生成和解析JSON
1.什么是JSON，JSON的作用是什么，如何编写JSON?
JSON(JavaScript Object Notation, JS 对象简谱) 是一种轻量级的数据交换格式。采用完全独立于编程语言的文本格式来存储和表示数据.
简洁和清晰的层次结构使得 JSON 成为理想的数据交换语言.
例如：
一个java对象转换成json对象以后是什么样子？
package com.wangxing.jsondemo1.bean;
public class Person {
private int perid;
private String pername;
private int perage;
private String peraddress;
public String getPeraddress() {
return peraddress;
}
public void setPeraddress(String peraddress) {
this.peraddress = peraddress;
}
public int getPerid() {
return perid;
}
public void setPerid(int perid) {
this.perid = perid;
}
public String getPername() {
return pername;
}
public void setPername(String pername) {
this.pername = pername;
}
public int getPerage() {
return perage;
}
public void setPerage(int perage) {
this.perage = perage;
}
}
//创建一个person类的对象
Person person1=new Person();
person1.setPerid(1001);
person1.setPername("zhangsan");
person1.setPerage(23);
person1.setPeraddress("西安");//将person1这个java对象转换成json对象对应的字符串数据
{"perid":1001,"pername":"zhangsan","perage":23,"peraddress":"西安"}
上面是将一个java对象写成json的样子。
假设现在有一组对象需要写成json的样子，那应该怎么写？
Person person1=new Person();
person1.setPerid(1001);
person1.setPername("zhangsan");
person1.setPerage(23);
person1.setPeraddress("西安");
Person person2=new Person();
person2.setPerid(1002);
person2.setPername("lisi");
person2.setPerage(24);
person2.setPeraddress("北京");
Person person3=new Person();
person3.setPerid(1003);
person3.setPername("wangwu");
person3.setPerage(25);
person3.setPeraddress("上海");//创建一个保存person对象的集合
List<Person> personlist=new ArrayList<Person>();//将上面创建的3个person对象保存到集合中
personlist.add(person1);
personlist.add(person2);
personlist.add(person3);将保存java对象的集合写成json的样子。
[
{"perid":1001,"pername":"zhangsan","perage":23,"peraddress":"西安"},
{"perid":1002,"pername":"lisi","perage":24,"peraddress":"北京"},
{"perid":1003,"pername":"wangwu","perage":25,"peraddress":"上海"}
]
注意:
- 用一组“{}”包围键/值对组合，键/值对组合中的键名写在前面并用双引号 "" 包裹，使用冒号 : 分隔，然后紧接着值，多个键/值对组合中间用“,”分隔,这就表示一个json对象。
- 用一组“[]”包围值/json对象这就表示一个json数组。json数组是用来保存java数组数据/集合数据。
- json对象中数字值和布尔值是不需要双引号。
通常情况下我们所遇到的json数据都是json对象中包含json数组，json数组中又包含json对象的复杂形式。
package com.wangxing.test2;
/**
* 保存地址信息的java类
* @author Administrator
*
*/
public class PersonAddress {
private String type; //地址类型【家庭/工作】
private String info; //地址信息
public String gettype(){
return type;
}
public void settype(String type){
this.type=type;
}
public String getinfo(){
return info;
}
public void setinfo(String info){
this.info=info;
}
}//创建三个person类的对象
Person person1=new Person();
person1.setPerid(1001);
person1.setPername("zhangsan");
person1.setPerage(23);
//创建保存地址信息的数组
PersonAddress peraddress[]=new PersonAddress[2];
//创建两个地址的对象
PersonAddress address1=new PersonAddress();
address1.setType("home");
address1.setInfo("西安");
PersonAddress address2=new PersonAddress();
address2.setType("work");
address2.setInfo("北京");
//将创建好的地址对象装入数组
peraddress[0]=address1;
peraddress[1]=address2;
person1.setPeraddress(peraddress);
Person person2=new Person();
person2.setPerid(1002);
person2.setPername("lisi");
person2.setPerage(24);
//创建保存地址信息的数组
PersonAddress peraddress2[]=new PersonAddress[2];
//创建两个地址的对象
PersonAddress address21=new PersonAddress();
address21.setType("home");
address21.setInfo("上海");
PersonAddress address22=new PersonAddress();
address22.setType("work");
address22.setInfo("重庆");
//将创建好的地址对象装入数组
peraddress2[0]=address21;
peraddress2[1]=address22;
person2.setPeraddress(peraddress2);
Person person3=new Person();
person3.setPerid(1003);
person3.setPername("wangwu");
person3.setPerage(25);
//创建保存地址信息的数组
PersonAddress peraddress3[]=new PersonAddress[2];
//创建两个地址的对象
PersonAddress address31=new PersonAddress();
address31.setType("home");
address31.setInfo("广州");
PersonAddress address32=new PersonAddress();
address32.setType("work");
address32.setInfo("西安");
//将创建好的地址对象装入数组
peraddress3[0]=address31;
peraddress3[1]=address32;
