Java - sending HTTP parameters via POST method easily

Question

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 amp param2 b amp 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

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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

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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 amp param2 b amp 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

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Try this pattern   public static PricesResponse getResponse EventRequestRaw request            String urlParameters     param1 a amp param2 b amp 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

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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

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I couldn t get Alan s example to actually do the post  so I ended up with this   String urlParameters    param1 a amp param2 b amp 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

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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 lt String  String gt  params   new HashMap lt String  String gt         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  lt  String  String  gt  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  amp  amp  params    null          for  Map Entry  lt  String  String  gt  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      amp     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  amp  amp  params    null          StringBuilder postData   new StringBuilder          for  Map Entry  lt  String  String  gt  item  params entrySet             if  postData length      0  postData append   amp            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  amp  amp  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

User · Answer

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  amp  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 lt NameValuePair gt  urlParameters   new ArrayList lt NameValuePair gt             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

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I higly recomend http-request built on apache http api   For your case you can see example   private static final HttpRequest lt String class gt  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 lt String gt  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 lt   gt  HTTP REQUEST         HttpRequestBuilder createPost  http   example com index php   build     public void sendRequest String request        ResponseHandler lt String gt  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

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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 lt String  Object gt  postsData  throws UnsupportedEncodingException       StringBuilder postData   new StringBuilder        for  Map Entry lt String Object gt  param   postsData entrySet              if  postData length      0  postData append   amp              Object value   param getValue            String key   param getKey             if value instanceof Object      value instanceof List lt   gt                         int size   value instanceof Object       Object   value  length     List lt   gt  value  size                for int i   0  i  lt  size  i                                  Object val   value instanceof Object       Object   value  i      List lt   gt  value  get i                   if i gt 0  postData append   amp                     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

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Hello pls use this class to improve your post method   public static JSONObject doPostRequest HashMap lt String  String gt  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

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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

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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

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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 lt String Object gt  params   new LinkedHashMap lt  gt             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 lt String Object gt  param   params entrySet                  if  postData length      0  postData append   amp                 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     gt   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     gt   0               sb append  char c           String response   sb toString

User · Answer

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 lt String Object gt  params   new LinkedHashMap lt  gt         params put  param1   param1       params put  param2   param2        StringBuilder postData   new StringBuilder        for  Map Entry lt String Object gt  param   params entrySet              if  postData length      0  postData append   amp             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 lt Element gt  opts   doc select  option   iterator        for   opts hasNext               Element item   opts next            if  item hasAttr  value                  System out println item attr  value

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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    lt dependency gt     lt groupId gt com google code gson lt  groupId gt     lt artifactId gt gson lt  artifactId gt     lt version gt 2 8 5 lt  version gt     lt scope gt compile lt  scope gt   lt  dependency gt    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

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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

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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 amp 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 lt Void  Void  Void gt          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 amp 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 - gt                     Log i  data   key                  request      key   postData get key   amp                             request   request replace           removeSuffix   amp                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 amp 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

[java] Java - sending HTTP parameters via POST method easily

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