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