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Thread: Java JSON question.

  1. #1
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    Default Java JSON question.

    Hello, I'm using Gson to take JSON from an api and put it into classes; however, I've come across a problem. I'm looking for a way to keep track of what parts belong to what larger parts. As an example:

    Lets say I have a base class that holds all the information, and inside that class Lists are populated using Gson. Those Lists must then be put into other classes, and inside those classes new Lists are formed. It's hard to track which part come from what. Right now I'm using multi-dimensional arrays, but it's getting rather complex to keep this going. Here is an example of the JSON:

    {  
       "item":1,
       "item":2,
       "list":[  
          {  
             "item":1,
             "item":2,
             "list":[  
                {  
                   "item":1,
                   "item":2,
                   "list":[  
                      {  
                         "item":1,
                         "item":2
                      }
                   ]
                }
             ]
          }
       ]
    }

    A big problem is when there are multiple Lists in a class, and a class array is made. A class could have 6 different instances, but only 3 belong to another class instance, and the other 3 to another. It's hard to explain. I need a better way to do this, any suggestions? Thanks, and sorry if this is confusing.


  2. #2
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    Default Re: Java JSON question.

    I use these online tools for a head start, google json to java online, they're not great but it's a start & once you already see some of the JSON in JAVA Objects it might save you some time in trying to figure out how to model your JSON in JAVA.
    public class Pojo
    {
        private String item;
     
        private List[] list;
     
        public String getItem ()
        {
            return item;
        }
     
        public void setItem (String item)
        {
            this.item = item;
        }
     
        public List[] getList ()
        {
            return list;
        }
     
        public void setList (List[] list)
        {
            this.list = list;
        }
    }

    Does this code makes sense to you? The model in your JSON is similar to a directory structure with folders containing files and other folders themselves containing containing files. It's a Tree model you're looking for.

    --- Update ---

    You could use something like this also I guess:
    import java.util.ArrayList;
    import java.util.HashMap;
     
    public class ListObject {
        private ListObject parent = null;
        private ArrayList<String> items;
        static HashMap<ListObject, ArrayList<ListObject>> tree  = new HashMap<ListObject, ArrayList<ListObject>>();
     
        public ListObject(ListObject parent) {
        	this.parent = parent;
     
            if (this.parent != null) {
            	if (tree.get(parent) != null) {
            		tree.get(parent).add(this);
            	}
            	else{
            		ArrayList<ListObject> tempList = new ArrayList<ListObject>();
            		tempList.add(this);
            		if (1 != tempList.size())
            			tree.put(this, tempList);
            	}
            }
        } 
     
        public ArrayList<ListObject> getChildren(){
        	return tree.get(this);
        }
     
        public void addItem (String item) {
            if (this.items == null) items = new ArrayList<>();
            this.items.add(item);
        }
     
        public ArrayList<String> getItems () {
            return this.items;
        }
    }
    Last edited by JasonX; September 20th, 2014 at 03:18 PM.

  3. #3
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    Default Re: Java JSON question.

    The tools found from your suggested google search have really helped. I had no idea about these tools, thanks.

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