本文实例讲述了Java编程实现服务器端支持断点续传的方法。分享给大家供大家参考，具体如下：
大家知道Tomcat之流对静态资源可以实现断点续传支持，但是如果是一个被控制的流，如有权限控制，或下载地址仅是个代理的时候，这时候需要自己实现断点续传的支持，小弟不才，这里提供基本断点续传[a-,-b,a-b]的简单实现，经验证，可支持迅雷7和火狐的多次断点续传。现贴出代码，大家共同分享：
Servlet
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.io.UnsupportedEncodingException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URLDecoder;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.bsteel.cloud.storage.servlet.base.BaseServlet;
import com.bsteel.cloud.storage.utils.FileUtil;
/**
* 文件下载(支持断点续传【迅雷\快车\旋风\Firefox\Chrome】)
* @author jdkleo
*
*/
public class FileIoServlet extends BaseServlet {
private static final long serialVersionUID = 1L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
this.doPost(req, resp);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{
download(request,response);
}
/**
* 文件下载
* @param request
* @param response
* @throws UnsupportedEncodingException
*/
private void download(HttpServletRequest request,HttpServletResponse response) throws UnsupportedEncodingException {
File downloadFile = getFile(request);
long pos = FileUtil.headerSetting(downloadFile, request, response);
// log.info("跳过"+pos);
ServletOutputStream os = null;
BufferedOutputStream out = null;
RandomAccessFile raf = null;
byte b[] = new byte[1024];//暂存容器
try {
os = response.getOutputStream();
out = new BufferedOutputStream(os);
raf = new RandomAccessFile(downloadFile, "r");
raf.seek(pos);
try {
int n = 0;
while ((n = raf.read(b, 0, 1024)) != -1) {
out.write(b, 0, n);
}
out.flush();
} catch(IOException ie) {
}
} catch (Exception e) {
log.error(e.getMessage(), e);
} finally {
if (out != null) {
try {
out.close();
} catch (IOException e) {
log.error(e.getMessage(), e);
}
}
if (raf != null) {
try {
raf.close();
} catch (IOException e) {
log.error(e.getMessage(), e);
}
}
}
}
private File getFile(HttpServletRequest request) throws UnsupportedEncodingException {
String uriStr = request.getParameter("uri");
if (null != uriStr){
uriStr = URLDecoder.decode(uriStr,"UTF-8");
if (uriStr.startsWith("file://")){
uriStr = uriStr.substring(7);
return new File(uriStr);
}else if (uriStr.startsWith("hbase://")){
try {
return new File(new URI(uriStr));
} catch (URISyntaxException e) {
log.error(e.getMessage(),e);
}
}
}
throw new RuntimeException("it's not a real uri");
}
}
Range支持
import java.io.File;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* 文件处理工具
* @author jdkleo
*
*/
public class FileUtil {
/**
* 断点续传支持
* @param file
* @param request
* @param response
* @return 跳过多少字节
*/
public static long headerSetting(File file,HttpServletRequest request, HttpServletResponse response) {
long len = file.length();//文件长度
if ( null == request.getHeader("Range") ){
setResponse(new RangeSettings(len),file.getName(),response);
return 0;
}
String range = request.getHeader("Range").replaceAll("bytes=", "");
RangeSettings settings = getSettings(len,range);
setResponse(settings,file.getName(),response);
return settings.getStart();
}
private static void setResponse(RangeSettings settings,String fileName, HttpServletResponse response) {
response.addHeader("Content-Disposition", "attachment; filename=\"" + IoUtil.toUtf8String(fileName) + "\"");
response.setContentType( IoUtil.setContentType(fileName));// set the MIME type.
