servlet3.0中提供了对文件上传的直接支持，不需要借助任何第三方上传组件，直接使用Servlet3.0提供的API就能够实现文件上传功能。
servlet 代码：
package ni.jun.yang.servlet; import java.io.File;
import java.io.IOException;
import java.util.UUID;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part; @WebServlet("/Upload")
@MultipartConfig //必须使用此注解，标志此servlet 支持文件上传
public class Upload extends HttpServlet {
private static final long serialVersionUID = 1L; public Upload() { } protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//设置请求编码
request.setCharacterEncoding("utf-8");
//(part)此类表示在multipart/form-dataPOST请求中收到的部分或表单项 。
//
Part part = request.getPart("filename");
//获取上下文对象，再获取某文件夹的位置
String path = request.getServletContext().getRealPath("file");
//获得头部信息
String headName = part.getHeader("content-disposition");
System.out.println(headName);
//截取文件后缀名
String end = headName.substring(headName.indexOf("."), headName.length()-1);
//随机生成一个文件名，并拼接完整路径
String filename = path +File.separator+UUID.randomUUID().toString()+end;
System.out.println(filename);
//将上传的项目写入磁盘的方便方法。
part.write(filename);
} protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
}
}
part接口：http://docs.oracle.com/javaee/6/api/javax/servlet/http/Part.html
html代码：文件上传一定要将enctype的值改为：enctype="multipart/form-data"
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>文件上传</title>
</head>
<body>
<form action="Upload" method="post" enctype="multipart/form-data">
<input type="file" name="filename"><br/><br/>
<input type="submit" value="上传">
</form>
</body>
</html>
请求头信息：
效果：
下载：
package ni.jun.yang.servlet; import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream; import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; @WebServlet("/DownServlet")
public class downServlet extends HttpServlet {
private static final long serialVersionUID = 1L; protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//1.获取要下载的文件的绝对路径
String realPath = this.getServletContext().getRealPath("111.txt");
System.out.println(realPath);
//2.获取要下载的文件名
String fileName = realPath.substring(realPath.lastIndexOf(File.separator)+1);
String userAgent = request.getHeader("User-Agent");
//针对IE或者以IE为内核的浏览器：
if (userAgent.contains("MSIE")||userAgent.contains("Trident")) {
fileName = java.net.URLEncoder.encode(fileName, "UTF-8");
} else {
//非IE浏览器的处理：
fileName = new String(fileName.getBytes("UTF-8"),"ISO-8859-1");
}
//3.设置content-disposition响应头控制浏览器以下载的方式打开文件
response.setHeader("content-disposition","attachment;filename="+fileName);
//4.获取要下载的文件输入流
InputStream in = new FileInputStream(realPath); int len = 0;
//5.创建书缓冲区
byte[] buffer = new byte[1024];
//6.通过response对象获取OutputStream输出流对象
OutputStream os = response.getOutputStream();
//7.将FileInputStream流对象写入到buffer缓冲区
while((len=in.read(buffer))>0){
os.write(buffer,0,len);
}
//8.关闭流
in.close();
os.close();
} protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
doGet(request, response);
} }