Weird @Autowired Behavior of @Configuration Class, which causes NPE

Hi,

I am running into a weird behavior of autowiring a @Configuration class inside another @Configuration class when there is a BeanFactoryPostProcessor in my application.

If I run MyAppTests.java as it is, an NPE will happen on line BizClient client = bizClientConfig.bizClient() inside MyAppConfig.java.

However, if I commented out line Map<String, Object> map = beanFactory.getBeansWithAnnotation(Configuration.c lass) in ConfigurationBeanFactoryPostProcessor.java then the NPE goes away.

I don't understand why calling beanFactory.getBeansWithAnnotation() causes NPE. Is this a bug or I am missing something?

This problem happens in both Spring version 3.0.5 as well as 3.0.6.

The complete project is attached.

Any ideas?

Here is the code.

Code:

---

@Configuration
public class MyAppConfig {
       
        @Autowired
        private BizClientConfig bizClientConfig;
       
        @Bean
        public MyApp myApp() {
                BizClient client = bizClientConfig.bizClient();
               
                return new MyApp(client);
        }
}

---

Code:

---

@Configuration
public class BizClientConfig {
       
        @Bean
        public BizClient bizClient() {
                return new BizClientImpl("no name");
        }

}

---

Code:

---

public class ConfigurationBeanFactoryPostProcessor implements
                BeanFactoryPostProcessor {

        public void postProcessBeanFactory(
                        ConfigurableListableBeanFactory beanFactory) throws BeansException {

                Map<String, Object> map = beanFactory.getBeansWithAnnotation(Configuration.class);
        }
}

---

app-context.xml

Code:

---

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns:context="http://www.springframework.org/schema/context"
        xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
                http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">

        <description>Example configuration to get you started.</description>

        <bean class="org.my.test.ConfigurationBeanFactoryPostProcessor" />
       
        <context:component-scan base-package="org.my.test" />

</beans>

---

Test class:

Code:

---

@ContextConfiguration(locations="classpath:/META-INF/spring/app-context.xml")
@RunWith(SpringJUnit4ClassRunner.class)
public class MyAppTests {
       
        @Autowired
        private MyApp myapp;

        @Test
        public void testMyApp() throws Exception {
                System.out.println("Spring version: " + SpringVersion.getVersion());
                assertNotNull(myapp);
        }
       
}

---

stack trace:

Code:

---

java.lang.IllegalStateException: Failed to load ApplicationContext
        at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:308)
        at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:109)
        at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75)
        at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:321)
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:211)
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:287)
        at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:289)
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
        at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
        at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
        at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
        at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
        at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
        at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
        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:236)
        at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
        at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:49)
        at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:467)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
        at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:197)
Caused by: org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'myApp' defined in class path resource [org/my/test/MyAppConfig.class]: Instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public org.my.test.MyApp org.my.test.MyAppConfig.myApp()] threw exception; nested exception is java.lang.NullPointerException
        at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:581)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:983)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:879)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:485)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:293)
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:290)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:192)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:585)
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
        at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
        at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:84)
        at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:1)
        at org.springframework.test.context.TestContext.loadApplicationContext(TestContext.java:280)
        at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:304)
        ... 24 more
Caused by: org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public org.my.test.MyApp org.my.test.MyAppConfig.myApp()] threw exception; nested exception is java.lang.NullPointerException
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:157)
        at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:570)
        ... 39 more
Caused by: java.lang.NullPointerException
        at org.my.test.MyAppConfig.myApp(MyAppConfig.java:17)
        at org.my.test.MyAppConfig$$EnhancerByCGLIB$$66367b2c.CGLIB$myApp$0(<generated>)
        at org.my.test.MyAppConfig$$EnhancerByCGLIB$$66367b2c$$FastClassByCGLIB$$123ec952.invoke(<generated>)
        at net.sf.cglib.proxy.MethodProxy.invokeSuper(MethodProxy.java:215)
        at org.springframework.context.annotation.ConfigurationClassEnhancer$BeanMethodInterceptor.intercept(ConfigurationClassEnhancer.java:210)
        at org.my.test.MyAppConfig$$EnhancerByCGLIB$$66367b2c.myApp(<generated>)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
        at java.lang.reflect.Method.invoke(Method.java:597)
        at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:145)
        ... 40 more

---

This is kind of disappointing that I haven't gotten any reply from any Spring experts.

My company is evaluating the Java-configuration support in Spring 3 and with this problem, we are not able to move forward.

I spent a little more time looking into this but haven't have any luck yet. I tried changing the autowired on member variable to a setter method (see below) in MyAppConfig.java and I can definitely confirmed that the setter method was not called.

@Autowired
public void setBizClientConfig(BizClientConfig bizClientConfig) {
this.bizClientConfig = bizClientConfig;
}

This seems like a bug to me.

Can some Spring expert from VMWare confirm this? or Should I go ahead and create a jira ticket for this issue?

NEVER MIND. I figured out the problem!!!

It is my misunderstanding of method org.springframework.beans.factory.ListableBeanFact ory.getBeansWithAnnotation().

Basically the above method will return a map of bean names and their corresponding bean instances as values, which means that those beans will get instantiated before AutowiredAnnotationBeanPostProcessor.java gets a chance to perform its autowiring magic. That's why bizClientConfig is null when myApp method is called.