如何用gson将对象转换为json

如何用gson将对象转换为json

使用Google的Gson实现对象和json字符串之间的转换

需要gson-1.4.jar

1.JsonUtil.java

Java代码
package com.snail.json;

import java.lang.reflect.Type;
import com.google.gson.Gson;

public final class JsonUtil {

private JsonUtil(){}


public static String toJson(Object obj) {
Gson gson = new Gson();
return gson.toJson(obj);
}


public static T fromJson(String str, Type type) {
Gson gson = new Gson();
return gson.fromJson(str, type);
}


public static T fromJson(String str, Class type) {
Gson gson = new Gson();
return gson.fromJson(str, type);
}

}

2. Person.java

Java代码
package com.snail.json;

public class Person {
private int id;
private String name;

public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}

}

3. Test.java

Java代码
package com.snail.json;

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

import com.google.gson.reflect.TypeToken;

public class Test {


public static void objectToJson(){
Person person = new Person();
person.setId(1);
person.setName("one");
//javabean转换成json字符串
String jsonStr = JsonUtil.toJson(person);
System.out.println(jsonStr);

//json字符串转换成javabean
Person newPerson = JsonUtil.fromJson(jsonStr, Person.class);
System.out.println(person == newPerson);
System.out.println(newPerson.getId()+","+newPerson.getName());
}


public static void listToJson(){
Person person1 = new Person();
person1.setId(1);
person1.setName("one");

Person person2 = new Person();
person2.setId(2);
person2.setName("two");

List list = new ArrayList();
list.add(person1);
list.add(person2);

//javabean转换成json字符串
String jsonStr = JsonUtil.toJson(list);
System.out.println(jsonStr);

//json字符串转换成javabean对象
List rtn = JsonUtil.fromJson(jsonStr, new TypeToken>(){}.getType());
for(Person person : rtn){
System.out.println(person.getId()+","+person.getName());
}
}


public static void mapToJson(){
Person person1 = new Person();
person1.setId(1);
person1.setName("one");
Person person2 = new Person();
person2.setId(2);
person2.setName("two");

Map map = new HashMap();
map.put(person1.getId(), person1);
map.put(person2.getId(), person2);

//javabean转换成json字符串
String jsonStr = JsonUtil.toJson(map);
System.out.println(jsonStr);

//json字符串转换成Map对象
Map rtn = JsonUtil.fromJson(jsonStr, new TypeToken>(){}.getType());
for(Entry entry : rtn.entrySet()){
Integer key = entry.getKey();
Person newPerson = entry.getValue();
System.out.println("key:"+key+","+newPerson.getId()+","+newPerson.getName());
}
}

public static void main(String[] args) {
objectToJson();
System.out.println("****************************");
listToJson();
System.out.println("****************************");
mapToJson();
}

}

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