defaultfileitem.java

java servlet著名论坛源代码

    /**
     * Returns the contents of the file as a String, using the specified
     * encoding.  This method uses {@link #get()} to retrieve the
     * contents of the file.
     *
     * @param encoding The character encoding to use.
     *
     * @return The contents of the file, as a string.
     *
     * @exception UnsupportedEncodingException if the requested character
     *                                         encoding is not available.
     */
    public String getString(String encoding)
        throws UnsupportedEncodingException
    {
        return new String(get(), encoding);
    }


    /**
     * Returns the contents of the file as a String, using the default
     * character encoding.  This method uses {@link #get()} to retrieve the
     * contents of the file.
     *
     * @return The contents of the file, as a string.
     */
    public String getString()
    {
        return new String(get());
    }


    /**
     * Returns the {@link java.io.File} object for the <code>FileItem</code>'s
     * data's temporary location on the disk. Note that for
     * <code>FileItem</code>s that have their data stored in memory,
     * this method will return <code>null</code>. When handling large
     * files, you can use {@link java.io.File#renameTo(File)} to
     * move the file to new location without copying the data, if the
     * source and destination locations reside within the same logical
     * volume.
     *
     * @return The data file, or <code>null</code> if the data is stored in
     *         memory.
     */
    public File getStoreLocation()
    {
        return storeLocation;
    }


    /**
     * A convenience method to write an uploaded file to disk. The client code
     * is not concerned whether or not the file is stored in memory, or on disk
     * in a temporary location. They just want to write the uploaded file to
     * disk.
     *
     * @param file The full path to location where the uploaded file should
     *             be stored.
     *
     * @exception Exception if an error occurs.
     */
    public void write(String file) throws Exception
    {
        if (isInMemory())
        {
            FileOutputStream fout = null;
            try
            {
                fout = new FileOutputStream(file);
                fout.write(get());
            }
            finally
            {
                if (fout != null)
                {
                    fout.close();
                }
            }
        }
        else if (storeLocation != null)
        {
            /*
             * The uploaded file is being stored on disk
             * in a temporary location so move it to the
             * desired file.
             */
            if (storeLocation.renameTo(new File(file)) == false)
            {
                BufferedInputStream in = null;
                BufferedOutputStream out = null;
                try
                {
                    in = new BufferedInputStream(
                        new FileInputStream(storeLocation));
                    out = new BufferedOutputStream(new FileOutputStream(file));
                    byte[] bytes = new byte[2048];
                    int s = 0;
                    while ((s = in.read(bytes)) != -1)
                    {
                        out.write(bytes, 0, s);
                    }
                }
                finally
                {
                    try
                    {
                        in.close();
                    }
                    catch (Exception e)
                    {
                        // ignore
                    }
                    try
                    {
                        out.close();
                    }
                    catch (Exception e)
                    {
                        // ignore
                    }
                }
            }
        }
        else
        {
            /*
             * For whatever reason we cannot write the
             * file to disk.
             */
            throw new FileUploadException(
                "Cannot write uploaded file to disk!");
        }
    }


    /**
     * Deletes the underlying storage for a file item, including deleting any
     * associated temporary disk file. Although this storage will be deleted
     * automatically when the <code>FileItem</code> instance is garbage
     * collected, this method can be used to ensure that this is done at an
     * earlier time, thus preserving system resources.
     */
    public void delete()
    {
        byteStream = null;
        content = null;
        if (storeLocation != null && storeLocation.exists())
        {
            storeLocation.delete();
        }
    }


    /**
     * Returns the name of the field in the multipart form corresponding to
     * this file item.
     *
     * @return The name of the form field.
     */
    public String getFieldName()
    {
        return fieldName;
    }


    /**
     * Sets the field name used to reference this file item.
     *
     * @param fieldName The name of the form field.
     */
    public void setFieldName(String fieldName)
    {
        this.fieldName = fieldName;
    }


    /**
     * Determines whether or not a <code>FileItem</code> instance represents
     * a simple form field.
     *
     * @return <code>true</code> if the instance represents a simple form
     *         field; <code>false</code> if it represents an uploaded file.
     */
    public boolean isFormField()
    {
        return isFormField;
    }


    /**
     * Specifies whether or not a <code>FileItem</code> instance represents
     * a simple form field.
     *
     * @param state <code>true</code> if the instance represents a simple form
     *              field; <code>false</code> if it represents an uploaded file.
     */
    public void setIsFormField(boolean state)
    {
        isFormField = state;
    }


    // --------------------------------------------------------- Public methods


    /**
     * Removes the file contents from the temporary storage.
     */
    protected void finalize()
    {
        if (storeLocation != null && storeLocation.exists())
        {
            storeLocation.delete();
        }
    }


    /**
     * Returns an {@link java.io.OutputStream OutputStream} that can
     * be used for storing the contents of the file.
     *
     * @return An {@link java.io.OutputStream OutputStream} that can be used
     *         for storing the contensts of the file.
     *
     * @exception IOException if an error occurs.
     */
    public OutputStream getOutputStream()
        throws IOException
    {
        if (storeLocation == null)
        {
            return byteStream;
        }
        else
        {
            return new FileOutputStream(storeLocation);
        }
    }


    /**
     * Instantiates a DefaultFileItem. It uses <code>requestSize</code> to
     * decide what temporary storage approach the new item should take.
     *
     * @param path        The path under which temporary files should be
     *                    created.
     * @param name        The original filename in the client's filesystem.
     * @param contentType The content type passed by the browser, or
     *                    <code>null</code> if not defined.
     * @param requestSize The total size of the POST request this item
     *                    belongs to.
     * @param threshold   The maximum size to store in memory.
     *
     * @return A <code>DefaultFileItem</code> instance.
     */
    public static FileItem newInstance(String path,
                                       String name,
                                       String contentType,
                                       int requestSize,
                                       int threshold)
    {
        DefaultFileItem item = new DefaultFileItem(name, contentType);
        if (requestSize > threshold)
        {
            String fileName = getUniqueId();
            fileName = "upload_" + fileName + ".tmp";
            fileName = path + "/" + fileName;
            File f = new File(fileName);
            f.deleteOnExit();
            item.storeLocation = f;
        }
        else
        {
            item.byteStream = new ByteArrayOutputStream();
        }
        return item;
    }


    // -------------------------------------------------------- Private methods


    /**
     * Returns an identifier that is unique within the class loader used to
     * load this class, but does not have random-like apearance.
     *
     * @return A String with the non-random looking instance identifier.
     */
    private static String getUniqueId()
    {
        int current;
        synchronized (DefaultFileItem.class)
        {
            current = counter++;
        }
        String id = Integer.toString(current);

        // If you manage to get more than 100 million of ids, you'll
        // start getting ids longer than 8 characters.
        if (current < 100000000)
        {
            id = ("00000000" + id).substring(id.length());
        }
        return id;
    }

}