How can I write a multidimensional JSON object in JSP and pass the JSON object back to JavaScript?

Question

I am currently trying to write a multidimensional object or array in JSP and then pass it back to an AJAX call from JavaScript. Now, decoding a JSON object using AJAX I have figured out (jQuery JSON). So, I'm good on that front.

But I am lost on creating a multidimensional JSON object or array in JSP.

I have been looking at json-simple for the JSON plugin for JSP (http://code.google.com/p/json-simple/). And it's not just this plugin, but I have been unable to find any examples of multidimensional JSON objects or array examples in JSP.

Like, I get this example but it's one-dimensional:

//import org.json.simple.JSONObject;

JSONObject obj=new JSONObject();
obj.put("name","foo");
obj.put("num",new Integer(100));
obj.put("balance",new Double(1000.21));
obj.put("is_vip",new Boolean(true));
obj.put("nickname",null);
System.out.print(obj);

I would like the JSON object to have a result like this:

{
  "results": [ {
    "address_components": [ {
      "long_name": "1600",
      "short_name": "1600",
      "types": [ "street_number" ]
    } ],
  } ]
}

Then, I'd pass it back to JavaScript and decode it.

To Sum up: How can I create a multidimensional object or array in JSP? The JSON plugin is inconsequential; whatever works, I'll be more than happy.

I would appreciate any help. Thank you in advance.

Pål Brattberg · Accepted Answer · 2011-05-11 19:27:31Z

1

To create a structure like this using Gson:

{
  "results": [ {
    "address_components": [ {
      "long_name": "1600",
      "short_name": "1600",
      "types": [ "street_number" ]
    } ],
  } ]
}

You could do something like this:

<%
String[] types = {"street_number"};
Hashtable address_components = new Hashtable();
address_components.put("long_name", 1600);
address_components.put("short_name", 1600);
address_components.put("types", types);
Hashtable results = new Hashtable();
results.put("address_components", address_components);

// Make sure you have the Gson JAR in your classpath
// (place it in the tomcat/classes directory)
com.google.gson.Gson gson = new com.google.gson.Gson();
String json = gson.toJson(obj);  
out.print(json);
%>

edited May 11, 2011 at 19:27

answered May 11, 2011 at 19:05

Pål Brattberg

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4 Comments

user717236 Over a year ago

Wow. Thank you. This looks really good. However, I copied he line "JSONObject obj = new JSONObject();" (without quotes) into the JSP page and it's producing an HTTP 500 error, which means there's an error. How do I import and what library do I have to import to support JSONObject in the JSP page? Thanks again.

Pål Brattberg Over a year ago

You would need a JSON library (a JAR-file typically) and use that. I've updated the code with an example using Gson.

user717236 Over a year ago

Actually, I did have one more question that is related to this discussion: If you look at the example I used above to pose the question, you'll see the hashtable "address_components". How can I have multiple address_components? I'm passing data from SQL to ultimately a JSON object, but it's just taking the last set of data in the loop, does that make sense? I want the address_components hashtable to act like an array. So, in another language, I may access a value like this: results->address_components[2]->long_name. I hope that makes sense. Thank you.

Pål Brattberg Over a year ago

Change results into an array instead of hashtable and you should be good to go.

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