JSON 修改问题：浅拷贝 和 深拷贝

JSON 修改问题：浅拷贝 和 深拷贝

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import net.sf.json.JSONArray;
import net.sf.json.JSONObject;

public class JsonUpdateProblem {

// json 在 add 的时候，会被拷贝。
public static void main(String[] args) throws Exception {
jsonUpdate(args);
System.out.println();
System.out.println();
javaUpdate(args);
}

public static void jsonUpdate(String[] args) throws Exception {

String originJsonText = "[{\"name\": \"jinan\", \"gdp\": 123},{\"name\": \"qingdao\", \"gdp\": 456}]";
JSONArray citiesJsonArray = JSONArray.fromObject(originJsonText);

JSONObject jinanJson = citiesJsonArray.getJSONObject(0); // get 浅拷贝(共享)
System.out.println("jinan origin << " + jinanJson);
System.out.println("cities origin << " + citiesJsonArray);

System.out.println();
jinanJson.element("gdp", "321");
System.out.println("jinan changed >> " + jinanJson);
System.out.println("cities changed ? >> " + citiesJsonArray); // true


System.out.println();
JSONObject hezeJson = JSONObject.fromObject("{\"name\": \"heze\", \"gdp\": 789}");
citiesJsonArray.add(hezeJson); // add 深拷贝（复制）
System.out.println("cities after heze added >> " + citiesJsonArray);

System.out.println();
hezeJson.element("gdp", 987);
System.out.println("heze updated >> " + hezeJson);
System.out.println("cities after heze updated ? >> " + citiesJsonArray); // false

// [{"name":"jinan","gdp":"321"},{"name":"qingdao","gdp":456},{"name":"heze","gdp":789}]
// heze 数据依然是 789，并没有发生变化。这种特性跟JAVA对象是不一样的。
}

public static void javaUpdate(String[] args) throws Exception {

List<City> cities = new ArrayList<>(Arrays.asList(new City("jinan", 123), (new City("qingdao", 456))));
City jinan = cities.get(0); // get 浅拷贝 （共享）
System.out.println("jinan origin << " + jinan);
System.out.println("cities origin << " + cities);


System.out.println();
jinan.setGdp(321);
System.out.println("jinan changed >> " + jinan);
System.out.println("cities changed ? >> " + cities); // true

System.out.println();
City heze = new City("heze", 789);
cities.add(heze); // add 浅拷贝（共享）
System.out.println("cities after heze added >> " + cities);

System.out.println();
heze.setGdp(987);
System.out.println("heze updated >> " + heze);
System.out.println("cities after heze updated ? >> " + cities); // true
// [City [name=jinan, gdp=321], City [name=qingdao, gdp=456], City [name=heze, gdp=987]]
// heze 数据被一同修改成 987
}


static class City {
private String name;
private Integer gdp;

public City(String name, Integer gdp) {
super();
this.name = name;
this.gdp = gdp;
}

public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public Integer getGdp() {
return gdp;
}
public void setGdp(Integer gdp) {
this.gdp = gdp;
}

@Override
public String toString() {
return "City [name=" + name + ", gdp=" + gdp + "]";
}

}

}

JSON-lib

1. <dependencies>  
2. <span style="white-space:pre">    </span><dependency>  
3.      <span style="white-space:pre">   </span><groupId>net.sf.json-lib</groupId>  
4.         <artifactId>json-lib</artifactId>  
5.         <version>2.4</version>  
6.         <classifier>jdk15</classifier>    
7.     </dependency>  
8. </dependencies>