Spring实战——通过Java代码装配bean
基于注解的自动化注入固然优雅，但是它也有鞭长莫及的时候，这时候就来看看Java代码如何装配bean的。
还记的上篇的配置类CDPlayerConfig是长这样的
@Configuration
@ComponentScan
publicclassCDPlayerConfig{
}
有了这个万能的组件扫描注解，一切都是那么只能，只需要在bean类上加上如@Component注解，Spring就会自动为该类创建相应的bean类。
但是现在因为我们有一些第三方类库，我们没办法去深入类中加上这些标记了，所以@ComponentScan就失去了威力和意义。
这篇的CDPlayerConfig应该长这样
@Configuration
publicclassCDPlayerConfig{
}
@Configuration注解表示该类是一个配置类。显然要创建的bean的信息是要放到这个类中的。
基于其他类以及类中的方法不变比如CompactDisc,CDPlayer,SgtPeppers等。编写测试方法如下
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=CDPlayerConfig.class)
publicclassCDPlayerTest{
@Rule
publicfinalStandardOutputStreamLoglog=newStandardOutputStreamLog();
@Autowired
privateMediaPlayerplayer;
@Autowired
privateCompactDisccd;
@Test
publicvoidcdShouldNotBeNull(){
assertNotNull(cd);
}
@Test
publicvoidplay(){
player.play();
assertEquals(
"PlayingSgt.Pepper''sLonelyHeartsClubBandbyTheBeatles\r\n",
log.getLog());
}
}
首先从代码来看就会出现如下的注入错误
这里显示MediaPlayer无法注入。同时运行程序得到结果如下
Testingstartedat0:20...
0:20:03:Executingexternaltasks''cleanTesttest''...
:cleanTest
:compileJava
:processResourcesUP-TO-DATE
:classes
:compileTestJava
:processTestResourcesUP-TO-DATE
:testClasses
:test
一月15,201712:20:06上午org.springframework.test.context.TestContextManagerretrieveTestExecutionListeners
信息:CouldnotinstantiateTestExecutionListener[org.springframework.test.context.web.ServletTestExecutionListener].Specifycustomlistenerclassesormakethedefaultlistenerclasses(andtheirrequireddependencies)available.Offendingclass:[javax/servlet/ServletContext]
一月15,201712:20:06上午org.springframework.test.context.TestContextManagerretrieveTestExecutionListeners
信息:CouldnotinstantiateTestExecutionListener[org.springframework.test.context.transaction.TransactionalTestExecutionListener].Specifycustomlistenerclassesormakethedefaultlistenerclasses(andtheirrequireddependencies)available.Offendingclass:[org/springframework/transaction/interceptor/TransactionAttributeSource]
一月15,201712:20:06上午org.springframework.context.support.GenericApplicationContextprepareRefresh
信息:Refreshingorg.springframework.context.support.GenericApplicationContext@6adf0b01:startupdate[SunJan1500:20:06CST2017];rootofcontexthierarchy
一月15,201712:20:06上午org.springframework.test.context.TestContextManagerprepareTestInstance
严重:CaughtexceptionwhileallowingTestExecutionListener[org.springframework.test.context.support.DependencyInjectionTestExecutionListener@61c715e8]topreparetestinstance[soundsystem.CDPlayerTest@1081b08c]
org.springframework.beans.factory.BeanCreationException:Errorcreatingbeanwithname''soundsystem.CDPlayerTest'':Injectionofautowireddependenciesfailed;nestedexceptionisorg.springframework.beans.factory.BeanCreationException:Couldnotautowirefield:privatesoundsystem.MediaPlayersoundsystem.CDPlayerTest.player;nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException:Noqualifyingbeanoftype[soundsystem.MediaPlayer]foundfordependency:expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{@org.springframework.beans.factory.annotation.Autowired(required=true)}
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:293)
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1186)
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireBeanProperties(AbstractAutowireCapableBeanFactory.java:384)
atorg.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:110)
atorg.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75)
atorg.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:331)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:213)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:290)
atorg.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:292)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:233)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:87)
atorg.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
atorg.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
atorg.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
atorg.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
atorg.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
atorg.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
atorg.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
atorg.junit.runners.ParentRunner.run(ParentRunner.java:309)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:176)
atorg.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:105)
atorg.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:56)
atorg.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:64)
atorg.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:50)
atsun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethod)
atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
