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How to iterate on a JSON objects using Java

Today we are going to see how to iterate on a JSON object or read a JSON file and fetch key and value from that JSON file using Java.

 Below is the example code snippet.



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package rashidjorvee;

import java.io.FileReader;

import org.json.simple.JSONArray;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
public class JsonReader {
 /* JSON data file
  * [
    {
      "componentName": "comp1""compKey": [
        {
          "keyname": "json_key1",
          "props": [
            {
              "fieldLabel": "Jorvee",
              "name": "./productProperty",
              "id": "productID",
              "sling:resourceType": "granite/ui/components/foundation/form/textfield"
            }
          ]
        }
      ]
    },
    {
      "componentName": "comp2""compKey": [
        {
          "keyname": "json_key2",
          "props": [
            {
              "fieldLabel": "Rashid",
              "name": "./productProperty",
              "id": "productID",
              "sling:resourceType": "foundation/components/parsys"
            }
          ]
        }
      ]
    }
  ]
  */
 public static void main(String[] args) {
  try{
   JSONParser parser=new JSONParser();
   JSONArray a = (JSONArray) parser.parse(new FileReader("D:\\json/jsonFile.json"));
   for (Object comp:a) {
    JSONObject key1 = (JSONObject) comp;
    String componentName = (String) key1.get("componentName");
    System.out.println("componentName: "+componentName);
    JSONArray compkeys = (JSONArray) key1.get("compKey");
    for (Object o : compkeys)
    {
     JSONObject key = (JSONObject) o;
     String keyName = (String) key.get("keyname");
     System.out.println("KeyName: "+keyName);
     
     JSONArray keys = (JSONArray) key.get("props");
     for (Object prop : keys) {
      JSONObject properties = (JSONObject) prop;
      
      String name = (String) properties.get("name");
      System.out.println("Name: " +name);
      
      String fieldLabel = (String) properties.get("fieldLabel");
      System.out.println("City: "+fieldLabel);
      
      String job = (String) properties.get("sling:resourceType");
      System.out.println("resourceType: "+job);
      
      String id = (String) properties.get("id");
      System.out.println("ID: "+id);
      
     }
     System.out.println("\n");
    }
   }
  } catch(Exception e) {}

 }

}
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How to store multiple values for a key into Map using JAVA

Today we will practice a program to assign or set multiple values or list of values or ArrayList for a key in Map. And also how to iterate on that map and find the value from the list of values.

Declare a Map, with a string or integer key and list or ArrayList type of value; as given in below code in line 10. In this Map, you can store a single value as a key and a list of values you could store into that key in form of a list or array list.
Line 10: Map<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();
In line 12 we are creating an ArrayList in which we will store the list of values and we will put this list into Map.
Line 12: ArrayList<String> list = new ArrayList<String>();
Later in line 13 and 14, we are adding values in ArrayList.
Line 13 and 14: list.add("A"+i);
                          list.add("B"+i);
On top of this ArrayList we have created a for loop which will help us to create the pair of 10 unique values of key and value and mapped and put those values into the map.

Line 15 of the code is to put a pair of key and value into a map.
Line 15: map.put("index"+i, list);
We have completed the creation of map. Now we will see how to iterate through the map and pull a particular key or value. or how to find a value into map? or how to find a matching value from a list stored into a map?
To iterate on map first we have to create an object of Entry class with the help of Map and entrySet(). Below is the foreach loop using that we can iterate on all keys of the map.  
Line 19: for(Map.Entry<String, ArrayList<String>> entry : map.entrySet())
Now using the entry object we can pull the key and values of the current iteration index. Below are the codes to getKey() and getValue() from the map. Line 20 of the code will return the value stored as a key, and line 21 will return a list of values stored into the value of the map of the current index.
Line 20: String key = entry.getKey();Line 21: ArrayList<String> value = entry.getValue();
To find a value from map or the list of values stored into the map we will use the matches() method and using regex we could find the matching values at the specified index. In line 23 of the code, we are searching a value B5 which we have stored in the list of values. If we have a list of values then we have to specify the index number using get(index) in which method matches() will search for the requested value.
Line 23: if(entry.getValue().get(1).matches("B5")) 
To search a value from simple key-value pairs of map then we could simply write the above line without get() method. e.g. if(entry.getValue().matches("B5")) and in similar way you could find a key as well. e.g. if(entry.getKey().matches("index7"))

Below is the complete example code which you could directly copy and paste in your IDE and practice this exercise.

