Unable to add array element under array using JSON

Question

I have to generate JSON in below sample format:

    [
    {   "roleName" : "Parent Folder", "folderId" : "role1", "expanded" : true, 
        "children" : 
                    [                                                                                                     
                      { "roleName" : "subUser1 non-openable folder", "folderId" : "role11","fileicon" : true },
                      { "roleName" : "subUser2", "folderId" : "role12", "expanded" : true, 
            "children" : 
                       [        
                          { "roleName" : "subUser2-1", "folderId" : "role121", "expanded" : true, "children" : 
                           [
                            { "roleName" : "subUser2-1-1 folder ico", "folderId" : "role1211" },
                            { "roleName" : "subUser2-1-2 file ico", "folderId" : "role1212" , "fileicon" : true}
                           ]
                          }
                      ]
                      }
                    ]
    }
 ]

I have created POJO for same and was able to add array elements in, but unable to add one more array inside or below the element. Please suggest.

below are the pojo I am using.

public class TargetFolder
{
    private TargetChildren[] children;

    private String roleName;

    private String expanded;

    private Long folderId;

    public TargetFolder(String roleName,
            String isFolder, Long folderId, TargetChildren[] folderList) {
        super();
        this.roleName = roleName;
        this.expanded = isFolder;
        this.folderId = folderId;
        this.children = folderList;
    }



    public TargetChildren[] getChildren ()
    {
        return children;
    }

    public void setChildren (TargetChildren[] children)
    {
        this.children = children;
    }

    public String getRoleName ()
    {
        return roleName;
    }

    public void setRoleName (String roleName)
    {
        this.roleName = roleName;
    }

    public String getExpanded ()
    {
        return expanded;
    }

    public void setExpanded (String expanded)
    {
        this.expanded = expanded;
    }

    public Long getFolderId ()
    {
        return folderId;
    }

    public void setFolderId (Long folderId)
    {
        this.folderId = folderId;
    }

    @Override
    public String toString()
    {
        return "ClassPojo [children = "+children+", roleName = "+roleName+", expanded = "+expanded+", folderId = "+folderId+"]";
    }
}

and

public class TargetChildren
{


    private String fileicon;

    private String roleName;

    private long folderId;


    public TargetChildren(String roleName, String fileicon, long folderId) {
        super();
        this.fileicon = fileicon;
        this.roleName = roleName;
        this.folderId = folderId;
    }


    public String getFileicon ()
    {
        return fileicon;
    }

    public void setFileicon (String fileicon)
    {
        this.fileicon = fileicon;
    }

    public String getRoleName ()
    {
        return roleName;
    }

    public void setRoleName (String roleName)
    {
        this.roleName = roleName;
    }

    public long getFolderId ()
    {
        return folderId;
    }

    public void setFolderId (long folderId)
    {
        this.folderId = folderId;
    }

    @Override
    public String toString()
    {
        return "ClassPojo [fileicon = "+fileicon+", roleName = "+roleName+", folderId = "+folderId+"]";
    }
}

and below is the logic I am using to generate the JSON:

for(int i  = 0; i<folderList.size();i++)
        {
            if(folderList!=null)
            {
                subList  = (List)folderList.get(i);
                childFolders[i] = new TargetChildren((String)subList.get(0),(String)subList.get(2),(Long)subList.get(1));
                JSONArray arr =  new JSONArray();
                if(((String)subList.get(2)).equals("true"))
                {
                    arr.put(i, childFolders[i]);
                }
                System.out.println(arr.toString());
                //TargetChildren [] testArr = new TargetChildren[] { new TargetChildren("Folder", "folderName", 226886843L)};
            }
        }
        TargetFolder targetFolder = new TargetFolder(parentFoldername,isFolder,folderId, childFolders);
        JSONObject jsonObject = new JSONObject(targetFolder);
        String jsonString = jsonObject.toString();
        System.out.println("JSON TO UI------ "+jsonString);

Answer 1

The most elegant and simple solution I can think of is adding a toJSON method to your POJOs and let it handle the serializing itself.

For the TargetFolder:

public JSONObject toJSON(){
    JSONObject out = new JSONObject();
    out.put("rolename", rolename);
    out.put("expanded", expanded);
    out.put("folderID", folderId);

    JSONArray children = new JSONArray();
    for(int i = 0; i < this.children.length; i++){
        children.push(this.children[i].toJSON());
    }
    out.put("children", children);

    return out;
}

Do the same for the TargetChildren and then you can convert it to JSON by calling:

myTargetFolder.toJSON();

This way you don't need to worry about the recursive structure of the resulting JSON.

If you add a constructor which takes a JSONObject, you can ensure consistent serialization and deserialization in one place.

There is also the GSON library from Google, which should achieve essentially the same, but I never used it, so I cannot say how it would work with that.

---

P.S.: You might want to create a common superclass for TargetFolder and TargetChild and use that as the datatype for the children-array, because from the JSON it seems like this array can contain objects with TargetFolder-properties ("expanded" and "children") and objects with TargetChild-properties ("fileicon")