Spring MVC 的怪事一椿

今天遇到怪事一椿, 其實已經困擾我一陣子了, 只是今天才發現原因所在.

Spring MVC 的 @RequestMapping 註解可用來標示 Url, 例如:

@RequestMapping(value={"index"}, method=RequestMethod.POST)

public ModelAndView index(HttpSession session) {

    ...

}

如果同時有二個相同的註解, spring 會報錯, 訊息如下:

2318 [main] ERROR org.springframework.web.context.ContextLoader - Context initialization failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping#0': Initialization of bean failed; nested exception is java.lang.IllegalStateException: Cannot map handler 'xxxxController' to URL path [/index]: There is already handler of type [class yyyyController$$EnhancerByCGLIB$$349da4f8] mapped.

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:295)

at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)

at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:292)

at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:194)

at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:580)

at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:900)

at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:455)

at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:294)

at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:215)

at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47)

at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4206)

at org.apache.catalina.core.StandardContext.start(StandardContext.java:4705)

at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1057)

at org.apache.catalina.core.StandardHost.start(StandardHost.java:840)

at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1057)

at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)

at org.apache.catalina.core.StandardService.start(StandardService.java:525)

at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)

at org.apache.catalina.startup.Catalina.start(Catalina.java:595)

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.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)

at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)

但有一個例外, 就是 / , 一般看到網站的 / 會參考 tomcat 的 web.xml中 welcome-file 的設定.

若是下面的寫法, spring 不會報錯, welcome-file也不會生效, 但會連到那個 URL 就不知道了...

@RequestMapping(value={"/", "index"})
public ModelAndView index(HttpSession session) {
...
}


@RequestMapping(value={"/", "login"})

public ModelAndView login(HttpSession session) {

...

}