老师，求分析异常原因，我把@Bean修改为这样，还会抛出异常，代码如下
来源：4-8 Spring Bean装配之基于Java的容器注解说明——基于泛型的自动装配
gao634209276
2016-04-08 17:20
//测试类不动
@Test
public void testG(){
Store store = super.getBean("stringStore");
}
//StoreConfig类中的@Bean
@Autowired
private Store<String> s1;
@Autowired
private Store<Integer> s2;
@Bean
public StringStore stringStore(){
System.out.println("s1"+s1.getClass().getName());
System.out.println("s2"+s2.getClass().getName());
return new StringStore();
}
@Bean
public IntegerStore integerStore(){
return new IntegerStore();
}
//然后抛出的异常和老师讲解的异常一样，我这样改了，s1，s2都没指定到多个bean的实例对象啊
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9回答
-
- 慕虎3005618
- 2019-07-28 11:22:15
因为stringStore()方法执行的目的就是为了实例化s1，在方法体中使用s1，此时还没有实例化完成，所以要报空指针异常。
-
- 慕村8951117
- 2018-01-20 17:21:18
你这种需要添加 过滤@Autowiere("mingzi")就没问题了 至于老师的为什么不报错 可能是版本问题
-
- 慕后端2198842
- 2016-10-26 15:59:03
......你这么写，当执行到 System.out.println("s1"+s1.getClass().getName())这句的时候，
return new StringStore();这句还没执行到啊 也就是说 此时IOC容器中连StringStore这个bean都是不存在的，
s1自然也是个空的喽，那你要它怎么输出，自然是个空指针喽
-
- 慕函数0662299
- 2016-09-21 13:13:10
可以这样写 stringStoreTest：
@Bean(name="stringStoreTest")
public StoreConfig stringStoreTest(){
System.out.println("s1:"+s1.getClass().getName());
System.out.println("s2:"+s2.getClass().getName());
return new StoreConfig();
}
测试类为：
@Test
public void testG() {
super.getBean("stringStoreTest");
}
结果跟老师显示的一样！否则会报 s1，s2 变量空指针异常！
-
- qq_戒烟人_03473214
- 2016-07-01 15:24:40
我也是啊 怎么解决呢？
-
- 末日小星
- 2016-05-15 15:55:30
我也碰到这个问题了, 修改测试类的返回类型不能为Store或或其子类即可. 我用的是Spring4.2.6版本
-
- 小鸡啄米的嗨皮
- 2016-05-05 15:10:15
System.out.println("s1"+s1.getClass().getName());
System.out.println("s2"+s2.getClass().getName());
这两个地方是需要对象不能为空的，而调用的时候是注解自动注入的，此时还没有注入，所以会出错误，你可以先去掉这两处，就可以通过；另外你如果想看一下注入是否成功，可以将成员变量变为公共的，然后去访问
-
- 辉扬
- 2016-04-19 14:40:29
你的spring版本是3 还是4，3好像不支持泛型。。。
-
- gao634209276
- 2016-04-08 17:24:55
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'storeConfig': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.imooc.beanannotation.javabased.Store com.imooc.beanannotation.javabased.StoreConfig.s1; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'stringStore' defined in class path resource [com/imooc/beanannotation/javabased/StoreConfig.class]: Instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public com.imooc.beanannotation.javabased.StringStore com.imooc.beanannotation.javabased.StoreConfig.stringStore()] threw exception; nested exception is java.lang.NullPointerException at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:292) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1185) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:537) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:304) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:300) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:195) at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:703) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:760) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:482) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139) at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:93) at com.imooc.test.UnitTestBase.before(UnitTestBase.java:27) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:45) at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15) at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:42) at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:27) at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:30) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:263) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:68) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:47) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:231) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:60) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:229) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:50) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:222) at org.junit.runners.ParentRunner.run(ParentRunner.java:300) at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86) at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382) at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192) Caused by: org.springframework.beans.factory.BeanCreationException: Could not autowire field: private com.imooc.beanannotation.javabased.Store com.imooc.beanannotation.javabased.StoreConfig.s1; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'stringStore' defined in class path resource [com/imooc/beanannotation/javabased/StoreConfig.class]: Instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public com.imooc.beanannotation.javabased.StringStore com.imooc.beanannotation.javabased.StoreConfig.stringStore()] threw exception; nested exception is java.lang.NullPointerException at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:508) at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:87) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:289) ... 37 more Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'stringStore' defined in class path resource [com/imooc/beanannotation/javabased/StoreConfig.class]: Instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public com.imooc.beanannotation.javabased.StringStore com.imooc.beanannotation.javabased.StoreConfig.stringStore()] threw exception; nested exception is java.lang.NullPointerException at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:597) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1094) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:989) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:504) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:475) at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:304) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:300) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:195) at org.springframework.beans.factory.support.DefaultListableBeanFactory.findAutowireCandidates(DefaultListableBeanFactory.java:1017) at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:960) at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:858) at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:480) ... 39 more Caused by: org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public com.imooc.beanannotation.javabased.StringStore com.imooc.beanannotation.javabased.StoreConfig.stringStore()] threw exception; nested exception is java.lang.NullPointerException at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:188) at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:586) ... 51 more Caused by: java.lang.NullPointerException at com.imooc.beanannotation.javabased.StoreConfig.stringStore(StoreConfig.java:52) at com.imooc.beanannotation.javabased.StoreConfig$$EnhancerBySpringCGLIB$$dac9b232.CGLIB$stringStore$0(<generated>) at com.imooc.beanannotation.javabased.StoreConfig$$EnhancerBySpringCGLIB$$dac9b232$$FastClassBySpringCGLIB$$198dfac8.invoke(<generated>) at org.springframework.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:228) at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:312) at com.imooc.beanannotation.javabased.StoreConfig$$EnhancerBySpringCGLIB$$dac9b232.stringStore(<generated>) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:606) at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:166) ... 52 more
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