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package rashidjorvee;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Map;

public class MultipleValuesInMap {

 public static void main(String[] args) {
  Map<String, ArrayList<String>> map = new HashMap<String, ArrayList<String>>();
  for(int i=1; i<=10; i++) {
   ArrayList<String> list = new ArrayList<String>();
   list.add("A"+i);
   list.add("B"+i);
   map.put("index"+i, list);
  }

  System.out.println(map);
  for(Map.Entry<String, ArrayList<String>> entry : map.entrySet()) {
   String key = entry.getKey();
   ArrayList<String> value = entry.getValue();
   //System.out.println(value.get(1).matches("(?i)b2|B3|B4"));
   if(entry.getValue().get(1).matches("B5")) {
    System.out.println(entry.getKey() +" " +entry.getValue().get(0) +" " +entry.getValue().get(1));
   }
  }
  System.out.println(map.size());

 }

}
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metatype=true in AEM

Why we add parameter metatype=true in @Component annotation?


When we add parameter metatype=true then Apache felix generate a metatype.xml file for that component, if we don’t then there will no metaype.xml file.
Metatype.xml file contains an element <OCD> which have parameters name and description of the component. Under the <OCD> we have another ta <AD> which have detail information of property which we want to make visible and configurable on Apache felix console localhost:4502/system/console/configMgr.
So if we specified ten properties in our component then there will be ten <AD> elements under the <OCD>

Metatype.xml file also contains the element <Designate> with attribute PID and <Object> which has parameter OCDREF under the <Designate> element, which represent and store the configured values. Value for PID and OCDREF is always used to same and that is also the name of the file which you will find in the CRX.  

When we add metatype=true in the parameter of @component that means we have made the property of that component or service configurable and visible on Felix console, which is an easy and helpful way to configure properties of any component and service. Felix web console uses the meta type information to show user-friendly and easy the GUI configuration.

interface MetaTypeService helps to obtain the meta type information of any bundle and component. MetaType Service will examine the specified bundle for meta type documents to create the returned MetaTypeInformation object.
If the specified bundle does not contain any meta type documents, then a MetaTypeInformation object will be returned that wrappers any ManagedService or ManagedServiceFactory services registered by the specified bundle that implement MetaTypeProvider. Thus the MetaType Service can be used to retrieve meta type information for bundles which contain a meta-type document or which provide their own MetaTypeProvider objects.

Where I could find the metatype.xml file in my project? Or Where metatype.xml file exist?

[PROJECT NAME]\core\bin\target\classes\OSGI-INF\metatype

Example of a metafile.xml



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<?xml version="1.0" encoding="UTF-8"?><metatype:MetaData xmlns:metatype="http://www.osgi.org/xmlns/metatype/v1.0.0" localization="OSGI-INF/metatype/com.rashid.jorvee.aem.services.MetaTypeExample">

    <OCD id="com.rashid.jorvee.aem.services.MetaTypeExample" name="%com.rashid.jorvee.aem.services.MetaTypeExample.name" description="%com.rashid.jorvee.aem.services.MetaTypeExample.description">

        <AD id="MetaType.userID" type="String" name="%com.rashid.jorvee.aem.services.MetaTypeExample.MetaType.userID.name" description="%com.rashid.jorvee.aem.services.MetaTypeExample.MetaType.userID.description"/>

        <AD id="MetaType.contact" type=" Integer " name="%com.rashid.jorvee.aem.services.MetaTypeExample.MetaType. contact.name" description="%com.rashid.jorvee.aem.services.MetaTypeExample.MetaType.contact.description"/>

        <AD id="MetaType.address" type="String" default="Boston, united States" name="%com.rashid.jorvee.aem.services.MetaTypeExample.MetaType.address.name" description="%com.rashid.jorvee.aem.services.MetaTypeExample.MetaType.address.description"/>

    </OCD>

    <Designate pid="com.rashid.jorvee.aem.services.MetaTypeExample">

        <Object ocdref="com.rashid.jorvee.aem.services.MetaTypeExample"/>

    </Designate>

</metatype:MetaData>

In the above example, we have created a service class MetaTypeExample which have following configurable properties.
  1. userID
  2. contact
  3. address


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