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]()
- 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