person3.setPeraddress(peraddress3);
//创建一个保存person对象的集合
List<Person> personlist=new ArrayList<Person>();
//将创建的person对象存储至集合中
personlist.add(person1);
personlist.add(person2);
personlist.add(person3);将上面的集合转换成json数据字符串以后是什么样子？？？
[
{ "perid":1001,
"pername":"zhangsan",
"perage":23,
"peraddress":[
{"type":"home","info":"西安"},
{"type":"work","info":"北京"}
]----json数组
}, -- json对象
{"perid":1002,
"pername":"lisi",
"perage":24,
"peraddress":[
{"type":"home","info":"上海"},
{"type":"work","info":"重庆"}
]
},
{"perid":1003,
"pername":"wangwu",
"perage":25,
"peraddress":[
{"type":"home","info":"广州"},
{"type":"work","info":"西安"}
]
}
当我们得到一个极其复杂的json数据后，搞不清楚这个json数据的结构。我们可以利用工具【https://www.json.cn/】得到明晰的json数据的结构。
2.JSON数据的生成方式和解析方式
2.1 JSON数据的生成【java对象---json数据】
1.json-simple-1.1.jar第三方的开发包生成json数据
package com.wangxing.jsondemo1.Helper;
import java.util.List;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import com.wangxing.jsondemo1.bean.Person;
import com.wangxing.jsondemo1.bean.PersonAddress;
public class JsonHelper {
/**
* 1.json-simple-1.1.jar第三方的开发包生成json数据
*/
public static String createJsonByjsonsimple(List<Person> personlist)throws Exception{
String jsoninfo="";
//创建json数组
JSONArray perlistarray=new JSONArray();
//便利集和得到person对象
for(Person person:personlist){
//创建JSON对象
JSONObject personObject=new JSONObject();
personObject.put("perid", person.getPerid());
personObject.put("pername", person.getPername());
personObject.put("perage", person.getPerage());
//创建保存personAddress对象JSONArray数组对象
JSONArray personAddressArray=new JSONArray();
for(PersonAddress peraddress:person.getPeraddress()){
//创建保存地址对象的json对象
JSONObject addressObject=new JSONObject();
addressObject.put("type", peraddress.getType());
addressObject.put("info", peraddress.getInfo());
personAddressArray.add(addressObject);
}
//将地址保存到person对象
personObject.put("peraddress", personAddressArray);
perlistarray.add(personObject);
}
jsoninfo=perlistarray.toJSONString();
return jsoninfo;
}
}2.gson-2.8.0.jar第三方的开发包生成json数据
package com.wangxing.jsondemo1.Helper;
import java.util.List;
import com.google.gson.Gson;
import com.wangxing.jsondemo1.bean.Person;
public class JsonHelper {
/**
* 2.gson-2.8.0.jar第三方的开发包生成json数据
*/
public static String createJsonBygson(List<Person> personlist){
String jsoninfo="";
jsoninfo=new Gson().toJson(personlist);
return jsoninfo;
}
}3.jackson第三方的开发包生成json数据
“jackson-core-2.9.5.jar”
“jackson-databind-2.9.5.jar”
“jackson-annotations-2.9.5.jar”
package com.wangxing.jsondemo1.Helper;
import java.util.List;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.wangxing.jsondemo1.bean.Person;
public class JsonHelper {
/**
* 3.jackson第三方的开发包生成JSON数据
*/
public static String createJsonByJackson(List<Person> personlist){
String jsoninfo="";
try {
jsoninfo=new ObjectMapper().writeValueAsString(personlist);
} catch (JsonProcessingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return jsoninfo;
}
}2.2JSON数据的解析【json数据---java对象】
1.json-simple-1.1.jar第三方的开发包解析json数据
package com.wangxing.jsondemo1.utils;
import java.util.ArrayList;
import java.util.List;
import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import com.wangxing.jsondemo1.bean.Person;
import com.wangxing.jsondemo1.bean.PersonAddress;
public class JsonUtils {
/**
* 1.json-simple-1.1.jar第三方的开发包解析json数据
*/
public static List<Person> parseJsonBysimple(String json)throws Exception{
List<Person> personlist = new ArrayList<Person>();
//创建一个json解析器对象
JSONParser jsonparser=new JSONParser();
//利用解析器将json解析为josn数组
JSONArray perlistArray = (JSONArray) jsonparser.parse(json);
for(int i=0;i<perlistArray.size();i++){
Person person = new Person();
//得到json里的第一层对象
JSONObject personObject = (JSONObject) perlistArray.get(i);
long id=(Long) personObject.get("perid");
int perid=(int)id;
person.setPerid(perid);
String pername=(String)personObject.get("pername");
person.setPername(pername);
