Read JSON message from HTTP POST request in Java

Read JSON message from HTTP POST request in Java - java

I am new to Java and to client- server programming.
I am using embedded Jetty, and I'm trying to send a JSON string to some address (http://localhost:7070/json) and then to display the JSON string in that address.
I tried the following code but all I get is null.
Embedded Jetty code:
public static void main(String[] args) throws Exception {
Server server = new Server(7070);
ServletContextHandler handler = new ServletContextHandler(server, "/json");
handler.addServlet(ExampleServlet.class, "/");
server.start();
}
Client side function for sending the Http POST:
public static void sendHttp(){
HttpClient httpClient = HttpClientBuilder.create().build(); //Use this instead
try {
HttpPost request = new HttpPost("http://localhost:7070/json");
JSONObject object = new JSONObject();
try {
object.put("name", "MyName");
object.put("age", "26");
} catch (Exception ex) {
System.out.println("Error: " + ex.getMessage());
}
String message = object.toString();
request.setEntity(new StringEntity(message, "UTF8"));
request.setHeader("Content-type", "application/json");
HttpResponse response = httpClient.execute(request);
// handle response here...
}catch (Exception ex) {
// handle exception here
} finally {
}
}
And Servlet functions:
public class ExampleServlet extends HttpServlet{
#Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
//System.out.println("test get\n");
doPost(req, resp);
}
#Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
//System.out.println("test post\n");
PrintWriter out = resp.getWriter();
String json_str = req.getParameter("name");
out.print(json_str);
}
}
I call the sendHttp() method from a test class, after running the embedded Jetty server code (if that matters).

To get the data from a Post request you need to obtain the content. Try this:
String data = IOUtils.toString(req.getInputStream(), "UTF-8");

You need to read the raw request body as below. Put this inside your doPost method of servlet for reading json from the request:
StringBuilder jsonBuff = new StringBuilder();
String line = null;
try {
BufferedReader reader = req.getReader();
while ((line = reader.readLine()) != null)
jsonBuff.append(line);
} catch (Exception e) { /*error*/ }
System.out.println("Request JSON string :" + jsonBuff.toString());
//write the response here by getting JSON from jasonBuff.toString()
try {
JSONObject jsonObject = JSONObject.fromObject(jb.toString());
out.print(jsonObject.get("name"));//writing output as you did
} catch (ParseException e) {
throw new IOException("Error parsing JSON ");
}
Note : You can access req.getParameter("name"); only when your headers would be like this:
content type: "application/x-www-form-urlencoded"
as in normal html form submission.

Here is my code this works fine
String data = "";
StringBuilder builder = new StringBuilder();
BufferedReader reader = request.getReader();
String line;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
data = builder.toString();
JSONObject object = new JSONObject(data);
//or JSONArray array = new JSONArray(data); which ever the one you want
Good luck.....

I have not used jetty but I have done similar comunications with this code (PUT, not POST):
URL url = new URL(desturl);
HttpURLConnection huc = (HttpURLConnection) url.openConnection();
huc.setRequestMethod("PUT");
byte[] postData = null;
int postDataLength;
huc.setDoOutput(true);
postData = data.getBytes( StandardCharsets.UTF_8 );
postDataLength = postData.length;
huc.setRequestProperty( "Content-Type", "application/json");
huc.setRequestProperty( "charset", "utf-8");
huc.setRequestProperty( "Content-Length", Integer.toString( postDataLength ));
huc.setUseCaches( false );
huc.connect();
huc.setConnectTimeout(10000);
DataOutputStream wr = new DataOutputStream( huc.getOutputStream());
wr.write( postData );
rd = new BufferedReader(new InputStreamReader(huc.getInputStream()));
retcode = huc.getResponseCode();

Related

Java: read data sent by HTTP POST (Android AVD)

I use a simple WebServer from http://www.java2s.com/Code/Java/Network-Protocol/AverysimpleWebserverWhenitreceivesaHTTPrequestitsendstherequestbackasthereply.htm
and Android code from Sending json object via http post method in android
In my main Activity:
AsyncT asyncT = new AsyncT();
asyncT.execute();
Class:
class AsyncT extends AsyncTask<Void,Void,Void>{
#Override
protected Void doInBackground(Void... params) {
try {
URL url = new URL(""); //Enter URL here
HttpURLConnection httpURLConnection = (HttpURLConnection)url.openConnection();
httpURLConnection.setDoOutput(true);
httpURLConnection.setRequestMethod("POST"); // here you are telling that it is a POST request, which can be changed into "PUT", "GET", "DELETE" etc.
httpURLConnection.setRequestProperty("Content-Type", "application/json"); // here you are setting the `Content-Type` for the data you are sending which is `application/json`
httpURLConnection.connect();
JSONObject jsonObject = new JSONObject();
jsonObject.put("para_1", "arg_1");
DataOutputStream wr = new DataOutputStream(httpURLConnection.getOutputStream());
wr.writeBytes(jsonObject.toString());
wr.flush();
wr.close();
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
}
return null;
}
}
The connection is established without any errors ("HostConnection::get() New Host Connection established"). However, I am not able to get in my Java server any information from the request. When I read from input stream
BufferedReader in = new BufferedReader(new InputStreamReader(client.getInputStream()));
System.out.println(in);
I get java.io.BufferedReader#4d7hge12
And this outputs nothing:
String line;
while ((line = in.readLine()) != null) {
if (line.length() == 0)
break;
System.out.println(line);
}

Don't re-invent the wheel and use a library for this.
For example okhttp:
public static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");
OkHttpClient client = new OkHttpClient();
String post(String url, String json) throws IOException {
RequestBody body = RequestBody.create(JSON, json);
Request request = new Request.Builder()
.url(url)
.post(body)
.build();
Response response = client.newCall(request).execute();
return response.body().string();
}
If you want to call a REST-API you can use retrofit (which is build ontop of okhttp)

Assuming you're doing this as a learning exercise, so using another library isn't what you're looking for, I would suggest a couple of things:
(1) install Wireshark and see what the actual response coming back the server is, does it look sensible?
(2) break that line of code out into separate lines, is the InputStream / InputStreamReader null?

