关于从HTML页面上传文件的问题：

关于这个问题，其实网上有现成的例子，我收集了一个，帖给你吧，不过要给分哦！！！
比较长的。/*

* A utility class to handle <tt>multipart/form-data</tt> requests,
* the kind of requests that support file uploads.  This class can
* receive arbitrarily large files (up to an artificial limit you can
set),
* and fairly efficiently too.
* It cannot handle nested data (multipart content within multipart co
ntent)
* or internationalized content (such as non Latin-1 filenames).
* <p>
* It's used like this:
* <blockquote><pre>

*指定上传文件最大字节
* MultipartRequest multi = new MultipartRequest(req, ".", 2*1024);
或使用默认2M，
  MultipartRequest multi = new MultipartRequest(req, ".");
*
* out.println("Params:");
* Enumeration params = multi.getParameterNames();
* while (params.hasMoreElements()) {
*   String name = (String)params.nextElement();
*   String value = multi.getParameter(name);
*   out.println(name + " = " + value);
* }
* out.println();
*
* out.println("Files:");
* Enumeration files = multi.getFileNames();
* while (files.hasMoreElements()) {
*   String name = (String)files.nextElement();
*   String filename = multi.getFilesystemName(name);
*   String type = multi.getContentType(name);
*   File f = multi.getFile(name);
*   out.println("name: " + name);
*   out.println("filename: " + filename);
*   out.println("type: " + type);
*   if (f != null) {
*     out.println("f.toString(): " + f.toString());
*     out.println("f.getName(): " + f.getName());
*     out.println("f.exists(): " + f.exists());
*     out.println("f.length(): " + f.length());
*     out.println();
*   }
* }
* </pre></blockquote>
*
* A client can upload files using an HTML form with the following str
ucture.
* Note that not all browsers support file uploads.
* <blockquote><pre>
* <FORM ACTION="/servlet/Handler" METHOD=POST
*          ENCTYPE="multipart/form-data">
* What is your name? <INPUT TYPE=TEXT NAME=submitter> <BR>
;
* Which file to upload? <INPUT TYPE=FILE NAME=file> <BR>  * <INPUT TYPE=SUBMIT>
* </FORM>
* </pre></blockquote>
* <p> */ import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*; public class MultipartRequest {   private static final int DEFAULT_MAX_POST_SIZE = 1024 * 1024;  // 1Meg
  private static final String NO_FILE = "unknown";   private HttpServletRequest req;
  private File dir;
  private int maxSize;   private Hashtable parameters = new Hashtable();  // name - Vector of values
  private Hashtable files = new Hashtable();       // name - UploadedFile   /**
   * Constructs a new MultipartRequest to handle the specified request,
   * saving any uploaded files to the given directory, and limiting the
   * upload size to 1 Megabyte.  If the content is too large, an
   * IOException is thrown.  This constructor actually parses the
   * <tt>multipart/form-data</tt> and throws an IOException if there's any
   * problem reading or parsing the request.
   *
   * @param request the servlet request
   * @param saveDirectory the directory in which to save any uploaded files
   * @exception IOException if the uploaded content is larger than 1 Megabyte
   * or there's a problem reading or parsing the request
   */

  public MultipartRequest(HttpServletRequest request, String saveDirectory)
       throws IOException
{
    this(request, saveDirectory, DEFAULT_MAX_POST_SIZE);
  }   /**
   * Constructs a new MultipartRequest to handle the specified request,
   * saving any uploaded files to the given directory, and limiting the
   * upload size to the specified length.  If the content is too large, an
   * IOException is thrown.  This constructor actually parses the
   * <tt>multipart/form-data</tt> and throws an IOException if there's any
   * problem reading or parsing the request.
   *
   * @param request the servlet request
   * @param saveDirectory the directory in which to save any uploaded files
   * @param maxPostSize the maximum size of the POST content
   * @exception IOException if the uploaded content is larger than
   * <tt>maxPostSize</tt> or there's a problem reading or parsing the request
   */