long age=(long) personObject.get("perage");
int perage=(int)age;
person.setPerage(perage);
JSONArray addressArray=(JSONArray) personObject.get("peraddress");
//定义保存PersonAddress对象的数组
PersonAddress parAddressArray[]=new PersonAddress[addressArray.size()];
for(int j=0;j<addressArray.size();j++){
PersonAddress address=new PersonAddress();
//获得json里第二层对象
JSONObject addressObject=(JSONObject) addressArray.get(j);
String type=(String) addressObject.get("type");
String info=(String) addressObject.get("info");
address.setType(type);
address.setInfo(info);
parAddressArray[j]=address;
}
person.setPeraddress(parAddressArray);
personlist.add(person);
}
return personlist;
}
}测试：
package com.wangxing.jsondemo1.test;
import java.util.ArrayList;
import java.util.List;
import com.wangxing.jsondemo1.Helper.JsonHelper;
import com.wangxing.jsondemo1.bean.Person;
import com.wangxing.jsondemo1.bean.PersonAddress;
import com.wangxing.jsondemo1.utils.JsonUtils;
public class TestMain {
public static void main(String a[]) throws Exception{
Person person1=new Person();
person1.setPerid(1001);
person1.setPername("zhangsan");
person1.setPerage(23);
PersonAddress address1=new PersonAddress();
address1.setType("家庭");
address1.setInfo("北京");
PersonAddress address2=new PersonAddress();
address2.setType("学校");
address2.setInfo("西安");
PersonAddress addressarray[]=new PersonAddress[2];
addressarray[0]=address1;
addressarray[1]=address2;
person1.setPeraddress(addressarray);
Person person2 = new Person();
person2.setPerid(1002);
person2.setPername("lisi");
person2.setPerage(24);
PersonAddress address3 = new PersonAddress();
address3.setType("家庭");
address3.setInfo("广州");
PersonAddress address4 = new PersonAddress();
address4.setType("学校");
address4.setInfo("深圳");
PersonAddress addressarray2[] = new PersonAddress[2];
addressarray2[0] = address3;
addressarray2[1] = address4;
person2.setPeraddress(addressarray2);
List<Person> personlist = new ArrayList<Person>();
personlist.add(person1);
personlist.add(person2);
//解析json测试
String json=JsonHelper.createJsonByJackson(personlist);
List<Person> perlist=JsonUtils.parseJsonBysimple(json);
for(Person per:perlist){
PersonAddress array[]=per.getPeraddress();
System.out.println(per.getPerid()+" "+per.getPername()+" "+per.getPerage()
+" "+array[0].getType()+" "+array[0].getInfo()+" "+array[1].getType()+" "+array[1].getInfo());
}
}
}2.gson-2.8.0.jar第三方的开发包解析json数据
package com.wangxing.jsondemo1.utils;
import java.util.List;
import com.google.gson.Gson;
import com.google.gson.reflect.TypeToken;
import com.wangxing.jsondemo1.bean.Person;
public class JsonUtils {
/**
* 2.gson-2.8.0.jar第三方的开发包解析json数据
*/
public static List<Person> parseJsonByGson(String json)throws Exception{
Gson gson=new Gson();
return gson.fromJson(json, new TypeToken<List<Person>>(){}.getType());
}
}测试：
package com.wangxing.jsondemo1.test;
import java.util.ArrayList;
import java.util.List;
import com.wangxing.jsondemo1.Helper.JsonHelper;
import com.wangxing.jsondemo1.bean.Person;
import com.wangxing.jsondemo1.bean.PersonAddress;
import com.wangxing.jsondemo1.utils.JsonUtils;
public class TestMain {
public static void main(String a[]) throws Exception{
Person person1=new Person();
person1.setPerid(1001);
person1.setPername("zhangsan");
person1.setPerage(23);
PersonAddress address1=new PersonAddress();
address1.setType("家庭");
address1.setInfo("北京");
PersonAddress address2=new PersonAddress();
address2.setType("学校");
address2.setInfo("西安");
PersonAddress addressarray[]=new PersonAddress[2];
addressarray[0]=address1;
addressarray[1]=address2;
person1.setPeraddress(addressarray);
Person person2 = new Person();
person2.setPerid(1002);
person2.setPername("lisi");
person2.setPerage(24);
PersonAddress address3 = new PersonAddress();
address3.setType("家庭");
address3.setInfo("广州");
PersonAddress address4 = new PersonAddress();