Can't seem to get http get parameters sent from my Android app to display on my PHP page

I can't seem to get my PHP page to display the data I have sent using a http client in Android. All I need now is displaying it in PHP which seems to be a challenge, I know I have done something wrong.
Any guidance would be much appreciated. I have tried everything from var_dump($_SERVER) to json_decode to display it in PHP. Is it even possible to display it on a PHP page?
private class Connection extends AsyncTask{
#Override
protected Object doInBackground(Object[] objects){
try{
PostData(R.id.fullscreen_content, 3);
}
catch(IOException exception){
exception.printStackTrace();
}
return null;
}
}
protected void PostData(Integer Question_ID,Integer ResponseChosen_ID) {
URL url = new URL("http://10.0.2.2:443/SwlLogin.php");
HttpURLConnection conn =(HttpURLConnection)url.openConnection();
conn.setDoOutput(true);
HttpClient httpClient = new DefaultHttpClient();
HttpGet post = new HttpGet(conn.getURL().toString());
post.setHeader("Content-type","application/json");
conn.connect();
Date date = new Date();
SimpleDateFormat dt = new SimpleDateFormat("yyyy-MM-dd", Locale.UK);
SimpleDateFormat time = new SimpleDateFormat("HH:mm:ss",Locale.UK);
String nowDate = dt.format(date);
String nowTime = time.format(date);
String phpDate = nowDate;
String phpTime = nowTime;
ArrayList<NameValuePair> params = new ArrayList<>();
params.add(new BasicNameValuePair("Question ID", Question_ID.toString()));
params.add(new BasicNameValuePair("Response_Chosen_ID", ResponseChosen_ID.toString()));
params.add(new BasicNameValuePair("TimestampDate", phpDate));
params.add(new BasicNameValuePair("time", phpTime));
JSONArray array = new JSONArray();
array.put(params);
post.setHeader("postData", params.toString());
post.getParams().setParameter("JSON", params);
HttpParams var = httpClient.getParams();
var.setParameter("GET",params);
HttpResponse response = httpClient.execute(post);
OutputStreamWriter write = new OutputStreamWriter(conn.getOutputStream());
BufferedReader reader = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));
StringBuilder builder = new StringBuilder();
String line = null;
while((line = reader.readLine()) != null){
builder.append(line);
}
Log.d("Response:", builder.toString());
builder.toString();
reader.close();
public void happy_click(View view) throws IOException {
try{
new Connection().execute();
report_success();
}
catch(Exception exception){
messageBox("Response was not successful","Failed to process response" + exception.getMessage());
}
}

you can not run this code on the UI thread or you will get a NetworkRequestOnUIThread exception. you have to do this on a different thread.
try using AsyncTask via
private class Uploader extends AsyncTask<Void,Void,Void>{
protected void doInBackground(){
// do network request here
}
private void onPostExecute(){
// handle UI updates here as is on ui Thread
}
}
or you could look at using OkHTTP library which I recommend highly. to do this download the jar from okHttp. add it to you libs folder then you can do network call like this
MediaType JSON = MediaType.parse("application/json; charset=utf-8");
JSONObject parcel = new JSONObject();
try{
parcel.put("email", emailEdit.getText().toString());
parcel.put("password", passwordEdit.getText().toString());
parcel.put("device", "Android");
parcel.put("hash", "1234");;
}catch (JSONException e ){
e.printStackTrace();
}
RequestBody body = RequestBody.create(JSON, parcel.toString());
Request request = new Request.Builder()
.header("Content-Type", "application/json")
.url("YOURURL")
.post(body)
.build();
client.newCall(request).enqueue(new Callback() {
#Override
public void onFailure(Call call, IOException e) {
if (null != e) {e.printStackTrace();}
}
#Override
public void onResponse(Call call, Response response) throws IOException {
if (null != response && response.message().equals(Constants.KEY_OK)) {
JSONObject serverResponse;
try{
serverResponse = new JSONObject(response.body().string());
if(serverResponse.getBoolean(Constants.KEY_SUCCESS)){
Constants.getInstance().setToken(serverResponse.getString(Constants.KEY_TOKEN));
moveToHomePage();
}else{
showLoginFail();
}
}catch (JSONException e ){
e.printStackTrace();
}
response.body().close();
} else {
showLoginFail();
}
}
});
also make sure you have
<uses-permission android:name="...permision.INTERNET">
in your manifest file

Android Retrieving JSON Object from URL

I am working on an app that makes an API call to a php script that echos a JSON Object. Testing the php file manually through a browser returns the expected information, but my app is acting as if the string that is returned is empty (before I even get to the point of decoding the JSON Object).
Here's the snippet of my code. I've used this script multiple times in my app successfully for api's that echo strings.
String urlParameters =
"request=item_search&item_num=" + barcode + "&ou=" + OU + "&user_tag=" + initials + "&version=" + version + "&scan_point=return";
URL url = null;
try {
if (testMode == true)
{
url = new URL("http://URL/api.php");
}
else
{
url = new URL("http://URL/api.php");
}
}
catch (MalformedURLException e)
{
e.printStackTrace();
}
StringBuilder output = new StringBuilder();
try
{
assert url != null;
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
writer.write(urlParameters);
writer.flush();
writer.close();
String line;
BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line = reader.readLine()) != null)
{
output.append(line);
}
writer.close();
reader.close();
}
catch (IOException e)
{
e.printStackTrace();
}
String outputString = output.toString();

