In this article, we will learn and implement an example to get header details of Restful web service using @HeaderParam and @Context annotations
Jersey is the most popular amongst Restful web service development. Latest Jersey 2.x version has been developed by Oracle/Glassfish team in accordance with JAX-RS 2.0 specification. Earlier Jersey 1.x version was developed and supported by Oracle/Sun team
Latest Jersey release version is 2.12 see here and look documentation and API for details. We will implement Jersey examples in the following articles based on latest 2.x version
@HeaderParam binds HTTP header to formal arguments of Java method
Using @Context annotation in the program, you can get all possible headers passed in the request like
- Content-Type
- Accept
- User-Agent
- Connection
- Host
- etc
Annotation Used
- @HeaderParam (javax.ws.rs.HeaderParam)
- @Context(javax.ws.rs.core.Context)
- @Path (javax.ws.rs.Path)
- @GET (javax.ws.rs.GET)
Files like
- pom.xml,
- web.xml
Remain the same with little modification in the package name used for the project from the previous one. Take a look at one of the following articles to understand these files and their description in detail
- @PathParam
- @QueryParam
- @MatrixParam
- @FormParam
Now, we move on to the implementation to retrieve HTTP headers from the requesting client
Let’s see coding in action
URL Pattern
Http url for any common web application is http://<server>:<port>/<root-context>/<from_here_application_specific_path>
In our example, we are going to deploy the war into Tomcat 8.0 server so our server and port are localhost and 8080 respectively. Context root is the project name i.e.; Jersey-HeaderParam. Initial path for this application is http://localhost:8080/Jersey-HeaderParam
We have configured “/rest/*” as url-pattern for the “jersey-servlet” servlet in web.xml and at class-level path configured is “/bookservice” using @Path annotation. Next respective path for each method annotated with @Path (method-level)
Book Service interface
Defines two abstract methods for retrieving headers sent along with HTTP request
NOTE: It’s always a good programming practice to do code-to-interface and have its implementation separately
IBookService.java
package com.jersey.series.headerparam; import javax.ws.rs.core.HttpHeaders; import javax.ws.rs.core.Response; public interface IBookService { public Response getHeaderDetails(String userAgent, String contentType, String accept); public Response getAllHeader(HttpHeaders httpHeaders); }
Book Service implementation
Implements above interface returning Response object for both methods
Defines two simple methods to retrieve HTTP header details from the requesting client
- First method takes three-arguments which are mapped to the formal arguments using @HeaderParam annotation
- Second method retrieves all possible header sent in the requesting client and their values using HttpHeaders which are mapped using @Context annotation
Note: Jersey doesn’t inherit JAX-RS annotations. So we are annotating Resource/Provider classes and then defining qualified package name in web.xml
BookServiceImpl.java
package com.jersey.series.headerparam; import javax.ws.rs.GET; import javax.ws.rs.HeaderParam; import javax.ws.rs.Path; import javax.ws.rs.core.Context; import javax.ws.rs.core.HttpHeaders; import javax.ws.rs.core.Response; @Path("bookservice") public class BookServiceImpl implements IBookService { // http://localhost:8080/Jersey-HeaderParam/rest/bookservice/getheader @GET @Path("getheader") public Response getHeaderDetails( @HeaderParam("User-Agent") String userAgent, @HeaderParam("Content-Type") String contentType, @HeaderParam("Accept") String accept ){ String header = "User-Agent: " + userAgent + "\nContent-Type: " + contentType + "\nAccept: " + accept; return Response.status(200).entity(header).build(); } // http://localhost:8080/Jersey-HeaderParam/rest/bookservice/getallheader @GET @Path("getallheader") public Response getAllHeader(@Context HttpHeaders httpHeaders){ // local variables StringBuffer stringBuffer = new StringBuffer(); String headerValue = ""; for(String header : httpHeaders.getRequestHeaders().keySet()) { headerValue = httpHeaders.getRequestHeader(header).get(0); stringBuffer.append(header + ": " + headerValue + "\n"); } return Response.status(200).entity(stringBuffer.toString()).build(); } }
Tomcat-8.0.12 Deployment
- Run maven command to build the war: mvn clean install (use command prompt or integrated maven in eclipse IDE
- Copy(ctrl+c) the war file from the target folder
- Paste(ctrl+v) it into apache tomcat (webapps folder)
- Start the tomcat server
Glassfish-4.1 Deployment
- Run maven command to build the war: mvn clean install (use command prompt or integrated maven in eclipse IDE
- Once you see “BUILD SUCCESS” after running maven command, keep the war file ready to be deployed
- There are two ways to deploy war file into Glassfish-4.1
- Online
- Offline
- Click here to understand above deployments process in detail
Test the service !!
