目录
1 需求背景
最近工作内容变化的很快，不到一个月的时间，已经交接了三个项目。目前遇到了一个新的需求，实现ftp的断点传输功能。
那么什么叫断点传输呢？理解起来其实很简单。断点，就是上次传输的时候突然断了，这次接着上次的传输的进度继续传。
2 原理介绍
那么字面意思，我们已经理解了，实际上ftp断点传输是怎么实现的呢？
实现起来也很简单，每次传输前，先检查下远程文件是否已经存在，如果存在了，那么我们就读取这个文件的大小。然后比较下带传输文件和现在的文件的大小。如果没有现在的文件大，那么可以认为之前上传的文件是完成的，本次不需要上传，但是，现在的文件要是比待上传的文件小的话，就需要重新或者继续上传了。选择继续上传的话，就是断点传输了。
3 代码实现
那么怎么实现这次上传接着上次上传呢？我们都知道，文件操作是有一个文件指针的，每次操作的时候，指针都会移动。因此，如果想实现继续接着上次上传文件，只需要将待上传的文件指针移动一个已经上传的文件的大小即可。明白了原理，代码也就好写了。
package ftpTest;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.RandomAccessFile;
import org.apache.commons.net.ftp.FTP;
import org.apache.commons.net.ftp.FTPClient;
import org.apache.commons.net.ftp.FTPFile;
import org.apache.commons.net.ftp.FTPReply;
public class FtpTransTest {
// 枚举类UploadStatus代码
public enum UploadStatus {
Create_Directory_Fail, // 远程服务器相应目录创建失败
Create_Directory_Success, // 远程服务器闯将目录成功
Upload_New_File_Success, // 上传新文件成功
Upload_New_File_Failed, // 上传新文件失败
File_Exits, // 文件已经存在
Remote_Bigger_Local, // 远程文件大于本地文件
Upload_From_Break_Success, // 断点续传成功
Upload_From_Break_Failed, // 断点续传失败
Delete_Remote_Faild; // 删除远程文件失败
}
// 枚举类DownloadStatus代码
public enum DownloadStatus {
Remote_File_Noexist, // 远程文件不存在
Local_Bigger_Remote, // 本地文件大于远程文件
Download_From_Break_Success, // 断点下载文件成功
Download_From_Break_Failed, // 断点下载文件失败
Download_New_Success, // 全新下载文件成功
Download_New_Failed; // 全新下载文件失败
}
public FTPClient ftpClient = new FTPClient();
private String ftpURL, username, pwd, ftpport, file1, file2;
public FtpTransTest(String _ftpURL, String _username, String _pwd,
String _ftpport, String _file1, String _file2) {
// 设置将过程中使用到的命令输出到控制台
ftpURL = _ftpURL;
username = _username;
pwd = _pwd;
ftpport = _ftpport;
file1 = _file1;
file2 = _file2;
}
/**
* 连接到FTP服务器
*
* @param hostname
* 主机名
* @param port
* 端口
* @param username
* 用户名
* @param password
* 密码
* @return 是否连接成功
* @throws IOException
*/
public boolean connect(String hostname, int port, String username,
String password) throws IOException {
ftpClient.connect(hostname, port);
ftpClient.setControlEncoding("GBK");
System.out.println("[connect] begin to connect");
if (FTPReply.isPositiveCompletion(ftpClient.getReplyCode())) {
if (ftpClient.login(username, password)) {
System.out.println("[connect] login success");
return true;
}
}
System.out.println("[connect] faild to connect.");
disconnect();
return false;
}
/**
* 从FTP服务器上下载文件,支持断点续传，上传百分比汇报
*
* @param remote
* 远程文件路径
* @param local
* 本地文件路径
* @return 上传的状态
* @throws IOException
*/
public DownloadStatus download(String remote, String local)
throws IOException {
// 设置被动模式
ftpClient.enterLocalPassiveMode();
// 设置以二进制方式传输
ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
DownloadStatus result;
// 检查远程文件是否存在
FTPFile[] files = ftpClient.listFiles(new String(
remote.getBytes("GBK"), "iso-8859-1"));
if (files.length != 1) {
System.out.println("远程文件不存在");
return DownloadStatus.Remote_File_Noexist;
}
long remoteSize = files[0].getSize();
File f = new File(local);
// 本地存在文件，进行断点下载
if (f.exists()) {
long localSize = f.length();
// 判断本地文件大小是否大于远程文件大小
if (localSize >= remoteSize) {
System.out.println("本地文件大于远程文件，下载中止");
return DownloadStatus.Local_Bigger_Remote;
}
// 进行断点续传，并记录状态
FileOutputStream out = new FileOutputStream(f, true);
