httpclient.java

简易的http客户端附源代码 能帮助分析某个http站点的信息~

package utils;

import java.io.*;
import java.net.*;
import javax.net.*;
import javax.net.ssl.*;
import java.security.cert.*;

public class HttpClient {

  public String getResponseStr(String url) {
    String responseStr = "";
    try {
      if ((!url.startsWith("http://")) && (!url.startsWith("https://"))) {
        url = "http://" + url;
      }
      URI uri = new URI(url);
      String protocol = uri.getScheme();
      String host = uri.getHost();
      int port = uri.getPort();
      String path = uri.getRawPath();
      if (path == null || path.length() == 0) {
        path = "/";
      }
      String query = uri.getRawQuery();
      if (query != null && query.length() > 0) {
        path += "?" + query;
      }

      Socket socket;

      if (protocol.equals("http")) {
        if (port == -1) {
          port = 80;
        }
        socket = new Socket(host, port);
      }
      else if (protocol.equals("https")) {
        if (port == -1) {
          port = 443;
        }
        SocketFactory factory = SSLSocketFactory.getDefault();
        SSLSocket ssock = (SSLSocket) factory.createSocket(host, port);

        SSLSession session = ssock.getSession();
        X509Certificate cert = null;
        try {
          cert = (X509Certificate) session.getPeerCertificates()[0];
        }
        catch (SSLPeerUnverifiedException e) {
          System.err.println(session.getPeerHost() +
                             " did not present a valid certificate");
          System.exit(1);
        }

        System.out.println(session.getPeerHost() +
                           " has presented a certificate belonging to:\t" + "[" +
                           cert.getSubjectDN() + "]\n" +
                           "The certificate was issued by: \t" + "[" +
                           cert.getIssuerDN() + "]");

        socket = ssock;
      }
      else {
        throw new IllegalArgumentException("URL must use http: or " +
                                           "https: protocol");
      }
      InputStream from_server = socket.getInputStream();
      PrintWriter to_server = new PrintWriter(socket.getOutputStream());

      to_server.print("GET " + path + " HTTP/1.0\r\n" + "Host: " + host +
                      "\r\n" + "Connection: close\r\n\r\n");
      to_server.flush();

      byte[] buffer = new byte[8 * 1024];
      int bytes_read;

      int numbytes = 0;
      while (true) {
        bytes_read = from_server.read(buffer, numbytes,
                                      buffer.length - numbytes);
        if (bytes_read == -1) {
          break;
        }
        numbytes += bytes_read;
        if (numbytes >= 4 * 1024) {
          break;
        }
      }

      int i = 0;
      while (i <= numbytes - 4) {
        if (buffer[i++] == 13 && buffer[i++] == 10 && buffer[i++] == 13 &&
            buffer[i++] == 10) {
          break;
        }
      }
      if (i > numbytes - 4) {
        throw new IOException("End of headers not found in first " + numbytes +
                              " bytes");
      }

      responseStr = new String(buffer);
      socket.close();
    }
    catch (UnknownHostException e) {
      responseStr = "域名解析失败，请检查网络设置：" + e.toString();
      System.err.println(e);
    }
    catch (IOException e) {
      responseStr = "文件传输失败：" + e.toString();
      System.err.println(e);
    }
    catch (URISyntaxException e) {
      responseStr = "URI构造语法出错：" + e.toString();
      System.err.println(e);
      System.err.println("Usage: java HttpClient <URL> [<filename>]");
    }
    return responseStr;
  }
}