Question

我刚开始学习spring4。在尝试运行我的hello world程序时出现以下错误，

Aug 22, 2015 9:37:17 AM org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
INFO: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@2b650cea: startup date [Sat Aug 22 09:37:17 IST 2015]; root of context hierarchy
Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'helloWorldBean' defined in class com.websystique.spring.configuration.HelloWorldConfig: Instantiation of bean failed; nested exception is org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public com.websystique.spring.domain.HelloWorld com.websystique.spring.configuration.HelloWorldConfig.helloWorld()] threw exception; nested exception is java.lang.ClassCastException: com.websystique.spring.domain.HelloWorldImpl cannot be cast to com.websystique.spring.domain.HelloWorld
    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:302)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:228)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:298)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    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.annotation.AnnotationConfigApplicationContext.<init>(AnnotationConfigApplicationContext.java:84)
    at com.websystique.spring.AppMain.main(AppMain.java:12)
Caused by: org.springframework.beans.factory.BeanDefinitionStoreException: Factory method [public com.websystique.spring.domain.HelloWorld com.websystique.spring.configuration.HelloWorldConfig.helloWorld()] threw exception; nested exception is java.lang.ClassCastException: com.websystique.spring.domain.HelloWorldImpl cannot be cast to com.websystique.spring.domain.HelloWorld
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:188)
    at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:586)
    ... 13 more
Caused by: java.lang.ClassCastException: com.websystique.spring.domain.HelloWorldImpl cannot be cast to com.websystique.spring.domain.HelloWorld
    at com.websystique.spring.configuration.HelloWorldConfig.helloWorld(HelloWorldConfig.java:16)
    at com.websystique.spring.configuration.HelloWorldConfig$$EnhancerBySpringCGLIB$$3c68b28f.CGLIB$helloWorld$0(<generated>)
    at com.websystique.spring.configuration.HelloWorldConfig$$EnhancerBySpringCGLIB$$3c68b28f$$FastClassBySpringCGLIB$$50c0f2d6.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.websystique.spring.configuration.HelloWorldConfig$$EnhancerBySpringCGLIB$$3c68b28f.helloWorld(<generated>)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:166)
    ... 14 more

我的代码如下，

配置类

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

import com.websystique.spring.domain.HelloWorld;
import com.websystique.spring.domain.HelloWorldImpl;

@Configuration
public class HelloWorldConfig {

    @Bean(name="helloWorldBean")
    @Description("This is a sample HelloWorld Bean")
    public HelloWorld helloWorld() {
        return (HelloWorld) new HelloWorldImpl();
    }
}

接口

package com.websystique.spring.domain;

public interface HelloWorld {

    void sayHello(String name);

}

实施班级

package com.websystique.spring.domain;

public class HelloWorldImpl {

     public void sayHello(String name) {
            System.out.println("Hello "+name);
        }
}

主要类

public class AppMain {

    public static void main(String args[]) {
        AbstractApplicationContext context = new AnnotationConfigApplicationContext(HelloWorldConfig.class);
        HelloWorld bean = (HelloWorld) context.getBean("helloWorldBean");
        bean.sayHello("Spring 4");
        context.close();
    }

}

任何人都可以告诉我错误来自何处以及如何解决错误。

也可以任何人请建议我尽可能早地学习春天的好博客或文档。

Answer 1

nested exception is java.lang.ClassCastException: com.websystique.spring.domain.HelloWorldImpl cannot be cast to com.websystique.spring.domain.HelloWorld

return (HelloWorld) new HelloWorldImpl();

要实现这一目标，您的HelloWorldImpl应该实施HelloWorld，而不是您甚至不需要将其投放到HelloWorld

Spring Helloworld计划的问题

1 个答案: