一分钟学会使用gson

标签：gson   java   json   arraylist   

Gson是一个超好用的json-对象相互转换的工具。如果您还没有，可以到这里去下载gson2.2.2.jar

首先准备两个类，如下：

public class One {
    int integer = 10;
    String a = null;
   Two comTwo = new Two();

   @Override
   public String toString() {
       return "integer: " + integer + "  ; a: " + a +"  ;  "+comTwo.toString() ;
   }
}

public static class Two {
        int twoINt;
        String twoStr;

        @Override
        public String toString() {
            // TODO Auto-generated method stub
            return "twoInt: " + twoINt + "  ; twoStr: " + twoStr;
        }

    }

new 一个One对象，将其转换为json：

<span style="color:#006600;">Gson gson = new Gson();
        One one = new One();
        String oneJstr = gson.toJson(one);
        System.out.println(oneJstr);</span>

结果为：

<span style="color:#006600;">{"integer":10,"comTwo":{"twoINt":0}}</span>

        Gson gson = new Gson();
        One one = new One();
        one.a = " zhang ting";
        String oneJstr = gson.toJson(one);
        System.out.println(oneJstr);

<span style="color:#990000;">{"integer":10,"a":" zhang ting","comTwo":{"twoINt":0}}</span>

        String js = "{\"integer\":10,\"comTwo\":{\"twoInt\":20}}";
        One oneObj = gson.fromJson(js, One.class);
        System.out.println(oneObj);

<span style="color:#006600;">integer: 10  ; a: null  ;  twoInt: 0  ; twoStr: null</span>

public static class OneChild extends One{
        String three = "i'm three ";
        List<String> list;
        List<CompObj> obList;
        public OneChild(){
            list = new ArrayList<String>();
            list.add("XXX");
            list.add("ting");
            obList = new ArrayList<CompObj>();
            CompObj d1 =  new CompObj();
            d1.data="good";
            CompObj d2 =  new CompObj();
            d2.data = "zhang";
            obList.add(d1);
            obList.add(d2);
        }
    }

public static class CompObj{
        String data = " comp obj";
        
    }

OneChild child = new OneChild();
        String thJstr = gson.toJson(child);
        System.out.println(thJstr);

<span style="color:#006600;">{"three":"i\u0027m three ","list":["XXX","ting"],"obList":[{"data":"good"},{"data":"zhang"}],"integer":10,"comTwo":{"twoINt":0}}</span>

Type listType = new TypeToken<List<String>>() {}.getType();
        List<String> target = new LinkedList<String>();
        target.add("blah");
        target.add("gao");
        target.add("zhang ting");

//        Gson gson = new Gson();
        String json = gson.toJson(target, listType);
        System.out.println(json);

<span style="color:#990000;">["blah","gao","zhang ting"]</span>

1、json数据中的key要和java对象中的变量名一致（区分大小写）

2、只有java对象有值（默认值都可以）才会转化到json数据中。

3、java对象中的变量不必和json数据中的key一一对应。

4、子类中找不到的变量会自动到父类中寻找。

一分钟学会使用gson

标签：gson   java   json   arraylist   

原文地址：http://blog.csdn.net/sun_star1chen/article/details/44086149