[KANMARS原创]-SpringMVC源码解析(4) - 视图处理器
三、SpringMVC的视图处理器
从上一篇文章我们已经看到了在获取到一个ModelAndView之后，会调用DispatcherServlet.processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);对用户进行响应
processDispatchResult(processedRequest, response, mappedHandler, mv, dispatchException);
├render(mv, request, response);
│ ├View view = viewResolver.resolveViewName(mv.getViewName(), locale);//此处viewResolover常用的是FreeMarkerViewResolver，返回FreeMarkerView
│ └view.render(mv.getModelInternal(), request, response);
│ ├Map<String, Object> mergedModel = createMergedOutputModel(model, request, response);
│ ├prepareResponse(request, response);
│ └renderMergedOutputModel(mergedModel, request, response);
│ └FreeMarkerView.doRender(model, request, response);
│ └template.process(model, response.getWriter());//给用户输出内容
│
└mappedHandler.triggerAfterCompletion(request, response, null);
├HandlerInterceptor[] interceptors = getInterceptors()
└for(HandlerInterceptor h : interceptors)h.afterCompletion(request, response, ex)
我们上一节已经大致描述了这个过程。
此处仅强调一下：
在视图解析器的解析过程中，采用的是如下代码：
for (ViewResolver viewResolver : this.viewResolvers) {
View view = viewResolver.resolveViewName(viewName, locale);
if (view != null) {
return view;
}
}
即：在系统中按照viewResolvers对view进行解析，如果解析成功，则直接返回，跳过其他viewResolvers
然后调用view.render(mv.getModelInternal(), request, response);
最终调用template.process(model, response.getWriter());把结果输出到用户
PS：依稀记得当年和九扬搞车险时，九扬整了一个同时支持ftl和jsp的解析器，我找找代码去………..
Spring配置如下：
<bean id="viewResolver" class="com.spring.action.MultiViewResover">
<property name="resolvers">
<map>
<entry key="jsp">
<bean
class="org.springframework.web.servlet.view.InternalResourceViewResolver">
<property name="viewClass"
value="org.springframework.web.servlet.view.JstlView"/>
<property name="prefix" value="/WEB-INF/jsp/"/>
<property name="suffix" value=".jsp"/>
</bean>
</entry>
<entry key="ftl">
<bean
class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">
<property name="cache" value="true"/>
<property name="prefix" value="/"/>
<property name="suffix" value=".ftl"/>
</bean>
</entry>
<entry key="vm">
<bean
class="org.springframework.web.servlet.view.velocity.VelocityViewResolver">
<property name="cache" value="true"/>
<property name="prefix" value="/"/>
<property name="suffix" value=".vm"/>
</bean>
</entry>
</map>
</property>
</bean>
JAVA类如下：
package com.spring.action;
import java.util.Locale;
import java.util.Map;
import org.springframework.web.servlet.View;
import org.springframework.web.servlet.ViewResolver;
/**
* @author Jeson
* @blog:http://www.gbsou.com
* @date:Oct 20, 2009 8:39:27 AM
* @version :1.0
*
*/
public class MultiViewResover implements ViewResolver {
private Map<String, ViewResolver> resolvers;
@Override
public View resolveViewName(String viewName, Locale locale)
throws Exception {
int n = viewName.lastIndexOf("_"); // 获取
// viewName(modelAndView中的名字)看其有没有下划线
if (n == (-1))
return null; // 没有则直接返回空
// 有的话截取下划线后面的字符串 这里一般是jsp,ftl,vm与配置文件中的<entry key="ftl">的key匹配
String suffix = viewName.substring(n + 1);
// 根据下划线后面的字符串去获取托管的视图解析类对象
ViewResolver resolver = resolvers.get(suffix);
// 取下划线前面的部分 那时真正的资源名.比如我们要使用hello.jsp 那viewName就应该是hello_jsp
viewName = viewName.substring(0, n);
if (resolver != null)
return resolver.resolveViewName(viewName, locale);
return null;
}
public Map<String, ViewResolver> getResolvers() {
return resolvers;
}
public void setResolvers(Map<String, ViewResolver> resolvers) {
this.resolvers = resolvers;
}
}
Controller如下
package com.spring.action;
import java.util.HashMap;
import java.util.Map;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;
@Controller
public class HelloWorldAction {
@RequestMapping(value = "/helloworld.do")
public ModelAndView hello() {
ModelAndView modelAndView = new ModelAndView();
modelAndView.setViewName("hello_jsp");
modelAndView.addObject("message", "Hello,SpringMvc");
return modelAndView;
}
@RequestMapping(value = "/welcome.do")
public ModelAndView helloVm() {
// ModelAndView modelAndView=new ModelAndView();
// modelAndView.setViewName("freemarker_ftl");
// modelAndView.addObject("message", "Hello,Velocity");
// return modelAndView;
Map map = new HashMap();
return new ModelAndView("freemarker_ftl", map); // 根据之前的解释这里就是去寻找
// user.ftl资源
}
@RequestMapping(value = "/free.do")
public ModelAndView helloFreeMarker() {
ModelAndView modelAndView = new ModelAndView();
modelAndView.setViewName("welcome");
modelAndView.addObject("message", "Hello,Freemarker");
return modelAndView;
}
}
这是大概四年前的代码了，而我今天才看懂其内部是怎么走的，惭愧惭愧。
更惭愧的是：因为一直没时间，我本来不计划看SpringMVC的。但是最近在看服务化，有同事推荐SpringCloud，然后SpringCloud的基础是SpringBoot，而SpringBoot的第一组件是SpringMVC，我在看完SpringBoot后发现自己对SpringMVC用了很多年但还是无知的概念，因此我决定沉下心来看一下SpringMVC的源码。
到今天终于看完了，终于可以回头看SpringCloud了。