Simplest way to read json from a URL in java

Question

This might be a dumb question but what is the simplest way to read and parse JSON from URL in Java   In Groovy  it s a matter of few lines of code  Java examples that I find are ridiculously long  and have huge exception handling block    All I want to do is to read the content of this link

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If you don t mind using a couple libraries it can be done in a single line  Include Apache Commons IOUtils  amp  json org libraries  JSONObject json   new JSONObject IOUtils toString new URL  quot https   graph facebook com me quot    Charset forName  quot UTF-8 quot

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It s very easy  using jersey-client  just include this maven dependency    lt dependency gt     lt groupId gt org glassfish jersey core lt  groupId gt     lt artifactId gt jersey-client lt  artifactId gt     lt version gt 2 25 1 lt  version gt   lt  dependency gt    Then invoke it using this example   String json   ClientBuilder newClient   target  http   api coindesk com v1 bpi currentprice json   request   accept MediaType APPLICATION JSON  get String class     Then use Google s Gson to parse the JSON   Gson gson   new Gson    Type gm   new TypeToken lt CoinDeskMessage gt       getType    CoinDeskMessage cdm   gson fromJson json  gm

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Using the Maven artifact org json json I got the following code  which I think is quite short  Not as short as possible  but still usable   package so4308554   import java io BufferedReader  import java io IOException  import java io InputStream  import java io InputStreamReader  import java io Reader  import java net URL  import java nio charset Charset   import org json JSONException  import org json JSONObject   public class JsonReader      private static String readAll Reader rd  throws IOException       StringBuilder sb   new StringBuilder        int cp      while   cp   rd read       -1          sb append  char  cp             return sb toString           public static JSONObject readJsonFromUrl String url  throws IOException  JSONException       InputStream is   new URL url  openStream        try         BufferedReader rd   new BufferedReader new InputStreamReader is  Charset forName  UTF-8            String jsonText   readAll rd         JSONObject json   new JSONObject jsonText         return json        finally         is close                 public static void main String   args  throws IOException  JSONException       JSONObject json   readJsonFromUrl  https   graph facebook com 19292868552        System out println json toString         System out println json get  id

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Here are couple of alternatives versions with Jackson  since there are more than one ways you might want data as      ObjectMapper mapper   new ObjectMapper       just need one      Got a Java class that data maps to nicely  If so    FacebookGraph graph   mapper readValue url  FaceBookGraph class        Or  if no class  and don t need one   just map to Map class    Map lt String Object gt  map   mapper readValue url  Map class     And specifically the usual  IMO  case where you want to deal with Java objects  can be made one liner   FacebookGraph graph   new ObjectMapper   readValue url  FaceBookGraph class     Other libs like Gson also support one-line methods  why many examples show much longer sections is odd  And even worse is that many examples use obsolete org json library  it may have been the first thing around  but there are half a dozen better alternatives so there is very little reason to use it

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I wanted to add an updated answer here since  somewhat  recent updates to the JDK have made it a bit easier to read the contents of an HTTP URL  Like others have said  you ll still need to use a JSON library to do the parsing  since the JDK doesn t currently contain one   Here are a few of the most commonly used JSON libraries for Java    org JSON FasterXML Jackson GSON   To retrieve JSON from a URL  this seems to be the simplest way using strictly JDK classes  but probably not something you d want to do for large payloads   Java 9 introduced  https   docs oracle com en java javase 11 docs api java base java io InputStream html readAllBytes    try java io InputStream is   new java net URL  https   graph facebook com me   openStream          String contents   new String is readAllBytes         To parse the JSON using the GSON library  for example  com google gson JsonElement element   com google gson JsonParser parseString contents     from  com google code gson gson 2 8 6

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The easiest way   Use gson  google s own goto json library  https   code google com p google-gson   Here is a sample  I m going to this free geolocator website and parsing the json and displaying my zipcode   just put this stuff in a main method to test it out       String sURL    http   freegeoip net json      just a string         Connect to the URL using java s native library     URL url   new URL sURL       URLConnection request   url openConnection        request connect            Convert to a JSON object to print data     JsonParser jp   new JsonParser      from gson     JsonElement root   jp parse new InputStreamReader  InputStream  request getContent        Convert the input stream to a json element     JsonObject rootobj   root getAsJsonObject      May be an array  may be an object       String zipcode   rootobj get  zip code   getAsString      just grab the zipcode

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Use HttpClient to grab the contents of the URL   And then use the library from json org to parse the JSON   I ve used these two libraries on many projects and they have been robust and simple to use   Other than that you can try using a Facebook API java library   I don t have any experience in this area  but there is a question on stack overflow related to using a Facebook API in java  You may want to look at RestFB as a good choice for a library to use

