如何在BPM中使用REST服务（1）：通过程序访问网页内容

　　这篇文章主要描述如何通过程序来访问网页内容，这是访问REST服务的基础。

　　在Java中，我们可以使用HttpUrlConnection类来实现，代码如下。

 package http.base;

 import java.io.BufferedReader;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.InputStreamReader;
 import java.net.HttpURLConnection;
 import java.net.URL;
 import java.nio.charset.Charset;
 import java.util.Map;
 import java.util.Vector;

 public class HttpRequester {
     private String defaultContentEncoding;

     public HttpRequester() {
         this.defaultContentEncoding = Charset.defaultCharset().name();
     }

     public HttpResponse sendGet(String urlString) throws IOException {
         return this.send(urlString, "GET", null, null);
     }

     public HttpResponse sendGet(String urlString, Map<String, String> params)
             throws IOException {
         return this.send(urlString, "GET", params, null);
     }

     public HttpResponse sendGet(String urlString, Map<String, String> params,
             Map<String, String> propertys) throws IOException {
         return this.send(urlString, "GET", params, propertys);
     }

     public HttpResponse sendPost(String urlString) throws IOException {
         return this.send(urlString, "POST", null, null);
     }

     public HttpResponse sendPost(String urlString, Map<String, String> params)
             throws IOException {
         return this.send(urlString, "POST", params, null);
     }

     public HttpResponse sendPost(String urlString, Map<String, String> params,
             Map<String, String> propertys) throws IOException {
         return this.send(urlString, "POST", params, propertys);
     }

     private HttpResponse send(String urlString, String method,
             Map<String, String> parameters, Map<String, String> propertys)
             throws IOException {
         HttpURLConnection urlConnection = null;

         if (method.equalsIgnoreCase("GET") && parameters != null) {
             StringBuffer param = new StringBuffer();
             int i = 0;
             for (String key : parameters.keySet()) {
                 if (i == 0)
                     param.append("?");
                 else
                     param.append("&");
                 param.append(key).append("=").append(parameters.get(key));
                 i++;
             }
             urlString += param;
         }
         URL url = new URL(urlString);
         urlConnection = (HttpURLConnection) url.openConnection();

         urlConnection.setRequestMethod(method);
         urlConnection.setDoOutput(true);
         urlConnection.setDoInput(true);
         urlConnection.setUseCaches(false);

         if (propertys != null)
             for (String key : propertys.keySet()) {
                 urlConnection.addRequestProperty(key, propertys.get(key));
             }

         if (method.equalsIgnoreCase("POST") && parameters != null) {
             StringBuffer param = new StringBuffer();
             for (String key : parameters.keySet()) {
                 param.append("&");
                 param.append(key).append("=").append(parameters.get(key));
             }
             urlConnection.getOutputStream().write(param.toString().getBytes());
             urlConnection.getOutputStream().flush();
             urlConnection.getOutputStream().close();
         }

         return this.makeContent(urlString, urlConnection);
     }

     private HttpResponse makeContent(String urlString,
             HttpURLConnection urlConnection) throws IOException {
         HttpResponse httpResponser = new HttpResponse();
         try {
             InputStream in = urlConnection.getInputStream();
             BufferedReader bufferedReader = new BufferedReader(
                     new InputStreamReader(in));
             httpResponser.contentCollection = new Vector<String>();
             StringBuffer temp = new StringBuffer();
             String line = bufferedReader.readLine();
             while (line != null) {
                 httpResponser.contentCollection.add(line);
                 temp.append(line).append("/r/n");
                 line = bufferedReader.readLine();
             }
             bufferedReader.close();

             String ecod = urlConnection.getContentEncoding();
             if (ecod == null)
                 ecod = this.defaultContentEncoding;

             httpResponser.urlString = urlString;

             httpResponser.defaultPort = urlConnection.getURL().getDefaultPort();
             httpResponser.file = urlConnection.getURL().getFile();
             httpResponser.host = urlConnection.getURL().getHost();
             httpResponser.path = urlConnection.getURL().getPath();
             httpResponser.port = urlConnection.getURL().getPort();
             httpResponser.protocol = urlConnection.getURL().getProtocol();
             httpResponser.query = urlConnection.getURL().getQuery();
             httpResponser.ref = urlConnection.getURL().getRef();
             httpResponser.userInfo = urlConnection.getURL().getUserInfo();

             httpResponser.content = new String(temp.toString().getBytes(), ecod);
             httpResponser.contentEncoding = ecod;
             httpResponser.code = urlConnection.getResponseCode();
             httpResponser.message = urlConnection.getResponseMessage();
             httpResponser.contentType = urlConnection.getContentType();
             httpResponser.method = urlConnection.getRequestMethod();
             httpResponser.connectTimeout = urlConnection.getConnectTimeout();
             httpResponser.readTimeout = urlConnection.getReadTimeout();

             return httpResponser;
         } catch (IOException e) {
             throw e;
         } finally {
             if (urlConnection != null)
                 urlConnection.disconnect();
         }
     }

     public String getDefaultContentEncoding() {
         return this.defaultContentEncoding;
     }

     public void setDefaultContentEncoding(String defaultContentEncoding) {
         this.defaultContentEncoding = defaultContentEncoding;
     }
 }

HttpRequest类

 package http.base;

 import java.util.Vector;

 public class HttpResponse {

     String urlString;
     int defaultPort;
     String file;
     String host;
     String path;
     int port;
     String protocol;
     String query;
     String ref;
     String userInfo;
     String contentEncoding;
     String content;
     String contentType;
     int code;
     String message;
     String method;
     int connectTimeout;
     int readTimeout;
     Vector<String> contentCollection;

     public String getContent() {
         return content;
     }

     public String getContentType() {
         return contentType;
     }

     public int getCode() {
         return code;
     }

     public String getMessage() {
         return message;
     }

     public Vector<String> getContentCollection() {
         return contentCollection;
     }

     public String getContentEncoding() {
         return contentEncoding;
     }

     public String getMethod() {
         return method;
     }

     public int getConnectTimeout() {
         return connectTimeout;
     }

     public int getReadTimeout() {
         return readTimeout;
     }

     public String getUrlString() {
         return urlString;
     }

     public int getDefaultPort() {
         return defaultPort;
     }

     public String getFile() {
         return file;
     }

     public String getHost() {
         return host;
     }

     public String getPath() {
         return path;
     }

     public int getPort() {
         return port;
     }

     public String getProtocol() {
         return protocol;
     }

     public String getQuery() {
         return query;
     }

     public String getRef() {
         return ref;
     }

     public String getUserInfo() {
         return userInfo;
     }

 }

HttpResponse类

　　下面是一个简单的测试类。

 package http.base;

 public class HttpTest {
     public static void main(String[] args) {
         try {
             HttpRequester request = new HttpRequester();
             HttpResponse hr = request.sendGet("http://www.baidu.com");            

             System.out.println(hr.getUrlString());
             System.out.println(hr.getProtocol());
             System.out.println(hr.getHost());
             System.out.println(hr.getPort());
             System.out.println(hr.getContentEncoding());
             System.out.println(hr.getMethod());

             System.out.println(hr.getContent());

         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 }

　　因为REST服务的返回值一般都是JSON对象，下一篇文章中，我们来看Java对象和JSON之间如何转换。