Spring拦截器中通过request获取到该请求对应Controller中的method对象

来源：http://chenzhou123520.iteye.com/blog/1702563

 

 

背景：项目使用Spring 3.1.0.RELEASE，从dao到Controller层全部是基于注解配置。我的需求是想在自定义的Spring拦截器中通过request获取到该请求对应于Controller中的目标method方法对象。Controller和拦截器代码如下：

 

AdminController

 

@Controller
 @RequestMapping("/admin")
 public class AdminController {

     /**
     * init:初始页面. <br/>
     *
     * @author chenzhou
     * @param request 请求
     * @param response 响应
     * @return 登陆页
     * @since JDK 1.6
     */
     @RequestMapping("/init")
     public ModelAndView init(HttpServletRequest request,
            HttpServletResponse response){
         Map<String, Object> model = new HashMap<String, Object>();
         List<Role> roleList = this.adminService.getRoleList();
         model.put("roleList", roleList);
         return new ModelAndView(this.getLoginPage(), model);
    }

     //……
}

@Controller
@RequestMapping("/admin")
public class AdminController {

	/**
	 * init:初始页面. <br/>
	 *
	 * @author chenzhou
	 * @param request 请求
	 * @param response 响应
	 * @return 登陆页
	 * @since JDK 1.6
	 */
	@RequestMapping("/init")
	public ModelAndView init(HttpServletRequest request,
			HttpServletResponse response){
		Map<String, Object> model = new HashMap<String, Object>();
		List<Role> roleList = this.adminService.getRoleList();
		model.put("roleList", roleList);
		return new ModelAndView(this.getLoginPage(), model);
	}

	//……
}

 

 

LoginInterceptor

 

public class LoginInterceptor extends HandlerInterceptorAdapter {
     /**
     * This implementation always returns <code>true</code>.
     */
     public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
         throws Exception {
         return true;
    }

     /**
     * This implementation is empty.
     */
     public void postHandle(
            HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
             throws Exception {
    }

     /**
     * This implementation is empty.
     */
     public void afterCompletion(
            HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
             throws Exception {
    }
}

public class LoginInterceptor extends HandlerInterceptorAdapter {
	/**
	 * This implementation always returns <code>true</code>.
	 */
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
	    throws Exception {
		return true;
	}

	/**
	 * This implementation is empty.
	 */
	public void postHandle(
			HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView)
			throws Exception {
	}

	/**
	 * This implementation is empty.
	 */
	public void afterCompletion(
			HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
			throws Exception {
	}
}

 

servlet xml配置文件定义：

<bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" />
 <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
 <bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
     <property name="interceptors">
         <list>
             <bean class="com.chenzhou.examples.erm.util.interceptor.LoginInterceptor"/>
         </list>
     </property>
 </bean>

<bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" /> 
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
	<property name="interceptors">
		<list>
			<bean class="com.chenzhou.examples.erm.util.interceptor.LoginInterceptor"/>
		</list>
	</property>
</bean>  

     我的需求是想在preHandle方法中通过request获取该请求访问的目标Controller中的方法对象。之前找了很久也没有找到比较好的方案，就采取了最老土的通过比较requestURL和Controller类和方法上的RequestMappingURL来进行获取，这样也能勉强实现，但是这种方式我自己都觉得特别恶心。首先，这种方式需要使用反射来获取Controller中的所有方法，然后遍历method数组，逐个进行RequestMappingURL的比对，效率低下。其次，如果RequestMapping定义了类似于@RequestMapping("/{id}")这种动态参数url，则无法进行比较。

     因为上面这种方式不好，我就一直想找一个更好的方案。不得已只能向人求助，第一个就想到了Iteye上对于Spring研究得很熟悉的jinnianshilongnian龙年兄，我相信经常上iteye的博友们对龙年兄应该都很熟悉。龙年兄给了我一个方案，就是通过把handler对象转换为HandlerMethod类型，然后直接getMethod，代码如下：

 

/**
 * This implementation always returns <code>true</code>.
 */
 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
     throws Exception {
     System.out.println("*********************preHandle********************");
    System.out.println(handler.getClass());
    HandlerMethod handlerMethod = (HandlerMethod) handler;
    System.out.println(handlerMethod.getMethod());
     return true;
}

/**
 * This implementation always returns <code>true</code>.
 */
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
    throws Exception {
	System.out.println("*********************preHandle********************");
	System.out.println(handler.getClass());
	HandlerMethod handlerMethod = (HandlerMethod) handler;
	System.out.println(handlerMethod.getMethod());
	return true;
}

 

