Java-Socket实现文件的断点续传
前段时间因为任务需要本人这个java渣渣开始研究如何用java实现简单的文件断点续传。所谓的文件断点续传,我的理解是文件在传输过程中因为某些原因程序停止运行文件终止传输,下一次重新传输文件的时候还能从上一次传输的位置开始传输,而不需要重新从头开始。
文件传输的过程分为发送方和接收方,最终我的思路是这样的:
1:传输开始之前发送方先向接收方发送一个确认信息,然后再向接收方发送准备发送的文件的文件名
2:接收方收到确认信息之后,接收从发送方发送过来的文件名,接收完之后向发送方发送一个确认信息表示文件名接收完毕,然后接收方根据收到的文件名创建一个“.temp”File对象和一个“.temp”RandomAccessFile对象。获取这个File对象所对应文件的长度(大小)(这个长度就是接收方已经接受的长度,如果之前没有接收过这个文件,长度就为0),并把文件长度发送给发送方。
3:发送方收到确认信息之后,接收接受方发送的文件长度,然后向接收方发送准备发送的文件的总长度,并向接收方发送一个确认信息。然后根据接收方发送的文件长度,从文件对应长度的位置开始发送。
4:接收方收到确认信息之后,接受发送方发送过来的数据,然后从此文件的末尾写入。接受完成之后再将“.temp”文件重命名为正常的文件名。
把过程画成图就是下面这样:
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.Socket;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
public class SendFile extends Thread{
private Socket socket=null;
private DataOutputStream dos;
private DataInputStream dis;
private RandomAccessFile rad;
private Container contentPanel;
private JFrame frame;
private JProgressBar progressbar;
private JLabel label;
public SendFile(){
frame=new JFrame("文件传输");
try {
socket=new Socket("localhost", 8080);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void run(){
JFileChooser fc = new JFileChooser();
int status=fc.showOpenDialog(null);
if (status==JFileChooser.APPROVE_OPTION) {
String path=fc.getSelectedFile().getPath();
try {
dos=new DataOutputStream(socket.getOutputStream());
dis=new DataInputStream(socket.getInputStream());
dos.writeUTF("ok");
rad=new RandomAccessFile(path, "r");
File file=new File(path);
byte[] buf=new byte[1024];
dos.writeUTF(file.getName());
dos.flush();
String rsp=dis.readUTF();
if (rsp.equals("ok")) {
long size=dis.readLong();//读取文件已发送的大小
dos.writeLong(rad.length());
dos.writeUTF("ok");
dos.flush();
long offset=size;//字节偏移量
int barSize=(int) (rad.length()/1024);
int barOffset=(int)(offset/1024);
//传输界面
frame.setSize(380,120);
contentPanel = frame.getContentPane();
contentPanel.setLayout(new BoxLayout(contentPanel, BoxLayout.Y_AXIS));
progressbar = new JProgressBar();//进度条
label=new JLabel(file.getName()+" 发送中");
contentPanel.add(label);
progressbar.setOrientation(JProgressBar.HORIZONTAL);
progressbar.setMinimum(0);
progressbar.setMaximum(barSize);
progressbar.setValue(barOffset);
progressbar.setStringPainted(true);
progressbar.setPreferredSize(new Dimension(150, 20));
progressbar.setBorderPainted(true);
progressbar.setBackground(Color.pink);
JButton cancel=new JButton("取消");
JPanel barPanel=new JPanel();
barPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
barPanel.add(progressbar);
barPanel.add(cancel);
contentPanel.add(barPanel);
cancel.addActionListener(new CancelActionListener());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
//从文件指定位置开始传输
int length;
if (offset<rad.length()) {
rad.seek(offset);
while((length=rad.read(buf))>0){
dos.write(buf,0,length);
progressbar.setValue(++barOffset);
dos.flush();
}
}
label.setText(file.getName()+" 发送完成");
}
dis.close();
dos.close();
rad.close();
} catch (IOException e) {
// TODO Auto-generated catch block
label.setText(" 取消发送,连接关闭");
}finally {
frame.dispose();
}
}
}
class CancelActionListener implements ActionListener{
public void actionPerformed(ActionEvent e3){
try {
label.setText(" 取消发送,连接关闭");
JOptionPane.showMessageDialog(frame, "取消发送给,连接关闭!", "提示:", JOptionPane.INFORMATION_MESSAGE);
dis.close();
dos.close();
rad.close();
frame.dispose();
socket.close();
} catch (IOException e1) {
}
}
}
}
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.net.ServerSocket;
import java.net.Socket;