Have you tried OkHttp.
HTTP is the way modern applications network. It’s how we exchange data & media. Doing HTTP efficiently makes your stuff load faster and saves bandwidth.
You can try following code:
package com.squareup.okhttp.guide;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import java.io.IOException;
public class GetExample {
OkHttpClient client = new OkHttpClient();
String run(String url) throws IOException {
Request request = new Request.Builder()
.url(url)
.build();
Response response = client.newCall(request).execute();
return response.body().string();
}
public static void main(String[] args) throws IOException {
GetExample example = new GetExample();
String response = example.run("https://raw.github.com/square/okhttp/master/README.md");
System.out.println(response);
}
}
For more you can visit:
Vogella's article
OkHttp 2.0

parse json data coming from webservice in java

I am developing android app where I am getting web-service data as:
"[{\"ID\":51,\"Text\":\"!! SAMPLE PROJECT !!\"},{\"ID\":58,\"Text\":\"01 Contracting Test Project\"},{\"ID\":64,\"Text\":\"1212\"},{\"ID\":45,\"Text\":\"CHEMICAL FACTORY PROJECT\"}]"
Now I want to parse this data in json I used replaceAll() function to replace backslashes from the string like this:
String jsonFormattedString = line.replaceAll("\\\\", "");
But I think this method isnot good to work with because it removes all the backslashes from the string which creates problems like I recieved json node like:
"[{\"ID\":9617,\"Text\":\"1 1\/4\\\" PVC\/GI CLAMPS\"}]"
where the string value for Text contains double quotes within string which creates problem for me. So my question is what is the best way to parse this json data in java.
My full json data returned by webservice is as:
"[{\"ID\":51,\"Text\":\"!! SAMPLE PROJECT !!\"},{\"ID\":58,\"Text\":\"01 Contracting Test Project\"},{\"ID\":64,\"Text\":\"1212\"},{\"ID\":45,\"Text\":\"CHEMICAL FACTORY PROJECT\"},{\"ID\":53,\"Text\":\"Kanix City\"},{\"ID\":54,\"Text\":\"KANIX DREAM CITY\"},{\"ID\":59,\"Text\":\"KANIX DREAM CITY -- PHASE II\"},{\"ID\":62,\"Text\":\"KANIX DREAM CITY PHASE I\"},{\"ID\":55,\"Text\":\"Kishor_TEST\"},{\"ID\":63,\"Text\":\"Next Generation Housing\"},{\"ID\":65,\"Text\":\"Nothing Job\"},{\"ID\":56,\"Text\":\"PAVAN_TEST\"},{\"ID\":46,\"Text\":\"PRODUCTION UNITS\"},{\"ID\":1,\"Text\":\"PROJECT-01(TYPE 1)\"},{\"ID\":3,\"Text\":\"PROJECT-02(TYPE 1)\"},{\"ID\":5,\"Text\":\"PROJECT-03(TYPE 1)\"},{\"ID\":6,\"Text\":\"PROJECT-04(TYPE 1)\"},{\"ID\":7,\"Text\":\"PROJECT-05(TYPE 1)\"},{\"ID\":8,\"Text\":\"PROJECT-06(TYPE 1)\"},{\"ID\":2,\"Text\":\"PROJECT-07(TYPE 2)\"},{\"ID\":4,\"Text\":\"PROJECT-08(TYPE 2)\"},{\"ID\":9,\"Text\":\"PROJECT-09(TYPE 3)\"},{\"ID\":10,\"Text\":\"PROJECT-10(TYPE 3)\"},{\"ID\":11,\"Text\":\"PROJECT-11(TYPE 4)\"},{\"ID\":57,\"Text\":\"Reviera Classic\"},{\"ID\":43,\"Text\":\"ROAD PROJECT\"},{\"ID\":41,\"Text\":\"SAMPLE PROJECT 1\"},{\"ID\":42,\"Text\":\"SAMPLE PROJECT 2\"},{\"ID\":52,\"Text\":\"Shailesh Test project#1000\"},{\"ID\":61,\"Text\":\"VISHAL PARADISE\"},{\"ID\":60,\"Text\":\"WTC\"}]"
my full code is like this:
#Override
protected List<CItem> doInBackground(String... params) {
try {
String line="";
String ur = "http://"+ServerDetails.hostServer+"/appservices.svc/Projects?Keyword=" ;
lstItm=new ArrayList<CItem>() ;
// Replace it with your own WCF service path
URL json = new URL(ur);
URLConnection jc = json.openConnection();
BufferedReader reader = new BufferedReader(new InputStreamReader(jc.getInputStream()));
line = reader.readLine();
Log.d("LINE",line);
JSONArray array=new JSONArray(line);
Itm=new CItem( "-1", "Select Project" );
lstItm.add(Itm);
for(int i=0; i < array.length(); i++) {
JSONObject tmpJson=array.getJSONObject(i);
Itm=new CItem(tmpJson.getString("ID"),tmpJson.getString("Text"));
lstItm.add(Itm);
}
return lstItm ;
}
catch(Exception e)
{
Log.d("ERRROR--->",e.getMessage());
}
return lstItm ;
}

#mubu9082 ..you dont need to remove these backslashes...
as this json string is shown with backslashes in log or by debugger..
just parse it as usual
public void jsonParser()
{
ArrayList<> list=new ArrayList<>(); //declare this as global
String responseString="[{\"ID\":51,\"Text\":\"!! SAMPLE PROJECT !!\"},{\"ID\":58,\"Text\":\"01 Contracting Test Project\"},{\"ID\":64,\"Text\":\"1212\"},{\"ID\":45,\"Text\":\"CHEMICAL FACTORY PROJECT\"}]";
JSONArray array=new JSONArray(responseString);
String id[]=new String[array.length()];
String text[]=new String[array.length()];
for(int i=0;i<array.length();i++)
{
JSONObject tmpJson=array.getJSONObject(i);
id[i]=tmpJson.getString("ID");
text[i]=tmpJson.getString("TEXT");
CItem Itm=new CItem(tmpJson.getString("ID"),tmpJson.getString("Text")); lstItm.add(Itm);
list.add(Itm);
}
}
do this to get response from server
try {
// create HttpClient
HttpClient httpclient = new DefaultHttpClient();
// make GET request to the given URL ...use
HttpResponse httpResponse = httpclient.execute(new HttpGet(url));
// receive response as inputStream
HttpEntity entity = httpResponse.getEntity();
String response= EntityUtils.toString(entity);
//pass this response to JSONArray object
//save response and then flush the entity.
entity.consumeContent();
} catch (Exception e) {
Log.d("InputStream", e.getLocalizedMessage());
}
pass this response to JSONArray object

