How can I cast a JSONObject to a custom Java class?

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深忆病人
深忆病人 2021-02-12 15:42

In Java (using json-simple) I have successfully parsed a JSON string which was created in JavaScript using JSON.stringify. It looks like this:

{\"teq\":14567,\"         


        
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  • 2021-02-12 16:08

    Add dependency from https://github.com/google/gson and use it like

    Gson gson= new Gson();
    CustomPOJOClass obj = gson.fromJson(jsonObject.toString(),CustomPOJOClass.class);
    
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  • 2021-02-12 16:16

    There are lot of libraries that does this. This is my suggestion. Here you can find the library

    import com.google.gson.Gson; 
    

    and then do,

    Gson gson = new Gson();  
    Student student = gson.fromJson(jsonStringGoesHere, Student.class);  
    

    Maven Dependency

        <dependency>
            <groupId>com.google.code.gson</groupId>
            <artifactId>gson</artifactId>
            <version>2.2.4</version>
        </dependency>
    
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  • 2021-02-12 16:22

    UPDATE 1/9/2018

    Some years have passed since this (now popular) question was asked. While I still agree that json-simple was my need at the time, upon reflection I think the SO community is better served by having the "checkmark" next to the Jackson solution. I am un-accepting my own answer today; Jackson is pretty great!


    I think that this decent json-simple library is the victim of poor documentation. If you don't use the JSONParser (go figure!) but instead use this JSONValue.parse() method, it all works out like so:

        //JSONParser parser = new JSONParser(); // DON'T USE THIS
        Object obj = JSONValue.parse("A JSON string - array of objects: [{},{}] - goes here");
        JSONArray arrFilings = (JSONArray)obj;
        System.out.println("We can print one this way...");
        System.out.println(arrFilings.get(5) + "\n");
    
        System.out.println("We can enumerate the whole array...");
        for(Object objFiling : arrFilings){
            System.out.println(objFiling);
        }
        System.out.println("\n");
    
        System.out.println("We can access object properties this way...");
        for(Object objFiling : arrFilings){
            JSONObject o = (JSONObject)objFiling; // MUST cast to access .get()
            MyJSObject.fyq = o.get("fyq");
        }
        System.out.println("\n");
    

    Thanks to all those who posted. Sticking with json-simple was the question and this is the only json-simple answer to-date. Jackson DOES look slick, and Amazon uses it in their SDK for Java too, sooo.... if its good enough for AWS....

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  • 2021-02-12 16:27

    use jackson library

        //create ObjectMapper instance
        ObjectMapper objectMapper = new ObjectMapper();
    
        //convert json string to object
        Employee emp = objectMapper.readValue(jsonData, Employee.class); 
    
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  • 2021-02-12 16:28

    JSON string to Java Class ? you can trying fastjson:

    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>fastjson</artifactId>
        <version>1.1.41</version>
    </dependency>
    

    and using java code:

    MyCustomJSObject object = JSON.parseObject(jsonString,MyCustomJSObject.class); 
    
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