  public MultipartRequest(HttpServletRequest request,String saveDirectory,int maxPostSize)
   throws IOException
{
    // Sanity check values
    if (request == null)
      throw new IllegalArgumentException("request cannot be null");
    if (saveDirectory == null)
      throw new IllegalArgumentException("saveDirectory cannot be null");
    if (maxPostSize <= 0)
    {
      throw new IllegalArgumentException("maxPostSize must be positive");
    }     // Save the request, dir, and max size
    req = request;
    dir = new File(saveDirectory);
    maxSize = maxPostSize;     // Check saveDirectory is truly a directory
    if (!dir.isDirectory())
      throw new IllegalArgumentException("Not a directory: " + saveDirectory);     // Check saveDirectory is writable
    if (!dir.canWrite())
      throw new IllegalArgumentException("Not writable: " + saveDirectory);     // Now parse the request saving data to "parameters" and "files";     // write the file contents to the saveDirectory
    readRequest();
  }   /**
   * Constructor with an old signature, kept for backward compatibility.
   * Without this constructor, a servlet compiled against a previous version
   * of this class (pre 1.4) would have to be recompiled to link with this
   * version.  This constructor supports the linking via the old signature.
   * Callers must simply be careful to pass in an HttpServletRequest.
   *
   */
  public MultipartRequest(ServletRequest request,String saveDirectory)
   throws IOException
  {
    this((HttpServletRequest)request, saveDirectory);
  }   /**
   * Constructor with an old signature, kept for backward compatibility.
   * Without this constructor, a servlet compiled against a previous version
   * of this class (pre 1.4) would have to be recompiled to link with this
   * version.  This constructor supports the linking via the old signature.
   * Callers must simply be careful to pass in an HttpServletRequest.
   *
   */
  public MultipartRequest(ServletRequest request,String saveDirectory,int maxPostSize)
   throws IOException
  {
    this((HttpServletRequest)request, saveDirectory, maxPostSize);
  }   /**
   * Returns the names of all the parameters as an Enumeration of
   * Strings.  It returns an empty Enumeration if there are no parameters.
   *
   * @return the names of all the parameters as an Enumeration of Strings
   */

  public Enumeration getParameterNames()
  {
    return parameters.keys();
  }  /**
   * Returns the names of all the uploaded files as an Enumeration of
   * Strings.  It returns an empty Enumeration if there are no uploaded
   * files.  Each file name is the name specified by the form, not by
   * the user.
   *
   * @return the names of all the uploaded files as an Enumeration of Strings
   */

  public Enumeration getFileNames()
  {
    return files.keys();
  }   /**
   * Returns the value of the named parameter as a String, or null if
   * the parameter was not sent or was sent without a value.  The value
   * is guaranteed to be in its normal, decoded form.  If the parameter
   * has multiple values, only the last one is returned (for backward
   * compatibility).  For parameters with multiple values, it's possible
   * the last "value" may be null.
   *
   * @param name the parameter name
   * @return the parameter value
   */

  public String getParameter(String name)
  {
    try {
      Vector values = (Vector)parameters.get(name);
      if (values == null || values.size() == 0)
      {
        return null;
      }
      String value = (String)values.elementAt(values.size() - 1);
      return value;
    }
    catch (Exception e)
    {
      return null;
    }
  }   /**
   * Returns the values of the named parameter as a String array, or null if
   * the parameter was not sent.  The array has one entry for each parameter
   * field sent.  If any field was sent without a value that entry is stored
   * in the array as a null.  The values are guaranteed to be in their
   * normal, decoded form.  A single value is returned as a one-element array.
   *
   * @param name the parameter name
   * @return the parameter values
   */

  public String[] getParameterValues(String name)
  {
    try {
      Vector values = (Vector)parameters.get(name);
      if (values == null || values.size() == 0) {
        return null;
      }
      String[] valuesArray = new String[values.size()];
      values.copyInto(valuesArray);
      return valuesArray;
    }
    catch (Exception e) {
      return null;
    }
  }   /**
   * Returns the filesystem name of the specified file, or null if the
   * file was not included in the upload.  A filesystem name is the name
   * specified by the user.  It is also the name under which the file is
   * actually saved.
   *
   * @param name the file name
   * @return the filesystem name of the file
   */

