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Java基於Socket完成HTTP下載客戶端

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Java基於Socket完成HTTP下載客戶端。本站提示廣大學習愛好者：（Java基於Socket完成HTTP下載客戶端）文章只能為提供參考，不一定能成為您想要的結果。以下是Java基於Socket完成HTTP下載客戶端正文

沒有借助任何第三方庫，完整基於JAVA Socket完成一個最小化的HTTP文件下載客戶端。完全的演示若何經由過程Socket完成下載文件的HTTP要求(request header)發送若何從Socket中接收HTTP呼應(Response header, Response body)報文並解析與保留文件內容。若何經由過程SwingWork完成UI刷新，及時顯示下載進度。

起首看一下UI部門：

【添加下載】按鈕：

點擊彈出URL輸出框，用戶Copy要下載文件URL到輸出框今後，點擊[OK]按鈕即開端

下載

【消除完成】按鈕：

消除一切曾經下載完成的文件列表

文件下載狀況分為以下幾種：

package com.gloomyfish.socket.tutorial.http.download; 
 
public enum DownLoadStatus { 
  NOT_STARTED, 
  IN_PROCESS, 
  COMPLETED, 
  ERROR 
}

UI部門重要是應用Swing組件完成。點擊【添加下載】履行的代碼以下：

final JDialog dialog = new JDialog(this,"Add File Link",true); 
dialog.getContentPane().setLayout(new BorderLayout()); 
// dialog.setSize(new Dimension(400,200)); 
final URLFilePanel panel = new URLFilePanel(); 
panel.setUpListener(new ActionListener(){ 
  @Override 
  public void actionPerformed(ActionEvent e) { 
    if("OK".equals(e.getActionCommand())){ 
      if(panel.validateInput()) { 
        DownloadDetailStatusInfoModel data = new DownloadDetailStatusInfoModel(panel.getValidFileURL()); 
        tableModel.getData().add(data); 
        startDownlaod(); 
        refreshUI(); 
      } 
      dialog.setVisible(false); 
      dialog.dispose(); 
    } else if("Cancel".equals(e.getActionCommand())) { 
      dialog.setVisible(false); 
      dialog.dispose(); 
    } 
  }}); 
 
dialog.getContentPane().add(panel, BorderLayout.CENTER); 
dialog.pack(); 
centre(dialog); 
dialog.setVisible(true);

【消除完成】按鈕履行的代碼以下：

private void clearDownloaded() { 
  List<DownloadDetailStatusInfoModel> downloadedList = new ArrayList<DownloadDetailStatusInfoModel>(); 
  for(DownloadDetailStatusInfoModel fileStatus : tableModel.getData()) { 
    if(fileStatus.getStatus().toString().equals(DownLoadStatus.COMPLETED.toString())) { 
      downloadedList.add(fileStatus); 
    } 
  } 
  tableModel.getData().removeAll(downloadedList); 
  refreshUI(); 
}

讓JFrame組件居中顯示的代碼以下：

public static void centre(Window w) { 
  Dimension us = w.getSize(); 
  Dimension them = Toolkit.getDefaultToolkit().getScreenSize(); 
  int newX = (them.width - us.width) / 2; 
  int newY = (them.height - us.height) / 2; 
  w.setLocation(newX, newY); 
}

HTTP協定完成部門：

概述：HTTP要求頭與響應頭報文根本構造與說明

HTTP要求：一個尺度的HTTP要求報文如

個中要求頭可以有多個，message-body可以沒有，不是必需的。要求行的格局以下：

Request-Line = Method SP Request-URI SPHTTP-Version CRLF 舉例解釋以下：

Request-Line = GET http://www.w3.org/pub/WWW/TheProject.htmlHTTP/1.1\r\n

個中SP表現空格， CRLF表現回車換行符\r\n

當你想要上傳文件時刻，應用Post方法來填寫數據到message-body中便可。發送一個

簡略的HTTP要求報文以下：

GET /pub/WWW/TheProject.html HTTP/1.1\r\n
Host: www.w3.org\r\n
\r\n

HTTP呼應：一個尺度的HTTP呼應報文以下

最早獲得是狀況行，其格局以下：

Status-Line = HTTP-Version SP Status-CodeSP Reason-Phrase CRLF, 一個狀況行的簡略例子以下：Status-Line = HTTP/1.1 200 OK普通年夜家最愛好的就是Status-Code會給你許多提醒，最多見的就是404，500等狀況碼。狀況碼的意思可以參考RFC2616中的說明。下載文件最要緊是的檢討HTTP呼應頭中的Content-Length與Content-Type兩

個平分別聲清楚明了文件的長度與文件的類型。其它如Accept-Ranges表現接收若干到若干的字節。能夠在多線程下載中應用。弄清晰了HTTP要求與呼應的報文格局今後，我們便可以經由過程Socket依照報文格局解析內容，發送與讀取HTTP要求與呼應。詳細步調

以下：

1、依據用戶輸出的文件URL樹立Socket銜接

URL url = new URL(fileInfo.getFileURL()); 
String host = url.getHost(); 
int port = (url.getPort() == -1) ? url.getDefaultPort():url.getPort(); 
System.out.println("Host Name = " + host); 
System.out.println("port = " + port); 
System.out.println("File URI = " + url.getFile()); 
 
