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REST-fähiger Java-Client mit Apache HttpClient

Apache HttpClient ist eine robuste und vollständige Lösungs-Java-Bibliothek zur Ausführung von HTTP-Vorgängen, einschließlich des RESTful-Dienstes. In diesem Lernprogramm zeigen wir Ihnen, wie Sie mit Apache HttpClient einen RESTful-Java-Client erstellen, um eine Anforderung " GET " und " POST " auszuführen.

1. Holen Sie sich Apache HttpClient

Apache HttpClient ist im zentralen Repository von Maven verfügbar und deklariert es einfach in Ihrer Maven-Datei pom.xml .

Datei: pom.xml 

    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
        <version>4.1.1</version>
    </dependency>

2. GET-Anfrage

Überprüfen Sie den letzten REST-Service erneut. 

@Path("/json/product")
public class JSONService {

    @GET
    @Path("/get")
    @Produces("application/json")
    public Product getProductInJSON() {

        Product product = new Product();
        product.setName("iPad 3");
        product.setQty(999);

        return product;

    }
   //...

Apache HttpClient zum Senden einer Anforderung "GET" 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;

public class ApacheHttpClientGet {

    public static void main(String[]args) {
      try {

        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpGet getRequest = new HttpGet(
            "http://localhost:8080/RESTfulExample/json/product/get");
        getRequest.addHeader("accept", "application/json");

        HttpResponse response = httpClient.execute(getRequest);

        if (response.getStatusLine().getStatusCode() != 200) {
            throw new RuntimeException("Failed : HTTP error code : "
               + response.getStatusLine().getStatusCode());
        }

        BufferedReader br = new BufferedReader(
                         new InputStreamReader((response.getEntity().getContent())));

        String output;
        System.out.println("Output from Server .... \n");
        while ((output = br.readLine()) != null) {
            System.out.println(output);
        }

        httpClient.getConnectionManager().shutdown();

      } catch (ClientProtocolException e) {

        e.printStackTrace();

      } catch (IOException e) {

        e.printStackTrace();
      }

    }

}

Ausgabe…​ 

Output from Server ....

{"qty":999,"name":"iPad 3"}

3. POST-Anfrage

Überprüfen Sie auch den letzten REST-Service. 

@Path("/json/product")
public class JSONService {

        @POST
    @Path("/post")
    @Consumes("application/json")
    public Response createProductInJSON(Product product) {

        String result = "Product created : " + product;
        return Response.status(201).entity(result).build();

    }
   //...

Apache HttpClient zum Senden einer "POST" -Anforderung. 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.MalformedURLException;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;

public class ApacheHttpClientPost {

    public static void main(String[]args) {

      try {

        DefaultHttpClient httpClient = new DefaultHttpClient();
        HttpPost postRequest = new HttpPost(
            "http://localhost:8080/RESTfulExample/json/product/post");

        StringEntity input = new StringEntity("{\"qty\":100,\"name\":\"iPad 4\"}");
        input.setContentType("application/json");
        postRequest.setEntity(input);

        HttpResponse response = httpClient.execute(postRequest);

        if (response.getStatusLine().getStatusCode() != 201) {
            throw new RuntimeException("Failed : HTTP error code : "
                + response.getStatusLine().getStatusCode());
        }

        BufferedReader br = new BufferedReader(
                        new InputStreamReader((response.getEntity().getContent())));

        String output;
        System.out.println("Output from Server .... \n");
        while ((output = br.readLine()) != null) {
            System.out.println(output);
        }

        httpClient.getConnectionManager().shutdown();

      } catch (MalformedURLException e) {

        e.printStackTrace();

      } catch (IOException e) {

        e.printStackTrace();

      }

    }

}

Ausgabe…​ 

Output from Server ....

Product created : Product[name=iPad 4, qty=100]....

===  Quellcode herunterladen

Download it - link://wp-content/uploads/2011/07/RESTful-Java-Client-ApacheHttpClient-Example.zip[RESTful-Java-Client-ApacheHttpClient-Example.zip](9 KB)

===  Referenzen

. http://jackson.codehaus.org/%20[Jackson Offizielle Website]

. http://hc.apache.org/httpcomponents-client-ga/index.html[Apache

HTTP-Client]. link://webservices/jax-rs/restfull-java-client-with-java-net-url/[RESTful

Java-Client mit java.net.URL]

link://tag/client/[client]link://tag/httpclient/[httpclient]link://tag/jax-rs/[jax-rs]link://tag/restful/[restful]
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