  public String getFilesystemName(String name) {
    try {
      UploadedFile file = (UploadedFile)files.get(name);
      return file.getFilesystemName();  // may be null
    }
    catch (Exception e) {
      return null;
    }
  }   /**
   * Returns the content type of the specified file (as supplied by the
   * client browser), or null if the file was not included in the upload.
   *
   * @param name the file name
   * @return the content type of the file
   */
  public String getContentType(String name) {
    try {
      UploadedFile file = (UploadedFile)files.get(name);
      return file.getContentType();  // may be null
    }
    catch (Exception e) {
      return null;
    }
  }   /**
   * Returns a File object for the specified file saved on the server's
   * filesystem, or null if the file was not included in the upload.
   *
   * @param name the file name
   * @return a File object for the named file
   */

  public File getFile(String name) {
    try {
      UploadedFile file = (UploadedFile)files.get(name);
      return file.getFile();  // may be null
    }
    catch (Exception e) {
      return null;
    }
  }   /**
   * The workhorse method that actually parses the request.  A subclass
   * can override this method for a better optimized or differently
   * behaved implementation.
   *
   * @exception IOException if the uploaded content is larger than
   * <tt>maxSize</tt> or there's a problem parsing the request
   */
  protected void readRequest() throws IOException {
    // Check the content length to prevent denial of service attacks
    int length = req.getContentLength();
    if (length > maxSize) {
      throw new IOException("Posted content length of " + length + " exceeds limit of " + maxSize);
    }     // Check the content type to make sure it's "multipart/form-data"     // Access header two ways to work around WebSphere oddities
    String type = null;
    String type1 = req.getHeader("Content-Type");
    String type2 = req.getContentType();
    // If one value is null, choose the other value
    if (type1 == null && type2 != null) {
      type = type2;
    }
    else if (type2 == null && type1 != null) {
      type = type1;
    }
    // If neither value is null, choose the longer value
    else if (type1 != null && type2 != null) {
      type = (type1.length() > type2.length() ? type1 : type2);
    }     if (type == null || !type.toLowerCase().startsWith("multipart/form-data")) {
      throw new IOException("Posted content type isn't multipart/form-data");
    }     // Get the boundary string; it's included in the content type.
    // Should look something like "------------------------12012133613061"

