diskfileitem.java

java上传文件的一个例子。使用了apache的第三方开源组件。

     * @return The contents of the file, as a string.
     *
     * @todo Consider making this method throw UnsupportedEncodingException.
     */
    public String getString() {
        byte[] rawdata = get();
        String charset = getCharSet();
        if (charset == null) {
            charset = DEFAULT_CHARSET;
        }
        try {
            return new String(rawdata, charset);
        } catch (UnsupportedEncodingException e) {
            return new String(rawdata);
        }
    }


    /**
     * 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.
     *
     * @throws 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) {
                // Save the length of the file
                size = outputFile.length();
                /*
                 * 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));
                        IOUtils.copy(in, out);
                    } finally {
                        if (in != null) {
                            try {
                                in.close();
                            } catch (IOException e) {
                                // ignore
                            }
                        }
                        if (out != null) {
                            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.
     *
     * @throws 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. The lifetime of
     * the file is tied to the lifetime of the <code>FileItem</code> instance;
     * the file will be deleted when the instance is garbage collected.
     *
     * @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_" + UID + "_" + getUniqueId() + ".tmp";

        File f = new File(tempDir, fileName);
        FileCleaner.track(f, this);
        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() {
        final int limit = 100000000;
        int current;
        synchronized (DiskFileItem.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 < limit) {
            id = ("00000000" + id).substring(id.length());
        }
        return id;
    }




    /**
     * Returns a string representation of this object.
     *
     * @return a string representation of this object.
     */
    public String toString() {
        return "name=" + this.getName()
            + ", StoreLocation="
            + String.valueOf(this.getStoreLocation())
            + ", size="
            + this.getSize()
            + "bytes, "
            + "isFormField=" + isFormField()
            + ", FieldName="
            + this.getFieldName();
    }


    // -------------------------------------------------- Serialization methods


    /**
     * Writes the state of this object during serialization.
     *
     * @param out The stream to which the state should be written.
     *
     * @throws IOException if an error occurs.
     */
    private void writeObject(ObjectOutputStream out) throws IOException {
        // Read the data
        if (dfos.isInMemory()) {
            cachedContent = get();
        } else {
            cachedContent = null;
            dfosFile = dfos.getFile();
        }

        // write out values
        out.defaultWriteObject();
    }

    /**
     * Reads the state of this object during deserialization.
     *
     * @param in The stream from which the state should be read.
     *
     * @throws IOException if an error occurs.
     * @throws ClassNotFoundException if class cannot be found.
     */
    private void readObject(ObjectInputStream in)
            throws IOException, ClassNotFoundException {
        // read values
        in.defaultReadObject();

        OutputStream output = getOutputStream();
        if (cachedContent != null) {
            output.write(cachedContent);
        } else {
            FileInputStream input = new FileInputStream(dfosFile);

            IOUtils.copy(input, output);
            dfosFile.delete();
            dfosFile = null;
        }
        output.close();

        cachedContent = null;
    }

}