1.json简单介绍
1.1 json是最流行和广泛通用的数据传输格式,简称JavaScript Object Notation,最早在JavaScript中使用.
1.2 举个例子,下面是一个json对象,名字叫王尼玛,他有两个粉丝组成数组,一个叫小王,一个叫小尼玛:
{
"name":"王尼玛",
"fans":[{
"name":"小王",
"age":"7"
},{
"name":"小尼玛",
"age":"10"
}]
}
2.json数据生成和解析
2.1 关于json处理的包有好几类,开源jackson,谷歌Gson,阿里巴巴的Fastjson.Gson功能强大,但是Fastjson性能更快.如何选择见仁见智就行
2.2 这里我开始都是用org.json,后面为了演示复杂json转java bean又导入了功能强大的Gjson,先附上两个maven依赖:
<!-- https://mvnrepository.com/artifact/org.json/json -->
<dependency>
<groupId>org.json</groupId>
<artifactId>json</artifactId>
<version>20160810</version>
</dependency>
<!-- https://mvnrepository.com/artifact/com.google.code.gson/gson -->
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.7</version>
</dependency>
2.3 json数据的生成,也就是各种类型转json.(String,map和java bean)
DemoCreateJson.java
import org.json.JSONObject;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map; /**
* Created by garfield on 2016/10/16.
* 举三种创建json的例子
*/
public class DemoCreateJson {
public static void main(String[] args) {
StringCreateJson();
mapCreateJson();
beanCreateJson();
}
//String创建json
/**
* {
"name":"王尼玛",
"fans":[{
"name":"小王",
"age":"7"
},{
"name":"小尼玛",
"age":"10"
}]
}
*/
static void StringCreateJson(){
JSONObject jsonObject = new JSONObject();
jsonObject.put("name","王尼玛"); //粉丝是个数组,其实就是嵌套json
JSONObject jsonObject1 = new JSONObject();
jsonObject1.put("name","小王");
jsonObject1.put("age",7); JSONObject jsonObject2 = new JSONObject();
jsonObject2.put("name","小尼玛");
jsonObject2.put("age",10); //从此处可以看出其实list和json也是互相转换的
List<JSONObject> jsonObjects = new ArrayList<JSONObject>();
jsonObjects.add(jsonObject1);
jsonObjects.add(jsonObject2);
jsonObject.put("fans",jsonObjects); System.out.println("jsonObject直接创建json:" + jsonObject);
}
//第二种方法,用map方式
static void mapCreateJson(){
Map<String,Object> map = new HashMap<String,Object>();
map.put("name","王尼玛");
Map<String,Object> map1 = new HashMap<String,Object>();
map1.put("name","小王");
map1.put("age",7);
Map<String,Object> map2 = new HashMap<String,Object>();
map2.put("name","小尼玛");
map2.put("age",10);
List<Map> jsonObjects = new ArrayList<Map>();
jsonObjects.add(map1);
jsonObjects.add(map2);
map.put("fans",jsonObjects);
System.out.println("集合中Map创建json对象:" + new JSONObject(map));
}
//第三种,也是比较常用的,用bean转换,(这里用的是map作为子json,如果必须要创建复杂bean对象,建议用Gjson操作)
static void beanCreateJson(){
Actor actor = new Actor();
actor.setName("王尼玛");
Map<String,Object> map1 = new HashMap<String,Object>();
map1.put("name","小王");
map1.put("age",7);
Map<String,Object> map2 = new HashMap<String,Object>();
map2.put("name","小尼玛");
map2.put("age",10);
List<Map> maps = new ArrayList<Map>();
maps.add(map1);
maps.add(map2);
actor.setFans(maps);
System.out.println("java bean创建json对象:" + new JSONObject(actor));
}
}
2.3.1上面类缺少基本bean
Actor.java
import java.util.List;
import java.util.Map; /**
* Created by garfield on 2016/10/16.
*/
public class Actor {
private String name;
private List<Map> fans; public String getName() {
return name;
} public void setName(String name) {
this.name = name;
} public List<Map> getFans() {
return fans;
} public void setFans(List<Map> fans) {
this.fans = fans;
} }
2.4 json的解析,这里写了两种解析方式,同样,比较常用的还是第二种,json转java bean
DemoParseJson.java
import com.google.gson.*;
import org.json.JSONObject; import java.util.Map; /**
* Created by garfield on 2016/10/16.
*/
public class DemoParseJson {
public static void main(String[] args) {
String jsonString = "{\"fans\":[{\"name\":\"小王\",\"age\":7},{\"name\":\"小尼玛\",\"age\":10}],\"name\":\"王尼玛\"}";
normalParse(jsonString);
beanParse(jsonString);
}
static void normalParse(String jsonString){
JSONObject jsonObject = new JSONObject(jsonString);
//获取普通属性
System.out.println("姓名:");
System.out.println(" " + jsonObject.getString("name"));
//获取数组
System.out.println("粉丝:");
for (Object fan : jsonObject.getJSONArray("fans")) {
JSONObject object = (JSONObject)fan;
System.out.println(" 姓名:" + object.get("name") + ",年龄:" + object.get("age"));
}
}
//org.json并不支持这种复杂的bean转换,所以这边又导入了gson的包
static void beanParse(String jsonString){
System.out.println("=========Gson解析=========");
JsonObject obj = new JsonParser().parse(jsonString).getAsJsonObject();
Actor actor = new Gson().fromJson(obj,Actor.class);
System.out.println("姓名:");
System.out.println(" " + obj.get("name"));
System.out.println("粉丝:");
for (Map map : actor.getFans()) {
System.out.println(" 姓名:" + map.get("name") + "年龄:" + map.get("age"));
}
}
}
2.4.1顺便附上执行结果:
姓名:
王尼玛
粉丝:
姓名:小王,年龄:7
姓名:小尼玛,年龄:10
=========Gson解析=========
姓名:
"王尼玛"
粉丝:
姓名:小王年龄7.0
姓名:小尼玛年龄10.0
ok,that's it...