if (!settings.isRange())
{
response.addHeader("Content-Length", String.valueOf(settings.getTotalLength()));
}
else
{
long start = settings.getStart();
long end = settings.getEnd();
long contentLength = settings.getContentLength();
response.setStatus(javax.servlet.http.HttpServletResponse.SC_PARTIAL_CONTENT);
response.addHeader("Content-Length", String.valueOf(contentLength));
String contentRange = new StringBuffer("bytes ").append(start).append("-").append(end).append("/").append(settings.getTotalLength()).toString();
response.setHeader("Content-Range", contentRange);
}
}
private static RangeSettings getSettings(long len, String range) {
long contentLength = 0;
long start = 0;
long end = 0;
if (range.startsWith("-"))// -500，最后500个
{
contentLength = Long.parseLong(range.substring(1));//要下载的量
end = len-1;
start = len - contentLength;
}
else if (range.endsWith("-"))//从哪个开始
{
start = Long.parseLong(range.replace("-", ""));
end = len -1;
contentLength = len - start;
}
else//从a到b
{
String[] se = range.split("-");
start = Long.parseLong(se[0]);
end = Long.parseLong(se[1]);
contentLength = end-start+1;
}
return new RangeSettings(start,end,contentLength,len);
}
}
Range封装
public class RangeSettings{
private long start;
private long end;
private long contentLength;
private long totalLength;
private boolean range;
public RangeSettings(){
super();
}
public RangeSettings(long start, long end, long contentLength,long totalLength) {
this.start = start;
this.end = end;
this.contentLength = contentLength;
this.totalLength = totalLength;
this.range = true;
}
public RangeSettings(long totalLength) {
this.totalLength = totalLength;
}
public long getStart() {
return start;
}
public void setStart(long start) {
this.start = start;
}
public long getEnd() {
return end;
}
public void setEnd(long end) {
this.end = end;
}
public long getContentLength() {
return contentLength;
}
public void setContentLength(long contentLength) {
this.contentLength = contentLength;
}
public long getTotalLength() {
return totalLength;
}
public void setTotalLength(long totalLength) {
this.totalLength = totalLength;
}
public boolean isRange() {
return range;
}
}
IO流相关处理工具类
import java.io.InputStream;
public class IoUtil {
public static String setContentType(String returnFileName){
String contentType = "application/octet-stream";
if (returnFileName.lastIndexOf(".") < 0)
return contentType;
returnFileName = returnFileName.toLowerCase();
returnFileName = returnFileName.substring(returnFileName.lastIndexOf(".")+1);
if (returnFileName.equals("html") || returnFileName.equals("htm") || returnFileName.equals("shtml")){
contentType = "text/html";
} else if (returnFileName.equals("css")){
contentType = "text/css";
} else if (returnFileName.equals("xml")){
contentType = "text/xml";
} else if (returnFileName.equals("gif")){
contentType = "image/gif";
} else if (returnFileName.equals("jpeg") || returnFileName.equals("jpg")){
contentType = "image/jpeg";
} else if (returnFileName.equals("js")){
contentType = "application/x-javascript";
} else if (returnFileName.equals("atom")){
contentType = "application/atom+xml";
} else if (returnFileName.equals("rss")){
contentType = "application/rss+xml";
} else if (returnFileName.equals("mml")){
contentType = "text/mathml";
} else if (returnFileName.equals("txt")){
contentType = "text/plain";
} else if (returnFileName.equals("jad")){
contentType = "text/vnd.sun.j2me.app-descriptor";
} else if (returnFileName.equals("wml")){
contentType = "text/vnd.wap.wml";
} else if (returnFileName.equals("htc")){
contentType = "text/x-component";
} else if (returnFileName.equals("png")){
contentType = "image/png";
} else if (returnFileName.equals("tif") || returnFileName.equals("tiff")){
contentType = "image/tiff";