public InsuranceDO getInsuranceData1(Context context) {
String urlStr = "http://192.168.2.11:8080/Service/category/sample";
InsuranceDO insuranceDO = new InsuranceDO();
HttpURLConnection urlConnection;
List<InsuranceDO> insList = new ArrayList<InsuranceDO>();
try {
String reqVal = "T=421D84EAC8DEB4878CE48C8A0CB870791EB96FE51C7800A8806032A8CE69A4966D87FFA2E139EE6586C1924F9BD070154CB7E8F92985AC6674B0AD37D9F3FC1ED7B2E4C2D01E5525DCE5E6FCDA26AF890633011894AA2B72604CC8B046E4F9C37DE9A61EECD7000325D3EC673E8609AAD753C52B9BC002C014BC18A35AA8AB3636C237088A08EEED72A7C5F2EDE60155E9111A6F74F082C0E4B45D484C00CA5AD5B3560B8A10D47616E48077EBDE490E&UserCode=172278&DBSource=bali";
URL url = new URL(urlStr);
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
urlConnection.setRequestMethod("POST");
urlConnection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
OutputStream outputStream = urlConnection.getOutputStream();
outputStream.write(reqVal.getBytes());
outputStream.flush();
int code = urlConnection.getResponseCode();
InputStream in = new BufferedInputStream(urlConnection.getInputStream());
StringBuilder result = new StringBuilder();
BufferedReader reader = new BufferedReader(new InputStreamReader(in));
String line;
while ((line = reader.readLine()) != null) {
result.append(line);
}
/**
* To parse json to list data
*/
JSONArray jsonArray = new JSONArray(result.toString());
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = (JSONObject) jsonArray.get(i);
insuranceDO.setAgeing(jsonObject.getString("xxx"));
insuranceDO.setInsuredName(jsonObject.getString("yyyy"));
insuranceDO.setProposalNumber(jsonObject.getString("zzzz"));
insuranceDO.setReason(jsonObject.getString("aaaa"));
insList.add(insuranceDO);
}
} catch (Exception e) {
Toast.makeText(context, e.toString(), Toast.LENGTH_LONG).show();
e.printStackTrace();
}
Toast.makeText(context, insList.toString(), Toast.LENGTH_LONG).show();
return insuranceDO;
}

Java - sending HTTP parameters via POST method easily

I am successfully using this code to send HTTP requests with some parameters via GET method
void sendRequest(String request)
{
// i.e.: request = "http://example.com/index.php?param1=a&param2=b&param3=c";
URL url = new URL(request);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
connection.setDoOutput(true);
connection.setInstanceFollowRedirects(false);
connection.setRequestMethod("GET");
connection.setRequestProperty("Content-Type", "text/plain");
connection.setRequestProperty("charset", "utf-8");
connection.connect();
}
Now I may need to send the parameters (i.e. param1, param2, param3) via POST method because they are very long.
I was thinking to add an extra parameter to that method (i.e. String httpMethod).
How can I change the code above as little as possible to be able to send paramters either via GET or POST?
I was hoping that changing
connection.setRequestMethod("GET");
to
connection.setRequestMethod("POST");
would have done the trick, but the parameters are still sent via GET method.
Has HttpURLConnection got any method that would help?
Is there any helpful Java construct?
Any help would be very much appreciated.

In a GET request, the parameters are sent as part of the URL.
In a POST request, the parameters are sent as a body of the request, after the headers.
To do a POST with HttpURLConnection, you need to write the parameters to the connection after you have opened the connection.
This code should get you started:
String urlParameters = "param1=a&param2=b&param3=c";
byte[] postData = urlParameters.getBytes( StandardCharsets.UTF_8 );
int postDataLength = postData.length;
String request = "http://example.com/index.php";
URL url = new URL( request );
HttpURLConnection conn= (HttpURLConnection) url.openConnection();
conn.setDoOutput( true );
conn.setInstanceFollowRedirects( false );
conn.setRequestMethod( "POST" );
conn.setRequestProperty( "Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty( "charset", "utf-8");
conn.setRequestProperty( "Content-Length", Integer.toString( postDataLength ));
conn.setUseCaches( false );
try( DataOutputStream wr = new DataOutputStream( conn.getOutputStream())) {
wr.write( postData );
}

Here is a simple example that submits a form then dumps the result page to System.out. Change the URL and the POST params as appropriate, of course:
import java.io.*;
import java.net.*;
import java.util.*;
class Test {
public static void main(String[] args) throws Exception {
URL url = new URL("http://example.net/new-message.php");
Map<String,Object> params = new LinkedHashMap<>();
params.put("name", "Freddie the Fish");
params.put("email", "fishie#seamail.example.com");
params.put("reply_to_thread", 10394);
params.put("message", "Shark attacks in Botany Bay have gotten out of control. We need more defensive dolphins to protect the schools here, but Mayor Porpoise is too busy stuffing his snout with lobsters. He's so shellfish.");
StringBuilder postData = new StringBuilder();
for (Map.Entry<String,Object> param : params.entrySet()) {
if (postData.length() != 0) postData.append('&');
postData.append(URLEncoder.encode(param.getKey(), "UTF-8"));
postData.append('=');
postData.append(URLEncoder.encode(String.valueOf(param.getValue()), "UTF-8"));
}
byte[] postDataBytes = postData.toString().getBytes("UTF-8");
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
conn.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
conn.setDoOutput(true);
conn.getOutputStream().write(postDataBytes);
Reader in = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
for (int c; (c = in.read()) >= 0;)
System.out.print((char)c);
}
}
If you want the result as a String instead of directly printed out do:
StringBuilder sb = new StringBuilder();
for (int c; (c = in.read()) >= 0;)
sb.append((char)c);
String response = sb.toString();

