Servlet之文件上传

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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.");   }}
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