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Here s a full sample of how to parse Json content  The example takes the Android versions statistics  found from Android Studio source code here  which links to here    Copy the  distributions json  file you get from there into res raw  as a fallback   build gradle      implementation  com google code gson gson 2 8 6    manifest     lt uses-permission android name  android permission INTERNET    gt    MainActivity kt  class MainActivity   AppCompatActivity         override fun onCreate savedInstanceState  Bundle             super onCreate savedInstanceState          setContentView R layout activity main          if  savedInstanceState    null              return         thread                  https   cs android com android platform superproject   studio-master-dev tools adt idea android src com android tools idea stats DistributionService java             var root  JsonArray             Log d  AppLog    loading                  try                   HttpURLConnection setFollowRedirects true                  val statsUrl    https   dl google com android studio metadata distributions json    just a string                 val url   URL statsUrl                  val request  HttpURLConnection   url openConnection   as HttpURLConnection                 request connectTimeout   3000                 request connect                   InputStreamReader request content as InputStream  use                       root   JsonParser parseReader it  asJsonArray                                 catch  e  Exception                    Log d  AppLog    error while loading from Internet  so using fallback                   e printStackTrace                   InputStreamReader resources openRawResource R raw distributions   use                       root   JsonParser parseReader it  asJsonArray                                             val decimalFormat   DecimalFormat  0 00               Log d  AppLog    result                 root forEach                   val androidVersionInfo   it asJsonObject                 val versionNickName   androidVersionInfo get  name   asString                 val versionName   androidVersionInfo get  version   asString                 val versionApiLevel   androidVersionInfo get  apiLevel   asInt                 val marketSharePercentage   androidVersionInfo get  distributionPercentage   asFloat   100f                 Log d  AppLog       versionNickName   -  versionName - API versionApiLevel -   decimalFormat format marketSharePercentage                                        As alternative to the dependency  you can also use this instead   InputStreamReader request content as InputStream  use       val jsonArray   JSONArray it readText        and the fallback   InputStreamReader resources openRawResource R raw distributions   use       val jsonArray   JSONArray it readText        The result of running this   loading    result   Ice Cream Sandwich  - 4 0 - API15 - 0 20   Jelly Bean  - 4 1 - API16 - 0 60   Jelly Bean  - 4 2 - API17 - 0 80   Jelly Bean  - 4 3 - API18 - 0 30   KitKat  - 4 4 - API19 - 4 00   Lollipop  - 5 0 - API21 - 1 80   Lollipop  - 5 1 - API22 - 7 40   Marshmallow  - 6 0 - API23 - 11 20   Nougat  - 7 0 - API24 - 7 50   Nougat  - 7 1 - API25 - 5 40   Oreo  - 8 0 - API26 - 7 30   Oreo  - 8 1 - API27 - 14 00   Pie  - 9 0 - API28 - 31 30   Android 10  - 10 0 - API29 - 8 20

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I have done the json parser in simplest way  here it is  package com inzane shoapp activity   import java io BufferedReader  import java io IOException  import java io InputStream  import java io InputStreamReader  import java io UnsupportedEncodingException   import org apache http HttpEntity  import org apache http HttpResponse  import org apache http client ClientProtocolException  import org apache http client methods HttpPost  import org apache http impl client DefaultHttpClient  import org json JSONException  import org json JSONObject   import android util Log   public class JSONParser    static InputStream is   null  static JSONObject jObj   null  static String json           constructor public JSONParser         public JSONObject getJSONFromUrl String url            Making HTTP request     try              defaultHttpClient         DefaultHttpClient httpClient   new DefaultHttpClient            HttpPost httpPost   new HttpPost url            HttpResponse httpResponse   httpClient execute httpPost           HttpEntity httpEntity   httpResponse getEntity            is   httpEntity getContent           catch  UnsupportedEncodingException e            e printStackTrace          catch  ClientProtocolException e            e printStackTrace          catch  IOException e            e printStackTrace               try           BufferedReader reader   new BufferedReader new InputStreamReader                  is   iso-8859-1    8           StringBuilder sb   new StringBuilder            String line   null          while   line   reader readLine       null                sb append line     n                System out println line                     is close            json   sb toString           catch  Exception e            Log e  Buffer Error    Error converting result     e toString                   try parse the string to a JSON object     try           jObj   new JSONObject json         catch  JSONException e            Log e  JSON Parser    Error parsing data     e toString             System out println  error on parse data in jsonparser java                  return JSON String     return jObj         this class returns the json object from the url  and when you want the json object you just call this class and the method in your Activity class  my code is here  String url    your url   JSONParser jsonParser   new JSONParser    JSONObject object   jsonParser getJSONFromUrl url   String content object getString  json key      here the  json key  is denoted that the key in your json file  this is a simple json file example         json   hi      Here  json  is key and  hi  is value  This will get your json value to string content

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I am not sure if this is efficient  but this is one of the possible ways   Read json from url use url openStream   and read contents into a string   construct a JSON object with this string  more at json org   JSONObject java lang String source        Construct a JSONObject from a source JSON text string

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I have found this to be the easiest way by far   Use this method   public static String getJSON String url            HttpsURLConnection con   null          try               URL u   new URL url               con    HttpsURLConnection  u openConnection                 con connect                  BufferedReader br   new BufferedReader new InputStreamReader con getInputStream                  StringBuilder sb   new StringBuilder                String line              while   line   br readLine       null                    sb append line     n                              br close                return sb toString                catch  MalformedURLException ex                ex printStackTrace              catch  IOException ex                ex printStackTrace              finally               if  con    null                    try                       con disconnect                      catch  Exception ex                        ex printStackTrace                                                      return null          And use it like this   String json   getJSON url   JSONObject obj     try            obj   new JSONObject json            JSONArray results arr   obj getJSONArray  results             final int n   results arr length                for  int i   0  i  lt  n    i                       get the place id of each object in JSON  Google Search API                  String place id   results arr getJSONObject i  getString  place id

[java] Simplest way to read json from a URL in java

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