如何在BPM中使用REST服務（1）：通過程式訪問網頁內容

 

　　這篇文章主要描述如何通過程式來訪問網頁內容，這是訪問REST服務的基礎。

　　在Java中，我們可以使用HttpUrlConnection類來實現，程式碼如下。

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;
    }
}

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;
    }
 
}

　　下面是一個簡單的測試類。

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();
        }
    }
}

　　因為REST服務的返回值一般都是JSON物件，下一篇文章中，我們來看Java物件和JSON之間如何轉換。