download.java

运用Java实现一个多线程文件下载

/*
 * download.java
 *
 * Created on 2008年5月19日, 上午10:52
 */

package 实验四;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLDecoder;
import javax.swing.JOptionPane;

/**
 *
 * @author  jsj
 */
public class download extends javax.swing.JFrame {
 
    /** Creates new form download */
    public download() {
        initComponents();
    }
    
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    // <editor-fold defaultstate="collapsed" desc="Generated Code">//GEN-BEGIN:initComponents
    private void initComponents() {

        jPanel1 = new javax.swing.JPanel();
        jTextFieldName = new javax.swing.JTextField();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jComboBox2 = new javax.swing.JComboBox();
        jLabel1 = new javax.swing.JLabel();
        jTextField1 = new javax.swing.JTextField();
        jButtonDown = new javax.swing.JButton();
        jScrollPane1 = new javax.swing.JScrollPane();
        jTextArea1 = new javax.swing.JTextArea();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
        setBackground(java.awt.Color.black);

        jPanel1.setBackground(new java.awt.Color(204, 204, 255));
        jPanel1.setBorder(new javax.swing.border.MatteBorder(null));

        jTextFieldName.setText(null);

        jLabel2.setFont(new java.awt.Font("宋体", 0, 14));
        jLabel2.setText("另存名称：");

        jLabel3.setFont(new java.awt.Font("宋体", 0, 14));
        jLabel3.setText("存储目录：");

        jComboBox2.setModel(new javax.swing.DefaultComboBoxModel(new String[] { "D:", "C:", "E:", "F:" }));

        jLabel1.setFont(new java.awt.Font("宋体", 0, 18));
        jLabel1.setText("URL:");

        jTextField1.setText("http://ty.cquc.edu.cn/upload/2008_05/08051410555815.wmv");

        jButtonDown.setText("确定");
        jButtonDown.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                jButtonDownActionPerformed(evt);
            }
        });

        jTextArea1.setColumns(20);
        jTextArea1.setRows(5);
        jScrollPane1.setViewportView(jTextArea1);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 350, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addGap(18, 18, 18)
                        .addComponent(jButtonDown))
                    .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, jPanel1Layout.createSequentialGroup()
                            .addComponent(jLabel3)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                            .addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, 81, javax.swing.GroupLayout.PREFERRED_SIZE)
                            .addGap(18, 18, 18)
                            .addComponent(jLabel2)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                            .addComponent(jTextFieldName))
                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, jPanel1Layout.createSequentialGroup()
                            .addComponent(jLabel1)
                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                            .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 365, javax.swing.GroupLayout.PREFERRED_SIZE))))
                .addContainerGap(17, Short.MAX_VALUE))
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel1)
                    .addComponent(jTextField1, javax.swing.GroupLayout.PREFERRED_SIZE, 26, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGap(18, 18, 18)
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(jLabel3)
                    .addComponent(jComboBox2, javax.swing.GroupLayout.PREFERRED_SIZE, 22, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addComponent(jLabel2)
                    .addComponent(jTextFieldName, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE))
                .addGroup(jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 131, javax.swing.GroupLayout.PREFERRED_SIZE))
                    .addGroup(jPanel1Layout.createSequentialGroup()
                        .addGap(42, 42, 42)
                        .addComponent(jButtonDown, javax.swing.GroupLayout.PREFERRED_SIZE, 37, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addGap(30, 30, 30))
        );

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addComponent(jPanel1, javax.swing.GroupLayout.DEFAULT_SIZE, 234, Short.MAX_VALUE)
        );

        pack();
    }// </editor-fold>//GEN-END:initComponents

    private void jButtonDownActionPerformed(java.awt.event.ActionEvent evt) {//GEN-FIRST:event_jButtonDownActionPerformed
        // TODO add your handling code here:
        xiazai();
    }//GEN-LAST:event_jButtonDownActionPerformed
    
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new download().setVisible(true);
            }
        });
    }
      private void xiazai()
      {   InputStream ins=null;
          try{
              URL u=new URL(URLDecoder.decode(jTextField1.getText(),"gbk"));
              HttpURLConnection us=(HttpURLConnection)u.openConnection();
              us.setRequestMethod("HEAD");
              String s = us.getHeaderField("Accept-Ranges");
            if (s != null && s.equals("bytes")) {
                JOptionPane.showMessageDialog(this, "请求的文件总长度为" + us.getContentLength() + "字节。");
            } else {
                JOptionPane.showMessageDialog(this, "请求的文件不支持断点下载！");
                return;
            }
            String pathName;
            pathName = u.getFile();
            fileName = pathName.substring(pathName.lastIndexOf('/')+1);
             if (jTextFieldName.getText().equals("")) {
                fileName = jTextFieldName.getText();
            }
             int number=us.getContentLength();
             length=number/threadCount;
           for(int i=1;i<=threadCount;i++)  
           {    int m,n;
                m=(i-1)*length;
                n=i*length-1;
                if(i!=threadCount){
               new Thread(new Myrunnable(m,n)).start();
                }
                else{
                  new Thread(new Myrunnable(m,number-1)).start();
                }
           }
          }catch(MalformedURLException e)
          {  
            jTextArea1.append("出现MalformedURLException异常");
          }catch(IOException e)
          {
              jTextArea1.append("出现IOException异常");
      }     
      }
      String fileName;
      int threadCount=5;
      int length;
      int total=0;
    // Variables declaration - do not modify//GEN-BEGIN:variables
    private javax.swing.JButton jButtonDown;
    private javax.swing.JComboBox jComboBox2;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JTextArea jTextArea1;
    private javax.swing.JTextField jTextField1;
    private javax.swing.JTextField jTextFieldName;
    // End of variables declaration//GEN-END:variables
  class Myrunnable implements Runnable{
      int start,end;
      Myrunnable(int a,int b){
          start=a;
          end=b;
      }
      public void run() {  
          BufferedInputStream bins=null;
             BufferedOutputStream bous=null;
         try{
              URL u=new URL(URLDecoder.decode(jTextField1.getText(),"gbk"));
              HttpURLConnection uc=(HttpURLConnection) u.openConnection();
              uc.setRequestMethod("GET");
               String mn="bytes="+start+"-"+end;      
               uc.setRequestProperty("Range", mn);
               bins=new BufferedInputStream(u.openStream());
              RandomAccessFile  f=new RandomAccessFile(jComboBox2.getSelectedItem()+fileName,"rw"); 
              f.seek(start);
                byte[] b = new byte[1024];
                int count;
                while ((count = bins.read(b, 0, b.length)) != -1) {
                f.write(b,0,count);
            }
               total=total+1;
               if(total==threadCount){
               jTextArea1.append("下载完毕");
               }
         } catch(MalformedURLException e){
            jTextArea1.append("出现MalformedURLException异常");
         }catch(IOException e){
                 jTextArea1.append("出现IOException异常");
      }finally{
          try{
              if(bins!=null)
              {
                  bins.close();
              }
             }catch(IOException e){
                  System.out.println(e);           
          }
      }
              
      
  }  
}
}