java下载文件流(java下载项目中的文件)
用java流的方式怎么指定下载到指定目录下
举例代码：
????/**
?????*?下载文件。
?????*?@param?urlStr?文件的URL
?????*?@param?savePath?保存到的目录
?????*?@param?fileName?保存的文件名称
?????*?@param?description?描述（如：歌曲，专辑封面，歌词等）
?????*?@throws?IOException
?????*/
????public?static?void?downLoad(String?urlStr,?String?savePath,?String?fileName,?String?description)?throws?IOException
????{
????????URL?url?=?new?URL(urlStr);
????????HttpURLConnection?conn?=?(HttpURLConnection)?url.openConnection();
????????conn.setConnectTimeout(100000);??//?设置超时间为10秒
????????conn.setRequestProperty("User-Agent",?"Mozilla/4.0?(compatible;?MSIE?5.0;?Windows?NT;?DigExt)");??//?防止屏蔽程序抓取而返回403错误
????????File?saveDir?=?new?File(savePath);
????????File?file?=?new?File(saveDir?+?File.separator?+?fileName);
????????try?(InputStream?inputStream?=?conn.getInputStream();
????????????????FileOutputStream?fos?=?new?FileOutputStream(file))
????????{
????????????byte[]?flowData?=?readInputStream(inputStream);
????????????fos.write(flowData);
????????}?catch?(Exception?e)?{
????????????MainFrame.logEvent("字节保存时出现意外："?+?e.getMessage());
????????}
????????MainFrame.logEvent(description?+?"下载完成："?+?url);
????}
MainFrame.logEvent()是我自己弄的日志记录而已，可以忽略不看
关于Java用输出流下载文件
通常可以直接通过FTPClient 工具类下载文件到本地的，可以通过ByteArrayOutputStream进行流的读取输出。
/**
*下载文件
*
* @param fileName
* @param date
* @param plainFilePath 明文文件路径路径
* @param filepath
* @return
* @throws Exception
*/
public static String encodeAESFileDownloadByFtp(String plainFilePath, String fileName, String date,String filepath) throws Exception {
FileInputStream fis = null;
ByteArrayOutputStream bos = null;
FileOutputStream fos = null;
FTPClient ftpClient = new FTPClient();
String bl = "false";
try {
// Log.info("下载并解密文件开始");
Log.info("连接远程下载服务器"+CMBCUtil.CMBCHOSTNAME+":"+2021);
ftpClient.connect(CMBCUtil.CMBCHOSTNAME, 2021);
ftpClient.login(CMBCUtil.CMBCLOGINNAME, CMBCUtil.CMBCLOGINPASSWORD);
FTPFile[] fs;
fs = ftpClient.listFiles();
for (FTPFile ff : fs) {
if (ff.getName().equals(filepath)) {
ftpClient.changeWorkingDirectory("/"+filepath+"/");
}
}
fs = ftpClient.listFiles();
for (FTPFile ff : fs) {
if (ff.getName().equals(date)) {
bl = "true";
ftpClient.changeWorkingDirectory("/"+filepath+"/" + date);
}
}
Log.info("检查文件路径是否存在：/"+filepath+"/"+date + " "+ bl);
if("false".equals(bl)){
ViewUtil.dataSEErrorPerformedCommon( "查询文件路径不存在："+"/"+filepath+"/" + date);
return bl;
}
bl = "false";
fs = ftpClient.listFiles();
for (FTPFile ff : fs) {
if (ff.getName().equals(fileName)) {
bl = "true";
Log.info("下载并解密文件开始。");
fos = new FileOutputStream(plainFilePath);
ftpClient.setBufferSize(1024);
// 设置文件类型（二进制）
ftpClient.setFileType(FTPClient.BINARY_FILE_TYPE);
InputStream is = ftpClient.retrieveFileStream(fileName);
bos = new ByteArrayOutputStream(is.available());
byte[] buffer = new byte[1024];
int count = 0;
while ((count = is.read(buffer)) != -1) {
bos.write(buffer, 0, count);
}
bos.flush();
byte[] bytes = decodeAES(key, bos.toByteArray());
fos = new FileOutputStream(plainFilePath);
fos.write(bytes);
Log.info("下载并解密文件结束："+plainFilePath);
}
}
Log.info("检查文件是否存："+fileName+" "+bl);
if("false".equals(bl)){
ViewUtil.dataSEErrorPerformedCommon("查询无结果，请稍后再查询。");
return bl;
}
return bl;
} catch (Exception e) {
throw e;
} finally {
if (fis != null) {
try {
fis.close();
} catch (Exception e) {
Log.info(e.getLocalizedMessage(), e);
}
}
if (bos != null) {
try {
bos.close();
} catch (Exception e) {
Log.info(e.getLocalizedMessage(), e);
}
}
if (fos != null) {
try {
fos.close();
} catch (Exception e) {
Log.info(e.getLocalizedMessage(), e);
}
}
}
}
怎样编一个能实现文件下载功能的JAVA程序
java实现文件下载
一、采用RequestDispatcher的方式进行
1、web.xml文件中增加
mime-mapping
extensiondoc/extension
mime-typeapplication/vnd.ms-word/mime-type
/mime-mapping
2、程序如下：
%@page language="java" import="java.net.*" pageEncoding="gb2312"%
%
response.setContentType("application/x-download");//设置为下载application/x-download
String filenamedownload = "/系统解决方案.doc";//即将下载的文件的相对路径
String filenamedisplay = "系统解决方案.doc";//下载文件时显示的文件保存名称
filenamedisplay = URLEncoder.encode(filenamedisplay,"UTF-8");
response.addHeader("Content-Disposition","attachment;filename=" + filenamedisplay);
try
{
RequestDispatcher dispatcher = application.getRequestDispatcher(filenamedownload);
