Java工具-JsonObject&JsonArray/Object/String相互转换（FastJson）-蒲公英云

前言

之前处理Json类型字符串. 对于相关细节有些疏忽了(Spark SQL 导入JSON文件).
借此机会将Json类型字符串全部梳理一遍.

Maven 引用

<dependencies>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.4</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.12</version>
            <scope>test</scope>
        </dependency>
  </dependencies>

Json 相关表示类型

Object对象(单个)

{“name”:”sean”,”age”:18,”sex”:”male”}
Object对象(多个)

{“name”:”sean”,”age”:18,”sex”:”male”},
{“name”:”coal”,”age”:18,”sex”:”male”}
数组&List

[{“age”:18,”sex”:”male”,”name”:”Sean”},{“age”:18,”sex”:”male”,”name”:”bruce”},{“age”:18,”sex”:”male”,”name”:”gogogo”}]
Map

{“sean”:”hello”,”bruce”:”gogogo”}
复杂数据类型(混合类)

{“list”:[“ListValue1”,”ListValue2”],”map”:{“map2”:”mapValue2”,”map1”:”mapValue1”},”name”:”sean”,”stringArray”:[“stringValue1”,”stringValue2”]}

相关POJO

People

import com.alibaba.fastjson.annotation.JSONField;

public class People {

@JSONField(ordinal = 1)
public String name;
// @JSONField()
public Integer age;
public String sex;
public People() {}
public People(String name,Integer age,String sex) {
    this.name = name;
    this.age = age;
    this.sex = sex;
}
public String getName() {
    return name;
}
public void setName(String name) {
    this.name = name;
}
public Integer getAge() {
    return age;
}
public void setAge(Integer age) {
    this.age = age;
}
public String getSex() {
    return sex;
}
public void setSex(String sex) {
    this.sex = sex;
}

}

ComplexPeople

package com.yanxml.arsenal.java.json.pojo;

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

public class ComplexPeople {
```
String name;
Map<String ,String> map;
List<String> list;
String [] stringArray;
```

    public ComplexPeople() {
        name  = "sean";
        // Map
        map = new HashMap();
        map.put("map1", "mapValue1");
        map.put("map2", "mapValue2");
        // List
        list = new ArrayList<String>();
        list.add("ListValue1");
        list.add("ListValue2");
        stringArray = new String[2];
        stringArray[0]="stringValue1";
        stringArray[1]="stringValue2";
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Map<String, String> getMap() {
        return map;
    }
    public void setMap(Map<String, String> map) {
        this.map = map;
    }
    public List<String> getList() {
        return list;
    }
    public void setList(List<String> list) {
        this.list = list;
    }
    public String[] getStringArray() {
        return stringArray;
    }
    public void setStringArray(String[] stringArray) {
        this.stringArray = stringArray;
    }
}

转换操作

Object 相关

//@Test

public void testForObject() {
    // 转换为 JSONOBJECT
    String peopleJsonString = "{\"name\":\"sean\",\"age\":18,\"sex\":\"male\"}";
    JSONObject jsonObject = JSONObject.parseObject(peopleJsonString);
    String peopleName = (String)jsonObject.get("name");
    Integer peopleAge = (Integer)jsonObject.get("age");
    System.out.println("name:"+peopleName+" age:"+peopleAge);
    // 转换为Object
    People people = JSONObject.parseObject(peopleJsonString,People.class);
    System.out.println(people.getName()+" / "+people.getAge());
}
//@Test
public void testForObjectToJson() {
    People people = new People("Sean", 18, "male");
    // 不指定顺序 {"age":18,"name":"Sean","sex":"male"}
    String peopleJsonStr = JSONObject.toJSONString(people);
    System.out.println(peopleJsonStr);
    // 指定顺序类型 -    @JSONField(ordinal = 1)
    // Object 转换为Jsonobject
    JSONObject object = (JSONObject) JSONObject.toJSON(people);
    System.out.println(object.get("name")+" : "+object.get("age"));
}