Testing
1. Using Google chrome web browser client
Enter URL for the 1st service
http://localhost:8080/Jersey-HeaderParam/rest/bookservice/getheader
Enter URL for the 2nd service
http://localhost:8080/Jersey-HeaderParam/rest/bookservice/getallheader
2. Java client
Uses Client, ClientBuilder, WebTarget and Response classes from core JAX-RS package javax.ws.rs.client for invoking Restful web service
Note: Commented lines will help out us to try (set) various request header parameters
TestHeaderParam.java
package test.jersey.series.headerparam; import javax.ws.rs.client.Client; import javax.ws.rs.client.ClientBuilder; import javax.ws.rs.client.Invocation.Builder; import javax.ws.rs.client.WebTarget; import javax.ws.rs.core.MediaType; import javax.ws.rs.core.Response; import org.glassfish.jersey.client.ClientConfig; public class TestHeaderParam { public static void main(String[] args) { // setting & invoking first request System.out.println("Using @HeaderParam"); System.out.println("---------------------"); String url = "http://localhost:8080/Jersey-HeaderParam/rest/bookservice/getheader"; String responseString1 = testGetHeaders(url); System.out.println("Response String for First Service : \n\n" + responseString1); // setting & invoking second request System.out.println("\n\nUsing @Context"); System.out.println("---------------------"); String url2 = "http://localhost:8080/Jersey-HeaderParam/rest/bookservice/getallheader"; String responseString2 = testGetHeaders(url2); System.out.println("Response String for Second Service : \n\n" + responseString2); } public static String testGetHeaders(String httpURL) { // local variables ClientConfig clientConfig = null; Client client = null; WebTarget webTarget = null; Builder builder = null; Response response = null; int responseCode; String responseMessageFromServer = null; String responseString = null; try{ // invoke service after setting necessary parameters clientConfig = new ClientConfig(); client = ClientBuilder.newClient(clientConfig); // client.property("Content-Type", MediaType.TEXT_PLAIN); // client.property("accept", MediaType.TEXT_PLAIN); webTarget = client.target(httpURL); // invoke service builder = webTarget.request(MediaType.TEXT_PLAIN).accept(MediaType.TEXT_PLAIN); response = builder.get(); // get response code responseCode = response.getStatus(); System.out.println("Response code: " + responseCode); if (response.getStatus() != 200) { throw new RuntimeException("Failed with HTTP error code : " + responseCode); } // get response message responseMessageFromServer = response.getStatusInfo().getReasonPhrase(); System.out.println("ResponseMessageFromServer: " + responseMessageFromServer); // get response string responseString = response.readEntity(String.class); } catch(Exception ex) { ex.printStackTrace(); } finally{ // release resources, if any response.close(); client.close(); } return responseString; } }
Output in console
Using @HeaderParam --------------------- Response code: 200 ResponseMessageFromServer: OK Response String for First Service : User-Agent: Jersey/2.12 (HttpUrlConnection 1.7.0_06-ea) Content-Type: null Accept: text/plain,text/plain Using @Context --------------------- Response code: 200 ResponseMessageFromServer: OK Response String for Second Service : accept: text/plain,text/plain user-agent: Jersey/2.12 (HttpUrlConnection 1.7.0_06-ea) host: localhost:8080 connection: keep-alive
Conclusion: When it is required to get HTTP header details along with requesting parameters either via query/path then @HeaderParam or @Context will be quite useful
Download project
Jersey-2x-HeaderParam (8kB)
Happy Coding !!
Happy Learning !!