// create socket and start to construct the request line 
Socket socket = new Socket(); 
SocketAddress address = new InetSocketAddress(host, port); 
socket.connect(address);

用了URL類來把用戶輸出的url string釀成輕易解析一點的URL。
2、結構HTTP要求

BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream(), "UTF8")); 
String requestStr = "GET " + url.getFile() + " HTTP/1.1\r\n"; // request line 
 
// construct the request header - 結構HTTP要求頭(request header) 
String hostHeader = "Host: " + host + "\r\n"; 
String acceptHeader = "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n"; 
String charsetHeader = "Accept-Charset: GBK,utf-8;q=0.7,*;q=0.3\r\n"; 
String languageHeader = "Accept-Language: zh-CN,zh;q=0.8\r\n"; 
String keepHeader = "Connection: close\r\n";

3、發送HTTP要求

// 發送HTTP要求 
bufferedWriter.write(requestStr); 
bufferedWriter.write(hostHeader); 
bufferedWriter.write(acceptHeader); 
bufferedWriter.write(charsetHeader); 
bufferedWriter.write(languageHeader); 
bufferedWriter.write(keepHeader); 
bufferedWriter.write("\r\n"); // 要求頭信息發送停止標記 
bufferedWriter.flush();

4、接收HTTP呼應並解析內容，寫入創立好的文件

// 預備接收HTTP呼應頭並解析 
CustomDataInputStream input = new CustomDataInputStream(socket.getInputStream()); 
File myFile = new File(fileInfo.getStoreLocation() + File.separator + fileInfo.getFileName()); 
String content = null; 
HttpResponseHeaderParser responseHeader = new HttpResponseHeaderParser(); 
BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream(myFile)); 
boolean hasData = false; 
while((content = input.readHttpResponseHeaderLine()) != null) { 
  System.out.println("response header contect -->> " + content); 
  responseHeader.addResponseHeaderLine(content); 
  if(content.length() == 0) { 
    hasData = true; 
  } 
  if(hasData) { 
    int totalBytes = responseHeader.getFileLength(); 
    if(totalBytes == 0) break; // no response body and data 
    int offset = 0; 
    byte[] myData = null; 
    if(totalBytes >= 2048) { 
      myData = new byte[2048]; 
    } else { 
      myData = new byte[totalBytes]; 
    } 
    int numOfBytes = 0; 
    while((numOfBytes = input.read(myData, 0, myData.length)) > 0 && offset < totalBytes) { 
      offset += numOfBytes; 
      float p = ((float)offset) / ((float)totalBytes) * 100.0f; 
      if(offset > totalBytes) { 
        numOfBytes = numOfBytes + totalBytes - offset; 
        p = 100.0f; 
      } 
      output.write(myData, 0, numOfBytes); 
      updateStatus(p); 
    } 
    hasData = false; 
    break; 
  } 
}

簡略的HTTP呼應頭解析類HttpResponseHeaderParser代碼以下：

package com.gloomyfish.socket.tutorial.http.download; 
 
import java.util.HashMap; 
import java.util.Map; 
 
/** 
 * it can parse entity header, response head 
 * and response line <status code, CharSet, ect...> 
 * refer to RFC2616，關於HTTP呼應頭，請看RFC文檔，描述的很具體啊！！ 
 */ 
public class HttpResponseHeaderParser { 
  public final static String CONTENT_LENGTH = "Content-Length"; 
  public final static String CONTENT_TYPE = "Content-Type"; 
  public final static String ACCEPT_RANGES = "Accetp-Ranges"; 
   
  private Map<String, String> headerMap; 
  public HttpResponseHeaderParser() { 
    headerMap = new HashMap<String, String>(); 
  } 
  /** 
   * <p> get the response header key value pair </p> 
   * @param responseHeaderLine 
   */ 
  public void addResponseHeaderLine(String responseHeaderLine) { 
    if(responseHeaderLine.contains(":")) { 
      String[] keyValue = responseHeaderLine.split(": "); 
      if(keyValue[0].equalsIgnoreCase(CONTENT_LENGTH)) { 
        headerMap.put(CONTENT_LENGTH, keyValue[1]); 
      } else if(keyValue[0].equalsIgnoreCase(CONTENT_TYPE)) { 
        headerMap.put(CONTENT_TYPE, keyValue[1]); 
      } else { 
        headerMap.put(keyValue[0], keyValue[1]); 
      } 
    } 
  } 
   
  public int getFileLength() { 
    if(headerMap.get(CONTENT_LENGTH) == null){ 
      return 0; 
    } 
    return Integer.parseInt(headerMap.get(CONTENT_LENGTH)); 
  } 
   
  public String getFileType() { 
    return headerMap.get(CONTENT_TYPE); 
  } 
  public Map<String, String> getAllHeaders() { 
    return headerMap; 
  } 
 
}

以上就是本文的全體內容，願望對年夜家的進修java法式設計有所贊助。