Develop Reference

Using JAVA, how to iterate (or traverse?) through json file with more than one level of data?

I have a snippet of a snippet of a json file that has 3 levels of key,value data I need to access. The tricky part is, sometimes it's a list and sometimes a tuple (or I can be corrected). Some have referred to this file as a map of maps, but I'm guessing that's just nested hashmaps.
Problem Statement: I can iterate through the first level of this JSON, but cannot iterate through the lists inside "data". Java barks at me saying I can't do that with a string. Sometimes the values under data/(next level random word) starts with a bracket [ then a squiggly and sometimes just a squiggly {.
There will be a few lines in there that won't make sense because I was trying different methods to unwrap those sublists.
Key is: raindrop, Value is : {".type":"uri",".value":"http:blahblahblah.info"}
Key is: apex, Value is : [{".type":"inet4",".value":"3.3.3.3"},{".type":"inet4",".value":"3.3.3.3"},{".type":"inet4",".value":"3.3.3.3"},{".type":"inet4",".value":"3.3.3.3"},{".type":"inet4",".value":"3.3.3.3"}]
This is the example of the json file I'm trying to cycle through to get these values so I can determine what kind of value it has (switch statement to count distinctive types).
{
"data": {
"coffee": [
{
".type": "bigdec",
".value": "2626262626.234234234234234"
And here is what I have so far that just gives me the first layer of data.
package com.mycompany.app;
import java.util.regex.Pattern;
import org.json.simple.JSONObject;
import org.json.simple.parser.JSONParser;
import java.util.*;
import java.io.*;
import java.util.Iterator;
import java.util.Map;
import java.io.FileReader;
public class App {
private static Object object;
public void countDistinctValues(String[] args){}
#SuppressWarnings("unchecked")
public static void main(String[] args) throws Exception
{
String filePath = "D:/sandbox/map03/my-app/data.json";
// parsing file
Object obj = new JSONParser().parse(new FileReader(filePath));
// typecasting obj to JSONObject
JSONObject jo = (JSONObject) obj;
System.out.println("--------------------------------------------------------------------");
Map theData = ((Map)jo.get("data"));
Map<String, String> runningMap = new HashMap<>();
Map<String, String> tempMap = new HashMap<>();
int matchCount = 0;
// iterating address Map
Iterator<Map.Entry> itr1 = theData.entrySet().iterator();
while (itr1.hasNext()) {
Map.Entry pair = itr1.next();
// System.out.println(pair.getKey() + " : " + pair.getValue());
runningMap.put(pair.getKey().toString(),pair.getValue().toString());
}
// THIS ENTIRE SECTION BELOW IS TO JUST TRYING TO COUNT EACH LEVEL - THOUGHT I COULD TAKE THE VALUE INTO A VARIABLE AND THEN ITERATE THROUGH IT, BUT IT ONLY SEES IT AS A STRING
System.out.println("--------------------------------------------------------------------");
for (Map.Entry<String, String> newPair : runningMap.entrySet()) {
System.out.println(String.format("Key is: %s, Value is : %s", newPair.getKey(), newPair.getValue()));
String pattern = ".*type.*";
boolean matches = Pattern.matches(pattern, newPair.getValue());
if (matches == true) {matchCount++; }}
System.out.println("--------------------------------------------------------------------");
System.out.println("matches = " + matchCount);
System.out.println("--------------------------------------------------------------------");
// System.out.println("Test Data --> " + newPair);
}
/* for (Map.Entry<String, String> book: pair.entrySet()) {
System.out.println("key: " + book.getKey() + " value: " + book.getValue());
} */
}
```

How to convert a string to JSONArray

I am hitting an api and getting a string response. The response is something like this
"["VU","Vanuatu",["Pacific/Efate","(GMT+11:00) Efate"],"VN","Vietnam",["Asia/Saigon","(GMT+07:00) Hanoi"]]"
And i want to convert this string into a json array of below type
[{"id":"VN","name":"Vanuatu","timezones":[{"id":Pacific/Efate,"name":"(GMT+11:00) Efate}]},"id":"VN","name":"Vietnam",[{"id":"Asia/Saigon","name":"(GMT+07:00) Hanoi"}]]
Can someone help

Looking at your String response, I've created a regular expression that will create four groups out of your response.