    String boundary = extractBoundary(type);
    if (boundary == null) {
      throw new IOException("Separation boundary was not specified");     }     // Construct the special input stream we'll read from
    MultipartInputStreamHandler in =
      new MultipartInputStreamHandler(req.getInputStream(), length);     // Read the first line, should be the first boundary
    String line = in.readLine();
    if (line == null) {
      throw new IOException("Corrupt form data: premature ending");
    }     // Verify that the line is the boundary
    if (!line.startsWith(boundary)) {
      throw new IOException("Corrupt form data: no leading boundary");     }     // Now that we're just beyond the first boundary, loop over each part
    boolean done = false;
    while (!done) {
      done = readNextPart(in, boundary);
    }
  }   /**
   * A utility method that reads an individual part.  Dispatches to
   * readParameter() and readAndSaveFile() to do the actual work.  A
   * subclass can override this method for a better optimized or
   * differently behaved implementation.
   *
   * @param in the stream from which to read the part
   * @param boundary the boundary separating parts
   * @return a flag indicating whether this is the last part
   * @exception IOException if there's a problem reading or parsing the
   * request
   *
   * @see readParameter
   * @see readAndSaveFile
   */
  protected boolean readNextPart(MultipartInputStreamHandler in,
                                 String boundary) throws IOException {     // Read the first line, should look like this:
    // content-disposition: form-data; name="field1"; filename="file1.txt"
    String line = in.readLine();
    if (line == null) {
      // No parts left, we're done
      return true;
    }
    else if (line.length() == 0) {
      // IE4 on Mac sends an empty line at the end; treat that as the end.
      // Thanks to Daniel Lemire and Henri Tourigny for this fix.
      return true;
    }     // Parse the content-disposition line
    String[] dispInfo = extractDispositionInfo(line);
    String disposition = dispInfo[0];
    String name = dispInfo[1];
    String filename = dispInfo[2];     // Now onto the next line.  This will either be empty
    // or contain a Content-Type and then an empty line.
    line = in.readLine();
    if (line == null) {
      // No parts left, we're done
      return true;
    }     // Get the content type, or null if none specified
    String contentType = extractContentType(line);
    if (contentType != null) {
      // Eat the empty line
      line = in.readLine();
      if (line == null || line.length() > 0) {  // line should be empty
        throw new
          IOException("Malformed line after content type: " + line);
      }
    }
    else {
      // Assume a default content type
      contentType = "application/octet-stream";
    }     // Now, finally, we read the content (end after reading the boundary)
    if (filename == null) {
      // This is a parameter, add it to the vector of values
      String value = readParameter(in, boundary);
      if (value.equals("")) {
        value = null;  // treat empty strings like nulls
      }
      Vector existingValues = (Vector)parameters.get(name);
      if (existingValues == null) {
        existingValues = new Vector();
        parameters.put(name, existingValues);
      }
      existingValues.addElement(value);
    }
    else {
      // This is a file
      readAndSaveFile(in, boundary, filename, contentType);
      if (filename.equals(NO_FILE)) {
        files.put(name, new UploadedFile(null, null, null));
      }
      else {
        files.put(name,
          new UploadedFile(dir.toString(), filename, contentType));
      }
    }
    return false;  // there's more to read
  }   /**
   * A utility method that reads a single part of the multipart request
   * that represents a parameter.  A subclass can override this method
   * for a better optimized or differently behaved implementation.
   *
   * @param in the stream from which to read the parameter information    * @param boundary the boundary signifying the end of this part
   * @return the parameter value
   * @exception IOException if there's a problem reading or parsing the
   * request
   */
  protected String readParameter(MultipartInputStreamHandler in,
                                 String boundary) throws IOException {     StringBuffer sbuf = new StringBuffer();
    String line;     while ((line = in.readLine()) != null) {
      if (line.startsWith(boundary)) break;
      sbuf.append(line + "\r\n");  // add the \r\n in case there are many lines
    }     if (sbuf.length() == 0) {
      return null;  // nothing read
    }     sbuf.setLength(sbuf.length() - 2);  // cut off the last line's \r\n
    return sbuf.toString();  // no URL decoding needed
  }   /**
   * A utility method that reads a single part of the multipart request
   * that represents a file, and saves the file to the given directory.
   * A subclass can override this method for a better optimized or
   * differently behaved implementation.
   *
   * @param in the stream from which to read the file
   * @param boundary the boundary signifying the end of this part
   * @param dir the directory in which to save the uploaded file
   * @param filename the name under which to save the uploaded file
   * @exception IOException if there's a problem reading or parsing the
   * request
   */
  protected void readAndSaveFile(MultipartInputStreamHandler in,
                                 String boundary,
                                 String filename,
                                 String contentType) throws IOException {
    OutputStream out = null;
    // A filename of NO_FILE means no file was sent, so just read to the
    // next boundary and ignore the empty contents
    if (filename.equals(NO_FILE)) {
      out = new ByteArrayOutputStream();  // write to nowhere
    }
    // A MacBinary file goes through a decoder
    else if (contentType.equals("application/x-macbinary")){
      File f = new File(dir + File.separator + filename);
      out = new MacBinaryDecoderOutputStream(
            new BufferedOutputStream(
            new FileOutputStream(f), 8 * 1024));
    }
    // A real file's contents are written to disk
    else {
      File f = new File(dir + File.separator + filename);
      out = new BufferedOutputStream(new FileOutputStream(f), 8 * 1024
);
    }     byte[] bbuf = new byte[100 * 1024];  // 100K
    int result;
    String line;     // ServletInputStream.readLine() has the annoying habit of
    // adding a \r\n to the end of the last line.
    // Since we want a byte-for-byte transfer, we have to cut those chars.
    boolean rnflag = false;
    while ((result = in.readLine(bbuf, 0, bbuf.length)) != -1) {
      // Check for boundary
      if (result > 2 && bbuf[0] == '-' && bbuf[1] == '-') { // quick pre-check
        line = new String(bbuf, 0, result, "ISO-8859-1");
        if (line.startsWith(boundary)) break;
      }
      // Are we supposed to write \r\n for the last iteration?
      if (rnflag) {
        out.write('\r'); out.write('\n');
        rnflag = false;
      }
      // Write the buffer, postpone any ending \r\n
      if (result >= 2 &&
          bbuf[result - 2] == '\r' &&
          bbuf[result - 1] == '\n') {
        out.write(bbuf, 0, result - 2);  // skip the last 2 chars
        rnflag = true;  // make a note to write them on the next iteration
      }
      else {
        out.write(bbuf, 0, result);
      }
    }
    out.flush();
    out.close();
  }   // Extracts and returns the boundary token from a line.
  //
