolder = new TemporaryFolder();
  public File addActiveDirectoryConfigurationToFile(ActiveDirectoryConfiguration configuration) throws IOException {
    File file = temporaryFolder.newFile();
    objectMapper.writeValue(file, configuration);
    return file;
  }
  private ObjectMapper registerJdk8ModuleAndGetObjectMapper() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.registerModule(new Jdk8Module());
    return objectMapper;
  }
}

在我的Test中，我将其用作

public class ActiveDirectoryConfigurationStoreTest {
      @Rule
      public ActiveDirectoryConfigurationRule configurationRule = new ActiveDirectoryConfigurationRule();
          @Test
          public void getWhenConfigurationExists() throws Exception {
            ActiveDirectoryConfiguration activeDirectoryConfiguration = //....;
            File configurationToFile = configurationRule.addActiveDirectoryConfigurationToFile(activeDirectoryConfiguration);
            ActiveDirectoryConfigurationStore configurationStore = new ActiveDirectoryConfigurationStore(configurationToFile);
            Optional<ActiveDirectoryConfiguration> mayBeConfiguration = configurationStore.getConfiguration();
            assertTrue(mayBeConfiguration.isPresent());
          }
        }

当我运行这个测试时，我得到错误作为

java.lang.IllegalStateException: the temporary folder has not yet been created
    at org.junit.rules.TemporaryFolder.getRoot(TemporaryFolder.java:145)
    at org.junit.rules.TemporaryFolder.newFile(TemporaryFolder.java:78)
    at com.conf.store.ActiveDirectoryConfigurationRule.addActiveDirectoryConfigurationToFile(ActiveDirectoryConfigurationRule.java:48)
    at com.conf.store.ActiveDirectoryConfigurationStoreTest.getWhenConfigurationExists(ActiveDirectoryConfigurationStoreTest.java:25)
    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.junit.rules.ExternalResource$1.evaluate(ExternalResource.java:48)
    at org.junit.rules.RunRules.evaluate(RunRules.java:20)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    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.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:119)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:42)
    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)

似乎在创建自己的@Rule时，我无法依赖任何现有的@Rule

这就是问题所在吗？我该如何解决？

Answer 1

是的，我认为JUnit中没有任何内置的东西可以让你像现在这样"嵌套"@Rule对象。

我认为最明显的选择是：

1. 在自定义@Rule中，在适当的时间调用子@Rule上的各种方法。（本质上，假设你是JUnit库，每个接口使用@Rule。）我还没有深入了解细节，看看它会有多复杂
2. 让@Rule扩展TemporaryFolder而不是ExternalResource，确保在要重写的任何方法中调用super()。这可以让你做"TemporaryFolder所做的一切，然后再做一些"，这可能不是完美的OO理论（因为它实际上不是TemporaryFolder的一种类型），但应该按照你想要的方式工作。我在设置一个特定的文件夹时使用了这种方法，该文件夹需要为我的测试设置一个特殊的环境，而且效果相当好
3. 让您的自定义@Rule将TemporaryFolder引用作为构造函数参数，然后将其保存在字段中，并根据需要使用。这要求@Rule的所有用户都包含两个@Rule对象，但也许可以清楚地表明，测试确实需要一个临时文件夹来完成它的工作，也需要特定的自定义设置

Answer 2

不支持在规则中声明@Rule的规则。但是您可以手动运行其他规则。

public class ActiveDirectoryConfigurationRule implements TestRule {
  private TemporaryFolder temporaryFolder = new TemporaryFolder();
  @Override
  public Statement apply(Statement base, Description description) {
    Statement testWrappedWithYourCode = new Statement() {
      public void evaluate() {
        before();
        List<Throwable> errors = new ArrayList<Throwable>();
        try {
          base.evaluate();
        } catch (Throwable t) {
          errors.add(t);
        } finally {
          try {
            after();
          } catch (Throwable t) {
            errors.add(t);
          }
        }
        MultipleFailureException.assertEmpty(errors);
      }
    }
    return temporaryFolder.apply(testWrappedWithYourCode, description);
  }
  public File addActiveDirectoryConfigurationToFile(ActiveDirectoryConfiguration configuration) throws IOException {
    File file = temporaryFolder.newFile();
    objectMapper.writeValue(file, configuration);
    return file;
  }
  private ObjectMapper registerJdk8ModuleAndGetObjectMapper() {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.registerModule(new Jdk8Module());
    return objectMapper;
  }
}