Java中的簡單REST客戶端

如今，大多數用于與某些服務器通信的移動應用程序都使用REST服務。這些服務也是與JavaScript或jQuery一起使用的常見做法。現在，我知道在Java中為REST服務創建客戶端的2種方法，在本文中，我將嘗試演示這兩種方法，希望它們能以某種方式對某人有所幫助。

1.使用Apache HttpClient

Apache HttpClient庫簡化了HTTP請求的處理。要使用此庫，您必須從其網站下載具有相關性的二進制文件。
這是HTTP GET方法的代碼：

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.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
public class Test {public static void main(String[] args) throws ClientProtocolException, IOException {HttpClient client = new DefaultHttpClient();HttpGet request = new HttpGet('http://restUrl');HttpResponse response = client.execute(request);BufferedReader rd = new BufferedReader (new InputStreamReader(response.getEntity().getContent()));String line = '';while ((line = rd.readLine()) != null) {System.out.println(line);}}
}

對于Post方法；用于在帖子中發送簡單的字符串：

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.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.DefaultHttpClient;
public class Test {public static void main(String[] args) throws ClientProtocolException, IOException {HttpClient client = new DefaultHttpClient();HttpPost post = new HttpPost('http://restUrl');StringEntity input = new StringEntity('product');post.setEntity(input);HttpResponse response = client.execute(post);BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));String line = '';while ((line = rd.readLine()) != null) {System.out.println(line);}}
}

您還可以通過以下方式發送POJO的完整JSON或XML ：將表示JSON或XML的String用作StringEntity的參數，然后設置輸入內容類型。像這樣：

StringEntity input = new StringEntity('{\'name1\':\'value1\',\'name2\':\'value2\'}'); //here instead of JSON you can also have XML
input.setContentType('application/json');

對于JSON，您可以使用JSONObject創建JSON的字符串表示形式。

JSONObject json = new JSONObject();
json.put('name1', 'value1');
json.put('name2', 'value2');
StringEntity se = new StringEntity( json.toString());

并在后請求中發送多個參數：

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
public class Test {public static void main(String[] args) throws ClientProtocolException, IOException {HttpClient client = new DefaultHttpClient();HttpPost post = new HttpPost('http://restUrl');List nameValuePairs = new ArrayList(1);nameValuePairs.add(new BasicNameValuePair('name', 'value')); //you can as many name value pair as you want in the list.post.setEntity(new UrlEncodedFormEntity(nameValuePairs));HttpResponse response = client.execute(post);BufferedReader rd = new BufferedReader(new InputStreamReader(response.getEntity().getContent()));String line = '';while ((line = rd.readLine()) != null) {System.out.println(line);}}
}

2.使用球衣

Jersey是JSR-311規范（Java中REST支持的規范）的參考實現。澤西島基本上包含一個REST服務器和一個REST客戶端。它提供了一個庫來與產生REST服務的服務器通信。對于http get方法：

import java.io.IOException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.UriBuilder;
import org.apache.http.client.ClientProtocolException;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;
public class Test {public static void main(String[] args) throws ClientProtocolException, IOException {ClientConfig config = new DefaultClientConfig();Client client = Client.create(config);WebResource service = client.resource(UriBuilder.fromUri('http://restUrl').build());// getting XML dataSystem.out.println(service. path('restPath').path('resourcePath').accept(MediaType.APPLICATION_JSON).get(String.class));// getting JSON dataSystem.out.println(service. path('restPath').path('resourcePath').accept(MediaType.APPLICATION_XML).get(String.class));}
}

您還可以通過其他媒體格式獲得響應，例如PLAIN或HTML。
對于HTTP POST方法：

import java.io.IOException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.MultivaluedMap;
import javax.ws.rs.core.UriBuilder;
import org.apache.http.client.ClientProtocolException;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;
import com.sun.jersey.core.util.MultivaluedMapImpl;
public class Test {public static void main(String[] args) throws ClientProtocolException, IOException {ClientConfig config = new DefaultClientConfig();Client client = Client.create(config);WebResource webResource = client.resource(UriBuilder.fromUri('http://restUrl').build());MultivaluedMap formData = new MultivaluedMapImpl();formData.add('name1', 'val1');formData.add('name2', 'val2');ClientResponse response = webResource.type(MediaType.APPLICATION_FORM_URLENCODED_TYPE).post(ClientResponse.class, formData);System.out.println('Response ' + response.getEntity(String.class));}
}

如果您在POST中使用POJO，則可以執行以下操作：

ClientResponse response = webResource.path('restPath').path('resourcePath').
type(MediaType.APPLICATION_JSON).accept(MediaType.APPLICATION_JSON).post(ClientResponse.class, myPojo);
System.out.println('Response ' + response.getEntity(String.class));

這里的myPojo是自定義POJO類的實例。
您還可以使用Jersey的Form類在POST請求中提交多個參數：

import java.io.IOException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.UriBuilder;
import org.apache.http.client.ClientProtocolException;
import com.sun.jersey.api.client.Client;
import com.sun.jersey.api.client.ClientResponse;
import com.sun.jersey.api.client.WebResource;
import com.sun.jersey.api.client.config.ClientConfig;
import com.sun.jersey.api.client.config.DefaultClientConfig;
import com.sun.jersey.api.representation.Form;
public class Test {public static void main(String[] args) throws ClientProtocolException, IOException {ClientConfig config = new DefaultClientConfig();Client client = Client.create(config);WebResource service = client.resource(UriBuilder.fromUri('http://restUrl').build());Form form = new Form();form.add('name1', 'value1');form.add('name2', 'value1');ClientResponse response = service.path('restPath').path('resourcePath').type(MediaType.APPLICATION_FORM_URLENCODED).post(ClientResponse.class, form);System.out.println('Response ' + response.getEntity(String.class));}
}

祝您編程愉快，別忘了分享！

參考：來自harryjoy博客的JCG合作伙伴 Harsh Raval的Java中的簡單REST客戶端。