Spring（创建bean错误，没有可见的构造函数）

Question

我有4个带有私有构造函数的单例类，我试图为所有4个类创建bean属性。

请在下面找到getInstance方法、私有构造函数和bean id声明。这在所有四个bean声明中都是相同的

但是如果我将构造函数从“private”更改为“public”，那么我就不会得到错误。有人能解释一下正在发生的事情吗？因为其他三个类都有私有构造函数，而且它们工作得非常好

getInstance（）方法

public static ApplicationConfiguration getInstance() throws IOException,
            IllegalArgumentException, InconsistentDataException {
        ApplicationConfiguration result = instance.get();
        if (result == null) {
            try {
                // Check again if already created
                result = instance.get();
                if (result == null) {
                    result = new ApplicationConfiguration();

                }
            } finally {
                // something here
            }
        } 
        return result;
    }

private ApplicationConfiguration() throws Exception {
        // call a method here
    }

<bean id="configManager" class="com.manager.ApplicationConfiguration" factory-method="getInstance" />

<bean id="configEnricher" class="com.enricher.ApplicationConfiguration" factory-method="getInstance" />

<bean id="configBussiness" class="com.validationservice.ApplicationConfiguration" factory-method="getInstance" />

<bean id="configEviction" class="com.evictionservice.ApplicationConfiguration" factory-method="getInstance" />

[#|2012-08-07 11:53:21,130|ERROR|RMI TCP Connection(226)-172.18.36.14|org.springframework.
web.context.ContextLoader||slodev-rhngp5.mblox.com|core-1|Context initialization failed|#]
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'co
nfigEviction' defined in ServletContext resource [/WEB-INF/camel-context.xml]: Initializat
ion of bean failed; nested exception is org.springframework.aop.framework.AopConfigExcepti
on: Could not generate CGLIB subclass of class [class com.evictionservice.ApplicationConfiguration]: 
Common causes of this problem include using
a final class or a non-visible class; nested exception is java.lang.IllegalArgumentExcepti
on: No visible constructors in class com.evictionservice.ApplicationConfiguration
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.do
CreateBean(AbstractAutowireCapableBeanFactory.java:526)
        at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.cr
eateBean(AbstractAutowireCapableBeanFactory.java:455)
        at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(Abstr
actBeanFactory.java:293)
        at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingl
eton(DefaultSingletonBeanRegistry.java:222)
        at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(Abstrac
tBeanFactory.java:290)
        at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractB
eanFactory.java:192)
        at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstant
iateSingletons(DefaultListableBeanFactory.java:585)
        at org.springframework.context.support.AbstractApplicationContext.finishBeanFactor
yInitialization(AbstractApplicationContext.java:895)
        at org.springframework.context.support.AbstractApplicationContext.refresh(Abstract
ApplicationContext.java:425)
:

Answer 1

问题不在于bean创建本身（正如您已经注意到的，这与其他bean没有什么不同）。这个问题似乎与您试图使用的某些AOP配置有关。如果您想为该类创建代理，它不能用CGLIB来完成，因为该类不能被子类化（因为它有一个私有构造函数）。

解决这个问题的唯一方法（给定当前的设计）是创建一个将由ApplicationConfiguration类实现的接口，然后为该接口创建代理，而不是代理该类。