spring 下配置 fastJson

利用@ResponseBody注解的方式序列化输出json字符串

首先是applicationContext.xml中的相关配置

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	xmlns:context="http://www.springframework.org/schema/context"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
						http://www.springframework.org/schema/beans/spring-beans-3.2.xsd
						http://www.springframework.org/schema/mvc
						http://www.springframework.org/schema/mvc/spring-mvc-3.2.xsd
						http://www.springframework.org/schema/context
						http://www.springframework.org/schema/context/spring-context-3.2.xsd">
	<context:component-scan base-package="com.jadyer"/>
	
	<mvc:annotation-driven>
		<mvc:message-converters register-defaults="true">
			<bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
				<property name="supportedMediaTypes" value="text/html;charset=UTF-8"/>
				<property name="features">
					<array>
						<value>WriteMapNullValue</value>
						<value>WriteNullStringAsEmpty</value>
					</array>
				</property>
			</bean>
		</mvc:message-converters>
	</mvc:annotation-driven>
	
	<!-- fastjson-1.1.41与SpringMVC整合 -->
	<!-- 
	1)若按照jackson和SpringMVC的整合方式,应按照下面的写法,但测试发现这样会报告"HTTP Status 406"
	  The resource identified by this request is only capable of generating responses
	  with characteristics not acceptable according to the request "accept" headers.
	2)测试通过的整合方式为上面那样在mvc:annotation-driven里面进行注册
	3)supportedMediaTypes增加[text/html;charset=UTF-8]值,是为了兼容IE6
	  否则[application/json]值在IE6中会导致弹出对话框询问是否保存文件,而firefox等高级浏览器会正常打印json字符串
	4)若像下面这样给supportedMediaTypes属性赋两个值[text/html;charset=UTF-8]和[application/json],则[application/json]是无效的
	  因为此时应答给浏览器(或者说请求方)的Content-Type头信息都是[text/html;charset=UTF-8],所以给它一个值就行了
	  如果给supportedMediaTypes的值为[application/json],则应答给浏览器的Content-Type头信息就是[application/json;charset=UTF-8]
	5)关于features属性,不是serializerFeature,而是features,详见FastJsonHttpMessageConverter.java
	  它是用来控制json序列化输出时的一些额外属性,比如说该字段是否输出、输出时key使用单引号还是双引号、key不使用任何引号等等
	  QuoteFieldNames----------输出key时是否使用双引号,默认为true
	  WriteMapNullValue--------是否输出值为null的字段,默认为false
	  WriteNullNumberAsZero----数值字段如果为null,输出为0,而非null
	  WriteNullListAsEmpty-----List字段如果为null,输出为[],而非null
	  WriteNullStringAsEmpty---字符类型字段如果为null,输出为"",而非null
	  WriteNullBooleanAsFalse--Boolean字段如果为null,输出为false,而非null
	6)通常在网上搜到的fastjson和springMVC整合的例子中都像下面注释的代码那样给了两个属性WriteMapNullValue和QuoteFieldNames
	  这就表示为json解析器设置QuoteFieldNames和WriteMapNullValue的值为true,即输出时key使用双引号,同时也输出值为null的字段
	7)输出时某字段为String类型,且值为null,此时若需要其输出,且输出值为空字符串,则需同时赋值WriteMapNullValue和WriteNullStringAsEmpty
	  经测试,若只赋值WriteNullStringAsEmpty,则不会输出该字段..加上WriteMapNullValue属性后,便输出了,且输出值不是null,而是预期的空字符串
	 -->
	<!-- 
	<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
		<property name="messageConverters">
			<list>
				<bean class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter">
					<property name="supportedMediaTypes">
						<list>
							<value>text/html;charset=UTF-8</value>
							<value>application/json</value>
						</list>
					</property>
					<property name="serializerFeature">
						<array>
							<value>QuoteFieldNames</value>
							<value>WriteMapNullValue</value>
						</array>
					</property>
				</bean>
			</list>
		</property>
	</bean>
	 -->
	<!-- 
	<bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
		<property name="messageConverters">
			<list>
				<bean class="org.springframework.http.converter.json.MappingJacksonHttpMessageConverter">
					<property name="supportedMediaTypes" value="text/html;charset=UTF-8"/>
				</bean>
			</list>
		</property>
	</bean>
	 -->
</beans>