转载 文件上传下载

web.xml 更新为:

web.xml
xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">

This is the description of my J2EE component
This is the display name of my J2EE component
FileUploadServlet
FileUploadServlet


FileUploadServlet
/FileUploadServlet


upload.html




其中,我把 index.jsp 的欢迎文件设为了upload.html,
这样等完成后可能直接用http://localhost:8080/FileUpload/ 来访问upload.html. 不改的话, 可以在http://localhost:8080/FileUpload/upload.html
页面上传文件. 在写FileUploadServlet 之前, 先将之前下载的commons-fileupload 和commons-io 组件包压缩文件解压出来, 把里面的
commons-fileupload-1.2.jar (lib文件夹下) 和 commons-io-1.3.2.jar 拷到WebRoot/WEB-INF/lib 文件夹下, 以便使用它们的功能.

FileUploadServlet.java 的源代码如下, 附有详细注解:
FileUploadServlet.java import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Iterator;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.FileUploadBase.SizeLimitExceededException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
public class FileUploadServlet extends HttpServlet {
public FileUploadServlet() {
super();
}
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
final long MAX_SIZE = 3 * 1024 * 1024;// 设置上传文件最大为 3M
// 允许上传的文件格式的列表
final String[] allowedExt = new String[] { "jpg", "jpeg", "gif", "txt",
"doc", "docx", "mp3", "wma", "m4a" };
response.setContentType("text/html");
// 设置字符编码为UTF-8, 这样支持汉字显示
response.setCharacterEncoding("UTF-8");
// 实例化一个硬盘文件工厂,用来配置上传组件ServletFileUpload
DiskFileItemFactory dfif = new DiskFileItemFactory();
dfif.setSizeThreshold(4096);// 设置上传文件时用于临时存放文件的内存大小,这里是4K.多于的部分将临时存在硬盘
dfif.setRepository(new File(request.getRealPath("/")
+ "ImagesUploadTemp"));// 设置存放临时文件的目录,web根目录下的ImagesUploadTemp目录
// 用以上工厂实例化上传组件
ServletFileUpload sfu = new ServletFileUpload(dfif);
// 设置最大上传尺寸
sfu.setSizeMax(MAX_SIZE);
PrintWriter out = response.getWriter();
// 从request得到 所有 上传域的列表
List fileList = null;
try {
fileList = sfu.parseRequest(request);
} catch (FileUploadException e) {// 处理文件尺寸过大异常
if (e instanceof SizeLimitExceededException) {
out.println("文件尺寸超过规定大小:" + MAX_SIZE + "字节

");
out.println("返回");
return;
}
e.printStackTrace();
}
// 没有文件上传
if (fileList == null || fileList.size() == 0) {
out.println("请选择上传文件

");
out.println("返回");
return;
}
// 得到所有上传的文件
Iterator fileItr = fileList.iterator();
// 循环处理所有文件
while (fileItr.hasNext()) {
FileItem fileItem = null;
String path = null;
long size = 0;
// 得到当前文件
fileItem = (FileItem) fileItr.next();
// 忽略简单form字段而不是上传域的文件域(等)
if (fileItem == null || fileItem.isFormField()) {
continue;
}
// 得到文件的完整路径
path = fileItem.getName();
// 得到文件的大小
size = fileItem.getSize();
if ("".equals(path) || size == 0) {
out.println("请选择上传文件

");
out.println("返回");
return;
}
// 得到去除路径的文件名
String t_name = path.substring(path.lastIndexOf("//") + 1);
// 得到文件的扩展名(无扩展名时将得到全名)
String t_ext = t_name.substring(t_name.lastIndexOf(".") + 1);
// 拒绝接受规定文件格式之外的文件类型
int allowFlag = 0;
int allowedExtCount = allowedExt.length;
for (; allowFlag < allowedExtCount; allowFlag++) {
if (allowedExt[allowFlag].equals(t_ext))
break;
}
if (allowFlag == allowedExtCount) {
out.println("请上传以下类型的文件

");
for (allowFlag = 0; allowFlag < allowedExtCount; allowFlag++)
out.println("*." + allowedExt[allowFlag]
+ "   ");
out.println("

返回");
return;
}
long now = System.currentTimeMillis();
// 根据系统时间生成上传后保存的文件名
String prefix = String.valueOf(now);
// 保存的最终文件完整路径,保存在web根目录下的ImagesUploaded目录下
String u_name = request.getRealPath("/") + "ImagesUploaded/"
+ prefix + "." + t_ext;
try {
// 保存文件
fileItem.write(new File(u_name));
out.println("文件上传成功. 已保存为: " + prefix + "." + t_ext
+ "   文件大小: " + size + "字节

");
out.println("继续上传");
} catch (Exception e) {
e.printStackTrace();
}
}
}
public void init() throws ServletException {
// Put your code here
}
}



保存后部署项目(MyEclipse下直接点击Deploy J2EE...按钮, 然后选择Tomcat服务器). 没有MyEclipse的话, 把WebRoot 拷到
Tomcat 主目录下的webapps 目录下, 并重命名为 FileUpload 然后启动Tomcat. (或直接下载我在文章开始提供的工程打包rar文件).
最后打开浏览器, 输入url:


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;
}

public void downloadLocal(HttpServletResponse response) throws FileNotFoundException {
// 下载本地文件
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();
}
}

public void downloadNet(HttpServletResponse response) throws MalformedURLException {
// 下载网络文件
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();
}
}