I couldn't get Alan's example to actually do the post, so I ended up with this:
String urlParameters = "param1=a&param2=b&param3=c";
URL url = new URL("http://example.com/index.php");
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
writer.write(urlParameters);
writer.flush();
String line;
BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
writer.close();
reader.close();

I find HttpURLConnection really cumbersome to use. And you have to write a lot of boilerplate, error prone code. I needed a lightweight wrapper for my Android projects and came out with a library which you can use as well: DavidWebb.
The above example could be written like this:
Webb webb = Webb.create();
webb.post("http://example.com/index.php")
.param("param1", "a")
.param("param2", "b")
.param("param3", "c")
.ensureSuccess()
.asVoid();
You can find a list of alternative libraries on the link provided.

import java.net.*;
public class Demo{
public static void main(){
String data = "data=Hello+World!";
URL url = new URL("http://localhost:8084/WebListenerServer/webListener");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("POST");
con.setDoOutput(true);
con.getOutputStream().write(data.getBytes("UTF-8"));
con.getInputStream();
}
}

i have read above answers and have created a utility class to simplify HTTP request. i hope it will help you.
Method Call
// send params with Hash Map
HashMap<String, String> params = new HashMap<String, String>();
params.put("email","me#example.com");
params.put("password","12345");
//server url
String url = "http://www.example.com";
// static class "HttpUtility" with static method "newRequest(url,method,callback)"
HttpUtility.newRequest(url,HttpUtility.METHOD_POST,params, new HttpUtility.Callback() {
#Override
public void OnSuccess(String response) {
// on success
System.out.println("Server OnSuccess response="+response);
}
#Override
public void OnError(int status_code, String message) {
// on error
System.out.println("Server OnError status_code="+status_code+" message="+message);
}
});
Utility Class
import java.io.*;
import java.net.*;
import java.util.HashMap;
import java.util.Map;
import static java.net.HttpURLConnection.HTTP_OK;
public class HttpUtility {
public static final int METHOD_GET = 0; // METHOD GET
public static final int METHOD_POST = 1; // METHOD POST
// Callback interface
public interface Callback {
// abstract methods
public void OnSuccess(String response);
public void OnError(int status_code, String message);
}
// static method
public static void newRequest(String web_url, int method, HashMap < String, String > params, Callback callback) {
// thread for handling async task
new Thread(new Runnable() {
#Override
public void run() {
try {
String url = web_url;
// write GET params,append with url
if (method == METHOD_GET && params != null) {
for (Map.Entry < String, String > item: params.entrySet()) {
String key = URLEncoder.encode(item.getKey(), "UTF-8");
String value = URLEncoder.encode(item.getValue(), "UTF-8");
if (!url.contains("?")) {
url += "?" + key + "=" + value;
} else {
url += "&" + key + "=" + value;
}
}
}
HttpURLConnection urlConnection = (HttpURLConnection) new URL(url).openConnection();
urlConnection.setUseCaches(false);
urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); // handle url encoded form data
urlConnection.setRequestProperty("charset", "utf-8");
if (method == METHOD_GET) {
urlConnection.setRequestMethod("GET");
} else if (method == METHOD_POST) {
urlConnection.setDoOutput(true); // write POST params
urlConnection.setRequestMethod("POST");
}
//write POST data
if (method == METHOD_POST && params != null) {
StringBuilder postData = new StringBuilder();
for (Map.Entry < String, String > item: params.entrySet()) {
if (postData.length() != 0) postData.append('&');
postData.append(URLEncoder.encode(item.getKey(), "UTF-8"));
postData.append('=');
postData.append(URLEncoder.encode(String.valueOf(item.getValue()), "UTF-8"));
}
byte[] postDataBytes = postData.toString().getBytes("UTF-8");
urlConnection.setRequestProperty("Content-Length", String.valueOf(postDataBytes.length));
urlConnection.getOutputStream().write(postDataBytes);
}
// server response code
int responseCode = urlConnection.getResponseCode();
if (responseCode == HTTP_OK && callback != null) {
BufferedReader reader = new BufferedReader(new InputStreamReader(urlConnection.getInputStream()));
StringBuilder response = new StringBuilder();
String line;
while ((line = reader.readLine()) != null) {
response.append(line);
}
// callback success
callback.OnSuccess(response.toString());
reader.close(); // close BufferReader
} else if (callback != null) {
// callback error
callback.OnError(responseCode, urlConnection.getResponseMessage());
}
urlConnection.disconnect(); // disconnect connection
} catch (IOException e) {
e.printStackTrace();
if (callback != null) {
// callback error
callback.OnError(500, e.getLocalizedMessage());
}
}
}
}).start(); // start thread
}
}

I see some other answers have given the alternative, I personally think that intuitively you're doing the right thing ;). Sorry, at devoxx where several speakers have been ranting about this sort of thing.
That's why I personally use Apache's HTTPClient/HttpCore libraries to do this sort of work, I find their API to be easier to use than Java's native HTTP support. YMMV of course!

