How to consume REST in Java

Question

Using Java tools   wscompile for RPC wsimport for Document etc     I can use WSDL to generate the stub and Classes required to hit the SOAP Web Service   But I have no idea how I can do the same in REST  How can I get the Java classes required for hitting the REST Web Service  What is the way to hit the service anyway   Can anyone show me the way

User · Answer

From your question its not clear whether you are using any frameworks For REST you will be getting an WADL  amp  Apache CXF recently added support for WADL-first development of REST services Please go through http   cxf apache org docs index html

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Apache Http Client APIs are very commonly used for calling HTTP Rest services   Here is one of example of consuming HTTP GET call   import java io IOException  import org apache http HttpResponse  import org apache http client ClientProtocolException  import org apache http client HttpClient  import org apache http client methods HttpGet  import org apache http client methods HttpUriRequest  import org apache http impl client HttpClientBuilder   public class CallHTTPGetService    public static void main String   args  throws ClientProtocolException  IOException         HttpClient client   HttpClientBuilder create   build        HttpUriRequest httpUriRequest   new HttpGet  URL         HttpResponse response   client execute httpUriRequest       System out println response          Use following maven dependency if using Maven project    lt dependency gt           lt groupId gt org apache httpcomponents lt  groupId gt           lt artifactId gt httpclient lt  artifactId gt           lt version gt 4 5 1 lt  version gt       lt  dependency gt       lt  -- https   mvnrepository com artifact org apache httpcomponents httpmime -- gt       lt dependency gt           lt groupId gt org apache httpcomponents lt  groupId gt           lt artifactId gt httpmime lt  artifactId gt           lt version gt 4 5 1 lt  version gt       lt  dependency gt

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The code below will help to consume rest api via Java   URL - end point rest  If you dont need any authentication you dont need to write the authStringEnd variable  The method will return a JsonObject with your response  public JSONObject getAllTypes   throws JSONException  IOException           String url     api atlas types           String authString   name         password          String authStringEnc   new BASE64Encoder   encode authString getBytes             javax ws rs client Client client   ClientBuilder newClient            WebTarget webTarget   client target host   url           Invocation Builder invocationBuilder   webTarget request MediaType APPLICATION JSON  header  Authorization    Basic     authStringEnc            Response response   invocationBuilder get            String output   response readEntity String class                     System out println response toString             JSONObject obj   new JSONObject output            return obj

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Look at Jersey  Again  REST is all about the data  And a tutorial here

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JAX-RS but you can also use regular DOM that comes with standard Java

User · Answer

Just make an http request to the required URL with correct query string  or request body   For example you could use java net HttpURLConnection and then consume via connection getInputStream    and then covnert to your objects   In spring there is a restTemplate that makes it all a bit easier

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You can able to consume a Restful Web service in Spring using RestTemplate class  Example   public class Application        public static void main String args              RestTemplate restTemplate   new RestTemplate            ResponseEntity lt String gt  call  restTemplate getForEntity  quot http   localhost 8080 SpringExample hello quot  String class           System out println call getBody              Reference

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Working example  try this   package restclient  import java io BufferedReader  import java io InputStreamReader  import java net HttpURLConnection  import java net URL   public class NetClientGet       public static void main String   args            try                URL url   new URL  http   localhost 3002 RestWebserviceDemo rest json product dynamicData size 5     your url i e fetch data from               HttpURLConnection conn    HttpURLConnection  url openConnection                conn setRequestMethod  GET                conn setRequestProperty  Accept    application json                if  conn getResponseCode      200                    throw new RuntimeException  Failed   HTTP Error code                               conn getResponseCode                               InputStreamReader in   new InputStreamReader conn getInputStream                 BufferedReader br   new BufferedReader in               String output              while   output   br readLine       null                    System out println output                             conn disconnect               catch  Exception e                System out println  Exception in NetClientGet -     e

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As others have said  you can do it using the lower level HTTP API  or you can use the higher level JAXRS APIs to consume a service as JSON  For example   Client client   ClientBuilder newClient    WebTarget target   client target  http   host 8080 context rest method    JsonArray response   target request MediaType APPLICATION JSON  get JsonArray class

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If you also need to convert that xml string that comes as a response to the service call  an x object you need can do it as follows   import java io BufferedReader  import java io IOException  import java io InputStreamReader  import java io StringReader  import java net HttpURLConnection  import java net MalformedURLException  import java net URL  import java util ArrayList  import java util List   import javax xml bind JAXB  import javax xml bind JAXBException  import javax xml parsers DocumentBuilder  import javax xml parsers DocumentBuilderFactory  import javax xml parsers ParserConfigurationException   import org w3c dom CharacterData  import org w3c dom Document  import org w3c dom Element  import org w3c dom Node  import org w3c dom NodeList  import org xml sax InputSource  import org xml sax SAXException   public class RestServiceClient       http   localhost 8080 RESTfulExample json product get public static void main String   args  throws ParserConfigurationException  SAXException    try    URL url   new URL       http   localhost 8080 CustomerDB webresources co com mazf ciudad    HttpURLConnection conn    HttpURLConnection  url openConnection    conn setRequestMethod  GET    conn setRequestProperty  Accept    application xml     if  conn getResponseCode      200    throw new RuntimeException  Failed   HTTP error code           conn getResponseCode        BufferedReader br   new BufferedReader new InputStreamReader       conn getInputStream        String output   Ciudades ciudades   new Ciudades    System out println  Output from Server       n    while   output   br readLine       null    System out println  12132312    System err println output    DocumentBuilder db   DocumentBuilderFactory newInstance        newDocumentBuilder    InputSource is   new InputSource    is setCharacterStream new StringReader output     Document doc   db parse is   NodeList nodes     org w3c dom Document  doc       getElementsByTagName  ciudad     for  int i   0  i  lt  nodes getLength    i          Ciudad ciudad   new Ciudad        Element element    Element  nodes item i        NodeList name   element getElementsByTagName  idCiudad        Element element2    Element  name item 0        ciudad setIdCiudad Integer          valueOf getCharacterDataFromElement element2          NodeList title   element getElementsByTagName  nomCiudad        element2    Element  title item 0        ciudad setNombre getCharacterDataFromElement element2         ciudades getPartnerAccount   add ciudad        for  Ciudad ciudad1   ciudades getPartnerAccount      System out println ciudad1 getIdCiudad     System out println ciudad1 getNombre        conn disconnect       catch  MalformedURLException e    e printStackTrace      catch  IOException e    e printStackTrace         public static String getCharacterDataFromElement Element e    Node child   e getFirstChild    if  child instanceof CharacterData    CharacterData cd    CharacterData  child  return cd getData      return           Note that the xml structure that I expected in the example was as follows    lt ciudad gt  lt idCiudad gt 1 lt  idCiudad gt  lt nomCiudad gt BOGOTA lt  nomCiudad gt  lt  ciudad gt

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Its just a 2 line of code   import org springframework web client RestTemplate   RestTemplate restTemplate   new RestTemplate    YourBean obj   restTemplate getForObject  http   gturnquist-quoters cfapps io api random   YourBean class     Ref  Spring io consuming-rest

[java] How to consume REST in Java

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