DEMO
Assuming that your output would come always in groups of four (i.e., id, name and timezones_id, timezones_name), this regular expression, would extract 4 groups out of the input string that you've provided:
Regex:
"([^"]*)",\s*"([^"]*)",\s*\["([^"]*)",\s*"([^"]*)"\]
Matches
Match 1
Full match 1-56 `"VU", "Vanuatu", ["Pacific/Efate", "(GMT+11:00) Efate"]`
Group 1. 2-4 `VU`
Group 2. 8-15 `Vanuatu`
Group 3. 20-33 `Pacific/Efate`
Group 4. 37-54 `(GMT+11:00) Efate`
Match 2
Full match 58-111 `"VN", "Vietnam", ["Asia/Saigon", "(GMT+07:00) Hanoi"]`
Group 1. 59-61 `VN`
Group 2. 65-72 `Vietnam`
Group 3. 77-88 `Asia/Saigon`
Group 4. 92-109 `(GMT+07:00) Hanoi`
 
Now once you've extracted these 4 groups, You can simply add appropriately in ArrayList and List and create JSONArray out of those lists.
The following program is self-explanatory with the inputs and outputs.
Input
["VU","Vanuatu",["Pacific/Efate","(GMT+11:00) Efate"],"VN","Vietnam",["Asia/Saigon","(GMT+07:00) Hanoi"]]
Output
[{"timezones":{"name":"(GMT+11:00) Efate","id":"Pacific/Efate"},"name":"Vanuatu","id":"VU"},{"timezones":{"name":"(GMT+07:00) Hanoi","id":"Asia/Saigon"},"name":"Vietnam","id":"VN"}]
Formatted Output
[{
"id" : "VU",
"name" : "Vanuatu",
"timezones" : {
"name" : "(GMT+11:00) Efate",
"id" : "Pacific/Efate"
}
}, {
"id" : "VN",
"name" : "Vietnam",
"timezones" : {
"name" : "(GMT+07:00) Hanoi",
"id" : "Asia/Saigon"
}
}
]
Code
import java.io.IOException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.json.JSONArray;
import org.json.JSONException;
public class Test
{
public static void main(String[] args) throws IOException, JSONException {
String serverResponse = "[\"VU\", \"Vanuatu\", [\"Pacific/Efate\", \"(GMT+11:00) Efate\"], \"VN\", \"Vietnam\", [\"Asia/Saigon\", \"(GMT+07:00) Hanoi\"]]";
Map<String, Object> prop, innerProp;
List<Object> arr = new ArrayList<>(), obj;
String pattern = "\"([^\"]*)\",\\s*\"([^\"]*)\",\\s*\\[\"([^\"]*)\",\\s*\"([^\"]*)\"\\]";
Pattern r = Pattern.compile(pattern);
Matcher m = r.matcher(serverResponse);
while (m.find()) {
prop = new HashMap<>();
prop.put("id", m.group(1));
prop.put("name", m.group(2));
innerProp = new HashMap<>();
innerProp.put("id", m.group(3));
innerProp.put("name", m.group(4));
prop.put("timezones", innerProp);
arr.add(prop);
}
JSONArray jsonArray = new JSONArray(arr);
System.out.println(jsonArray.toString());
}
}

An option you have is to first create a JSONArray off of the string, and then read elements 3 by 3 from that array to create your output:
public static void main(String[] args) {
String input = "[\"VU\",\"Vanuatu\",[\"Pacific/Efate\",\"(GMT+11:00) Efate\"],\"VN\",\"Vietnam\",[\"Asia/Saigon\",\"(GMT+07:00) Hanoi\"]]";
JSONArray inputArray = new JSONArray(input);
JSONArray outputArray = new JSONArray();
for (int i = 0; i < inputArray.length(); i += 3) {
JSONObject obj = readCountry(inputArray, i);
outputArray.put(obj);
}
System.out.println(outputArray);
}
private static JSONObject readCountry(JSONArray array, int index) {
JSONObject country = new JSONObject();
country.put("id", array.getString(index));
country.put("name", array.getString(index + 1));
country.put("timezones", readTimeZones(array.getJSONArray(index + 2)));
return country;
}
private static JSONArray readTimeZones(JSONArray array) {
JSONArray timezones = new JSONArray();
JSONObject timezone = new JSONObject();
timezone.put("id", array.getString(0));
timezone.put("name", array.getString(1));
timezones.put(timezone);
return timezones;
}
You may add some error handling to fail gracefully or even recover with best effort if the input doesn't match.

read a string in JSON format in JAVA

I want to read a string as a JSON format(it doesn't have to be JSON, but it seems like JSON format) and represent it to a hashMap(key : Keyword, value : COUNT)
for example, assume I have a String.
String s ={"Welcome":1,"Hi":2,"Hello":1,"Jin":1};
Then, make it classification.(for Hashmap key --> word, value--> number). final result would be something like as below.
