用 Java 实现断点续传-实现 (HTTP)
断点续传内核的实现
主要用了 6 个类，包括一个测试类。
SiteFileFetch.java 负责整个文件的抓取，控制内部线程 (FileSplitterFetch 类 )。
FileSplitterFetch.java 负责部分文件的抓取。
FileAccess.java 负责文件的存储。
SiteInfoBean.java 要抓取的文件的信息，如文件保存的目录，名字，抓取文件的 URL 等。
Utility.java 工具类，放一些简单的方法。
TestMethod.java 测试类。
下面是源程序：
主要用了 6 个类，包括一个测试类。
SiteFileFetch.java 负责整个文件的抓取，控制内部线程 (FileSplitterFetch 类 )。
FileSplitterFetch.java 负责部分文件的抓取。
FileAccess.java 负责文件的存储。
SiteInfoBean.java 要抓取的文件的信息，如文件保存的目录，名字，抓取文件的 URL 等。
Utility.java 工具类，放一些简单的方法。
TestMethod.java 测试类。
下面是源程序：
package cn.hiservice.download;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
/**
*
* @author Administrator
*
*/
public class SiteFileFetch extends Thread {
SiteInfoBean siteInfoBean = null; // 文件信息 Bean
long[] nStartPos; // 开始位置
long[] nEndPos; // 结束位置
FileSplitterFetch[] fileSplitterFetch; // 子线程对象
long nFileLength; // 文件长度
boolean bFirst = true; // 是否第一次取文件
boolean bStop = false; // 停止标志
File tmpFile; // 文件下载的临时信息
DataOutputStream output; // 输出到文件的输出流
public SiteFileFetch(SiteInfoBean bean) throws IOException {
siteInfoBean = bean;
tmpFile = new File(bean.getSFilePath() + File.separator
+ bean.getSFileName() + ".info");
System.out.println(tmpFile);
if (tmpFile.exists()) {
bFirst = false;
read_nPos();
} else {
nStartPos = new long[bean.getNSplitter()];
nEndPos = new long[bean.getNSplitter()];
}
}
public void run() {
// 获得文件长度
// 分割文件
// 实例 FileSplitterFetch
// 启动 FileSplitterFetch 线程
// 等待子线程返回
try {
if (bFirst) {
nFileLength = getFileSize();
if (nFileLength == -1) {
System.err.println("File Length is not known!");
} else if (nFileLength == -2) {
System.err.println("File is not access!");
} else {
for (int i = 0; i < nStartPos.length; i++) {
nStartPos[i] = (long) (i * (nFileLength / nStartPos.length));
}
for (int i = 0; i < nEndPos.length - 1; i++) {
nEndPos[i] = nStartPos[i + 1];
}
nEndPos[nEndPos.length - 1] = nFileLength;
}
}
// 启动子线程
fileSplitterFetch = new FileSplitterFetch[nStartPos.length];
for (int i = 0; i < nStartPos.length; i++) {
fileSplitterFetch[i] = new FileSplitterFetch(siteInfoBean
.getSSiteURL(), siteInfoBean.getSFilePath()
+ File.separator + siteInfoBean.getSFileName(),
nStartPos[i], nEndPos[i], i);
Utility.log("Thread " + i + " , nStartPos = " + nStartPos[i]
+ ", nEndPos = " + nEndPos[i]);
fileSplitterFetch[i].start();
}
/*
* fileSplitterFetch[nPos.length-1] = new
* FileSplitterFetch(siteInfoBean.getSSiteURL(),
* siteInfoBean.getSFilePath() + File.separator +
* siteInfoBean.getSFileName
* (),nPos[nPos.length-1],nFileLength,nPos.length-1);
*/
// Utility.log("Thread " +(nPos.length-1) +
// ",nStartPos = "+nPos[nPos.length-1]+",
// nEndPos = " + nFileLength);
// fileSplitterFetch[nPos.length-1].start();
// 等待子线程结束
// int count = 0;
// 是否结束 while 循环
boolean breakWhile = false;
while (!bStop) {
write_nPos();
Utility.sleep(500);
breakWhile = true;
for (int i = 0; i < nStartPos.length; i++) {
if (!fileSplitterFetch[i].bDownOver) {
breakWhile = false;
break;
}
}
if (breakWhile)
break;
// count++;
// if(count>4)
// siteStop();
}
System.err.println("文件下载结束！");
} catch (Exception e) {
e.printStackTrace();
}
}
// 获得文件长度
public long getFileSize() {
int nFileLength = -1;
try {
URL url = new URL(siteInfoBean.getSSiteURL());
HttpURLConnection httpConnection = (HttpURLConnection) url
.openConnection();
httpConnection.setRequestProperty("User-Agent", "NetFox");
int responseCode = httpConnection.getResponseCode();
if (responseCode >= 400) {
processErrorCode(responseCode);
return -2; // -2 represent access is error
}
String sHeader;
for (int i = 1;; i++) {
// DataInputStream in = new
// DataInputStream(httpConnection.getInputStream ());
// Utility.log(in.readLine());
sHeader = httpConnection.getHeaderFieldKey(i);
if (sHeader != null) {
if (sHeader.equals("Content-Length")) {
nFileLength = Integer.parseInt(httpConnection
.getHeaderField(sHeader));
break;
}
} else
break;
}
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
Utility.log(nFileLength);
return nFileLength;
}
// 保存下载信息（文件指针位置）
private void write_nPos() {
try {
output = new DataOutputStream(new FileOutputStream(tmpFile));
output.writeInt(nStartPos.length);
for (int i = 0; i < nStartPos.length; i++) {
// output.writeLong(nPos[i]);
output.writeLong(fileSplitterFetch[i].nStartPos);
output.writeLong(fileSplitterFetch[i].nEndPos);
}
output.close();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
// 读取保存的下载信息（文件指针位置）
private void read_nPos() {
try {
DataInputStream input = new DataInputStream(new FileInputStream(
tmpFile));
int nCount = input.readInt();
nStartPos = new long[nCount];
nEndPos = new long[nCount];
for (int i = 0; i < nStartPos.length; i++) {