GET and POST method set like this... Two types for api calling 1)get() and 2) post() . get() method to get value from api json array to get value & post() method use in our data post in url and get response.
public class HttpClientForExample {
private final String USER_AGENT = "Mozilla/5.0";
public static void main(String[] args) throws Exception {
HttpClientExample http = new HttpClientExample();
System.out.println("Testing 1 - Send Http GET request");
http.sendGet();
System.out.println("\nTesting 2 - Send Http POST request");
http.sendPost();
}
// HTTP GET request
private void sendGet() throws Exception {
String url = "http://www.google.com/search?q=developer";
HttpClient client = new DefaultHttpClient();
HttpGet request = new HttpGet(url);
// add request header
request.addHeader("User-Agent", USER_AGENT);
HttpResponse response = client.execute(request);
System.out.println("\nSending 'GET' request to URL : " + url);
System.out.println("Response Code : " +
response.getStatusLine().getStatusCode());
BufferedReader rd = new BufferedReader(
new InputStreamReader(response.getEntity().getContent()));
StringBuffer result = new StringBuffer();
String line = "";
while ((line = rd.readLine()) != null) {
result.append(line);
}
System.out.println(result.toString());
}
// HTTP POST request
private void sendPost() throws Exception {
String url = "https://selfsolve.apple.com/wcResults.do";
HttpClient client = new DefaultHttpClient();
HttpPost post = new HttpPost(url);
// add header
post.setHeader("User-Agent", USER_AGENT);
List<NameValuePair> urlParameters = new ArrayList<NameValuePair>();
urlParameters.add(new BasicNameValuePair("sn", "C02G8416DRJM"));
urlParameters.add(new BasicNameValuePair("cn", ""));
urlParameters.add(new BasicNameValuePair("locale", ""));
urlParameters.add(new BasicNameValuePair("caller", ""));
urlParameters.add(new BasicNameValuePair("num", "12345"));
post.setEntity(new UrlEncodedFormEntity(urlParameters));
HttpResponse response = client.execute(post);
System.out.println("\nSending 'POST' request to URL : " + url);
System.out.println("Post parameters : " + post.getEntity());
System.out.println("Response Code : " +
response.getStatusLine().getStatusCode());
BufferedReader rd = new BufferedReader(
new InputStreamReader(response.getEntity().getContent()));
StringBuffer result = new StringBuffer();
String line = "";
while ((line = rd.readLine()) != null) {
result.append(line);
}
System.out.println(result.toString());
}
}

I had the same issue. I wanted to send data via POST.
I used the following code:
URL url = new URL("http://example.com/getval.php");
Map<String,Object> params = new LinkedHashMap<>();
params.put("param1", param1);
params.put("param2", param2);
StringBuilder postData = new StringBuilder();
for (Map.Entry<String,Object> param : params.entrySet()) {
if (postData.length() != 0) postData.append('&');
postData.append(URLEncoder.encode(param.getKey(), "UTF-8"));
postData.append('=');
postData.append(URLEncoder.encode(String.valueOf(param.getValue()), "UTF-8"));
}
String urlParameters = postData.toString();
URLConnection conn = url.openConnection();
conn.setDoOutput(true);
OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
writer.write(urlParameters);
writer.flush();
String result = "";
String line;
BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
while ((line = reader.readLine()) != null) {
result += line;
}
writer.close();
reader.close()
System.out.println(result);
I used Jsoup for parse:
Document doc = Jsoup.parseBodyFragment(value);
Iterator<Element> opts = doc.select("option").iterator();
for (;opts.hasNext();) {
Element item = opts.next();
if (item.hasAttr("value")) {
System.out.println(item.attr("value"));
}
}

Try this pattern:
public static PricesResponse getResponse(EventRequestRaw request) {
// String urlParameters = "param1=a&param2=b&param3=c";
String urlParameters = Piping.serialize(request);
HttpURLConnection conn = RestClient.getPOSTConnection(endPoint, urlParameters);
PricesResponse response = null;
try {
// POST
OutputStreamWriter writer = new OutputStreamWriter(conn.getOutputStream());
writer.write(urlParameters);
writer.flush();
// RESPONSE
BufferedReader reader = new BufferedReader(new InputStreamReader((conn.getInputStream()), StandardCharsets.UTF_8));
String json = Buffering.getString(reader);
response = (PricesResponse) Piping.deserialize(json, PricesResponse.class);
writer.close();
reader.close();
} catch (Exception e) {
e.printStackTrace();
}
conn.disconnect();
System.out.println("PricesClient: " + response.toString());
return response;
}
public static HttpURLConnection getPOSTConnection(String endPoint, String urlParameters) {
return RestClient.getConnection(endPoint, "POST", urlParameters);
}
public static HttpURLConnection getConnection(String endPoint, String method, String urlParameters) {
System.out.println("ENDPOINT " + endPoint + " METHOD " + method);
HttpURLConnection conn = null;
try {
URL url = new URL(endPoint);
conn = (HttpURLConnection) url.openConnection();
conn.setRequestMethod(method);
conn.setDoOutput(true);
conn.setRequestProperty("Content-Type", "text/plain");
} catch (IOException e) {
e.printStackTrace();
}
return conn;
}

This answer covers the specific case of the POST Call using a Custom Java POJO.
Using maven dependency for Gson to serialize our Java Object to JSON.
Install Gson using the dependency below.
<dependency>
<groupId>com.google.code.gson</groupId>
<artifactId>gson</artifactId>
<version>2.8.5</version>
<scope>compile</scope>
</dependency>
For those using gradle can use the below
dependencies {
implementation 'com.google.code.gson:gson:2.8.5'
}
Other imports used:
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.*;
import org.apache.http.impl.client.CloseableHttpClient;
import com.google.gson.Gson;
Now, we can go ahead and use the HttpPost provided by Apache
private CloseableHttpClient httpclient = HttpClients.createDefault();
HttpPost httppost = new HttpPost("https://example.com");
Product product = new Product(); //custom java object to be posted as Request Body
Gson gson = new Gson();
String client = gson.toJson(product);
httppost.setEntity(new StringEntity(client, ContentType.APPLICATION_JSON));
httppost.setHeader("RANDOM-HEADER", "headervalue");
//Execute and get the response.
HttpResponse response = null;
try {
response = httpclient.execute(httppost);
} catch (IOException e) {
throw new InternalServerErrorException("Post fails");
}
Response.Status responseStatus = Response.Status.fromStatusCode(response.getStatusLine().getStatusCode());
return Response.status(responseStatus).build();
The above code will return with the response code received from the POST Call