数组相关

//@Test

public void testForArray() {
    // 转换为JsonObject
    String arrayJson = "[{\"age\":18,\"sex\":\"male\",\"name\":\"Sean\"},{\"age\":18,\"sex\":\"male\",\"name\":\"bruce\"},{\"age\":18,\"sex\":\"male\",\"name\":\"gogogo\"}]\n";
    JSONArray jsonArray = JSONObject.parseArray(arrayJson);
    System.out.println(jsonArray.get(1).toString());
    // 转换为ObjectArray
    List<People> peopleList = JSON.parseArray(arrayJson, People.class);
    People[] peopleArray = (People[])peopleList.toArray();
    // Array转变为List
    List<String> arrayList = Arrays.asList(new String[] {""});
}

    //@Test
    public void testForArrayJson() {
        People[] peopleArray = new People[3];
        peopleArray[0] = new People("Sean",18,"male");
        peopleArray[1] = new People("bruce",18,"male");
        peopleArray[2] = new People("gogogo",18,"male");
        String jsonString = JSONObject.toJSONString(peopleArray);
        System.out.println(jsonString);
    }

Map相关

// Map数据类型转换

//@Test
public void testForMap() {
    String mapString = "{\"sean\":\"hello\",\"bruce\":\"gogogo\"}";
    JSONObject jsonObject = JSONObject.parseObject(mapString);
    Map<String,Object> map = (Map<String, Object>)jsonObject;
}

    //@Test
    public void testForMapJson() {
        Map<String,String> map = new HashMap();
        map.put("sean", "hello");
        map.put("bruce", "gogogo");
        String jsonString = JSONObject.toJSONString(map);
        System.out.println(jsonString);
    }

复杂数据类型相关

// 复杂数据类型转换为JsonString字符串

//@Test
public void testForComplexObject() {
    String jsonString = JSONObject.toJSONString(new ComplexPeople());
    System.out.println(jsonString);
    JSONObject jsonObject = (JSONObject) JSONObject.toJSON(new ComplexPeople());
}
@Test
public void testForComplexJson() {
    String jsonString ="{\"list\":[\"ListValue1\",\"ListValue2\"],\"map\":{\"map2\":\"mapValue2\",\"map1\":\"mapValue1\"},\"name\":\"sean\",\"stringArray\":[\"stringValue1\",\"stringValue2\"]}";
    // 转换为ComplexPeople实体类
    ComplexPeople complexPeople = JSONObject.parseObject(jsonString,ComplexPeople.class);
    System.out.println("map2:"+complexPeople.getMap().get("map2"));
    System.out.println("stringArray:"+complexPeople.getStringArray().toString());

        // 转换为JsonObject
        JSONObject jsonObject = JSONObject.parseObject(jsonString);
    }

注意事项

所有需要Json转换的字段必须设置public, 或者设置public接口get/set方法.
忽略某些字段 & 输出Json顺序. 可以使用框架的@JsonField实现. @JSONField(ordinal = 1)/@JSONField(serialize = false)
其他Json标签.

Json必须有可以访问的缺省构造函数. 否则报告如下异常.

com.alibaba.fastjson.JSONException: default constructor not found. class com.yanxml.arsenal.java.json.pojo.People

at com.alibaba.fastjson.util.DeserializeBeanInfo.computeSetters(DeserializeBeanInfo.java:182)
at com.alibaba.fastjson.parser.ParserConfig.createJavaBeanDeserializer(ParserConfig.java:469)
at com.alibaba.fastjson.parser.ParserConfig.getDeserializer(ParserConfig.java:427)
at com.alibaba.fastjson.parser.ParserConfig.getDeserializer(ParserConfig.java:348)
at com.alibaba.fastjson.parser.DefaultJSONParser.parseObject(DefaultJSONParser.java:548)
at com.alibaba.fastjson.JSON.parseObject(JSON.java:250)
at com.alibaba.fastjson.JSON.parseObject(JSON.java:226)
at com.alibaba.fastjson.JSON.parseObject(JSON.java:185)
at com.alibaba.fastjson.JSON.parseObject(JSON.java:303

Reference

[1]. JAVA中使用alibaba fastjson实现JSONObject、Object、Json字符串的转换
[2]. 阿里FastJson常见类型解析
[3]. 使用FastJSON 对Map/JSON/String 进行互相转换
[4]. java对象转JSONObject
[5]. fastjson —JSONObject 和JSONArray 转换
[6]. Fastjson转换时，忽略某字段
[7]. 对象转json 方式方法与顺序问题