注：HandlerMethod类是Spring 3.1.0.RELEASE版本中才有的，之前我使用的Spring 3.0.6.RELEASE版本，里面是找不到这个类的

 

根据龙年兄提供的方法，测试之后报错，报错信息如下：

 

*********************preHandle********************
class com.chenzhou.examples.erm.web.AdminController
 2012-10-21 16:28:25 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet erm threw exception
java.lang.ClassCastException: com.chenzhou.examples.erm.web.AdminController cannot be cast to org.springframework.web.method.HandlerMethod
     at com.chenzhou.examples.erm.util.interceptor.LoginInterceptor.preHandle(LoginInterceptor.java:37)
     at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:891)
     at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)
     at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
     at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
……

*********************preHandle********************
class com.chenzhou.examples.erm.web.AdminController
2012-10-21 16:28:25 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet erm threw exception
java.lang.ClassCastException: com.chenzhou.examples.erm.web.AdminController cannot be cast to org.springframework.web.method.HandlerMethod
	at com.chenzhou.examples.erm.util.interceptor.LoginInterceptor.preHandle(LoginInterceptor.java:37)
	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:891)
	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:827)
	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
	at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:778)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:617)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
……

 

    根据错误提示可以看出是HandlerMethod handlerMethod = (HandlerMethod) handler;这一步报错了，根据System.out.println(handler.getClass());打印的结果可以得知handler是该请求访问的Controller类，无法转换成HandlerMethod对象。这次还是龙年兄帮我找出了原因，解决方案是使用

<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"> 
替换 
<bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping"/> 

因为DefaultAnnotationHandlerMapping只能返回Controller对象，不会映射到Controller中的方法级别。替换之后servlet xml配置如下：

 

<bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" />
 <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
 <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping">
     <property name="interceptors">
         <list>
             <bean class="com.chenzhou.examples.erm.util.interceptor.LoginInterceptor"/>
         </list>
     </property>
 </bean>

<bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" /> 
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"> 
	<property name="interceptors">
		<list>
			<bean class="com.chenzhou.examples.erm.util.interceptor.LoginInterceptor"/>
		</list>
	</property>
</bean>

 

    重启tomcat测试之后发现再次报错，报了另外一个错误，具体信息如下：

 

2012-10-21 16:39:39 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet erm threw exception
javax.servlet.ServletException: No adapter for handler [public org.springframework.web.servlet.ModelAndView com.chenzhou.examples.erm.web.AdminController.init(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)]: Does your handler implement a supported interface like Controller?
……

2012-10-21 16:39:39 org.apache.catalina.core.StandardWrapperValve invoke
严重: Servlet.service() for servlet erm threw exception
javax.servlet.ServletException: No adapter for handler [public org.springframework.web.servlet.ModelAndView com.chenzhou.examples.erm.web.AdminController.init(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)]: Does your handler implement a supported interface like Controller?
……

 

    这一次，请求根本没有到达拦截器容器就已经报错了，错误提示的意思是找不到handler对象对应的Adapter类。我在RequestMappingHandlerMapping类对应的spring-webmvc-3.1.0.RELEASE.jar 包里找到了该类对应的Adapter类：RequestMappingHandlerAdapter，然后在servlet xml中进行了配置：

 

<bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" />
 <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
 <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping">
     <property name="interceptors">
         <list>
             <bean class="com.chenzhou.examples.erm.util.interceptor.LoginInterceptor"/>
         </list>
     </property>
 </bean>
 <bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"/>

<bean class="org.springframework.aop.aspectj.annotation.AnnotationAwareAspectJAutoProxyCreator" /> 
<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping"> 
	<property name="interceptors">
		<list>
			<bean class="com.chenzhou.examples.erm.util.interceptor.LoginInterceptor"/>
		</list>
	</property>
</bean>
<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter"/>

 

    然后重新启动tomcat后访问http://localhost:8080/erm/admin/init 结果正常，控制台日志信息如下：

*********************preHandle********************
class org.springframework.web.method.HandlerMethod
public org.springframework.web.servlet.ModelAndView com.chenzhou.examples.erm.web.AdminController.init(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)

*********************preHandle********************
class org.springframework.web.method.HandlerMethod
public org.springframework.web.servlet.ModelAndView com.chenzhou.examples.erm.web.AdminController.init(javax.servlet.http.HttpServletRequest,javax.servlet.http.HttpServletResponse)

    从日志信息可以看出，handler对象在经过类型转换后转换成了HandlerMethod类型，通过handler.getMethod方法，获取到了该请求访问的方法为com.chenzhou.examples.erm.web.AdminController.init