atjava.lang.reflect.Method.invoke(Method.java:497)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
atorg.gradle.messaging.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
atorg.gradle.messaging.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
atcom.sun.proxy.$Proxy2.processTestClass(UnknownSource)
atorg.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:106)
atsun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethod)
atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
atjava.lang.reflect.Method.invoke(Method.java:497)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
atorg.gradle.messaging.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:360)
atorg.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
atorg.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
atjava.lang.Thread.run(Thread.java:745)
Causedby:org.springframework.beans.factory.BeanCreationException:Couldnotautowirefield:privatesoundwww.tt951.comsystem.MediaPlayersoundsystem.CDPlayerTest.player;nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException:Noqualifyingbeanoftype[soundsystem.MediaPlayer]foundfordependency:expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{@org.springframework.beans.factory.annotation.Autowired(required=true)}
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:509)
atorg.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:290)
...46more
Causedby:org.springframework.beans.factory.NoSuchBeanDefinitionException:Noqualifyingbeanoftype[soundsystem.MediaPlayer]foundfordependency:expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{@org.springframework.beans.factory.annotation.Autowired(required=true)}
atorg.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1118)
atorg.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:967)
atorg.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:862)
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:481)
...48more
Errorcreatingbeanwithname''soundsystem.CDPlayerTest'':Injectionofautowireddependenciesfailed;nestedexceptionisorg.springframework.beans.factory.BeanCreationException:Couldnotautowirefield:privatesoundsystem.MediaPlayersoundsystem.CDPlayerTest.player;nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException:Noqualifyingbeanoftype[soundsystem.MediaPlayer]foundfordependency:expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{@org.springframework.beans.factory.annotation.Autowired(required=true)}
org.springframework.beans.factory.BeanCreationException:Errorcreatingbeanwithname''soundwww.baiyuewang.netsystem.CDPlayerTest'':Injectionofautowireddependenciesfailed;nestedexceptionisorg.springframework.beans.factory.BeanCreationException:Couldnotautowirefield:privatesoundsystem.MediaPlayersoundsystem.CDPlayerTest.player;nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException:Noqualifyingbeanoftype[soundsystem.MediaPlayer]foundfordependency:expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{@org.springframework.beans.factory.annotation.Autowired(required=true)}
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:293)
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1186)
atorg.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireBeanProperties(AbstractAutowireCapableBeanFactory.java:384)
atorg.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:110)
atorg.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75)
atorg.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:331)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:213)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:290)
atorg.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:292)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:233)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:87)
atorg.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
atorg.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
atorg.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
atorg.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
atorg.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
atorg.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
atorg.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
atorg.junit.runners.ParentRunner.run(ParentRunner.java:309)
atorg.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:176)
atorg.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.runTestClass(JUnitTestClassExecuter.java:105)
atorg.gradle.api.internal.tasks.testing.junit.JUnitTestClassExecuter.execute(JUnitTestClassExecuter.java:56)
atorg.gradle.api.internal.tasks.testing.junit.JUnitTestClassProcessor.processTestClass(JUnitTestClassProcessor.java:64)
atorg.gradle.api.internal.tasks.testing.SuiteTestClassProcessor.processTestClass(SuiteTestClassProcessor.java:50)
