jackson读写json

╰+哭是因爲堅強的太久メ 2022-06-16 01:52 201阅读 0赞

之前用的gson，尽管很方便，但是今天公司项目要求用jackson，快速学习一下  
**一.快速读、写：**  
**参考：[http://www.hankcs.com/program/java-object-to-json-demo.html][http_www.hankcs.com_program_java-object-to-json-demo.html]**

public class Main
    {
    
        public static void main(String[] args)
        {
            ObjectMapper mapper = new ObjectMapper(); // can reuse, share globally
            try
            {
                // 读取JSON数据
                Map<String,Object> userData = mapper.readValue(new File("user.json"), Map.class);
                System.out.println(userData);
                // 写入JSON数据
                userData = new HashMap<String,Object>();
                Map<String,String> nameStruct = new HashMap<String,String>();
                nameStruct.put("first", "Joe");
                nameStruct.put("last", "Hankcs");
                userData.put("name", nameStruct);
                userData.put("gender", "MALE");
                userData.put("verified", Boolean.FALSE);
                userData.put("userImage", "Rm9vYmFyIQ==");
                mapper.writeValue(new File("user-modified.json"), userData);
            } catch (IOException e)
            {
                e.printStackTrace();
            }
        }
    }

结果输出：

{
       name={
       first=Joe, last=Sixpack}, gender=MALE, verified=false, userImage=Rm9vYmFyIQ==}
    {
       "verified":false,"name":{
       "last":"Hankcs","first":"Joe"},"userImage":"Rm9vYmFyIQ==","gender":"MALE"}

**二.对象–json**

String json=mapper.writeValueAsString(user); //将对象转换成json

**三.json–map**

Map m = (Map) mapper.readValue(json, Map.class); //json转换成map

**四.map–json**

json=mapper.writeValueAsString(m); //map转json

**五.json–对象**

User u=(User) mapper.readValue(json, User.class); //json转java对象。

[http_www.hankcs.com_program_java-object-to-json-demo.html]: http://www.hankcs.com/program/java-object-to-json-demo.html