Spring MVC 3.1多视图协商配置(json、xml、freemarker)

Spring mvc可以配置多种视图，比如json、xml、ftl等等(REST内容协商)。

RESTful服务中很重要的一个特性是对于同一资源,可以有多种表述形式。

既然是协商视图，那么Spring MVC REST改如何决定采用何种方式(视图)展示内容呢？

第一种：根据http request header中的Accept

Accept: text/css,*/*;q=0.1               //返回css格式数据
Accept: application/xml                  //返回xml格式数据
Accept: application/json                 //返回json格式数据

缺点：

chrome:
Accept:application/xml,application/xhtml+xml,textml;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
 
firefox:
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8

IE8:
Accept:image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash,

application/x-silverlight, application/x-ms-application, application/x-ms-xbap,

application/vnd.ms-xpsdocument, application/xaml+xml, */*

用户直接通过浏览器访问，由于各个浏览器发送的Accept的不一致，

将导致服务器不知要返回什么格式的数据。

第二种：根据扩展名

http://www.sxrczx.com/rest.xml           //将返回xml格式数据
http://www.sxrczx.com/rest.json          //将返回json格式数据
http://www.sxrczx.com/rest.htm           //将返回html格式数据

缺点：

不能统一通过同一URL实现多种展示视图。

第三种：根据format参数

http://www.sxrczx.com/rest?format=xml    //将返回xml格式数据
http://www.sxrczx.com/rest?format=json   //将返回json格式数据
http://www.sxrczx.com/rest?format=htm    //将返回html格式数据

缺点：

需要额外的传递format参数，URL变得冗余，繁琐，缺少了REST的简洁风范。

配置：web.xml,显示Spring的配置文件位置

...
<!-- spring mvc -->
<servlet>
    <servlet-name>SpringMvc</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
       <param-name>contextConfigLocation</param-name>
         <param-value>/WEB-INF/config/spring/appContext.xml</param-value>
      </init-param>
    <load-on-startup>1</load-on-startup>
  </servlet>
<servlet-mapping>
    <servlet-name>SpringMvc</servlet-name>
    <url-pattern>*.htm</url-pattern>
    <url-pattern>*.json</url-pattern>
    <!-- <url-pattern>*.xml</url-pattern> -->
</servlet-mapping>
...

===================================================================================

Spring配置appContext.xml(无扩展名(jsp作为视图)/json/xml)

<!-- 根据客户端的不同的请求决定不同的view进行响应, 
如 http://www.sxrczx.com/rest.json http://www.sxrczx.com/rest.xml -->
<bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">  
<!-- 设置为true以忽略对Accept Header的支持-->
<property name="ignoreAcceptHeader" value="true"/>  
<!-- 在没有扩展名时即: "http://www.sxrczx.com/rest" 时的默认展现形式 -->
<property name="defaultContentType" value="text/html"/>  
<!-- 扩展名至mimeType的映射,即 http://www.sxrczx.com/rest.json 
映射为 application/json -->
<property name="mediaTypes">  
<map>  
<entry key="json" value="application/json" />  
<entry key="xml" value="application/xml" />  
</map>  
</property>  
<!-- 用于开启 http://www.sxrczx.com/rest?format=json 的支持 -->
<property name="favorParameter" value="false"/>  
<property name="viewResolvers">  
<list>  
<bean class="org.springframework.web.servlet.view.BeanNameViewResolver" />  
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">  
<property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/>  
<property name="prefix" value="/pages"/>  
<property name="suffix" value=".jsp"></property>  
</bean>  
</list>  
</property>  

<property name="defaultViews">  
<list>  
<!-- for application/json -->
<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView" />  
<!-- for application/xml -->
<!--   
<bean class="org.springframework.web.servlet.view.xml.MarshallingView" >  
<property name="marshaller">  
<bean class="org.springframework.oxm.xstream.XStreamMarshaller"/>  
</property>  
</bean> 

-->
</list>  
</property>  
</bean>

============================================================================================

Spring配置appContext.xml(freemarker/json)

<bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
<property name="order" value="1" />
<property name="favorParameter" value="false" />
<property name="ignoreAcceptHeader" value="true" />
<property name="defaultContentType" value="application/json" />
<property name="mediaTypes">
<map>
<entry key="json" value="application/json" />
</map>
</property>
<property name="viewResolvers">
<list>
<!--  配置freemarker作为视图层 -->
<bean id="freeMarkerViewResolver" 
class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">
<property name="cache" value="true" />
<property name="order" value="0" />
<property name="prefix" value="" />
<property name="suffix" value=".htm" />
<property name="contentType" value="text/html;charset=utf-8" />
<!--  把contextPath暴露给freemaker，前端可以通过${request.getContextPath()} 
来获取上下文路径<property name="requestContextAttribute" value="request"/>
-->
<property name="viewClass" 
value="org.springframework.web.servlet.view.freemarker.FreeMarkerView"/>
</bean>
</list>
</property>
<property name="defaultViews">
<list>
<bean class="org.springframework.web.servlet.view.json.MappingJacksonJsonView" />
</list>
</property>
</bean>
     
<!-- Freemarker -->
<bean id="freeMarkerViewResolver" 
class="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">
<property name="cache" value="true" />
<property name="order" value="0" />
<property name="prefix" value="" />
<property name="suffix" value=".htm" />
<property name="contentType" value="text/html;charset=utf-8" />
<!-- 把contextPath暴露给freemaker，前端可以通过￥{request.getContextPath()} 
来获取上下文路径 
<property name="requestContextAttribute" value="request"/>
-->
<property name="viewClass" 
value="org.springframework.web.servlet.view.freemarker.FreeMarkerView" />
</bean>

<!-- ftl参数配置 -->
<bean id="freemarkerConfiguration" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
	<property name="location" value="/WEB-INF/config/ftl/freemarker.properties"/>
</bean>
<bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">
	<property name="defaultEncoding" value="utf-8"/>
	<property name="templateLoaderPath" value="/WEB-INF/template"/>
	<property name="freemarkerSettings" ref="freemarkerConfiguration"/>
</bean>

freemarker.properties

datetime_format=yyyy-MM-dd HH:mm:ss
date_format=yyyy-MM-dd
time_format=HH:mm:ss
number_format=0.######;
boolean_format=true,false
#auto_import="/common/index.ftl" as ui
whitespace_stripping=true
default_encoding=UTF-8
tag_syntax=square_bracket
url_escaping_charset=UTF-8
#开启默认容错，既null时，默认使用""代替
classic_compatible=true