HashMap<String,String> result;
result.get("Jin"); // output : 1
result.get("Hi"); // output : 2
but my codes, it doesn't go with right way.
JSONParser parser = new JSONParser();
Object obj = parser.parse(s);
JSONArray array = new JSONArray();
array.add(obj);
System.out.println(array.get(0)); //output: {"Welcome":1,"Hi":2,"Hello":1,"Jin":1}
can it be possible with JSON? or should I split them one by one? (such as split them with "," first and ":" ... so on)
Please give me your kind advice.

Try with below code snippet.
public static void main(final String[] args) throws ParseException {
String s = "{\"Welcome\":1,\"Hi\":2,\"Hello\":1,\"Jin\":1}";
JSONParser parser = new JSONParser();
HashMap<String, Long> obj = (HashMap<String, Long>) parser.parse(s);
for(String key : obj.keySet()) {
System.out.println("Key:" + key + " value:" + obj.get(key));
}
}

You can use org.json to fulfill your requirement.
E.g.
String s = "{\"Welcome\":1,\"Hi\":2,\"Hello\":1,\"Jin\":1}";
JSONObject result = new JSONObject(s);
System.out.println(result.get("Jin")); // output : 1
System.out.println(result.get("Hi")); // output : 2

The easiest to achieve this is by using JACKSON parsers.
import java.util.HashMap;
import java.util.Map;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.type.TypeReference;
String s = "{\"Welcome\":1,\"Hi\":2,\"Hello\":1,\"Jin\":1}";
ObjectMapper mapper = new ObjectMapper();
Map<String, String> map = mapper.readValue(s, new TypeReference<HashMap<String, String>>() {
});
map.forEach((k, v) -> System.out.println("Key is " + k + " value is " + v));
Prints :
Key is Hi value is 2
Key is Hello value is 1
Key is Welcome value is 1
Key is Jin value is 1

Its a json object not an array...
try this one :
JSONObject jsonObj = new JSONObject(jsonString.toString());

Use Google JSON i.e gson library(2.6.2) and your problem will be solved.
Please have a look to the following code
import java.util.HashMap;
import java.util.Map.Entry;
import java.util.Set;
import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
public class StackOverFlowQuestionset {
public static void main(String[] args) {
String s ="{\"Welcome\":1,\"Hi\":2,\"Hello\":1,\"Jin\":1}";
HashMap<String,String> result=new HashMap<String,String>();
Gson gson = new Gson();
JsonElement jsonElement = gson.fromJson(s, JsonElement.class);
JsonObject jsonObject = jsonElement.getAsJsonObject();
Set<Entry<String, JsonElement>> jsonEntrySet = jsonObject.entrySet();
for(Entry<String, JsonElement> entry:jsonEntrySet){
result.put(entry.getKey(), entry.getValue().toString());
}
System.out.println(result.get("Jin"));
System.out.println(result.get("Welcome"));
System.out.println(result.get("Hi"));
}
}

Java MAP to JSON

First of all, I'm new to Java so please be kind with me :-).
I have a map and I want to parse into JSON Object:
private static final Map<String, Queue<String>> myMap = new HashMap<String, Queue<String>>();
My Key is the login (email) of a user.
I would like to create a JSON Object like this one :
{
Login1: {
itemOne: 'item one',
itemTwo: 'item two'
},
Login2: {
itemOne: 'item one',
itemTwo: 'item two'
}
}
I have tried it using JSONObject or ObjectMapper but it didn't worked. I'm looking for some tips / advices.
Thanks,

The way you have it now, parsing Map<String, Queue<String>> into valid JSON would mean that you'd get something like this:
{
queueOne: {
itemOne: 'item one',
itemTwo: 'item two'
},
queueTwo: {
itemOne: 'item one',
itemTwo: 'item two'
}
}
If there's only one queue, putting it in a map isn't necessary. If there's multiple you'll have to iterate over the Map, create a JSONArray from the Queue and then put a JSONObject with the String as key and Queue as value into a main JSONArray.

It's strange, but the key of your map is never used in your example.
