SpringMVC 4.x输出JSON数据配置

SpringMVC 4.x输出JSON数据配置

我们在日常开发工作中，会遇到需要输出JSON格式数据的需求，特别是rest风格盛行的今日。那么怎么来配置JSON格式结果输出呢？一般情况我们采用jackson-databind或者fastjson来做返回数据的JSON序列化处理。

依赖jar包引入
使用jackson-databind时需要引入如下依赖

<dependency>
    <groupId>com.fasterxml.jackson.coregroupId>
    <artifactId>jackson-databindartifactId>
    <version>2.8.5version>
dependency>

使用fastjson时需要引入如下依赖

<dependency>
    <groupId>com.alibabagroupId>
    <artifactId>fastjsonartifactId>
    <version>1.2.23version>
dependency>

建议尽量使用新版本，避免出现奇怪的版本问题异常。
怎么配置到我们的工程中呢，我们一般有如下几种方式
第一种方法
我们可以在xml配置文件的配置RequestMappingHandlerAdapter对应的Bean

<bean class="org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter">
    <property name="messageConverters">
        <list>
            
            <ref bean="stringHttpMessageConverter"/>
            
            <ref bean="fastJsonHttpMessageConverter"/>
            
            
        list>
    property>
bean>

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

<bean id="mappingJacksonHttpMessageConverter"
      class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
    <property name="objectMapper">
        
        <bean class="com.fasterxml.jackson.databind.ObjectMapper">
            <property name="dateFormat">
                <bean class="java.text.SimpleDateFormat">
                    <constructor-arg type="java.lang.String" value="yyyy-MM-dd HH:mm:ss"/>
                bean>
            property>
            <property name="serializationInclusion">
                
                <value type="com.fasterxml.jackson.annotation.JsonInclude.Include">NON_NULLvalue>
            property>
        bean>
    property>
    <property name="supportedMediaTypes">
        <list>
            
            <value>text/html;charset=UTF-8value>
            <value>application/json;charset=UTF-8value>
        list>
    property>
bean>

<bean id="fastJsonHttpMessageConverter"
      class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter4">
    <property name="supportedMediaTypes">
        <list>
            
            <value>text/html;charset=UTF-8value>
            <value>application/json;charset=UTF-8value>
        list>
    property>
    <property name="fastJsonConfig">
        <bean class="com.alibaba.fastjson.support.config.FastJsonConfig">
            <property name="dateFormat" value="yyyy-MM-dd HH:mm:ss"/>
            <property name="serializerFeatures">
                <array>
                    
                    <value>WriteDateUseDateFormatvalue>
                array>
            property>
        bean>
    property>
bean>

第二种方式
我们可以在 添加 变量信息，具体代码如下:

<mvc:annotation-driven>
    <mvc:message-converters>
        <bean id="stringHttpMessageConverter"
              class="org.springframework.http.converter.StringHttpMessageConverter">
            <property name="supportedMediaTypes">
                <list>
                    
                    <value>text/html;charset=UTF-8value>
                    <value>application/json;charset=UTF-8value>
                list>
            property>
        bean>
        
        <bean id="mappingJacksonHttpMessageConverter"
              class="org.springframework.http.converter.json.MappingJackson2HttpMessageConverter">
            <property name="objectMapper">
                
                <bean class="com.fasterxml.jackson.databind.ObjectMapper">
                    <property name="dateFormat">
                        <bean class="java.text.SimpleDateFormat">
                            <constructor-arg type="java.lang.String" value="yyyy-MM-dd HH:mm:ss"/>
                        bean>
                    property>
                    <property name="serializationInclusion">
                        
                        <value type="com.fasterxml.jackson.annotation.JsonInclude.Include">NON_NULLvalue>
                    property>
                bean>
            property>
            <property name="supportedMediaTypes">
                <list>
                    
                    <value>text/html;charset=UTF-8value>
                    <value>application/json;charset=UTF-8value>
                list>
            property>
        bean>
    mvc:message-converters>
mvc:annotation-driven>

其中mappingJacksonHttpMessageConverter 可以替换为fastjson版本的配置

<bean id="fastJsonHttpMessageConverter"
      class="com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter4">
    <property name="supportedMediaTypes">
        <list>
            
            <value>text/html;charset=UTF-8value>
            <value>application/json;charset=UTF-8value>
        list>
    property>
    <property name="fastJsonConfig">
        <bean class="com.alibaba.fastjson.support.config.FastJsonConfig">
            <property name="dateFormat" value="yyyy-MM-dd HH:mm:ss"/>
            <property name="serializerFeatures">
                <array>
                    <value>WriteDateUseDateFormatvalue>
                array>
            property>
        bean>
    property>
bean>