  private String extractBoundary(String line) {
    // Use lastIndexOf() because IE 4.01 on Win98 has been known to send the
    // "boundary=" string multiple times.  Thanks to David Wall for this fix.
    int index = line.lastIndexOf("boundary=");
    if (index == -1) {
      return null;
    }
    String boundary = line.substring(index + 9);  // 9 for "boundary="
    // The real boundary is always preceeded by an extra "--"
    boundary = "--" + boundary;     return boundary;
  }   // Extracts and returns disposition info from a line, as a String array
  // with elements: disposition, name, filename.  Throws an IOException
  // if the line is malformatted.
  //
  private String[] extractDispositionInfo(String line) throws IOException {
    // Return the line's data as an array: disposition, name, filename     String[] retval = new String[3];     // Convert the line to a lowercase string without the ending \r\n     // Keep the original line for error messages and for variable names.
    String origline = line;
    line = origline.toLowerCase();     // Get the content disposition, should be "form-data"
    int start = line.indexOf("content-disposition: ");
    int end = line.indexOf(";");
    if (start == -1 || end == -1) {
      throw new IOException("Content disposition corrupt: " + origline
);
    }
    String disposition = line.substring(start + 21, end);
    if (!disposition.equals("form-data")) {
      throw new IOException("Invalid content disposition: " + disposition);
    }     // Get the field name
    start = line.indexOf("name=\"", end);  // start at last semicolon     end = line.indexOf("\"", start + 7);   // skip name=\"
    if (start == -1 || end == -1) {
      throw new IOException("Content disposition corrupt: " + origline);
    }
    String name = origline.substring(start + 6, end);     // Get the filename, if given
    String filename = null;
    start = line.indexOf("filename=\"", end + 2);  // start after name     end = line.indexOf("\"", start + 10);          // skip filename=\"     if (start != -1 && end != -1) {                // note the !=
      filename = origline.substring(start + 10, end);
      // The filename may contain a full path.  Cut to just the filename.
      int slash =
        Math.max(filename.lastIndexOf('/'), filename.lastIndexOf('\\'));
      if (slash > -1) {
        filename = filename.substring(slash + 1);  // past last slash
      }
      if (filename.equals("")) filename = NO_FILE; // sanity check
    }     // Return a String array: disposition, name, filename
    retval[0] = disposition;
    retval[1] = name;
    retval[2] = filename;
    return retval;
  }   // Extracts and returns the content type from a line, or null if the   // line was empty.  Throws an IOException if the line is malformatted.
  //
  private String extractContentType(String line) throws IOException {     String contentType = null;     // Convert the line to a lowercase string
    String origline = line;
    line = origline.toLowerCase();     // Get the content type, if any
    if (line.startsWith("content-type")) {
      int start = line.indexOf(" ");
      if (start == -1) {
        throw new IOException("Content type corrupt: " + origline);
      }
      contentType = line.substring(start + 1);
    }
    else if (line.length() != 0) {  // no content type, so should be empty
      throw new IOException("Malformed line after disposition: " + origline);
    }     return contentType;
  }
}
// A class to hold information about an uploaded file.
//
class UploadedFile {   private String dir;
  private String filename;
  private String type;   UploadedFile(String dir, String filename, String type) {
    this.dir = dir;
    this.filename = filename;
    this.type = type;
  }   public String getContentType() {
    return type;
  }   public String getFilesystemName() {
    return filename;
  }   public File getFile() {
    if (dir == null || filename == null) {
      return null;
    }
    else {
      return new File(dir + File.separator + filename);
    }
  }
}
// A class to aid in reading multipart/form-data from a ServletInputStream.
// It keeps track of how many bytes have been read and detects when the
// Content-Length limit has been reached.  This is necessary since some
// servlet engines are slow to notice the end of stream.
//
// Mac users: The Mac doesn't like class names which exceed 32 characters
// (including the ".class") so while this class is usable from a JAR
// anywhere, it won't compile on a Mac.
// class MultipartInputStreamHandler {   ServletInputStream in;
  int totalExpected;
  int totalRead = 0;
  byte[] buf = new byte[8 * 1024];   public MultipartInputStreamHandler(ServletInputStream in,
                                     int totalExpected) {
    this.in = in;
    this.totalExpected = totalExpected;
  }   // Reads the next line of input.  Returns null to indicate the end
  // of stream.
  //
  public String readLine() throws IOException {
    StringBuffer sbuf = new StringBuffer();
    int result;
    String line;     do {
      result = this.readLine(buf, 0, buf.length);  // this.readLine() does +=
      if (result != -1) {
        sbuf.append(new String(buf, 0, result, "ISO-8859-1"));
      }
    } while (result == buf.length);  // loop only if the buffer was filled     if (sbuf.length() == 0) {
      return null;  // nothing read, must be at the end of stream
    }     sbuf.setLength(sbuf.length() - 2);  // cut off the trailing \r\n
    return sbuf.toString();
  }   // A pass-through to ServletInputStream.readLine() that keeps track
  // of how many bytes have been read and stops reading when the
  // Content-Length limit has been reached.
  //
  public int readLine(byte b[], int off, int len) throws IOException {     if (totalRead >= totalExpected) {
      return -1;
    }
    else {
      if (len > (totalExpected - totalRead)) {
        len = totalExpected - totalRead;  // keep from reading off end
      }
      int result = in.readLine(b, off, len);
      if (result > 0) {
        totalRead += result;
      }
      return result;
    }
  }
}
// Class to filters MacBinary files to normal files on the fly
// Optimized for speed more than readability
class MacBinaryDecoderOutputStream extends FilterOutputStream {   int bytesFiltered = 0;
  int dataForkLength = 0;   public MacBinaryDecoderOutputStream(OutputStream out) {
    super(out);
  }   public void write(int b) throws IOException {
    // Bytes 83 through 86 are a long representing the data fork length
    // Check <= 86 first to short circuit early in the common case
    if (bytesFiltered <= 86 && bytesFiltered >= 83) {
      int leftShift = (86 - bytesFiltered) * 8;
      dataForkLength = dataForkLength | (b & 0xff) << leftShift;
    }
    // Bytes 128 up to (128 + dataForkLength - 1) are the data fork
    else if (bytesFiltered < (128 + dataForkLength) && bytesFiltered >= 128) {
      out.write(b);
    }
    bytesFiltered++;
  }   public void write(byte b[]) throws IOException {
    write(b, 0, b.length);
  }   public void write(byte b[], int off, int len) throws IOException {
    // If the write is for content past the end of the data fork, ignore
    if (bytesFiltered >= (128 + dataForkLength)) {
      bytesFiltered += len;
    }
    // If the write is entirely within the data fork, write it directly
    else if (bytesFiltered >= 128 &&
             (bytesFiltered + len) <= (128 + dataForkLength)) {
      out.write(b, off, len);
      bytesFiltered += len;
    }
    // Otherwise, do the write a byte at a time to get the logic above
    else {
      for (int i = 0 ; i < len ; i++) {
        write(b[off + i]);
      }
    }
  }
}

