怎么从服务器那里下载文件到本地？

直接把要下载的文件的路径插入数据库中，路径是WEB应用的相对路径噢！然后在取这个文件的记录的时候，就可以通过HTTP协议进行下载了

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.URL;
import java.util.ArrayList;public class URLDownloadFiles { private String _desRoot = null;
private String _locRoot = null;
private ArrayList<URL> _listURL = null;
private ArrayList<File> _listFile = null;
private final int _buffSize = 512;

public URLDownloadFiles (String desRoot, String locRoot) {
this._desRoot = desRoot;
this._locRoot = locRoot;
inti();
}

/*
     * inti
     */
private void inti() {
_listURL = new ArrayList<URL>();
_listFile = new ArrayList<File>();
// Get all files' URL and files' list
if (!getFiles(_desRoot, _listFile, _listURL)) {
return;
}
// copy the dest files to local files
copyFiles();
}

/*
     * @param desRoot
     * @param listFile
     * @param listURL
     */
private boolean getFiles(String desRoot, ArrayList<File>listFile, ArrayList<URL> listURL) {
File[] fileList = null;
URL[] urlList = null;
File desRootFile = new File(desRoot);
try {
// desRootFile does not exist
if (!desRootFile.exists()) {
System.out.println("DesRoot does not exist");
return false;
}
// desRootFile exist
else {
// desRootFile is not a directory
if (!desRootFile.isDirectory()) {
System.out.println("This is not a directory!");
if (!desRootFile.isFile()) {
System.out.println("This is not a file too! Plz chk the root!");
return false;
} else {
System.out.println("This is a file!");
return false;
}
}
// desRootFile is a directory, get all sub files and folders
else {
fileList = desRootFile.listFiles();
urlList = new URL[fileList.length];
for (int i = 0; i < fileList.length; i++) {
if (fileList[i].isDirectory()) {
listFile.add(fileList[i]);
urlList[i] = new URL("file:" + fileList[i].getPath());
listURL.add(urlList[i]);
// get sub folders
getFiles(fileList[i].getPath(), listFile, listURL);
} else {
listFile.add(fileList[i]);
urlList[i] = new URL("file:" + fileList[i].getPath());
listURL.add(urlList[i]);
}
}
}
}
} catch (IOException e) {
System.out.println(e);
return false;
} catch (Exception e) {
System.out.println(e);
return false;
}
return true;
}

/*
     */
private boolean copyFiles() {
File dir, locFile;
BufferedInputStream buffIn = null;
BufferedOutputStream buffOut = null;
dir = new File(_locRoot);
try {
// dir doesn't exist
if (!dir.exists()) {
//create dir
dir.mkdir();
//copy new files
for (int i = 0; i < _listFile.size(); i++) {
if (_listFile.get(i).isDirectory()) {
System.out.println(_listFile.get(i) + " isDirectory");
continue;
} else {
locFile = new File(dir, _listFile.get(i).getName());
buffIn = new BufferedInputStream(_listURL.get(i).openStream());
buffOut = new BufferedOutputStream(new FileOutputStream(locFile));
byte buffer[] = new byte[_buffSize];
int count = _buffSize;
while ((count = buffIn.read(buffer)) != -1) {
buffOut.write(buffer, 0, count);
}
buffOut.flush();
buffIn.close();
buffOut.close();
buffIn = null;
buffOut = null;
}
}
}
// dir exist
else {
// delete old files
File[] files = dir.listFiles();
for (int i = 0; i < files.length; i++) {
files[i].delete();
}
// copy new files
for (int i = 0; i < _listFile.size(); i++) {
if (_listFile.get(i).isDirectory()) {
System.out.println(_listFile.get(i) + " isDirectory");
continue;
} else {
locFile = new File(dir, _listFile.get(i).getName());
buffIn = new BufferedInputStream(_listURL.get(i).openStream());
buffOut = new BufferedOutputStream(new FileOutputStream(locFile));
byte buffer[] = new byte[_buffSize];
int count = _buffSize;
while ((count = buffIn.read(buffer)) != -1) {
buffOut.write(buffer, 0, count);
}
buffOut.flush();
buffIn.close();
buffOut.close();
buffIn = null;
buffOut = null;
}
}
}
} catch (IOException e) {
System.out.println(e);
return false;
} catch (Exception e) {
System.out.println(e);
return false;
}
return true;
}
/**
* @param args　temp
*/
public static void main(String[] args) {
String desRoot = "\\\\192.168.1.153\\api\\allclasses-noframe.html";
// String desRoot = "\\E:\\api";
String locRoot = "\\E:\\api copy";
URLDownloadFiles test = new URLDownloadFiles(desRoot, locRoot);
// test
for (int i = 0; i < test._listFile.size(); i++) {
if (!test._listFile.get(i).isDirectory()) {
System.out.println(test._listFile.get(i));
System.out.println(test._listURL.get(i));
}
}
}}

楼上这种方法最简单，不用特别的写其它代码；
如果楼主对文件下载有权限控制，或者文件想放在浏览器不能访问的地方，如：/WEB-INF/下面，可以自己写一个servlet来读取文件，然后再输出到输出流中；

1.得到客户端文件流对象
2.设置客户端文件类型
3.将流写到本地目录
public void writeResponse(
FileInputStream is,
HttpServletResponse res,
String fileName) {
try {
                           //取扩展名
String fileExt = getFileExt(fileName);
                          //得到文件类型
                          String contentType = getContentType(fileExt);

res.setContentType(contentType);
fileName = new String(fileName.getBytes("GB2312"), "ISO-8859-1");
ServletOutputStream out = res.getOutputStream();
String contentHeader = "attachment; filename=\"" + fileName + "\"";
res.setHeader("Content-disposition", contentHeader);
int MAX_FILE_SIZE = 3 * 1024 * 1024; //3M
byte[] buffer = new byte[MAX_FILE_SIZE];
         int length = 0;
while ((length = is.read(buffer)) != -1) {
   out.write(buffer, 0, length);
}
if (is != null) is.close();
if (out != null)out.close();
}
         catch (Exception e)
        {
System.out.println("writeResponse error");
}
}
//获得内容类型
private String getContentType(String fileExt) {
String contentType = "";
if (fileExt == null)
contentType = "";
else if (fileExt.equals("doc"))
contentType = "application/msword";
else if (fileExt.equals("pdf"))
contentType = "application/pdf";
else if (fileExt.equals("jpg"))
contentType = "image/jpeg";
else if (fileExt.equals("gif"))
contentType = "image/gif";
else if (fileExt.equals("bmp"))
contentType = "image/bmp";
else if (fileExt.equals("txt"))
contentType = "text/plain"; return contentType;
}

http本身就可以下载文件，有必要自己搞吗？楼主也没有说出必须自己搞的理由。

调试易

怎么从服务器那里下载文件到本地？

解决方案 »