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

ゝ一纸荒年。 2023-02-23 09:27 1阅读 0赞

### 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`.  
    ![在这里插入图片描述][20200707010116889.png]
 *  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][JAVA_alibaba fastjson_JSONObject_Object_Json]  
\[2\]. [阿里FastJson常见类型解析][FastJson]  
\[3\]. [使用FastJSON 对Map/JSON/String 进行互相转换][FastJSON _Map_JSON_String]  
\[4\]. [java对象转JSONObject][java_JSONObject]  
\[5\]. [fastjson --JSONObject 和JSONArray 转换][fastjson --JSONObject _JSONArray]  
\[6\]. [Fastjson转换时，忽略某字段][Fastjson]  
\[7\]. [对象转json 方式方法与顺序问题][json]

[20200707010116889.png]: https://img-blog.csdnimg.cn/20200707010116889.png
[JAVA_alibaba fastjson_JSONObject_Object_Json]: https://blog.csdn.net/qq_29468573/article/details/82190005
[FastJson]: https://blog.csdn.net/Dota2_TA/article/details/89492506
[FastJSON _Map_JSON_String]: https://blog.csdn.net/liu59412/article/details/87935888
[java_JSONObject]: https://blog.csdn.net/qq_39705793/article/details/85161086
[fastjson --JSONObject _JSONArray]: https://www.cnblogs.com/paisen/p/5487138.html
[Fastjson]: https://blog.csdn.net/Ming_key/article/details/86554284
[json]: https://www.cnblogs.com/CAOXIAOYANG/p/10036571.html