if(dispatcher != null)
{
dispatcher.forward(request,response);
}
response.flushBuffer();
}
catch(Exception e)
{
e.printStackTrace();
}
finally
{
}
%
二、采用文件流输出的方式下载
1、web.xml文件中增加
mime-mapping
extensiondoc/extension
mime-typeapplication/vnd.ms-word/mime-type
/mime-mapping
2、程序如下：
%@page language="java" contentType="application/x-msdownload" import="java.io.*,java.net.*" pageEncoding="gb2312"%
%
//关于文件下载时采用文件流输出的方式处理：
//加上response.reset()，并且所有的％后面不要换行，包括最后一个；
//因为Application Server在处理编译jsp时对于％和％之间的内容一般是原样输出，而且默认是PrintWriter，
//而你却要进行流输出：ServletOutputStream，这样做相当于试图在Servlet中使用两种输出机制，
//就会发生：getOutputStream() has already been called for this response的错误
//详细请见《More Java Pitfill》一书的第二部分 Web层Item 33：试图在Servlet中使用两种输出机制 270
//而且如果有换行，对于文本文件没有什么问题，但是对于其它格式，比如AutoCAD、Word、Excel等文件
//下载下来的文件中就会多出一些换行符0x0d和0x0a，这样可能导致某些格式的文件无法打开，有些也可以正常打开。
response.reset();//可以加也可以不加
response.setContentType("application/x-download");//设置为下载application/x-download
// /../../退WEB-INF/classes两级到应用的根目录下去，注意Tomcat与WebLogic下面这一句得到的路径不同，WebLogic中路径最后没有/
System.out.println(this.getClass().getClassLoader().getResource("/").getPath());
String filenamedownload = this.getClass().getClassLoader().getResource("/").getPath() + "/../../系统解决方案.doc";
String filenamedisplay = "系统解决方案.doc";//系统解决方案.txt
filenamedisplay = URLEncoder.encode(filenamedisplay,"UTF-8");
response.addHeader("Content-Disposition","attachment;filename=" + filenamedisplay);
OutputStream output = null;
FileInputStream fis = null;
try
{
output = response.getOutputStream();
fis = new FileInputStream(filenamedownload);
byte[] b = new byte[1024];
int i = 0;
while((i = fis.read(b)) 0)
{
output.write(b, 0, i);
}
output.flush();
}
catch(Exception e)
{
System.out.println("Error!");
e.printStackTrace();
}
finally
{
if(fis != null)
{
Java 下载文件的方法怎么写
参考下面
public HttpServletResponse download(String path, HttpServletResponse response) {
try {
// path是指欲下载的文件的路径。
File file = new File(path);
// 取得文件名。
String filename = file.getName();
// 取得文件的后缀名。
String ext = filename.substring(filename.lastIndexOf(".") + 1).toUpperCase();
// 以流的形式下载文件。
InputStream fis = new BufferedInputStream(new FileInputStream(path));
byte[] buffer = new byte[fis.available()];
fis.read(buffer);
fis.close();
// 清空response
response.reset();
// 设置response的Header
response.addHeader("Content-Disposition", "attachment;filename=" + new String(filename.getBytes()));
response.addHeader("Content-Length", "" + file.length());
OutputStream toClient = new BufferedOutputStream(response.getOutputStream());
response.setContentType("application/octet-stream");
toClient.write(buffer);
toClient.flush();
toClient.close();
} catch (IOException ex) {
ex.printStackTrace();
}
return response;
}
// 下载本地文件
public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {
String fileName = "Operator.doc".toString(); // 文件的默认保存名
// 读到流中
InputStream inStream = new FileInputStream("c:/Operator.doc");// 文件的存放路径
// 设置输出的格式
response.reset();
response.setContentType("bin");
response.addHeader("Content-Disposition", "attachment; filename=\"" + fileName + "\"");
// 循环取出流中的数据
byte[] b = new byte[100];
int len;
try {
while ((len = inStream.read(b)) 0)
response.getOutputStream().write(b, 0, len);
inStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
// 下载网络文件
public void downloadNet(HttpServletResponse response) throws MalformedURLException {
int bytesum = 0;
int byteread = 0;
URL url = new URL("windine.blogdriver.com/logo.gif");
try {
URLConnection conn = url.openConnection();
InputStream inStream = conn.getInputStream();
FileOutputStream fs = new FileOutputStream("c:/abc.gif");
byte[] buffer = new byte[1204];
int length;
while ((byteread = inStream.read(buffer)) != -1) {
bytesum += byteread;
System.out.println(bytesum);
fs.write(buffer, 0, byteread);
}
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
//支持在线打开文件的一种方式
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("" + 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();
}
Java实现文件流下载文件，浏览器无反应，后台无错误！如何解决？
ServletOutputStream out = response.getOutputStream();
byte[] outputByte = new byte[4096];
while(text.read(outputByte, 0, 4096) != -1)
{
out.write(outputByte, 0, 4096);
}
fileIn.close();
out.flush();
out.close();