首页 / JAVA / java-在Spring 3.1中实例化bean时出错

java-在Spring 3.1中实例化bean时出错

内容导读

互联网集市收集整理的这篇技术教程文章主要介绍了java-在Spring 3.1中实例化bean时出错，小编现在分享给大家，供广大互联网技能从业者学习和参考。文章包含5262字，纯文字阅读大概需要8分钟。

内容图文

我有以下课程：

public abstract class AbstractBusinessModule {

}

public class MS3BusinessModule extends AbstractBusinessModule 
{
    public MS3BusinessModule(SomeOtherClass value)
    {

    }
}

以及以下bean声明：

<bean id="ms3BusinessModule" class="com.hba.MS3BusinessModule" >
    <constructor-arg index="0">
        <ref bean="someOtherBeanID"/>
    </constructor-arg>
    <aop:scoped-proxy />
</bean>

启动我的应用程序时,出现以下错误：

Exception in thread "main" org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'ms3BusinessModule' defined in BeanDefinition defined in class path resource [spring.xml]: Initialization of bean failed; nested exception is org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class com.hba.MS3BusinessModule]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:527)
    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:567)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:139)
    at org.springframework.context.support.ClassPathXmlApplicationContext.<init>(ClassPathXmlApplicationContext.java:83)
    at com.hba.EhCacheTest.main(EhCacheTest.java:16)
Caused by: org.springframework.aop.framework.AopConfigException: Could not generate CGLIB subclass of class [class com.hba.MS3BusinessModule]: Common causes of this problem include using a final class or a non-visible class; nested exception is java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
    at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:212)
    at org.springframework.aop.framework.ProxyFactory.getProxy(ProxyFactory.java:112)
    at org.springframework.aop.scope.ScopedProxyFactoryBean.setBeanFactory(ScopedProxyFactoryBean.java:109)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeAwareMethods(AbstractAutowireCapableBeanFactory.java:1439)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1408)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    ... 11 more
Caused by: java.lang.IllegalArgumentException: Superclass has no null constructors but no arguments were given
    at net.sf.cglib.proxy.Enhancer.emitConstructors(Enhancer.java:721)
    at net.sf.cglib.proxy.Enhancer.generateClass(Enhancer.java:499)
    at net.sf.cglib.transform.TransformingClassGenerator.generateClass(TransformingClassGenerator.java:33)
    at net.sf.cglib.core.DefaultGeneratorStrategy.generate(DefaultGeneratorStrategy.java:25)
    at net.sf.cglib.core.AbstractClassGenerator.create(AbstractClassGenerator.java:216)
    at net.sf.cglib.proxy.Enhancer.createHelper(Enhancer.java:377)
    at net.sf.cglib.proxy.Enhancer.create(Enhancer.java:285)
    at org.springframework.aop.framework.Cglib2AopProxy.getProxy(Cglib2AopProxy.java:200)
    ... 16 more

可能出什么问题了？

如果我删除了< aop：scoped-proxy />从bean的声明,它的工作原理.

更新：如果我将默认构造函数放在MS3BusinessModule中,它将起作用.我不明白为什么需要默认构造函数的原因.有人可以解释一下.

解决方法:

If I put a default constructor in MS3BusinessModule, it works. I do not understand the reason why a default constructor is required. can somebody explain please.

< aop：scoped-proxy />其工作是用另一个名称隐藏“真实” bean,并创建一个CGLIB代理类,该代理类是真实bean类的子类,并将所有方法调用委托给目标bean的正确实例.因此,这里有两种不同的对象：

>每个会话/请求/范围的n个com.hba.MS3BusinessModule实例,以及
>动态生成的代理类的一个单例实例.

n个目标bean是使用带有参数的构造函数以及您的< constructor-arg>构造的.传递给它的值,但是代理类需要一个无参数的超类构造函数来调用(当然可以将其声明为protected而不是public).代理机制永远不会在代理实例上实际调用任何超类方法,因为所有调用都将转到目标实例,但是代理类需要扩展目标Bean类,以使代理成为对象的实例.正确的类型.

一种替代解决方案是提供M3BusinessModule实现的接口,并使其他bean对此接口的所有引用都使用接口类型而不是具体的类类型.这将允许Spring使用java.lang.reflect代理而不是CGLIB代理,从而无需扩展具体类即可实现接口.

内容总结

以上是互联网集市为您收集整理的java-在Spring 3.1中实例化bean时出错全部内容，希望文章能够帮你解决java-在Spring 3.1中实例化bean时出错所遇到的程序开发问题。 如果觉得互联网集市技术教程内容还不错，欢迎将互联网集市网站推荐给程序员好友。

内容备注

版权声明：本文内容由互联网用户自发贡献，该文观点与技术仅代表作者本人。本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌侵权/违法违规的内容， 请发送邮件至 gblab@vip.qq.com 举报，一经查实，本站将立刻删除。

内容手机端

扫描二维码推送至手机访问。

本文链接：https://qyyshop.com/info/676154.html

来源：【匿名】