Java Json 序列化与反序列化

JSON(JavaScript Object Notation) 是一种轻量级的数据交换格式。 易于人阅读和编写。同时也易于机器解析和生成。 它基于JavaScript Programming Language, Standard ECMA-262 3rd Edition - December 1999的一个子集。 JSON采用完全独立于语言的文本格式，这些特性使JSON成为理想的数据交换语言。

下面介绍两款自己在开发中常用的处理Json的Java开源类库：Gson和Fastjson

1、Gson

Gson is a Java library that can be used to convert Java Objects into their JSON representation. It can also be used to convert a JSON string to an equivalent Java object. Gson can work with arbitrary Java objects including pre-existing objects that you do not have source-code of.

Gson官网：http://code.google.com/p/google-gson/

Gson User Guide：https://sites.google.com/site/gson/gson-user-guide

2、Fastjson

Fastjson是一个json处理工具包，由阿里巴巴公司开发，包括“序列化”和“反序列化”两部分，它具备如下特征：

1. 速度最快，测试表明，fastjson具有极快的性能，超越任其他的java json parser。包括自称最快的jackson。
2. 功能强大，完全支持java bean、集合、Map、日期、Enum，支持范型，支持自省。
3. 无依赖，能够直接运行在Java SE 5.0以上版本
4. 支持Android。
5. 开源 (Apache 2.0)

Fastjson 官网：http://code.alibabatech.com/wiki/display/FastJSON/Overview

下面通过一个简单Demo，对比两者 序列化与反序列化的用法

JavaBean实体Person

package com.example.testjson.entity; 

import java.util.Date;
import java.util.List;
import java.util.Map; 

public class Person {
    private String name;
    private FullName fullName;
    private int age;
    private Date birthday;
    private List<String> hobbies;
    private Map<String, String> clothes;
    private List<Person> friends; 

    public String getName() {
        return name;
    } 

    public void setName(String name) {
        this.name = name;
    } 

    public FullName getFullName() {
        return fullName;
    } 

    public void setFullName(FullName fullName) {
        this.fullName = fullName;
    } 

    public int getAge() {
        return age;
    } 

    public void setAge(int age) {
        this.age = age;
    } 

    public Date getBirthday() {
        return birthday;
    } 

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    } 

    public List<String> getHobbies() {
        return hobbies;
    } 

    public void setHobbies(List<String> hobbies) {
        this.hobbies = hobbies;
    } 

    public Map<String, String> getClothes() {
        return clothes;
    } 

    public void setClothes(Map<String, String> clothes) {
        this.clothes = clothes;
    } 

    public List<Person> getFriends() {
        return friends;
    } 

    public void setFriends(List<Person> friends) {
        this.friends = friends;
    } 

    @Override
    public String toString() {
        String str= "Person [name=" + name + ", fullName=" + fullName + ", age="
                + age + ", birthday=" + birthday + ", hobbies=" + hobbies
                + ", clothes=" + clothes +  "]\n";
        if(friends!=null){
            str+="Friends:\n";
            for (Person f : friends) {
                str+="\t"+f;
            }
        }
        return str;
    } 

} 

class FullName {
    private String firstName;
    private String middleName;
    private String lastName; 

    public FullName(){
    } 

    public FullName(String firstName, String middleName, String lastName) {
        super();
        this.firstName = firstName;
        this.middleName = middleName;
        this.lastName = lastName;
    } 

    public String getFirstName() {
        return firstName;
    } 

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    } 

    public String getMiddleName() {
        return middleName;
    } 

    public void setMiddleName(String middleName) {
        this.middleName = middleName;
    } 

    public String getLastName() {
        return lastName;
    } 

    public void setLastName(String lastName) {
        this.lastName = lastName;
    } 

    @Override
    public String toString() {
        return "[firstName=" + firstName + ", middleName="
                + middleName + ", lastName=" + lastName + "]";
    } 

}

负责创建Person的Bean Factory

package com.example.testjson.entity; 

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

public class PersonFactory { 

    private static Person createABSPerson(String name,List<Person> friends) {
        Person newPerson = new Person();
        newPerson.setName(name);
        newPerson.setFullName(new FullName(name+"_first", name+"_middle", name+"_last"));
        newPerson.setAge(24);
        List<String> hobbies=new ArrayList<String>();
        hobbies.add("篮球");
        hobbies.add("游泳");
        hobbies.add("coding");
        newPerson.setHobbies(hobbies);
        Map<String,String> clothes=new HashMap<String, String>();
        clothes.put("coat", "Nike");
        clothes.put("trousers", "adidas");
        clothes.put("shoes", "安踏");
        newPerson.setClothes(clothes);
        newPerson.setFriends(friends);
        return newPerson;
    } 

    public static Person create(String name){
        List<Person> friends=new ArrayList<Person>();
        friends.add(createABSPerson("小明",null));
        friends.add(createABSPerson("Tony",null));
        friends.add(createABSPerson("陈小二",null)); 

        return createABSPerson(name,friends);
    }
}

GSON工具类

package com.example.testjson.gson; 

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonElement;
import com.google.gson.JsonParser; 

public class GsonUtil {
private static Gson gson = new GsonBuilder().create(); 

    public static String bean2Json(Object obj){
        return gson.toJson(obj);
    } 

    public static <T> T json2Bean(String jsonStr,Class<T> objClass){
        return gson.fromJson(jsonStr, objClass);
    } 

    public static String jsonFormatter(String uglyJsonStr){
        Gson gson = new GsonBuilder().setPrettyPrinting().create();
        JsonParser jp = new JsonParser();
        JsonElement je = jp.parse(uglyJsonStr);
        String prettyJsonString = gson.toJson(je);
        return prettyJsonString;
    }
}

Fastjson工具类FastJsonUtil

package com.example.testjson.fastjson; 

import com.alibaba.fastjson.JSON; 

public class FastJsonUtil { 

    public static String bean2Json(Object obj){
        return JSON.toJSONString(obj);
    } 

    public static <T> T json2Bean(String jsonStr,Class<T> objClass){
        return JSON.parseObject(jsonStr, objClass);
    }
}

最后两个测试类

GsonTest

package com.example.testjson; 

import com.example.testjson.entity.Person;
import com.example.testjson.entity.PersonFactory;
import com.example.testjson.gson.GsonUtil; 

public class GsonTest { 

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Person p = PersonFactory.create("Kobe");
        String json = GsonUtil.bean2Json(p);
        String prettyJsonString = GsonUtil.jsonFormatter(json); 

        System.out.println("FastJson Serializing="+json);
        System.out.println("FastJson Serializing PrettyPrinting="+prettyJsonString); 

        Person newPerson = GsonUtil.json2Bean(json, Person.class); 

        System.out.println("FastJson Deserializing="+newPerson);
    } 

}

FastJsonTest

package com.example.testjson; 

import com.example.testjson.entity.Person;
import com.example.testjson.entity.PersonFactory;
import com.example.testjson.fastjson.FastJsonUtil; 

public class FastJsonTest { 

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub 

        Person p = PersonFactory.create("Kobe");
        String json = FastJsonUtil.bean2Json(p); 

        System.out.println("FastJson Serializing="+json); 

        Person newPerson = FastJsonUtil.json2Bean(json, Person.class); 

        System.out.println("FastJson Deserializing="+newPerson);
    } 

}