低迷現狀，彈簧廠豆

//兩個第三方工廠：低迷現狀，彈簧廠豆

public class OneStaticMethodFactory { 
... 
public static Object createFactory(String oneInstanceMethodFactoryClassName) { 
    ... 
} 
} 

public class OneInstanceMethodFactory { 
... 
public OneObject createObject() { 
    ... 
} 
}

//硬連線代碼：

OneInstanceMethodFactory oneInstanceMethodFactory = 
(OneInstanceMethodFactory) 
    OneStaticMethodFactory.createFactory("pkg.to.OneInstanceMethodFactory"); 

OneObject oneObject = 
oneInstanceMethodFactory.createObject();

//嘗試由Spring bean來替換它們：

<bean id="oneInstanceMethodFactory" class="pkg.to.OneStaticMethodFactory" 
factory-method="createFactory"> 
    <constructor-arg value="pkg.to.OneInstanceMethodFactory"> 
    </constructor-arg> 
</bean> 

<bean id="oneObject" factory-bean="oneInstanceMethodFactory" 
factory-method="createObject"> 
</bean>

// Run Spring IoC：

java.lang.IllegalStateException: Failed to load ApplicationContext 
    ... 
Caused by: org.springframework.beans.factory.BeanCreationException: 
Error creating bean with name 'oneObject' defined in class path resource [applicationContext.xml]: 
No matching factory method found: factory bean 'oneInstanceMethodFactory'; 
factory method 'createObject()'. 
Check that a method with the specified name and arguments exists and that it is non-static. 
     at org.springframework.beans.factory.support.ConstructorResolver.instantiateUsingFactoryMethod(ConstructorResolver.java:528) 
     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateUsingFactoryMethod(AbstractAutowireCapableBeanFactory.java:1015) 
     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:911) 
     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:294) 
     at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225) 
     at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291) 
     at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193) 
     at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:605) 
     at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:925) 
     at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:472) 
     at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:103) 
     at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:1) 
     at org.springframework.test.context.support.DelegatingSmartContextLoader.loadContext(DelegatingSmartContextLoader.java:228) 
     at org.springframework.test.context.TestContext.loadApplicationContext(TestContext.java:124) 
     at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:148) 
     ... 26 more

要解決上面的問題，如何downcast oneInstanceMethodFactory bean從編譯時類型Object到運行時類型Spring中的OneInstanceMethodFactory？（這兩個第三方工廠類的修改不會對問題的地步。）

@EDIT

感謝來自@Boris Treukhov的提示，我終於想通了，這個問題已經無關type downcast，但確實OneStaticMethodFactory#createFactory由於我自己的拼寫錯誤而返回了除OneInstanceMethodFactory之外的其他運行時類型。現在，從硬連線代碼遷移到上面的Spring IoC/DI後，所有內容都按預期工作。

來源

2012-11-23 sof

您確定createFactory返回OneInstanceMethodFactory實例嗎？ –

是的，當我手動連線他們在Java代碼。 – sof

他們沒有實現任何Spring接口？ –

你應該檢查'oneInstanceMethodFactory'，確實是一個OneInstanceMethodFactory情況下，無論是通過檢查什麼豆型與名稱"oneInstanceMethodFactory"通過容器的getBean()方法或通過檢查createFactory在調試器返回的值創建。

以我的經驗來看，這個異常非常簡單，通常沒有這樣的公共非靜態方法。

向下轉換沒有區別，因爲通過反射方法調用方法，該方法將Object實例作爲this參數。 bean的類型由工廠方法返回的值決定，Spring在bean初始化之前不需要知道該類。實際上，oneObject bean取決於oneInstanceMethodFactory，因此後一個bean將在前者完全初始化，並且Spring將能夠調用它的createObject方法。

來源

2012-11-23 22:49:27

低迷現狀，彈簧廠豆

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