FastJson、Gson对json解析详解

青旅半醒 2022-05-15 03:16 299阅读 0赞

现在主流的对json解析比较流行的主要是**ali的FastJson和google的Gson**

# 一、FastJson #

git地址：[fastjson][]

maven：[fastjson][fastjson 1]

主要的类是：

JSON

JSONObject：fastjson提供的json对象

JSONArray：fastjson提供的json数组对象

## 序列化 ##

User user = new User();
    user.setName("xl");
    user.setAddr("hangzhou");
    
    Role role = new Role();
    role.setMemo("all");
    role.setRoleName("admin");
    
    user.setRole(role);

例1.将javaBean转json

String userStr = com.alibaba.fastjson.JSONObject.toJSONString(user);
    System.out.println("user:"+userStr);

user:{"addr":"hangzhou","name":"xl","role":{"memo":"all","roleName":"admin"}}

例2.将map转json

Map<String,Object> map = new HashMap<String,Object>();
    map.put("a", "1");
    map.put("b", "2");
    map.put("c", "3");
    String mapStr = com.alibaba.fastjson.JSONObject.toJSONString(map);
    System.out.println("mapStr:"+mapStr);

mapStr:{"a":"1","b":"2","c":"3"}

例3.将List<javaBean>转json

List<User> users = new ArrayList<User>();
    users.add(user);
    users.add(user);
    String userListStr = JSONObject.toJSONString(users);
    System.out.println("userListStr:"+userListStr);

userListStr:[{"addr":"hangzhou","name":"xl","role":{"memo":"all","roleName":"admin"}},
    {"$ref":"$[0]"}]

这里可以设置格式化显示：

List<User> users = new ArrayList<User>();
    users.add(user);
    users.add(user);
    String userListStr = JSONArray.toJSONString(users,true);
    System.out.println("userListStr:"+userListStr);

userListStr:[
    	{
    		"addr":"hangzhou",
    		"name":"xl",
    		"role":{
    			"memo":"all",
    			"roleName":"admin"
    		}
    	},
    	{"$ref":"$[0]"}
    ]

例4.将List<Map>转json

List<Map<String,Object>> mapList = new ArrayList<Map<String,Object>>();
    mapList.add(map);
    mapList.add(map);
    String mapListStr = com.alibaba.fastjson.JSONObject.toJSONString(mapList);
    System.out.println("mapListStr:"+mapListStr);

mapListStr:[{"a":"1","b":"2","c":"3"},{"$ref":"$[0]"}]

## 反序列化 ##

例5.将json转javaBean

String userJsonStr = "{\"addr\":\"hangzhou\",\"name\":\"xl\",
    \"role\":{\"memo\":\"all\",\"roleName\":\"admin\"}}";
    
    User userTmp = JSONObject.parseObject(userJsonStr,User.class);
    System.out.println(userTmp.toString());

例6.将json转map

String mapStr = "{\"a\":\"1\",\"b\":\"2\",\"c\":\"3\"}";
    Map<String,Object> map = JSONObject.parseObject(mapStr);
    System.out.println("mapStr:"+map.get("a"));
    System.out.println("mapStr:"+map.get("b"));
    System.out.println("mapStr:"+map.get("c"));

mapStr:1
    mapStr:2
    mapStr:3

例7.将json转List<javaBean>

采用TypeReference

String jsonArrs = "[{\"addr\":\"hangzhou\",\"name\":\"xl\",
    \"role\":{\"memo\":\"all\",\"roleName\":\"admin\"}},
    {\"addr\":\"hangzhou\",\"name\":\"xl\",
    \"role\":{\"memo\":\"all\",\"roleName\":\"admin\"}}]";
    List<User> userJsons = JSONArray.parseArray(jsonArrs,User.class);
    System.out.println("[userJsons]:"+userJsons);
    
    List<User> userList = JSONArray.parseObject(jsonArrs, 
    new com.alibaba.fastjson.TypeReference<ArrayList<User>>(){});
    System.out.println("[userJsons]:"+userList);

例8.将json转List<Map>

String mapStr = "[{\"a\":\"1\",\"b\":\"2\",\"c\":\"3\"},{\"a\":\"1\",\"b\":\"2\",\"c\":\"3\"}]";
    List<Map> maps = JSON.parseArray(mapStr,Map.class);
    for(Map map : maps){
    	System.out.println("mapStr:"+map.get("a"));
    	System.out.println("mapStr:"+map.get("b"));
    	System.out.println("mapStr:"+map.get("c"));
    }