以上是直接使用Spring 4.2.x以上版本时候的配置方式，如果我们使用spring boot，那么该怎么配置呢？我们可以WebMvcConfigurerAdapter并重写extendMessageConverters方法，具体格式如下

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter4;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.http.converter.StringHttpMessageConverter;
import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

import java.nio.charset.Charset;
import java.util.ArrayList;
import java.util.List;

/**
 * Created by comven on 2017/1/20.
 */
@Configuration
@EnableWebMvc
public class AutoConfig extends WebMvcConfigurerAdapter {
    private Charset default_charset = Charset.forName("UTF-8");

    private static List buildDefaultMediaTypes() {
        List list = new ArrayList<>();
        list.add(MediaType.TEXT_HTML);
        list.add(MediaType.APPLICATION_JSON_UTF8);
        return list;
    }

    @Override
    public void extendMessageConverters(List> converters) {
        converters.add(stringHttpMessageConverter());
        converters.add(mappingJackson2HttpMessageConverter());
        //如果不使用MappingJackson2HttpMessageConverter，可使用如下的转换器
        //spring4.2以上使用如下转换器
        //converters.add(fastJsonHttpMessageConverter4());
        //spring4.2以下使用如下转换器
        //converters.add(fastJsonHttpMessageConverter());
        super.extendMessageConverters(converters);
    }

    @Bean
    public StringHttpMessageConverter stringHttpMessageConverter() {
        StringHttpMessageConverter converter = new StringHttpMessageConverter(default_charset);
        List list = buildDefaultMediaTypes();
        converter.setSupportedMediaTypes(list);
        return converter;
    }

    /**
     * 创建jackson类型的JsonHttpMessageConverter
     *
     * @return MappingJackson2HttpMessageConverter
     */
    @Bean
    public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() {
        MappingJackson2HttpMessageConverter converter = new MappingJackson2HttpMessageConverter();
        ObjectMapper objectMapper = new ObjectMapper();
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);//此设置使输出json时不显示null类型的字段
        converter.setObjectMapper(objectMapper);
        List list = buildDefaultMediaTypes();
        converter.setSupportedMediaTypes(list);
        return converter;
    }

    /**
     * spring4.2以后建议采用这个方式创建
     *
     * @return FastJsonHttpMessageConverter4
     */
    @Bean
    public FastJsonHttpMessageConverter4 fastJsonHttpMessageConverter4() {
        FastJsonHttpMessageConverter4 converter = new FastJsonHttpMessageConverter4();
        List list = buildDefaultMediaTypes();
        converter.setSupportedMediaTypes(list);
        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setDateFormat("yyyy-MM-dd HH:mm:ss");
        fastJsonConfig.setCharset(default_charset);
        //此处是可变参数可以配置多个
        fastJsonConfig.setSerializerFeatures(SerializerFeature.WriteDateUseDateFormat);//SerializerFeature.WriteMapNullValue此配置加上后会输出null
        converter.setFastJsonConfig(fastJsonConfig);
        return converter;
    }

    /**
     * spring4.2以前可以采用这个方式创建
     *
     * @return FastJsonHttpMessageConverter
     */
    @Bean
    public FastJsonHttpMessageConverter fastJsonHttpMessageConverter() {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig fastJsonConfig = new FastJsonConfig();
        fastJsonConfig.setDateFormat("yyyy-MM-dd HH:mm:ss");
        fastJsonConfig.setCharset(default_charset);
        //此处是可变参数可以配置多个
        fastJsonConfig.setSerializerFeatures(SerializerFeature.WriteDateUseDateFormat);//SerializerFeature.WriteMapNullValue此配置加上后会输出null
        converter.setFastJsonConfig(fastJsonConfig);
        List list = buildDefaultMediaTypes();
        converter.setSupportedMediaTypes(list);
        return converter;
    }
}

使用此方式后不需要在xml文件中配置 申明。

使用以上三种配置方式之后，只需要在Controller的方法上使用@ResponseBody注解或者Controller采用@RestController 我们的controller方法就会输出对应的String数据或者JSON格式数据

特别说明:
fastjson提供的MessageConverter分为两个版本，一个是spring4.0以下类名为FastJsonHttpMessageConverter，spring4.0以上使用FastJsonHttpMessageConverter4。