here i sent jsonobject as parameter //jsonobject={"name":"lucifer","pass":"abc"}//serverUrl = "http://192.168.100.12/testing" //host=192.168.100.12
public static String getJson(String serverUrl,String host,String jsonobject){
StringBuilder sb = new StringBuilder();
String http = serverUrl;
HttpURLConnection urlConnection = null;
try {
URL url = new URL(http);
urlConnection = (HttpURLConnection) url.openConnection();
urlConnection.setDoOutput(true);
urlConnection.setRequestMethod("POST");
urlConnection.setUseCaches(false);
urlConnection.setConnectTimeout(50000);
urlConnection.setReadTimeout(50000);
urlConnection.setRequestProperty("Content-Type", "application/json");
urlConnection.setRequestProperty("Host", host);
urlConnection.connect();
//You Can also Create JSONObject here
OutputStreamWriter out = new OutputStreamWriter(urlConnection.getOutputStream());
out.write(jsonobject);// here i sent the parameter
out.close();
int HttpResult = urlConnection.getResponseCode();
if (HttpResult == HttpURLConnection.HTTP_OK) {
BufferedReader br = new BufferedReader(new InputStreamReader(
urlConnection.getInputStream(), "utf-8"));
String line = null;
while ((line = br.readLine()) != null) {
sb.append(line + "\n");
}
br.close();
Log.e("new Test", "" + sb.toString());
return sb.toString();
} else {
Log.e(" ", "" + urlConnection.getResponseMessage());
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (JSONException e) {
e.printStackTrace();
} finally {
if (urlConnection != null)
urlConnection.disconnect();
}
return null;
}

Hello pls use this class to improve your post method
public static JSONObject doPostRequest(HashMap<String, String> data, String url) {
try {
RequestBody requestBody;
MultipartBuilder mBuilder = new MultipartBuilder().type(MultipartBuilder.FORM);
if (data != null) {
for (String key : data.keySet()) {
String value = data.get(key);
Utility.printLog("Key Values", key + "-----------------" + value);
mBuilder.addFormDataPart(key, value);
}
} else {
mBuilder.addFormDataPart("temp", "temp");
}
requestBody = mBuilder.build();
Request request = new Request.Builder()
.url(url)
.post(requestBody)
.build();
OkHttpClient client = new OkHttpClient();
Response response = client.newCall(request).execute();
String responseBody = response.body().string();
Utility.printLog("URL", url);
Utility.printLog("Response", responseBody);
return new JSONObject(responseBody);
} catch (UnknownHostException | UnsupportedEncodingException e) {
JSONObject jsonObject=new JSONObject();
try {
jsonObject.put("status","false");
jsonObject.put("message",e.getLocalizedMessage());
} catch (JSONException e1) {
e1.printStackTrace();
}
Log.e(TAG, "Error: " + e.getLocalizedMessage());
} catch (Exception e) {
e.printStackTrace();
JSONObject jsonObject=new JSONObject();
try {
jsonObject.put("status","false");
jsonObject.put("message",e.getLocalizedMessage());
} catch (JSONException e1) {
e1.printStackTrace();
}
Log.e(TAG, "Other Error: " + e.getLocalizedMessage());
}
return null;
}

I higly recomend http-request built on apache http api.
For your case you can see example:
private static final HttpRequest<String.class> HTTP_REQUEST =
HttpRequestBuilder.createPost("http://example.com/index.php", String.class)
.responseDeserializer(ResponseDeserializer.ignorableDeserializer())
.build();
public void sendRequest(String request){
String parameters = request.split("\\?")[1];
ResponseHandler<String> responseHandler =
HTTP_REQUEST.executeWithQuery(parameters);
System.out.println(responseHandler.getStatusCode());
System.out.println(responseHandler.get()); //prints response body
}
If you are not interested in the response body
private static final HttpRequest<?> HTTP_REQUEST =
HttpRequestBuilder.createPost("http://example.com/index.php").build();
public void sendRequest(String request){
ResponseHandler<String> responseHandler =
HTTP_REQUEST.executeWithQuery(parameters);
}
For general sending post request with http-request: Read the documentation and see my answers HTTP POST request with JSON String in JAVA, Sending HTTP POST Request In Java, HTTP POST using JSON in Java

I took Boann's answer and used it to create a more flexible query string builder that supports lists and arrays, just like php's http_build_query method:
public static byte[] httpBuildQueryString(Map<String, Object> postsData) throws UnsupportedEncodingException {
StringBuilder postData = new StringBuilder();
for (Map.Entry<String,Object> param : postsData.entrySet()) {
if (postData.length() != 0) postData.append('&');
Object value = param.getValue();
String key = param.getKey();
if(value instanceof Object[] || value instanceof List<?>)
{
int size = value instanceof Object[] ? ((Object[])value).length : ((List<?>)value).size();
for(int i = 0; i < size; i++)
{
Object val = value instanceof Object[] ? ((Object[])value)[i] : ((List<?>)value).get(i);
if(i>0) postData.append('&');
postData.append(URLEncoder.encode(key + "[" + i + "]", "UTF-8"));
postData.append('=');
postData.append(URLEncoder.encode(String.valueOf(val), "UTF-8"));
}
}
else
{
postData.append(URLEncoder.encode(key, "UTF-8"));
postData.append('=');
postData.append(URLEncoder.encode(String.valueOf(value), "UTF-8"));
}
}
return postData.toString().getBytes("UTF-8");
}

