Servlet之文件上传

上传表单中的注意事项：

表单 method 属性应该设置为 POST 方法，不能使用 GET 方法

表单 enctype 属性应该设置为multipart/form-data

下面的实例是借助于commons-fileupload和commons-io相关包来实现的

import java.io.*;
import java.util.*;

import javax.servlet.ServletConfig;
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.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;
import org.apache.commons.io.output.*;

public class UploadServletextends HttpServlet {

   private boolean isMultipart;
   private String filePath;
   private int maxFileSize = 50 * 1024;
   private int maxMemSize = 4 * 1024;
   private File file ;

   public void init( ){
      // 获取文件将被存储的位置
      filePath =
            getServletContext().getInitParameter("file-upload");
   }
   public void doPost(HttpServletRequestrequest,
               HttpServletResponse response)
              throws ServletException,java.io.IOException {
      // 检查我们有一个文件上传请求
      isMultipart = ServletFileUpload.isMultipartContent(request);
     response.setContentType("text/html");
      java.io.PrintWriter out =response.getWriter( );
      if( !isMultipart ){
         out.println("<html>");
         out.println("<head>");
         out.println("<title>Servletupload</title>");
        out.println("</head>");
         out.println("<body>");
         out.println("<p>No fileuploaded</p>");
        out.println("</body>");
        out.println("</html>");
         return;
      }
      DiskFileItemFactoryfactory = new DiskFileItemFactory();
      //设置上传文件时用于临时存放文件的内存大小
      factory.setSizeThreshold(maxMemSize);
      //设置存放临时文件的目录，这个目录需要事先建立好
      factory.setRepository(new File("c:\\temp"));

      // 创建一个新的文件上传处理程序
      ServletFileUploadupload = new ServletFileUpload(factory);
      // 允许上传的文件大小的最大值
      upload.setSizeMax( maxFileSize );

      try{
      // 解析请求，获取文件项
      List fileItems = upload.parseRequest(request);

      // 处理上传的文件项
      Iterator i = fileItems.iterator();

      out.println("<html>");
      out.println("<head>");
      out.println("<title>Servletupload</title>");
      out.println("</head>");
      out.println("<body>");
      while ( i.hasNext () )
      {
         FileItem fi = (FileItem)i.next();
         if ( !fi.isFormField () )  //是文件域
         {
            // 获取上传文件的参数
            String fieldName = fi.getFieldName();
            String fileName = fi.getName();  //文件的全路径
            String contentType = fi.getContentType();
            boolean isInMemory =fi.isInMemory();
            long sizeInBytes = fi.getSize();
           //得到去除路径的文件名
            if(fileName.lastIndexOf("\\") >= 0 ){   //路径中包含“\”时
               file = new File( filePath +
               fileName.substring( fileName.lastIndexOf("\\")));
            }else{   //路径中不包含“\”时
               file = new File( filePath +
              fileName.substring(fileName.lastIndexOf("\\")+1)) ;
            }
            fi.write( file ) ;   // 写入文件
            out.println("UploadedFilename: " + fileName + "<br>");
         }
      }
      out.println("</body>");
      out.println("</html>");
   }catch(Exception ex) {
       System.out.println(ex);
   }
   }
   public void doGet(HttpServletRequestrequest,
                       HttpServletResponseresponse)
        throws ServletException,java.io.IOException {

        throw new ServletException("GETmethod used with " +
                getClass( ).getName( )+":POST method required.");
   }
}