} else if (returnFileName.equals("wbmp")){
contentType = "image/vnd.wap.wbmp";
} else if (returnFileName.equals("ico")){
contentType = "image/x-icon";
} else if (returnFileName.equals("jng")){
contentType = "image/x-jng";
} else if (returnFileName.equals("bmp")){
contentType = "image/x-ms-bmp";
} else if (returnFileName.equals("svg")){
contentType = "image/svg+xml";
} else if (returnFileName.equals("jar") || returnFileName.equals("var") || returnFileName.equals("ear")){
contentType = "application/java-archive";
} else if (returnFileName.equals("doc")){
contentType = "application/msword";
} else if (returnFileName.equals("pdf")){
contentType = "application/pdf";
} else if (returnFileName.equals("rtf")){
contentType = "application/rtf";
} else if (returnFileName.equals("xls")){
contentType = "application/vnd.ms-excel";
} else if (returnFileName.equals("ppt")){
contentType = "application/vnd.ms-powerpoint";
} else if (returnFileName.equals("7z")){
contentType = "application/x-7z-compressed";
} else if (returnFileName.equals("rar")){
contentType = "application/x-rar-compressed";
} else if (returnFileName.equals("swf")){
contentType = "application/x-shockwave-flash";
} else if (returnFileName.equals("rpm")){
contentType = "application/x-redhat-package-manager";
} else if (returnFileName.equals("der") || returnFileName.equals("pem") || returnFileName.equals("crt")){
contentType = "application/x-x509-ca-cert";
} else if (returnFileName.equals("xhtml")){
contentType = "application/xhtml+xml";
} else if (returnFileName.equals("zip")){
contentType = "application/zip";
} else if (returnFileName.equals("mid") || returnFileName.equals("midi") || returnFileName.equals("kar")){
contentType = "audio/midi";
} else if (returnFileName.equals("mp3")){
contentType = "audio/mpeg";
} else if (returnFileName.equals("ogg")){
contentType = "audio/ogg";
} else if (returnFileName.equals("m4a")){
contentType = "audio/x-m4a";
} else if (returnFileName.equals("ra")){
contentType = "audio/x-realaudio";
} else if (returnFileName.equals("3gpp") || returnFileName.equals("3gp")){
contentType = "video/3gpp";
} else if (returnFileName.equals("mp4") ){
contentType = "video/mp4";
} else if (returnFileName.equals("mpeg") || returnFileName.equals("mpg") ){
contentType = "video/mpeg";
} else if (returnFileName.equals("mov")){
contentType = "video/quicktime";
} else if (returnFileName.equals("flv")){
contentType = "video/x-flv";
} else if (returnFileName.equals("m4v")){
contentType = "video/x-m4v";
} else if (returnFileName.equals("mng")){
contentType = "video/x-mng";
} else if (returnFileName.equals("asx") || returnFileName.equals("asf")){
contentType = "video/x-ms-asf";
} else if (returnFileName.equals("wmv")){
contentType = "video/x-ms-wmv";
} else if (returnFileName.equals("avi")){
contentType = "video/x-msvideo";
}
return contentType;
}
// UTF8转码
public static String toUtf8String(String s) {
StringBuffer sb = new StringBuffer();
int len = s.toCharArray().length;
for (int i = 0; i < len; i++) {
char c = s.charAt(i);
if (c >= 0 && c <= 255) {
sb.append(c);
} else {
byte[] b;
try {
b = Character.toString(c).getBytes("utf-8");
} catch (Exception ex) {
System.out.println(ex);
b = new byte[0];
}
for (int j = 0; j < b.length; j++) {
int k = b[j];
if (k < 0)
k += 256;
sb.append("%" + Integer.toHexString(k).toUpperCase());
}
}
}
String s_utf8 = sb.toString();
sb.delete(0, sb.length());
sb.setLength(0);
sb = null;
return s_utf8;
}
public static InputStream skipFully(InputStream in,long howMany)throws Exception{
long remainning = howMany;
long len = 0;
while(remainning>0){
len = in.skip(len);
remainning -= len;
}
return in;
}
}
注有些类比如IoUtil方法来自于CSDN的网友总结，另外此类还不支持多Range配置如[a-b,c-d,-e]等。
希望本文所述对大家Java程序设计有所帮助。