import javax.swing.BoxLayout;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JProgressBar;
public class ReceiveFile extends Thread{
private ServerSocket connectSocket=null;
private Socket socket=null;
private JFrame frame;
private Container contentPanel;
private JProgressBar progressbar;
private DataInputStream dis;
private DataOutputStream dos;
private RandomAccessFile rad;
private JLabel label;
public ReceiveFile(){
frame=new JFrame("接收文件");
try {
connectSocket=new ServerSocket(8080);//发送方和接收方的端口必须一致
socket=connectSocket.accept();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public void run(){
try {
dis=new DataInputStream(socket.getInputStream());
dos=new DataOutputStream(socket.getOutputStream());
dis.readUTF();
int permit=JOptionPane.showConfirmDialog(frame, "是否接收文件","文件传输请求:", JOptionPane.YES_NO_OPTION);
if (permit==JOptionPane.YES_OPTION) {
String filename=dis.readUTF();
dos.writeUTF("ok");
dos.flush();
File file=new File(filename+".temp");
rad=new RandomAccessFile(filename+".temp", "rw");
//获得文件大小
long size=0;
if(file.exists()&& file.isFile()){
size=file.length();
}
dos.writeLong(size);//发送已接收的大小
dos.flush();
long allSize=dis.readLong();
String rsp=dis.readUTF();
int barSize=(int)(allSize/1024);
int barOffset=(int)(size/1024);
//传输界面
frame.setSize(300,120);
contentPanel =frame.getContentPane();
contentPanel.setLayout(new BoxLayout(contentPanel, BoxLayout.Y_AXIS));
progressbar = new JProgressBar();//进度条
label=new JLabel(filename+" 接收中");
contentPanel.add(label);
progressbar.setOrientation(JProgressBar.HORIZONTAL);
progressbar.setMinimum(0);
progressbar.setMaximum(barSize);
progressbar.setValue(barOffset);
progressbar.setStringPainted(true);
progressbar.setPreferredSize(new Dimension(150, 20));
progressbar.setBorderPainted(true);
progressbar.setBackground(Color.pink);
JButton cancel=new JButton("取消");
JPanel barPanel=new JPanel();
barPanel.setLayout(new FlowLayout(FlowLayout.LEFT));
barPanel.add(progressbar);
barPanel.add(cancel);
contentPanel.add(barPanel);
cancel.addActionListener(new CancelActionListener());
frame.setDefaultCloseOperation(
JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
//接收文件
if (rsp.equals("ok")) {
rad.seek(size);
int length;
byte[] buf=new byte[1024];
while((length=dis.read(buf, 0, buf.length))!=-1){
rad.write(buf,0,length);
progressbar.setValue(++barOffset);
}
System.out.println("FileReceive end...");
}
label.setText(filename+" 结束接收");
dis.close();
dos.close();
rad.close();
frame.dispose();
//文件重命名
if (barOffset>=barSize) {
file.renameTo(new File(filename));
}
}else{
dis.close();
dos.close();
frame.dispose();
}
} catch (IOException e) {
// TODO Auto-generated catch block
label.setText(" 已取消接收,连接关闭!");
}finally {
frame.dispose();
}
}
class CancelActionListener implements ActionListener{
public void actionPerformed(ActionEvent e){
try {
dis.close();
dos.close();
rad.close();
JOptionPane.showMessageDialog(frame, "已取消接收,连接关闭!", "提示:", JOptionPane.INFORMATION_MESSAGE);
label.setText(" 取消接收,连接关闭");
} catch (IOException e1) {
}
}
}
}
public class FileReceiveTest{//接收方
public static void main(String[] args) {
// TODO Auto-generated method stub
ReceiveFile rf=new ReceiveFile();
rf.start();
}
}
public class FileSendTest{//发送方
public static void main(String[] args) {
// TODO Auto-generated method stub
SendFile sf=new SendFile();
sf.start();
}
}
![](https://img2018.cnblogs.com/blog/1508950/201903/1508950-20190304172938553-774312528.png)
点击是后,开始接收,点击否就取消
至此就成功结束了!