json jackson

1.引入依赖

        <dependency>
            <groupId>com.fasterxml.jackson.core</groupId>
            <artifactId>jackson-databind</artifactId>
            <version>2.8.3</version>
        </dependency>

2.添加 conventer

    <mvc:annotation-driven>
        <mvc:message-converters>
            <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
                <property name="objectMapper" ref="objectMapper" />
            </bean>
        </mvc:message-converters>
    </mvc:annotation-driven>

    <bean id="objectMapper" class="org.springframework.http.converter.json.Jackson2ObjectMapperFactoryBean"
        p:indentOutput="false" p:simpleDateFormat="yyyy-MM-dd'T'HH:mm:ss.SSSZ" />

indentOutput 缩进打印，false 无缩进 ，true 有缩进（格式化）

{
  "b" : "你好",
  "a" : "2016-10-06T14:54:16.918+0800"
}

{"b":"你好","a":"2016-10-06T14:57:33.724+0800"}

simpleDateFormat 可以将日期类型自动转为指定格式字符串

具体用法可以查看该类

MappingJackson2HttpMessageConverter

By default, this converter supports application/json and application/*+json with UTF-8 character
set. This can be overridden by setting the supportedMediaTypes property.

这样重写

    <bean class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
        <property name="supportedMediaTypes">
            <list>
                <value>application/json;charset=UTF-8</value>
            </list>
        </property>
    </bean>

3. 设置controller 的 response

关于controller 返回时由哪个 conventer 处理的问题

首先 如果不是加 @ResponseBody 则由viewresolver 处理

在 @Controller + @ResponseBody = @RestController

You can use the new @RestController annotation with Spring MVC applications, removing the need to add @ResponseBody to each of your @RequestMapping methods.

这种情况下 converter就生效了，会根据 Content-Type:text/html;charset=ISO-8859-1 类型分配给具体的 converter 处理

默认有一个 

2016-10-06 15:39:48 DEBUG RequestResponseBodyMethodProcessor:250 - Written [你好] as "text/html" using [org.springframework.http.converter.StringHttpMessageConverter@407305a3]

这个默认的 StringHttpMessageConverter 使用的编码是 

public static final Charset DEFAULT_CHARSET = Charset.forName("ISO-8859-1");

可以覆盖这个 converter

            <bean class="org.springframework.http.converter.StringHttpMessageConverter">
                <constructor-arg value="UTF-8" />
            </bean>

有这么多 HttpMessageConverter 视情况增加到 <mvc:message-converters>...