Completed example would be:
{
"key":{
"item2":"SecondItemOnTheQueue",
"item1":"FirstItemOnTheQueue",
"item3":"ThirdItemOnTheQueue"
}
}
Java code below:
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Queue;
import org.json.JSONObject;
public class App {
public static void main(String[] args) {
Map<String, Queue<String>> map = new HashMap<String, Queue<String>>();
map.put("key", new LinkedList<String>(){{
add("FirstItemOnTheQueue");
add("SecondItemOnTheQueue");
add("ThirdItemOnTheQueue");
}});
System.out.println(generateFromMapOfQueues(map));
}
private static JSONObject generateFromMapOfQueues(Map<String, Queue<String>> map) {
JSONObject result = new JSONObject();
for(String key : map.keySet()){
JSONObject queueJson = new JSONObject();
int initSize = map.get(key).size();
for (int i = 0; i < initSize; i++) {
queueJson.append("item" + (i + 1), map.get(key).poll());
}
result.put(key, queueJson);
}
return result;
}
}
The map after completion will contain empty queues... That's the only problem.

Parsing JSON array

I'm using GSON for parsing JSON response.
Unfortunately the WebApi on the server has quite untypical JSON objects.
I need to parse Attachments array from this JSON (there can be more attachments):
{"htmlMessage":"text","Attachments":{"8216096_0":{"content":null,"filename":"plk.jpg","contentType":"image/jpeg","contentDisposition":"attachment","size":86070}}}
Where 8216096_0 is attachments id.
I can't do it with Gson (or I don't know how) so I'm trying to do it with JSONObjects:
// parse attachments
JSONObject attachmentsJson = result.getJSONObject("Attachments");
Then I have one JSONObject with an array of attachments, but I don't know how to get them to the ArrayList from JSONObject because the key value isn't static but generated id..
Thank you
//EDIT:
Thanks to all guys for helping! My final solution looks like this especially thanks to #Jessie A. Morris and his final answer!
List<AttachmentModel> attachmentsList = new ArrayList<AttachmentModel>();
for( Map.Entry<String, JsonElement> attachment : attachments.entrySet()) {
AttachmentModel attachmentModel = new AttachmentModel();
attachmentModel = gson.fromJson(attachment.getValue().getAsJsonObject().toString(), AttachmentModel.class);;
attachmentModel.setmUid(attachment.getKey());
attachmentsList.add(attachmentModel);
}

Okay, I've changed my example a little bit and am certain that this does work correctly (I just tested it):
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParser;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
/**
* Created by jessie on 14-07-09.
*/
public class TestGson {
private static String JSON = "{\"htmlMessage\":\"text\",\"Attachments\":{\"8216096_0\":{\"content\":null,\"filename\":\"plk.jpg\",\"contentType\":\"image/jpeg\",\"contentDisposition\":\"attachment\",\"size\":86070}}}\n";
public static void main(String[] args) {
JsonObject json = new JsonParser().parse(JSON).getAsJsonObject();
JsonObject attachments = json.getAsJsonObject("Attachments");
List<JsonObject> attachmentsList = new ArrayList<JsonObject>();
for( Map.Entry<String, JsonElement> attachment : attachments.entrySet()) {
attachmentsList.add(attachment.getValue().getAsJsonObject());
}
System.out.println("attachmentsList at the end? " + attachmentsList);
}
}

I'm not completely sure if this really works:
final Map<String,JSONObject> attachmentsJson = (Map<String,JSONObject>) jsonArray.getJSONObject("Attachments");
for(String attachmentId : attachmentsJson.keySet()) {
final JSONObject attachmentJson = attachmentsJson.get(attachmentId);
}

The "Attachments" obj in your example is not an array.
Json arrays are denoted by [....].
"Attachments" is a Json object holding an inner object called "8216096_0".
so to get the inner values do as follows:
JSONObject attachmentsJson = result.getJSONObject("Attachments");
JSONObject inner = attachmentsJson.getJSONObject("8216096_0");
// and interrogate the inner obj:
String content = inner.getString("content");
String filename = inner.getString("filename");
Finally, and for example sake, I will add the code for processing a (real) Json array:
{"htmlMessage":"text",
"Attachments":[{"8216096_0":{"content":null,"filename":"plk.jpg","contentType":"image/jpeg",
"contentDisposition":"attachment","size":86070}},
{"8216096_1":{"content":null,"filename":"plk.jpg","contentType":"image/jpeg",
"contentDisposition":"attachment","size":86070}},
]
}
It will go like this:
JSONArray attachmentsJson = result.getJSONObject("Attachments");
int len = attachmentsJson.length();
for (int i = 0; i < len; i++) {
JSONObject elem = attachmentsJson.getJSONObject(i); // <------ get array element
JSONObject inner = elem.getJSONObject("8216096_0");
// and interrogate the inner obj:
String content = inner.getString("content");
String filename = inner.getString("filename");
}
..Or similar, depending on your Json's exact format.