老兄，你给的source也太长了，我们的工程师小姐说她看不懂!
你能不能讲一讲这个程序的思想!
暂且先给你10分!

我再帖一个使用例子吧：import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;
import java.util.*;
public class UploadTest extends HttpServlet
{  public void doGet(HttpServletRequest req,
                    HttpServletResponse resp)
    throws ServletException, java.io.IOException
    {
      // Set the content type of the response
      resp.setContentType("text/html");      // Get the PrintWriter to write the response
      java.io.PrintWriter out = resp.getWriter();      // Create the HTML form
      out.println("<html>");
      out.println("<head>");
      out.println("<title>Send Email</title>");
      out.println("<center><h2>Send Email to Karl Moss</h2>");
      out.println("<br><form method=POST action=\"" +
                  req.getRequestURI()+"/banner"+ "\" ENCTYPE=\"multipart/form-data\" >");
      out.println("<table>");
      out.println("<tr><td>Name:</td>");
      out.println("<td><input type=text name=name size=30></td></tr>");
      out.println("<tr><td>File:</td>");
      out.println("<td><input type=file name=img></td></tr>");
      out.println("</table><br>");
      out.println("<input type=submit value=\"Send\">");
      out.println("<input type=reset value=\"Reset\">");
      out.println("</form></center></body></html>");

