Java中json的生成和解析

盼盼盼231

1、json格式化工具 http://www.json.cn

1.fastjson List转JSONArray

List<T> list = new ArrayList<T>();
JSONArray array= JSONArray.parseArray(JSON.toJSONString(list))；

2.fastjson JSONArray转List

JSONArray array = new JSONArray();
List<EventColAttr> list = JSONObject.parseArray(array.toJSONString(), EventColAttr.class);

3.fastjson 字符串转List

String str = "";
List<T> list = JSONObject.parseArray(str,T.class);

4、gson 字符串转list,list转string

        String s = "[\"ff\",\"dwe\",\"好的\"]";
        Gson gson = new Gson();
        ArrayList arrayList = gson.fromJson(s, ArrayList.class);
        if (arrayList!=null && arrayList.size()>0) {
            String join = String.join(" ", arrayList);
            System.out.println("keywords_text is : "+join);
        }

2、生成json

（1）方法一：需要jar包：gson-2.8.2.jar

链接： https:// pan.baidu.com/s/1jLgB-l -UHxetmQ9Xtw6iZA 提取码：gapa

<1>生成json

package casia.cmp; import com.google.gson.JsonArray; import com.google.gson.JsonObject; public class TestJson { public static void main(String[] args) { //创建一个json对象，相当于一个容器，当然这个容器还可以套在另外一个容器里面，这个看业务需要 JsonObject jsonContainer =new JsonObject(); //为当前的json对象添加键值对 jsonContainer.addProperty("category", "nba"); jsonContainer.addProperty("team", "lakers"); //构建json数组，数组里面也是json JsonArray arrayPlayer = new JsonArray(); //构建json数组中的对象 JsonObject player1 = new JsonObject(); player1.addProperty("name", "kobe"); player1.addProperty("height", "198cm"); player1.addProperty("weight", "115kg"); JsonObject player2 = new JsonObject(); player2.addProperty("name", "fisher"); player2.addProperty("height", "183cm"); player2.addProperty("weight", "85kg"); //将json对象添加到数组中 arrayPlayer.add(player1); arrayPlayer.add(player2); //最后将json数组装到jsonContainer中 jsonContainer.add("player", arrayPlayer); System.out.println(jsonContainer); }

<2>根据对象生成json

构建一个Student类

package casia.cmp; public class Student { private String name; private int age; private String id; private String address; public Student() { public Student(String name, int age, String id, String address) { this.name = name; this.age = age; this.id = id; this.address = address;

实例化一个Student对象，将该对象的信息转为json字符串

package casia.cmp; import com.google.gson.Gson; import java.util.ArrayList; import java.util.List; public class Test { public static void main(String[] args) { Student student = new Student("cmp", 23, "1401104010076", "北京"); //对象转json Gson gson = new Gson(); String json = gson.toJson(student);//参数为object，所以也可以是一个map System.out.println(json);

（2）方法二：需要jar包：fastjson-1.2.41.jar

链接： https:// pan.baidu.com/s/1FNYw-v 3Vek4N_3-21g1URw 提取码：obnf

JSONObject jsonObject = new JSONObject(); jsonObject.put("f1", "xxx"); jsonObject.put("f2", "xxx"); String json = jsonObject.toJSONString(); JSONArray jsonArray = new JSONArray(); jsonArray.add(index,jsonObject);//json数组增加元素 jsonArray.add(index,jsonObject);//替换json数组中第index的元素

3、json解析

（1）方法一：需要jar包：gson-2.8.2.jar

json字符串转对象

//json转对象 Gson gson = new Gson(); Student student = gson.fromJson(jsonString, Student.class);

示例

package casia.cmp; import com.google.gson.Gson; public class Test { public static void main(String[] args) { String jsonString = "{\"name\":\"cmp\",\"age\":23,\"id\":\"1401104010076\",\"address\":\"北京\"}"; Gson gson = new Gson(); //json转对象 Student student = gson.fromJson(jsonString, Student.class); System.out.println(student);

json字符串转json对象/数组

JsonObject returnData = new JsonParser().parse(jsonString).getAsJsonObject(); JsonArray returnData = new JsonParser().parse(jsonString).getAsJsonArray(); String category = returnData.get("category").getAsString();

示例：

public static void main(String[] args) { String jsonString = "{\"category\":\"nba\",\"team\":\"lakers\",\"player\":[{\"name\":\"kobe\",\"height\":\"198cm\",\"weight\":\"115kg\"},{\"name\":\"fisher\",\"height\":\"183cm\",\"weight\":\"85kg\"}]}"; JsonObject returnData = new JsonParser().parse(jsonString).getAsJsonObject(); JsonElement category = returnData.get("category"); String asString = category.getAsString(); System.out.println("JsonElement category:" + category); System.out.println("JsonElement category to String :" + asString); JsonElement player1 = returnData.get("player");//获得元素 System.out.println("player1: " + player1); JsonArray asJsonArray = player1.getAsJsonArray();//转为json数组 System.out.println("asJsonArray: " + asJsonArray); JsonArray asJsonArray2 = returnData.getAsJsonArray("player");//获取key对应的value，并转为json数组 System.out.println("asJsonArray2: " + asJsonArray2); //asJsonArray和asJsonArray2等价 JsonElement jsonElement = asJsonArray2.get(0); JsonObject asJsonObject = jsonElement.getAsJsonObject(); System.out.println("asJsonObject: " + asJsonObject); System.out.println(asJsonObject.get("name")); }

（2）方法二：需要jar包：fastjson-1.2.41.jar

json字符串转json数组对象

String jsonArray = "[{"key1":"value1"},{"key2":"value2"},{"key3":"value3"},{"key4":"value4"},{"key5":"value5"}]" String jsonString ="{\"category\":\"nba\",\"team\":\"lakers\",\"player\":[{\"name\":\"kobe\",\"height\":\"198cm\",\"weight\":\"115kg\"},{\"name\":\"fisher\",\"height\":\"183cm\",\"weight\":\"85kg\"}]}"; //转为json数组 JSONArray json = (JSONArray) JSONArray.parse(jsonArray.trim()); JSONObject jo = (JSONObject) json.get(int index);