For those having trouble receiving the request on a php page using $_POST because you expect key-value pairs:
While all the answers where very helpful, I lacked some basic understanding on which string actually to post, since in the old apache HttpClient I used
new UrlEncodedFormEntity(nameValuePairs); (Java)
and then could use $_POST in php do get the key-value pairs.
To my understanding now one has build that string manually before posting. So the string needs to look like
val data = "key1=val1&key2=val2"
but instead just adding it to the url it is posted (in the header).
The alternative would be to use a json-string instead:
val data = "{\"key1\":\"val1\",\"key2\":\"val2\"}" // {"key1":"val1","key2":"val2"}
and pull it in php without $_POST:
$json_params = file_get_contents('php://input');
// echo_p("Data: $json_params");
$data = json_decode($json_params, true);
Here you find a sample code in Kotlin:
class TaskDownloadTest : AsyncTask<Void, Void, Void>() {
override fun doInBackground(vararg params: Void): Void? {
var urlConnection: HttpURLConnection? = null
try {
val postData = JsonObject()
postData.addProperty("key1", "val1")
postData.addProperty("key2", "val2")
// reformat json to key1=value1&key2=value2
// keeping json because I may change the php part to interpret json requests, could be a HashMap instead
val keys = postData.keySet()
var request = ""
keys.forEach { key ->
// Log.i("data", key)
request += "$key=${postData.get(key)}&"
}
request = request.replace("\"", "").removeSuffix("&")
val requestLength = request.toByteArray().size
// Warning in Android 9 you need to add a line in the application part of the manifest: android:usesCleartextTraffic="true"
// https://stackoverflow.com/questions/45940861/android-8-cleartext-http-traffic-not-permitted
val url = URL("http://10.0.2.2/getdata.php")
urlConnection = url.openConnection() as HttpURLConnection
// urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded") // apparently default
// Not sure what these are for, I do not use them
// urlConnection.setRequestProperty("Content-Type", "application/json")
// urlConnection.setRequestProperty("Key","Value")
urlConnection.readTimeout = 5000
urlConnection.connectTimeout = 5000
urlConnection.requestMethod = "POST"
urlConnection.doOutput = true
// urlConnection.doInput = true
urlConnection.useCaches = false
urlConnection.setFixedLengthStreamingMode(requestLength)
// urlConnection.setChunkedStreamingMode(0) // if you do not want to handle request length which is fine for small requests
val out = urlConnection.outputStream
val writer = BufferedWriter(
OutputStreamWriter(
out, "UTF-8"
)
)
writer.write(request)
// writer.write("{\"key1\":\"val1\",\"key2\":\"val2\"}") // {"key1":"val1","key2":"val2"} JsonFormat or just postData.toString() for $json_params=file_get_contents('php://input'); json_decode($json_params, true); in php
// writer.write("key1=val1&key2=val2") // key=value format for $_POST in php
writer.flush()
writer.close()
out.close()
val code = urlConnection.responseCode
if (code != 200) {
throw IOException("Invalid response from server: $code")
}
val rd = BufferedReader(
InputStreamReader(
urlConnection.inputStream
)
)
var line = rd.readLine()
while (line != null) {
Log.i("data", line)
line = rd.readLine()
}
} catch (e: Exception) {
e.printStackTrace()
} finally {
urlConnection?.disconnect()
}
return null
}
}

Now I had to do an HTTP request class, it is probably not the most efficient class, but it works.
I collected some codes from this page and made it more dynamic.
Anyone who needs a complete code, I attached it below.
For an example of how to use it, you can look at the main method.
Also, if you are willing to improve classes online, you are more than welcome to help me make this class better.
import java.net.*;
import java.util.*;
import java.nio.charset.*;
import java.io.*;
public class HttpRequest {
String result = "";
HttpRequest(String _url, String _method, Map<String, String> _postData, String _contentType) {
try {
URL url = new URL( _url );
URLConnection con = url.openConnection();
HttpURLConnection http = (HttpURLConnection)con;
http.setRequestMethod(_method); // PUT is another valid option
http.setDoOutput(true);
StringJoiner sj = new StringJoiner("&");
for(Map.Entry<String,String> entry : _postData.entrySet())
sj.add(URLEncoder.encode(entry.getKey(), "UTF-8") + "=" + entry.getValue());
//sj.add(URLEncoder.encode(entry.getKey(), "UTF-8") + "=" + URLEncoder.encode(entry.getValue()));
byte[] out = sj.toString().getBytes(StandardCharsets.UTF_8);
int length = out.length;
http.setFixedLengthStreamingMode(length);
http.setRequestProperty("Content-Type", _contentType);
http.setRequestProperty( "charset", "utf-8");
http.setRequestProperty( "Content-Length", Integer.toString( length ));
http.setInstanceFollowRedirects( false );
http.setUseCaches( false );
http.connect();
try(OutputStream os = http.getOutputStream()) {
os.write(out);
}
if (http.getResponseCode() == HttpURLConnection.HTTP_OK) {
try (BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(http.getInputStream()))) {
String line;
while ((line = bufferedReader.readLine()) != null) {
result = result + line;
}
}
} else {
System.out.println("Bad response!");
}
}catch (IOException e) {
// writing exception to log
e.printStackTrace();
}
}
HttpRequest(String _url, String _method, Map<String, String> _postData) {
this(_url, _method, _postData, "text/html");
}
HttpRequest(String _url, String _method) {
this(_url, _method, new HashMap<String, String>());
}
HttpRequest(String _url) {
this(_url, "GET");
}
public String toString() {
return result;
}
public static void main(String[] args) {
// TODO Auto-generated method stub
Map<String, String> postData = new HashMap<String, String>();
postData.putIfAbsent("email", "test#test.com");
postData.putIfAbsent("password", "test");
HttpRequest result = new HttpRequest("https://httpbin.org/anything", "POST", postData, "application/x-www-form-urlencoded");
System.out.println(result.toString());
}
}

Appears that you also have to callconnection.getOutputStream() "at least once" (as well as setDoOutput(true)) for it to treat it as a POST.
So the minimum required code is:
URL url = new URL(urlString);
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
//connection.setRequestMethod("POST"); this doesn't seem to do anything at all..so not useful
connection.setDoOutput(true); // set it to POST...not enough by itself however, also need the getOutputStream call...
connection.connect();
connection.getOutputStream().close();
You can even use "GET" style parameters in the urlString, surprisingly. Though that might confuse things.
You can also use NameValuePair apparently.

We Keep Coding

Java is a programming language and computing platform first released by Sun Microsystems in 1995.

Read JSON message from HTTP POST request in Java - java

To get the data from a Post request you need to obtain the content. Try this: String data = IOUtils.toString(req.getInputStream(), "UTF-8");

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