      // Wrap up
      out.println("</body>");
      out.println("</html>");
      out.flush();
    }

  /**
    * <p>Performs the HTTP POST operation
    *
    * @param req The request from the client
    * @param resp The response from the servlet
    */
  public void doPost(HttpServletRequest req,
                     HttpServletResponse resp)
    throws ServletException, java.io.IOException
    {
      // Set the content type of the response
      resp.setContentType("text/html");      // Create a PrintWriter to write the response
      java.io.PrintWriter out =
        new java.io.PrintWriter(resp.getOutputStream()); //指定上传文件最大字节
//String dirName=getServletContext().getRealPath("/");
String dirName=req.getPathTranslated();
//MultipartRequest multi = new MultipartRequest(req,".",2*1024);
//或用默认2M，
MultipartRequest multi = new MultipartRequest(req, dirName);

out.println("Params:");
Enumeration params = multi.getParameterNames();
while (params.hasMoreElements()) {
    String name = (String)params.nextElement();
      String value = multi.getParameter(name);
      out.println(name + " = " + value);
     }
   out.println();

   out.println("Files:");
   Enumeration files = multi.getFileNames();
   while (files.hasMoreElements()) {
     String name = (String)files.nextElement();
     String filename = multi.getFilesystemName(name);
     String type = multi.getContentType(name);
     File f = multi.getFile(name);
     out.println("name: " + name);
     out.println("filename: " + filename);
     out.println("type: " + type);
     if (f != null) {
       out.println("f.toString(): " + f.toString());
       out.println("f.getName(): " + f.getName());
       out.println("f.exists(): " + f.exists());
       out.println("f.length(): " + f.length());
       out.println();
     }
   }

      // Wrap up
      out.flush();
    }  /**
    * <p>Initialize the servlet. This is called once when the
    * servlet is loaded. It is guaranteed to complete before any
    * requests are made to the servlet
    *
    * @param cfg Servlet configuration information
    */  public void init(ServletConfig cfg)
    throws ServletException
    {
      super.init(cfg);
    }  /**
    * <p>Destroy the servlet. This is called once when the servlet
    * is unloaded.
    */  public void destroy()
    {
      super.destroy();
    }}

go to http://www.cn.ibm.com/developer/cnpapers.nsf/java-papers-bynewest?OpenView&Count=500

调试易

关于从HTML页面上传文件的问题：

解决方案 »