nStartPos[i] = input.readLong();
nEndPos[i] = input.readLong();
}
input.close();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}
}
private void processErrorCode(int nErrorCode) {
System.err.println("Error Code : " + nErrorCode);
}
// 停止文件下载
public void siteStop() {
bStop = true;
for (int i = 0; i < nStartPos.length; i++)
fileSplitterFetch[i].splitterStop();
}
public static void main(String[] args) {
new TestMethod();
}
}
package cn.hiservice.download;
/*
**FileSplitterFetch.java
*/
import java.io.*;
import java.net.*;
public class FileSplitterFetch extends Thread {
String sURL; // File URL
long nStartPos; // File Snippet Start Position
long nEndPos; // File Snippet End Position
int nThreadID; // Thread's ID
boolean bDownOver = false; // Downing is over
boolean bStop = false; // Stop identical
FileAccessI fileAccessI = null; // File Access interface
public FileSplitterFetch(String sURL, String sName, long nStart, long nEnd,
int id) throws IOException {
this.sURL = sURL;
this.nStartPos = nStart;
this.nEndPos = nEnd;
nThreadID = id;
fileAccessI = new FileAccessI(sName, nStartPos);
}
public void run() {
while (nStartPos < nEndPos && !bStop) {
try {
URL url = new URL(sURL);
HttpURLConnection httpConnection = (HttpURLConnection) url
.openConnection();
httpConnection.setRequestProperty("User-Agent", "NetFox");
String sProperty = "bytes=" + nStartPos + "-";
httpConnection.setRequestProperty("RANGE", sProperty);
Utility.log(sProperty);
InputStream input = httpConnection.getInputStream();
// logResponseHead(httpConnection);
byte[] b = new byte[1024];
int nRead;
while ((nRead = input.read(b, 0, 1024)) > 0
&& nStartPos < nEndPos && !bStop) {
nStartPos += fileAccessI.write(b, 0, nRead);
// if(nThreadID == 1)
// Utility.log("nStartPos = " + nStartPos + ", nEndPos = " +
// nEndPos);
}
Utility.log("Thread " + nThreadID + " is over!");
bDownOver = true;
// nPos = fileAccessI.write (b,0,nRead);
} catch (Exception e) {
e.printStackTrace();
}
}
}
// 打印回应的头信息
public void logResponseHead(HttpURLConnection con) {
for (int i = 1;; i++) {
String header = con.getHeaderFieldKey(i);
if (header != null)
// responseHeaders.put(header,httpConnection.getHeaderField(header));
Utility.log(header + " : " + con.getHeaderField(header));
else
break;
}
}
public void splitterStop() {
bStop = true;
}
}
package cn.hiservice.download;
public class SiteInfoBean {
private String sSiteURL; // Site's URL
private String sFilePath; // Saved File's Path
private String sFileName; // Saved File's Name
private int nSplitter; // Count of Splited Downloading File
public SiteInfoBean() {
// default value of nSplitter is 5
this("", "", "", 5);
}
public SiteInfoBean(String sURL, String sPath, String sName, int nSpiltter) {
sSiteURL = sURL;
sFilePath = sPath;
sFileName = sName;
this.nSplitter = nSpiltter;
}
public String getSSiteURL() {
return sSiteURL;
}
public void setSSiteURL(String value) {
sSiteURL = value;
}
public String getSFilePath() {
return sFilePath;
}
public void setSFilePath(String value) {
sFilePath = value;
}
public String getSFileName() {
return sFileName;
}
public void setSFileName(String value) {
sFileName = value;
}
public int getNSplitter() {
return nSplitter;
}
public void setNSplitter(int nCount) {
nSplitter = nCount;
}
}
package cn.hiservice.download;
/*
**FileAccess.java
*/
import java.io.*;
public class FileAccessI implements Serializable {
private static final long serialVersionUID = 1L;
RandomAccessFile oSavedFile;
long nPos;
public FileAccessI() throws IOException {
this("", 0);
}
public FileAccessI(String sName, long nPos) throws IOException {
oSavedFile = new RandomAccessFile(sName, "rw");
this.nPos = nPos;
oSavedFile.seek(nPos);
}
public synchronized int write(byte[] b, int nStart, int nLen) {
int n = -1;
try {
oSavedFile.write(b, nStart, nLen);
n = nLen;
} catch (IOException e) {
e.printStackTrace();
}
return n;
}
}
package cn.hiservice.download;
/*
**Utility.java
*/
public class Utility {
public Utility() {
}
public static void sleep(int nSecond) {
try {
Thread.sleep(nSecond);
} catch (Exception e) {
e.printStackTrace();
}
}
public static void log(String sMsg) {
// System.err.println(sMsg);
}
public static void log(int sMsg) {
System.err.println(sMsg);
}
}
package cn.hiservice.download;
import org.junit.Test;
/*
**TestMethod.java
*/
public class TestMethod {
public TestMethod() {
try {
SiteInfoBean bean = new SiteInfoBean(
"http://localhost:8088/FileDownLoad/Ducati_Windows7.themepack", "D:\\temp",
"Ducati_Windows7.themepack", 3);
SiteFileFetch fileFetch = new SiteFileFetch(bean);
fileFetch.start();
} catch (Exception e) {
e.printStackTrace();
}
}
}