atsun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethod)
atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
atjava.lang.reflect.Method.invoke(Method.java:497)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
atorg.gradle.messaging.dispatch.ContextClassLoaderDispatch.dispatch(ContextClassLoaderDispatch.java:32)
atorg.gradle.messaging.dispatch.ProxyDispatchAdapter$DispatchingInvocationHandler.invoke(ProxyDispatchAdapter.java:93)
atcom.sun.proxy.$Proxy2.processTestClass(UnknownSource)
atorg.gradle.api.internal.tasks.testing.worker.TestWorker.processTestClass(TestWorker.java:106)
atsun.reflect.NativeMethodAccessorImpl.invoke0(NativeMethod)
atsun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
atsun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
atjava.lang.reflect.Method.invoke(Method.java:497)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:35)
atorg.gradle.messaging.dispatch.ReflectionDispatch.dispatch(ReflectionDispatch.java:24)
atorg.gradle.messaging.remote.internal.hub.MessageHub$Handler.run(MessageHub.java:360)
atorg.gradle.internal.concurrent.ExecutorPolicy$CatchAndRecordFailures.onExecute(ExecutorPolicy.java:54)
atorg.gradle.internal.concurrent.StoppableExecutorImpl$1.run(StoppableExecutorImpl.java:40)
atjava.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
atjava.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
atjava.lang.Thread.run(Thread.java:745)
Causedby:org.springframework.beans.factory.BeanCreationException:Couldnotautowirefield:privatesoundsystem.MediaPlayersoundsystem.CDPlayerTest.player;nestedexceptionisorg.springframework.beans.factory.NoSuchBeanDefinitionException:Noqualifyingbeanoftype[soundsystem.MediaPlayer]foundfordependency:expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{@org.springframework.beans.factory.annotation.Autowired(required=true)}
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:509)
atorg.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87)
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:290)
...46more
Causedby:org.springframework.beans.factory.NoSuchBeanDefinitionException:Noqualifyingbeanoftype[soundsystem.MediaPlayer]foundfordependency:expectedatleast1beanwhichqualifiesasautowirecandidateforthisdependency.Dependencyannotations:{@org.springframework.beans.factory.annotation.Autowired(required=true)}
atorg.springframework.beans.factory.support.DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(DefaultListableBeanFactory.java:1118)
atorg.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:967)
atorg.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:862)
atorg.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:481)
...48more
soundsystem.CDPlayerTest>playFAILED
org.springframework.beans.factory.BeanCreationException
Causedby:org.springframework.beans.factory.BeanCreationException
Causedby:org.springframework.beans.factory.NoSuchBeanDefinitionException
1testcompleted,1failed
:testFAILED
FAILURE:Buildfailedwithanexception.
Whatwentwrong:
Executionfailedfortask'':test''.
>Therewerefailingtests.Seethereportat:file:///C:/Users/Administrator/Desktop/spring_video/SpringiA4_SourceCode/Chapter_02/stereo-javaconfig/build/reports/tests/index.html
Try:
Runwith--stacktraceoptiontogetthestacktrace.Runwith--infoor--debugoptiontogetmorelogoutput.
BUILDFAILED
Totaltime:4.59secs
Therewerefailingtests.Seethereportat:file:///C:/Users/Administrator/Desktop/spring_video/SpringiA4_SourceCode/Chapter_02/stereo-javaconfig/build/reports/tests/index.html
究其原因，主要是既没有在xml中没有声明相应的bean，也没有添加@ComponentScan启动自动扫描组件机制。
所以这里还是需要在CDPlayerConfig配置类中做文章。
声明bean
通过注解@Bean声明一个bean对象。
@Bean
publicCompactDisccompactDisc(){
returnnewSgtPeppers();
}
该声明好比在xml中添加
1
通过这种方式，Spring会默认为SgtPeppers创建一个名为sgtPeppers的bean，如果你想换个名字，只需要在@Bean后面加上类似(name="lonelyHeartClubBand")这样的属性即可。
如果你的野心远不止满足于通过Java代码创建一个bean的话，其实你还试试如何在CDPlayer中播放CompactDisc，那就需要在CDPlayer中注入CompactDisc的bean了。于是我们可以这样声明
@Bean
publicCDPlayercdPlayer(CompactDisccompactDisc){
returnnewCDPlayer(compactDisc);
}
加上@Bean注解，表明cdPlayer()方法会创建一个bean实例并将其注册到Spring的应用上下文中，显然bean的名字默认就是cdPlayer。在执行这个方法的时候，Spring会拦截所有对方法的调用，当然这里会传入Spring注册好的CompactDisc的实例bean给cdPlayer方法来确保返回的是创建好的cdPlayer的bean。注意这里的bean是单例的，其实在xml中配置的bean如果没有特殊声明，默认也是单例的。也就是说即使这里创建了多个类似cdPlayer的方法，得到的仍然是同一个cdPlayer的bean。
这时候运行测试类CDPlayerTest
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes=CDPlayerConfig.class)
publicclassCDPlayerTest{
@Rule
publicfinalStandardOutputStreamLoglog=newStandardOutputStreamLog();
@Autowired
privateMediaPlayerplayer;
@Test
publicvoidplay(){
player.play();
assertEquals(
"PlayingSgt.Pepper''sLonelyHeartsClubBandbyTheBeatles\r\n",
log.getLog());
}
|
|
