defaultfileitem.java

java上传组件源码

        return fileData;
    }


    /**
     * 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());
    }


    /**
     * A convenience method to write an uploaded item to disk. The client code
     * is not concerned with whether or not the item is stored in memory, or on
     * disk in a temporary location. They just want to write the uploaded item
     * to a file.
     * <p>
     * This implementation first attempts to rename the uploaded item to the
     * specified destination file, if the item was originally written to disk.
     * Otherwise, the data will be copied to the specified file.
     * <p>
     * This method is only guaranteed to work <em>once</em>, the first time it
     * is invoked for a particular item. This is because, in the event that the
     * method renames a temporary file, that file will no longer be available
     * to copy or rename again at a later time.
     *
     * @param file The <code>File</code> into which the uploaded item should
     *             be stored.
     *
     * @exception Exception if an error occurs.
     */
    public void write(File file) throws Exception
    {
        if (isInMemory())
        {
            FileOutputStream fout = null;
            try
            {
                fout = new FileOutputStream(file);
                fout.write(get());
            }
            finally
            {
                if (fout != null)
                {
                    fout.close();
                }
            }
        }
        else
        {
            File outputFile = getStoreLocation();
            if (outputFile != null)
            {
                /*
                 * The uploaded file is being stored on disk
                 * in a temporary location so move it to the
                 * desired file.
                 */
                if (!outputFile.renameTo(file))
                {
                    BufferedInputStream in = null;
                    BufferedOutputStream out = null;
                    try
                    {
                        in = new BufferedInputStream(
                            new FileInputStream(outputFile));
                        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 (IOException e)
                        {
                            // ignore
                        }
                        try
                        {
                            out.close();
                        }
                        catch (IOException 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()
    {
        cachedContent = null;
        File outputFile = getStoreLocation();
        if (outputFile != null && outputFile.exists())
        {
            outputFile.delete();
        }
    }


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


    /**
     * Sets the field name used to reference this file item.
     *
     * @param fieldName The name of the form field.
     *
     * @see #getFieldName()
     *
     */
    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.
     *
     * @see #setFormField(boolean)
     *
     */
    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.
     *
     * @see #isFormField()
     *
     */
    public void setFormField(boolean state)
    {
        isFormField = state;
    }


    /**
     * 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 (dfos == null)
        {
            File outputFile = getTempFile();
            dfos = new DeferredFileOutputStream(sizeThreshold, outputFile);
        }
        return dfos;
    }


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


    /**
     * 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(java.io.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 dfos.getFile();
    }


    // ------------------------------------------------------ Protected methods


    /**
     * Removes the file contents from the temporary storage.
     */
    protected void finalize()
    {
        File outputFile = dfos.getFile();

        if (outputFile != null && outputFile.exists())
        {
            outputFile.delete();
        }
    }


    /**
     * Creates and returns a {@link java.io.File File} representing a uniquely
     * named temporary file in the configured repository path.
     *
     * @return The {@link java.io.File File} to be used for temporary storage.
     */
    protected File getTempFile()
    {
        File tempDir = repository;
        if (tempDir == null)
        {
            tempDir = new File(System.getProperty("java.io.tmpdir"));
        }

        String fileName = "upload_" + getUniqueId() + ".tmp";

        File f = new File(tempDir, fileName);
        f.deleteOnExit();
        return f;
    }


    // -------------------------------------------------------- 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;
    }

}