Android Open Source - RestIt Rest It Mapper

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License

The source code is released under:
Apache License
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Java Source Code

package org.restit.objectmapping;
// w w  w. j av a 2s. co  m
import java.io.StringReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;

import android.util.Log;

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonSerializer;
import com.google.gson.stream.JsonReader;

public class RestItMapper {

  private static final String LOG_TAG = RestItMapper.class.getName();
  protected static Map<String, ClassRegistration> classMaps;
  
  /**
   * Get the map of java classes and json class names
   * @return
   */
  protected static Map<String, ClassRegistration> getClassMaps()
  {
    if(classMaps == null)
    {
      classMaps = new HashMap<String, ClassRegistration>();
    }
    
    return classMaps;
  }
  
  /**
   * Register a java class with a json class
   * @param jsonName The name of the json key
   * @param clazz The java class that is associated with the json key
   */
  public static void addClass(String jsonName, Class clazz)
  {
    if(jsonName == null || clazz == null)
      return;
    
    addClass(jsonName, clazz, null, null);
  }
  
  /**
   * Register a java class with a json class
   * @param jsonName The name of the json key
   * @param clazz The java class that is associated with the json key
   * @param jsonSerializer Custom object to json mappings
   * @param jsonDeserializer Cutom json to object mappings
   */
  public static void addClass(String jsonName, Class clazz, JsonSerializer jsonSerializer, JsonDeserializer jsonDeserializer)
  {
    if(jsonName == null || clazz == null)
      return;
    
    //create class registration object
    ClassRegistration classRegistration = new ClassRegistration(clazz, jsonSerializer, jsonDeserializer);
    
    //store relationship
    getClassMaps().put(jsonName, classRegistration);
  }
  
  /**
   * Parse the response from the server. Map it to a POJO if possible. Otherwise return the raw string;
   * @param responseString Server response in JSON string format
   * @return
   */
  public static Object parseResponse(String responseString)
  {
    if(responseString == null || responseString.isEmpty())
      return null;
    
    try 
    {  
      //first create JSON object
      JSONObject parentObject = new JSONObject(responseString);
      
      //first see if there is a matching key to map the POJO to
      String key = getResponseObjectKey(parentObject);
      if(key == null)
      {
        //no key was found that matches the registered POJO, return original response
        return responseString;
      } else
      {
        //key was found and registered, convert response to POJO
        return toPojo(key, parentObject);
      }
    
    } catch (JSONException e) {
      Log.w(LOG_TAG, e.getMessage(), e);
      
      //there was an error reading the JSON, just return the original response string
      return responseString;
    }
  }
  
  /**
   * Look at the first part of the JSON response and see if the parent object key matches a 
   * register RestItkey
   * @param parentObject Server response in JSON format
   * @return String of parent key in JSON object
   */
  protected static String getResponseObjectKey(JSONObject parentObject) throws JSONException
  {
    if(parentObject != null && parentObject.length() > 0)
    {
      //get the first key to see if it matches a known class
      String key = (String)parentObject.names().get(0);
      if(key != null && getClassMaps().containsKey(key))
      {
        return key;
      } else
      {
        Log.d(LOG_TAG, "No class is registered for response key '"+ key +"'");
      }
    }
    
    //key not found
    return null;
  }
  
  /**
   * Convert a json string to a registered Pojo Object
   * @param jsonString
   * @return
   */
  protected static Object toPojo(String key, JSONObject parentObject) throws JSONException
  {
    if(key == null || parentObject == null)
      return null;
    
      Object convertedObject = null;

      if(parentObject.length() > 0)
      {
        //the key that we have found matches a known class
        ClassRegistration classRegistration = getClassMaps().get(key);
        Object childObject = parentObject.get(key);
        if(classRegistration != null && classRegistration.getClass() != null && childObject != null)
        {  
          
          String json = null;
    
          if(childObject instanceof JSONArray)
          {
            json = childObject.toString();
            
            //loop through JSON Array and parse each object
            List<Object> results = new ArrayList<Object>();
            JSONArray array = (JSONArray) childObject;
            for(int i = 0; i < array.length(); i++)
            {
              JSONObject jsonObject = (JSONObject)array.get(i);
              Object value = toPojo(jsonObject.toString(), classRegistration.getClazz(), classRegistration.getJsonDeserializer());
              results.add(value);
            }
            
            return results;
          }
          else if(childObject instanceof JSONObject)
          {
            JSONObject jsonObject = (JSONObject)childObject;
            
            if(jsonObject.length() == 0)
            {
              //no keys have been defined, return null
              return null;
            }
            
            json = jsonObject.toString();
          } else
          {
            //if we are dealing with a json object use that. If we ended up with a key value pair, use the parent Object
            json = parentObject.toString();
          }
          

          convertedObject = toPojo(json, classRegistration.getClazz(), classRegistration.getJsonDeserializer());
        }
          
      }
      
      
      
      
      return convertedObject;
    
  }
  
  /**
   * Create a POJO from a json string
   * @param json
   * @param clazz
   * @param jsonDeserializer
   * @return
   */
  private static Object toPojo(String json, Class clazz, JsonDeserializer jsonDeserializer)
  {
    Gson gson = null;
    Object convertedObject = null;
    
    JsonReader reader = new JsonReader(new StringReader(json));
    //reader.setLenient(true); //allow malformed JSON
    
    
    if(jsonDeserializer != null)
    {
      //perform custom object mapping
      GsonBuilder builder = new GsonBuilder();
      builder.registerTypeAdapter(clazz, jsonDeserializer);

      gson = builder.create();
        
    } else
    {
      //do simple automatic mapping
      gson = new Gson();
    }
    
    //convert to pojo
    convertedObject =  gson.fromJson(reader, clazz);
    
    return convertedObject;
  }
}
Java Source Code List