ftpClient.setRestartOffset(localSize);
InputStream in = ftpClient.retrieveFileStream(new String(remote
.getBytes("GBK"), "iso-8859-1"));
byte[] bytes = new byte[1024];
long step = remoteSize / 100;
long process = localSize / step;
int c;
while ((c = in.read(bytes)) != -1) {
out.write(bytes, 0, c);
localSize += c;
long nowProcess = localSize / step;
if (nowProcess > process) {
process = nowProcess;
if (process % 10 == 0)
System.out.println("下载进度：" + process);
// TODO 更新文件下载进度,值存放在process变量中
}
}
in.close();
out.close();
boolean isDo = ftpClient.completePendingCommand();
if (isDo) {
result = DownloadStatus.Download_From_Break_Success;
} else {
result = DownloadStatus.Download_From_Break_Failed;
}
} else {
OutputStream out = new FileOutputStream(f);
InputStream in = ftpClient.retrieveFileStream(new String(remote
.getBytes("GBK"), "iso-8859-1"));
byte[] bytes = new byte[1024];
long step = remoteSize / 100;
long process = 0;
long localSize = 0L;
int c;
while ((c = in.read(bytes)) != -1) {
out.write(bytes, 0, c);
localSize += c;
long nowProcess = localSize / step;
if (nowProcess > process) {
process = nowProcess;
if (process % 10 == 0)
System.out.println("下载进度：" + process);
// TODO 更新文件下载进度,值存放在process变量中
}
}
in.close();
out.close();
boolean upNewStatus = ftpClient.completePendingCommand();
if (upNewStatus) {
result = DownloadStatus.Download_New_Success;
} else {
result = DownloadStatus.Download_New_Failed;
}
}
return result;
}
/**
* 上传文件到FTP服务器，支持断点续传
*
* @param local
* 本地文件名称，绝对路径
* @param remote
* 远程文件路径，使用/home/directory1/subdirectory/file.ext或是
* http://www.guihua.org /subdirectory/file.ext
* 按照Linux上的路径指定方式，支持多级目录嵌套，支持递归创建不存在的目录结构
* @return 上传结果
* @throws IOException
*/
public UploadStatus upload(String local, String remote) throws IOException {
// 设置PassiveMode传输
ftpClient.enterLocalPassiveMode();
// 设置以二进制流的方式传输
ftpClient.setFileType(FTP.BINARY_FILE_TYPE);
ftpClient.setControlEncoding("GBK");
UploadStatus result;
// 对远程目录的处理
String remoteFileName = remote;
if (remote.contains("/")) {
remoteFileName = remote.substring(remote.lastIndexOf("/") + 1);
// 创建服务器远程目录结构，创建失败直接返回
if (CreateDirecroty(remote, ftpClient) == UploadStatus.Create_Directory_Fail) {
return UploadStatus.Create_Directory_Fail;
}
}
System.out.println("[upload]begin to check file exists or not ");
// 检查远程是否存在文件
FTPFile[] files = ftpClient.listFiles(new String(remoteFileName
.getBytes("GBK"), "iso-8859-1"));
System.out.println("[upload] check over");
if (files.length == 1) {
long remoteSize = files[0].getSize();
File f = new File(local);
long localSize = f.length();
if (remoteSize == localSize) {
return UploadStatus.File_Exits;
} else if (remoteSize > localSize) {
return UploadStatus.Remote_Bigger_Local;
}
// 尝试移动文件内读取指针,实现断点续传
result = uploadFile(remoteFileName, f, ftpClient, remoteSize);
// 如果断点续传没有成功，则删除服务器上文件，重新上传
if (result == UploadStatus.Upload_From_Break_Failed) {
if (!ftpClient.deleteFile(remoteFileName)) {
return UploadStatus.Delete_Remote_Faild;
}
result = uploadFile(remoteFileName, f, ftpClient, 0);
}
} else {
result = uploadFile(remoteFileName, new File(local), ftpClient, 0);
}
return result;
}
/**
* 断开与远程服务器的连接
*
* @throws IOException
*/
public void disconnect() throws IOException {
if (ftpClient.isConnected()) {
