java - Spring实战第2章把XML bean改成JavaConfig过不了关

Question

下面是我的 Bean 配置代码，但是配置没有通过测试，因为它说加载 ApplicationContext 失败。我做错了什么吗？我在每个需要的类的方法中添加了@Autowire(接口(interface)方法除外)，但我仍然不知道为什么它没有加载

package soundsystems;

import java.util.ArrayList;
import java.util.List;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class CDPlayerConfig 
{
    @Bean
    public CompactDisc sgtPeppers()
    {
        return new SgtPeppers();
    }

    @Bean(name = "SgtPepperPlayer")
    public CDPlayer cdPlayer()
    {
        return new CDPlayer(sgtPeppers());
    }

    @Bean(name = "AnyCDPlayer")
    public CDPlayer cdPlayer(CompactDisc cd)
    {
        return new CDPlayer(cd);
    }

    @Bean
    public BlankDisc reallyBlankDisc()
    {
        return new BlankDisc();
    }

    @Bean
    public BlankDisc blankDisc()
    {
        BlankDisc bd = new BlankDisc();

        String title = "Sgt. Pepper's Lonely Hearts Club Band";
        String artist = "The Beatles";

        List<String> tracks = new ArrayList<String>();
        tracks.add("Sgt. Pepper's Lonely Hearts Club Band");
        tracks.add("With a Little Help from My Friends");
        tracks.add("Lucy in the Sky with Diamonds");
        tracks.add("Getting Better");
        tracks.add("Fixing a Hole");

        bd.setTitle(title);
        bd.setArtist(artist);
        bd.setTracks(tracks);

        return bd;
    }

    @Bean
    public Discography beatlesDiscography()
    {
        Discography dg = new Discography();

        String artist = "The Beatles";
        CompactDisc SgtPeppers = new SgtPeppers();
        CompactDisc WhiteAlbum = new WhiteAlbum();
        CompactDisc HardDaysNight = new HardDaysNight();
        CompactDisc Revolver = new Revolver();

        List<CompactDisc> cds = new ArrayList<CompactDisc>();
        cds.add(SgtPeppers);
        cds.add(WhiteAlbum);
        cds.add(HardDaysNight);
        cds.add(Revolver);

        dg.setArtist(artist);
        dg.setCDs(cds);     

        return dg;
    }

}



package soundsystems;

import static org.junit.Assert.*;

import org.junit.Rule;
import org.junit.Test;
import org.junit.contrib.java.lang.system.SystemOutRule;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = CDPlayerConfig.class)
public class CDPlayerTest 
{
    @Rule
    public final SystemOutRule log = new SystemOutRule().enableLog();

    @Autowired
    private CompactDisc cd;

    @Autowired
    private MediaPlayer player;

    @Test
    public void cdShouldNotBeNull()
    {
        assertNotNull(cd);
    }

    @Test
    public void play()
    {
        player.play();
        assertEquals("Playing Sgt. Pepper's Lonely Hearts Club Band" + " by The Beatles\n", log.getLog());
    }
}

感谢您的关注。

编辑:错误

    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:228)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:230)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:289)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:291)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:249)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    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:193)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'AnyCDPlayer': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire method: public void soundsystems.CDPlayer.setCompactDisc(soundsystems.CompactDisc); nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [soundsystems.CompactDisc] is defined: expected single matching bean but found 3: blankDisc,sgtPeppers,reallyBlankDisc
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:334)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1214)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:543)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:482)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:772)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:839)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:538)
    at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:125)
    at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:60)
    at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.delegateLoading(AbstractDelegatingSmartContextLoader.java:109)
    at org.springframework.test.context.support.AbstractDelegatingSmartContextLoader.loadContext(AbstractDelegatingSmartContextLoader.java:261)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContextInternal(DefaultCacheAwareContextLoaderDelegate.java:98)
    at org.springframework.test.context.cache.DefaultCacheAwareContextLoaderDelegate.loadContext(DefaultCacheAwareContextLoaderDelegate.java:116)
    ... 25 more
Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire method: public void soundsystems.CDPlayer.setCompactDisc(soundsystems.CompactDisc); nested exception is org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [soundsystems.CompactDisc] is defined: expected single matching bean but found 3: blankDisc,sgtPeppers,reallyBlankDisc
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredMethodElement.inject(AutowiredAnnotationBeanPostProcessor.java:661)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:331)
    ... 41 more
Caused by: org.springframework.beans.factory.NoUniqueBeanDefinitionException: No qualifying bean of type [soundsystems.CompactDisc] is defined: expected single matching bean but found 3: blankDisc,sgtPeppers,reallyBlankDisc
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1126)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1014)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredMethodElement.inject(AutowiredAnnotationBeanPostProcessor.java:618)
    ... 43 more

Answer 1

我相信 Spring 的 @Autowired 默认模式是按类型的。这意味着 Spring 将尝试按接口(interface)类型 Autowiring bean，顺便说一句，你有 3 个具有相同接口(interface)的 bean，而 Spring 对选择哪一个感到困惑。如果你想通过名称实现 Autowiring ，你应该使用 @Qualifier:@Qualifier("beanname")