# 二、Gson #

git地址：[gson][]

maven：[gson][gson 1]

主要类：

Gson

## 序列化 ##

例1.将javabean转json

User user = new User();
    
    user.setName("xl");
    user.setAddr("hangzhou");
    Role role = new Role();
    role.setMemo("all");
    role.setRoleName("admin");
    user.setRole(role);
    
    Gson gson = new Gson();
    
    String userStr = gson.toJson(user);
    System.out.println(userStr);

{"name":"xl","addr":"hangzhou","role":{"roleName":"admin","memo":"all"}}

例2.将List<javaBean>转json

List<User> users = new ArrayList<User>();
    users.add(user);
    users.add(user);
    users.add(user);
    
    String usersStr = gson.toJson(users);
    System.out.println(usersStr);

[{"name":"xl","addr":"hangzhou","role":{"roleName":"admin","memo":"all"}},
    {"name":"xl","addr":"hangzhou","role":{"roleName":"admin","memo":"all"}},
    {"name":"xl","addr":"hangzhou","role":{"roleName":"admin","memo":"all"}}]

例3.将map转json

Map<String,String> map = new HashMap<String,String>();
    map.put("a", "1");
    map.put("b", "2");
    map.put("c", "3");
    
    String mapStr = gson.toJson(map);
    System.out.println(mapStr);

{"a":"1","b":"2","c":"3"}

例4.将List<Map>转json

List<Map<String,String>> maps = new ArrayList<Map<String,String>>();
    maps.add(map);
    maps.add(map);
    System.out.println(gson.toJson(maps));

[{"a":"1","b":"2","c":"3"},{"a":"1","b":"2","c":"3"}]

## 反序列化 ##

例5.将json转javaBean

String objStr = "{\"name\":\"xl\",\"addr\":\"hangzhou\",
        \"role\":{\"roleName\":\"admin\",\"memo\":\"all\"}}";
    java.lang.reflect.Type type = new com.google.gson.reflect.TypeToken<User>(){}.getType();
    
    User u = gson.fromJson(objStr, type);
    System.out.println(u.getAddr());
    System.out.println(u.getName());

例6.将json转List<javaBean>

String objStr = "[{\"name\":\"xl\",\"addr\":\"hangzhou\",
    \"role\":{\"roleName\":\"admin\",\"memo\":\"all\"}},
    {\"name\":\"xl\",\"addr\":\"hangzhou\",
    \"role\":{\"roleName\":\"admin\",\"memo\":\"all\"}}]";
    java.lang.reflect.Type type = 
            new com.google.gson.reflect.TypeToken<ArrayList<User>>(){}.getType();
    
    List<User> list = gson.fromJson(objStr, type);
    for(User u : list){
    	System.out.println(u.getAddr());
    	System.out.println(u.getName());
    }

例7.将json转map

String mapGson = "{\"a\":\"1\",\"b\":\"2\",\"c\":\"3\"}";
    java.lang.reflect.Type mapType = 
    new com.google.gson.reflect.TypeToken<Map<String,String>>(){}.getType(); 
    
    Map<String,String> mapGsonStr = gson.fromJson(mapGson, mapType);
    System.out.println(mapGsonStr.get("a"));
    System.out.println(mapGsonStr.get("b"));
    System.out.println(mapGsonStr.get("c"));

例8.将json转List<Map>

String mapListGson = "[{\"a\":\"1\",\"b\":\"2\",\"c\":\"3\"},"
    		+ "{\"a\":\"1\",\"b\":\"2\",\"c\":\"3\"}]";
    // 借助于java.lang.reflect.Type
    java.lang.reflect.Type mapListType = 
        new com.google.gson.reflect.TypeToken<List<Map<String,String>>>(){}.getType(); 
    List<Map<String,String>> mapGsonStr = gson.fromJson(mapListGson, mapListType);
    for(Map<String,String> map : mapGsonStr){
    	System.out.println(map.get("a"));
    	System.out.println(map.get("b"));
    	System.out.println(map.get("c"));
    }

[fastjson]: https://github.com/alibaba/fastjson
[fastjson 1]: http://mvnrepository.com/artifact/com.alibaba/fastjson
[gson]: https://github.com/google/gson
[gson 1]: http://mvnrepository.com/artifact/com.google.code.gson/gson