亲爱的stackoverflow专家。
我们正在解决当前冲刺中的有趣问题，我们对春季工作流程的理解不允许我们找到解决方案。因此，我们要求您分享您对下一个问题的想法：
我们需要从现在无法修改的库中导入类。事实是，我们需要导入的类具有实现" ApplicationListener"的类的自动依赖性。我们不会在代码中使用此依赖关系（用于我们不会调用的方法）。
我们试图将所有未使用的依赖项设置为null。但是，当我们将此类设置为null时，我们会得到一个例外：
Caused by: java.lang.IllegalArgumentException: Delegate listener must not be null
显然，我们不想在应用程序中实例化应用程序列表类。
重现我们的情况，我们创建了一个简单的单元测试：
应用程序配置：
@Configuration
public class TestApplicationConfiguration {
@Bean
public ApplicationListener<ContextRefreshedEvent> applicationListener() {
return null;
}
}
测试类：
@ContextConfiguration(classes = TestApplicationConfiguration.class)
public class ConfigurationManagerTests extends AbstractTestNGSpringContextTests {
@Autowired
private ApplicationListener<ContextRefreshedEvent> applicationListener;
@Test
public void dummyTest() {
Assert.assertNull(applicationListener);
}
}
以下列出的例外的完整堆栈。
java.lang.IllegalStateException: Failed to load ApplicationContext
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:124)
at org.springframework.test.context.support.DefaultTestContext.getApplicationContext(DefaultTestContext.java:83)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:117)
at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:83)
at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:230)
at org.springframework.test.context.testng.AbstractTestNGSpringContextTests.springTestContextPrepareTestInstance(AbstractTestNGSpringContextTests.java:149)
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.testng.internal.MethodInvocationHelper.invokeMethod(MethodInvocationHelper.java:86)
at org.testng.internal.Invoker.invokeConfigurationMethod(Invoker.java:514)
at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:215)
at org.testng.internal.Invoker.invokeConfigurations(Invoker.java:142)
at org.testng.internal.TestMethodWorker.invokeBeforeClassMethods(TestMethodWorker.java:178)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:108)
at org.testng.TestRunner.privateRun(TestRunner.java:782)
at org.testng.TestRunner.run(TestRunner.java:632)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:366)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:361)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:319)
at org.testng.SuiteRunner.run(SuiteRunner.java:268)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1244)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1169)
at org.testng.TestNG.run(TestNG.java:1064)
at org.testng.IDEARemoteTestNG.run(IDEARemoteTestNG.java:72)
at org.testng.RemoteTestNGStarter.main(RemoteTestNGStarter.java:124)
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 com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)
Caused by: java.lang.IllegalArgumentException: Delegate listener must not be null
at org.springframework.util.Assert.notNull(Assert.java:115)
at org.springframework.context.event.GenericApplicationListenerAdapter.<init>(GenericApplicationListenerAdapter.java:48)
at org.springframework.context.event.AbstractApplicationEventMulticaster.supportsEvent(AbstractApplicationEventMulticaster.java:280)
at org.springframework.context.event.AbstractApplicationEventMulticaster.retrieveApplicationListeners(AbstractApplicationEventMulticaster.java:229)
at org.springframework.context.event.AbstractApplicationEventMulticaster.getApplicationListeners(AbstractApplicationEventMulticaster.java:185)
at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:127)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:382)
at org.springframework.context.support.AbstractApplicationContext.publishEvent(AbstractApplicationContext.java:336)
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:877)
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:544)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:128)
at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:60)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:108)
at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:251)
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:98)
at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:116)
... 33 more
谢谢。
看起来Spring本身不允许bean无效，所以为什么不创建一个无用的假人呢？
@Bean
public ApplicationListener<ContextRefreshedEvent> applicationListener() {
return new ApplicationListener<ContextRefreshedEvent>() {
@Override
public void onApplicationEvent(ContextRefreshedEvent event) {
// Do nothing
}
};
}