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Converting JSON to Java

I want to be able to access properties from a JSON string within my Java action method. The string is available by simply saying myJsonString = object.getJson(). Below is an example of what the string can look like:


{
    "title": "ComputingandInformationsystems",
    "id": 1,
    "children": "true",
    "groups": [{
        "title": "LeveloneCIS",
        "id": 2,
        "children": "true",
        "groups": [{
            "title": "IntroToComputingandInternet",
            "id": 3,
            "children": "false",
            "groups": []
        }]
    }]
}


In this string every JSON object contains an array of other JSON objects. The intention is to extract a list of IDs where any given object possessing a group property that contains other JSON objects. I looked at Google"s Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

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I looked at Google's Gson as a potential JSON plugin. Can anyone offer some form of guidance as to how I can generate Java from this JSON string?

Google Gson supports generics and nested beans. The [] in JSON represents an array and should map to a Java collection such as List or just a plain Java array. The {} in JSON represents an object and should map to a Java Map or just some JavaBean class.

You have a JSON object with several properties of which the groups property represents an array of nested objects of the very same type. This can be parsed with Gson the following way:


package com.kodetalk;

import java.util.List;
import com.google.gson.Gson;

public class Test {

    public static void main(String... args) throws Exception {
        String json =
            "{"
                + "'title': 'Computing and Information systems',"
                + "'id' : 1,"
                + "'children' : 'true',"
                + "'groups' : [{"
                    + "'title' : 'Level one CIS',"
                    + "'id' : 2,"
                    + "'children' : 'true',"
                    + "'groups' : [{"
                        + "'title' : 'Intro To Computing and Internet',"
                        + "'id' : 3,"
                        + "'children': 'false',"
                        + "'groups':[]"
                    + "}]"
                + "}]"
            + "}";

        // Now do the magic.
        Data data = new Gson().fromJson(json, Data.class);

        // Show it.
        System.out.println(data);
    }

}

class Data {
    private String title;
    private Long id;
    private Boolean children;
    private List<Data> groups;

    public String getTitle() { return title; }
    public Long getId() { return id; }
    public Boolean getChildren() { return children; }
    public List<Data> getGroups() { return groups; }

    public void setTitle(String title) { this.title = title; }
    public void setId(Long id) { this.id = id; }
    public void setChildren(Boolean children) { this.children = children; }
    public void setGroups(List<Data> groups) { this.groups = groups; }

    public String toString() {
        return String.format("title:%s,id:%d,children:%s,groups:%s", title, id, children, groups);
    }
}

See also:


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