下载.txt

写在txt里的描述用java实现下载的原码

}

public void setSaveDir(String saveDir) { //设置上载文件要保存的路径

this.saveDir = saveDir; 

File testdir = new File(saveDir); //为了保证目录存在,如果没有则新建该目录

if (!testdir.exists()) {

testdir.mkdirs(); 

}

}

public void setCharset(String charset) { //设置字符集

this.charset = charset; 

}

public boolean uploadFile() throws ServletException, IOException { //用户调用的上载方法

setCharset(request.getCharacterEncoding()); 

return uploadFile(request.getInputStream()); 

}

private boolean uploadFile(ServletInputStream servletinputstream) throws //取得央存数据的主方法

ServletException, IOException {

String line = null; 

byte[] buffer = new byte[256]; 

while ( (line = readLine(buffer, servletinputstream, charset)) != null) {

if (line.startsWith("Content-Disposition: form-data; ")) {

int i = line.indexOf("filename="); 

if (i 〉= 0) { //如果一段分界符内的描述中有filename=,说明是文件的编码内容

String fName = getFileName(line); 

if (fName.equals("")) {

continue; 

}

if (count == 0 && tagFileName.length() != 0) {

String ext = fName.substring( (fName.lastIndexOf(".") + 1)); 

fName = tagFileName + "." + ext; 

}

tmpFileName.add(fName); 

count++; 

while ( (line = readLine(buffer, servletinputstream, charset)) != null) {

if (line.length() 〈= 2) {

break; 

}

}

File f = new File(saveDir, fName); 

FileOutputStream dos = new FileOutputStream(f); 

long size = 0l; 

while ( (line = readLine(buffer, servletinputstream, null)) != null) {

if (line.indexOf(boundary) != -1) {

break; 

}

size += len; 

if (size 〉 maxFileSize) {

throw new IOException("文件超过" + maxFileSize + "字节!"); 

}

dos.write(buffer, 0, len); 

}

dos.close(); 

}

else { //否则是字段编码的内容

String key = getKey(line); 

String value = ""; 

while ( (line = readLine(buffer, servletinputstream, charset)) != null) {

if (line.length() 〈= 2) {

break; 

}

}

while ( (line = readLine(buffer, servletinputstream, charset)) != null) {

if (line.indexOf(boundary) != -1) {

break; 

}

value += line; 

}

put(key, value.trim(), parameter); 

}

}

}

if (queryString != null) {

String[] each = split(queryString, "&"); 

for (int k = 0; k 〈 each.length; k++) {

String[] nv = split(each[k], "="); 

if (nv.length == 2) {

put(nv[0], nv[1], parameter); 

}

}

}

fileName = new String[tmpFileName.size()]; 

for (int k = 0; k 〈 fileName.length; k++) {

fileName[k] = (String) tmpFileName.get(k); //把ArrayList中临时文件名倒入数据中供用户调用

}

if (fileName.length == 0) {

return false; //如果fileName数据为空说明没有上载任何文件

}

return true; 

}

private void put(String key, String value, Hashtable ht) {

if (!ht.containsKey(key)) {

ht.put(key, value); 

}

else { //如果已经有了同名的KEY,就要把当前的key更名,同时要注意不能构成和KEY同名

try {

Thread.currentThread().sleep(1); //为了不在同一ms中产生两个相同的key

}

catch (Exception e) {}

key += "||||||||||" + System.currentTimeMillis(); 

ht.put(key, value); 

}

}

/*

调用ServletInputstream.readLine(byte[] b,int offset,length)方法,该方法是从ServletInputstream流中读一行

到指定的byte数组,为了保证能够容纳一行,该byte[]b不应该小于256,重写的readLine中,调用了一个成员变量len为

实际读到的字节数(有的行不满256),则在文件内容写入时应该从byte数组中写入这个len长度的字节而不是整个byte[]

的长度,但重写的这个方法返回的是String以便分析实际内容,不能返回len,所以把len设为成员变量,在每次读操作时

把实际长度赋给它.

也就是说在处理到文件的内容时数据既要以String形式返回以便分析开始和结束标记,又要同时以byte[]的形式写到文件

输出流中.

*/

private String readLine(byte[] Linebyte,

ServletInputStream servletinputstream, String charset) {

try {

len = servletinputstream.readLine(Linebyte, 0, Linebyte.length); 

if (len == -1) {

return null; 

}

if (charset == null) {

return new String(Linebyte, 0, len); 

}

else {

return new String(Linebyte, 0, len, charset); 

}

}

catch (Exception _ex) {

return null; 

}

}

private String getFileName(String line) { //从描述字符串中分离出文件名

if (line == null) {

return ""; 

}

int i = line.indexOf("filename="); 

line = line.substring(i + 9).trim(); 

i = line.lastIndexOf(""); 

if (i 〈 0 || i 〉= line.length() - 1) {

i = line.lastIndexOf("/"); 

if (line.equals("""")) {

return ""; 

}

if (i 〈 0 || i 〉= line.length() - 1) {

return line; 

}

}

return line.substring(i + 1, line.length() - 1); 

}

private String getKey(String line) { //从描述字符串中分离出字段名

if (line == null) {

return ""; 

}

int i = line.indexOf("name="); 

line = line.substring(i + 5).trim(); 

return line.substring(1, line.length() - 1); 

}

public static String[] split(String strOb, String mark) {

if (strOb == null) {

return null; 

}

StringTokenizer st = new StringTokenizer(strOb, mark); 

ArrayList tmp = new ArrayList(); 

while (st.hasMoreTokens()) {

tmp.add(st.nextToken()); 

}

String[] strArr = new String[tmp.size()]; 

for (int i = 0; i 〈 tmp.size(); i++) {

strArr[i] = (String) tmp.get(i); 

}

return strArr; 

}

}

下载其实非常简单，只要如下处理，就不会发生问题。

public void downLoad(String filePath,HttpServletResponse response,boolean isOnLine)

throws Exception{

File f = new File(filePath); 

if(!f.exists()){

response.sendError(404,"File not found!"); 

return; 

}

BufferedInputStream br = new BufferedInputStream(new FileInputStream(f)); 

byte[] buf = new byte[1024]; 

int len = 0; 

response.reset(); //非常重要

if(isOnLine){ //在线打开方式

URL u = new URL("file:///"+filePath); 

response.setContentType(u.openConnection().getContentType()); 

response.setHeader("Content-Disposition", "inline; filename="+f.getName()); 

//文件名应该编码成UTF-8

}

else{ //纯下载方式

response.setContentType("application/x-msdownload"); 

response.setHeader("Content-Disposition", "attachment; filename=" + f.getName()); 

}

OutputStream out = response.getOutputStream(); 

while((len = br.read(buf)) 〉0)

out.write(buf,0,len); 

br.close(); 

out.close(); 

}