address4.setType("学校");
address4.setInfo("深圳");
PersonAddress addressarray2[] = new PersonAddress[2];
addressarray2[0] = address3;
addressarray2[1] = address4;
person2.setPeraddress(addressarray2);
List<Person> personlist = new ArrayList<Person>();
personlist.add(person1);
personlist.add(person2);
//解析json测试
String json=JsonHelper.createJsonByJackson(personlist);
List<Person> perlist=JsonUtils.parseJsonByGson(json);
for(Person per:perlist){
PersonAddress array[]=per.getPeraddress();
System.out.println(per.getPerid()+" "+per.getPername()+" "+per.getPerage()
+" "+array[0].getType()+" "+array[0].getInfo()+" "+array[1].getType()+" "+array[1].getInfo());
}
}
}3.jackson第三方的开发包解析json数据
package com.wangxing.jsondemo1.utils;
import java.util.ArrayList;
import java.util.List;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.wangxing.jsondemo1.bean.Person;
import com.wangxing.jsondemo1.bean.PersonAddress;
public class JsonUtils {
/**
* 3.jackson第三方的开发包解析json数据
*/
public static List<Person> parseJsonByjackson(String json)throws Exception{
//创建保存数据的集和
List<Person> personlist = new ArrayList<Person>();
//创建解析器对象
ObjectMapper objectMapper = new ObjectMapper();
//创建保存json中第一层对象的数组[节点集和]
JsonNode personArray=objectMapper.readTree(json);
for(int i=0;i<personArray.size();i++){
Person person = new Person();
//从数组中获得节点对象
JsonNode personobj=personArray.get(i);
//利用节点对象获取 节点中的数据值
int perid=personobj.get("perid").asInt();
person.setPerid(perid);
String pername=personobj.get("pername").asText();
person.setPername(pername);
int perage=personobj.get("perage").asInt();
person.setPerage(perage);
//personlist.add(person);
//创建保存json中第二层对象的数组[节点集和]
JsonNode addressArray=personobj.get("peraddress");
PersonAddress perAddressArray[] = new PersonAddress[addressArray.size()];
for(int j=0;j<addressArray.size();j++){
PersonAddress address = new PersonAddress();
//从数组中得到节点对象
JsonNode addressObj=addressArray.get(j);
String type=addressObj.get("type").asText();
address.setType(type);
String info=addressObj.get("info").asText();
address.setInfo(info);
perAddressArray[j]=address;
}
person.setPeraddress(perAddressArray);
personlist.add(person);
}
return personlist;
}
}测试：
package com.wangxing.jsondemo1.test;
import java.util.ArrayList;
import java.util.List;
import com.wangxing.jsondemo1.Helper.JsonHelper;
import com.wangxing.jsondemo1.bean.Person;
import com.wangxing.jsondemo1.bean.PersonAddress;
import com.wangxing.jsondemo1.utils.JsonUtils;
public class TestMain {
public static void main(String a[]) throws Exception{
Person person1=new Person();
person1.setPerid(1001);
person1.setPername("zhangsan");
person1.setPerage(23);
PersonAddress address1=new PersonAddress();
address1.setType("家庭");
address1.setInfo("北京");
PersonAddress address2=new PersonAddress();
address2.setType("学校");
address2.setInfo("西安");
PersonAddress addressarray[]=new PersonAddress[2];
addressarray[0]=address1;
addressarray[1]=address2;
person1.setPeraddress(addressarray);
Person person2 = new Person();
person2.setPerid(1002);
person2.setPername("lisi");
person2.setPerage(24);
PersonAddress address3 = new PersonAddress();
address3.setType("家庭");
address3.setInfo("广州");
PersonAddress address4 = new PersonAddress();
address4.setType("学校");
address4.setInfo("深圳");
PersonAddress addressarray2[] = new PersonAddress[2];
addressarray2[0] = address3;
addressarray2[1] = address4;
person2.setPeraddress(addressarray2);
List<Person> personlist = new ArrayList<Person>();
personlist.add(person1);
personlist.add(person2);
//解析json测试
String json=JsonHelper.createJsonByJackson(personlist);
List<Person> perlist=JsonUtils.parseJsonByjackson(json);
for(Person per:perlist){
PersonAddress array[]=per.getPeraddress();
System.out.println(per.getPerid()+" "+per.getPername()+" "+per.getPerage()
+" "+array[0].getType()+" "+array[0].getInfo()+" "+array[1].getType()+" "+array[1].getInfo());
}
}
}