ftpClient.disconnect();
}
}
/**
* 递归创建远程服务器目录
*
* @param remote
* 远程服务器文件绝对路径
* @param ftpClient
* FTPClient 对象
* @return 目录创建是否成功
* @throws IOException
*/
public UploadStatus CreateDirecroty(String remote, FTPClient ftpClient)
throws IOException {
UploadStatus status = UploadStatus.Create_Directory_Success;
String directory = remote.substring(0, remote.lastIndexOf("/") + 1);
if (!directory.equalsIgnoreCase("/")
&& !ftpClient.changeWorkingDirectory(new String(directory
.getBytes("GBK"), "iso-8859-1"))) {
// 如果远程目录不存在，则递归创建远程服务器目录
int start = 0;
int end = 0;
if (directory.startsWith("/")) {
start = 1;
} else {
start = 0;
}
end = directory.indexOf("/", start);
while (true) {
String subDirectory = new String(remote.substring(start, end)
.getBytes("GBK"), "iso-8859-1");
if (!ftpClient.changeWorkingDirectory(subDirectory)) {
if (ftpClient.makeDirectory(subDirectory)) {
ftpClient.changeWorkingDirectory(subDirectory);
} else {
System.out.println("创建目录失败");
return UploadStatus.Create_Directory_Fail;
}
}
start = end + 1;
end = directory.indexOf("/", start);
// 检查所有目录是否创建完毕
if (end <= start) {
break;
}
}
}
return status;
}
/** */
/**
* 上传文件到服务器,新上传和断点续传
*
* @param remoteFile
* 远程文件名，在上传之前已经将服务器工作目录做了改变
* @param localFile
* 本地文件 File句柄，绝对路径
* @param processStep
* 需要显示的处理进度步进值
* @param ftpClient
* FTPClient 引用
* @return
* @throws IOException
*/
public UploadStatus uploadFile(String remoteFile, File localFile,
FTPClient ftpClient, long remoteSize) throws IOException {
UploadStatus status;
// 显示进度的上传
System.out.println("[uploadFile]begin to upload file");
long step = localFile.length() / 100;
long process = 0;
long localreadbytes = 0L;
RandomAccessFile raf = new RandomAccessFile(localFile, "r");
OutputStream out = ftpClient.appendFileStream(new String(remoteFile
.getBytes("GBK"), "iso-8859-1"));
// 断点续传
if (remoteSize > 0) {
ftpClient.setRestartOffset(remoteSize);
process = remoteSize / step;
raf.seek(remoteSize);
localreadbytes = remoteSize;
}
byte[] bytes = new byte[1024];
int c;
while ((c = raf.read(bytes)) != -1) {
out.write(bytes, 0, c);
localreadbytes += c;
if (localreadbytes / step != process) {
process = localreadbytes / step;
System.out.println("上传进度:" + process);
}
}
out.flush();
raf.close();
out.close();
boolean result = ftpClient.completePendingCommand();
if (remoteSize > 0) {
status = result ? UploadStatus.Upload_From_Break_Success
: UploadStatus.Upload_From_Break_Failed;
} else {
status = result ? UploadStatus.Upload_New_File_Success
: UploadStatus.Upload_New_File_Failed;
}
return status;
}
public void run() {
try {
System.out.println("begin to connect");
this.connect(ftpURL, new java.lang.Integer(ftpport), username, pwd);
System.out.println("[run] begin to upload file.");
this.upload(file1, file2);
this.disconnect();
} catch (IOException e) {
System.out.println("连接FTP出错：" + e.getMessage());
}
}
public static void main(String[] args) {
// TODO Auto-generated method stub
String _ftpURL = "ip";
String _ftpport = "21";
String _username = "账户";
String _pwd = "密码";
String _file1 = "本地文件";
String _file2 = "远程保存的文件和文件名";
FtpTransTest ftpTransTes = new FtpTransTest(_ftpURL, _username, _pwd, _ftpport, _file1, _file2);
ftpTransTes.run();
}
}
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