Servlet实现文件上传

WEB上传采用POST方式，form中设置enctype属性为 multipart/form-data ----> 指定浏览器使用二进制进行上传 

　　　　　　　　　　默认为：application/x-www-form-unclearded --->使用ASCII向服务器发送数据

因为上传文件是采用二进制方式发送，所以servlet中就不能通过HttpServletRequest对象的getParameter方法来获取了，需要按照HTTP协议规定的格式对浏览器提交的request进行解析。

import java.io.*;
import java.util.*;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.tomcat.util.http.fileupload.DiskFileUpload;
import org.apache.tomcat.util.http.fileupload.FileItem;
import org.apache.tomcat.util.http.fileupload.FileUploadException;

public class UpServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException {
        File file1 = null; 
        File file2 = null;
        String description1 = null, description2 = null;
        PrintWriter out = resp.getWriter();
        DiskFileUpload diskFileUpload = new DiskFileUpload();        //用于解释request,因为form中的 enctype属性设置为multipart/form-data指定浏览器通过二进制上传
        
        try{
            List<FileItem> list = diskFileUpload.parseRequest(req);        //将获取的结果集放入到一个list
            out.println("Traverse all of the FileItem...<br/>");
            for(FileItem fileItem : list) {                                //增强的for循环遍历所有FileItem
                if(fileItem.isFormField()) {                            //判断是否为文本域
                    if("desription1".equals(fileItem.getFieldName())) {        //判断是否为该参数
                        out.println("<遍历>Traversal to desciption1 ... <br/>");
                        description1 = new String(fileItem.getString().getBytes(), "ISO-8859-1");
                    }
                    if("description2".equals(fileItem.getFieldName())) {
                        out.println("<遍历>Traversal to description2 ...<br/>");
                        description2 = new String(fileItem.getString().getBytes(), "ISO-8859-1");
                    }
                } else {
                    if("file1".equals(fileItem.getFieldName())) {
                        File remoteFile = new File(new String(fileItem.getName().getBytes(), "ISO-8895-1"));
                        out.println("<遍历>Traversal to file1 ...<br/>");
                        out.println("Client File Location: " + remoteFile.getAbsolutePath() + "<br/>");
                        
                        //服务器端文件放在upload下
                        file1 = new File(this.getServletContext().getRealPath("attachment"), remoteFile.getName());
                        file1.getParentFile().mkdirs();                 //创建一个文件夹路径
                        file1.createNewFile();                            //创建一个新的文件
                        
                        InputStream is = fileItem.getInputStream();            //将fileItem中的内容输出到文件中
                        
                        OutputStream os = new FileOutputStream(file1);
                        
                        try{
                            byte[] buffer = new byte[1024];                //建立一个缓冲区
                            int len = 0;                                //设定实际缓存的长度
                            while((len=is.read(buffer)) > -1) {            //读入缓存
                                os.write(buffer, 0 ,len);
                            }
                            out.println("Save the file has been " + file1.getAbsolutePath() + "<br/>");
                        } finally {
                            is.close();
                        }
                        if("file2".equals(fileItem.getFieldName())) {
                            
                        }
                    }
                }
            }
            out.println("Request Analysis completed");
        } catch(FileUploadException e) {
        }
    }

}