spring boot 读书笔记2返回Json数据及数据封装

创建实体类

public class User {
    private Integer id;
    private String username;
    private Integer age;

    public void setId(Integer id) {
        this.id = id;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public Integer getId() {
        return id;
    }

    public String getUsername() {
        return username;
    }

    public Integer getAge() {
        return age;
    }
    public User(Integer id,String username,Integer age){
        this.id=id;
        this.username=username;
        this.age=age;

    }

　创建controller

package com.example.spring2.controller;

import com.example.spring2.entity.User;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@RestController
@RequestMapping("/api")
public class UserController {
    @RequestMapping("getUser")
    public User getUser(){
        return new User(1,"测试",10);
    }
    @RequestMapping("getList")
    public List<User> getList(){
        List<User> myuser=new ArrayList<>();
        myuser.add(new User(2,"网名",55));
        myuser.add(new User(3,"订单名",15));
        myuser.add(new User(4,"嗯嗯名",25));
        return myuser;
    }
    @RequestMapping("/map")
    public Map<String, Object> getMap() {
        Map<String, Object> map = new HashMap<>(3);
        User user = new User(1, "事实上", 34);
        map.put("作者信息", user);
        map.put("博客地址", "http://www.baidu.com");
        map.put("CSDN地址", null);
        map.put("粉丝数量", 4153);
        return map;
    }
}

　需要对null值处理时

jackson

package com.example.spring2.config;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.SerializerProvider;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;

import java.io.IOException;

@Configuration
public class JacksonConfig {
    @Bean
    @Primary
    @ConditionalOnMissingBean(ObjectMapper.class)
    public ObjectMapper jacksonObjectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();
        objectMapper.getSerializerProvider().setNullValueSerializer(new JsonSerializer<Object>() {
            @Override
            public void serialize(Object o, JsonGenerator jsonGenerator, SerializerProvider serializerProvider) throws IOException, IOException {
                jsonGenerator.writeString("");
            }
        });
        return objectMapper;
    }
}

　　fastjson

package com.example.spring2.config;

import com.alibaba.fastjson.serializer.SerializerFeature;
import com.alibaba.fastjson.support.config.FastJsonConfig;
import com.alibaba.fastjson.support.spring.FastJsonHttpMessageConverter;
import org.springframework.context.annotation.Configuration;
import org.springframework.http.MediaType;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import java.nio.charset.StandardCharsets;
import java.util.ArrayList;
import java.util.List;

/*@Configuration
public class fastJsonConfig extends WebMvcConfigurationSupport {
    @Override
    public void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
        FastJsonHttpMessageConverter converter = new FastJsonHttpMessageConverter();
        FastJsonConfig config = new FastJsonConfig();
        config.setSerializerFeatures(
                // 保留map空的字段
                SerializerFeature.WriteMapNullValue,
                // 将String类型的null转成""
                SerializerFeature.WriteNullStringAsEmpty,
                // 将Number类型的null转成0
                SerializerFeature.WriteNullNumberAsZero,
                // 将List类型的null转成[]
                SerializerFeature.WriteNullListAsEmpty,
                // 将Boolean类型的null转成false
                SerializerFeature.WriteNullBooleanAsFalse,
                // 避免循环引用
                SerializerFeature.DisableCircularReferenceDetect);

        converter.setFastJsonConfig(config);
        converter.setDefaultCharset(StandardCharsets.UTF_8);
        List<MediaType> mediaTypeList = new ArrayList<>();
        // 解决中文乱码问题，相当于在Controller上的@RequestMapping中加了个属性produces = "application/json"
        mediaTypeList.add(MediaType.APPLICATION_JSON);
        converter.setSupportedMediaTypes(mediaTypeList);
        converters.add(converter);
    }
}*/

　　

封装统一返回的数据结构

创建实体类

package com.example.spring2.entity;

public class JsonResult<T> {
    private T data;
    private String code;
    private String msg;

    /**
     * 若没有数据返回，默认状态码为0，提示信息为：操作成功！
     */
    public JsonResult() {
        this.code = "0";
        this.msg = "操作成功！";
    }

    /**
     * 若没有数据返回，可以人为指定状态码和提示信息
     * @param code
     * @param msg
     */
    public JsonResult(String code, String msg) {
        this.code = code;
        this.msg = msg;
    }

    /**
     * 有数据返回时，状态码为0，默认提示信息为：操作成功！
     * @param data
     */
    public JsonResult(T data) {
        this.data = data;
        this.code = "0";
        this.msg = "操作成功！";
    }

    /**
     * 有数据返回，状态码为0，人为指定提示信息
     * @param data
     * @param msg
     */
    public JsonResult(T data, String msg) {
        this.data = data;
        this.code = "0";
        this.msg = msg;
    }
    public T getData() {
        return data;
    }

    public void setData(T data) {
        this.data = data;
    }

    public String getCode() {
        return code;
    }

    public void setCode(String code) {
        this.code = code;
    }

    public String getMsg() {
        return msg;
    }

    public void setMsg(String msg) {
        this.msg = msg;
    }
}

　　创建返回封装格式的controller

package com.example.spring2.controller;

import com.example.spring2.entity.JsonResult;
import com.example.spring2.entity.User;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

@RestController
@RequestMapping("/newapi")
public class JsonResultController {
    @RequestMapping("getUser")
    public JsonResult<User> getUser(){
        return new JsonResult<>( new User(1,"测试",10));
    }
    @RequestMapping("getList")
    public JsonResult<List<User>> getList(){
        List<User> myuser=new ArrayList<>();
        myuser.add(new User(2,"网名",55));
        myuser.add(new User(3,"订单名",15));
        myuser.add(new User(4,"嗯嗯名",25));
        return new JsonResult<> (myuser,"获取成功");
    }
    @RequestMapping("/map")
    public JsonResult<Map<String, Object>> getMap() {
        Map<String, Object> map = new HashMap<>(3);
        User user = new User(1, "事实上", 34);
        map.put("作者信息", user);
        map.put("博客地址", "http://www.baidu.com");
        map.put("CSDN地址", null);
        map.put("粉丝数量", 4153);
        return new JsonResult<> (map);
    }
}