multipartiterator.java

来自「这是一个轻便的j2ee的web应用框架,是一个在多个项目中运用的实际框架,采用s」· Java 代码 · 共 456 行 · 第 1/2 页

        else
        {
            //default to system-wide tempdir
            this.tempDir = System.getProperty("java.io.tmpdir");
        }
        this.maxLengthExceeded = false;
        this.inputStream = new MultipartBoundaryInputStream();
        parseRequest();
    }

    /**
     * Handles retrieving the boundary and setting the input stream
     */
    protected void parseRequest() throws IOException
    {
        //get the content-type header, which contains the boundary used for separating multipart elements
        getContentTypeOfRequest();
        //get the content-length header, used to prevent denial of service attacks and for detecting
        //whether a file size is over the limit before the client sends the file
        this.contentLength = this.request.getContentLength();
        //parse the boundary from the content-type header's value
        getBoundaryFromContentType();
        //don't let the stream read past the content length
        this.inputStream.setMaxLength(this.contentLength+1);
        //just stop now if the content length is bigger than the maximum allowed size
        if ((this.maxSize > -1) && (this.contentLength > this.maxSize))
        {
            this.maxLengthExceeded = true;
        }
        else
        {
            InputStream requestInputStream = this.request.getInputStream();
            //mark the input stream to allow multiple reads
            if (requestInputStream.markSupported())
            {
                requestInputStream.mark(contentLength+1);
            }
            this.inputStream.setBoundary(this.boundary);
            this.inputStream.setInputStream(requestInputStream);
        }
    }

    /**
     * Retrieves the next element in the iterator if one exists.
     *
     * @throws IOException if the post size exceeds the maximum file size
     *         passed in the 3 argument constructor or if the "ISO-8859-1" encoding isn't found
     * @return a {@link org.apache.struts.upload.MultipartElement MultipartElement}
     *         representing the next element in the request data
     *
     */
    public MultipartElement getNextElement() throws IOException
    {
        //the MultipartElement to return
        MultipartElement element = null;
        if (!isMaxLengthExceeded())
        {
            if (!this.inputStream.isFinalBoundaryEncountered())
            {
                if (this.inputStream.isElementFile())
                {
                    //attempt to create the multipart element from the collected data
                    element = createFileMultipartElement();
                }
                //process a text element
                else
                {
                    String encoding = getElementEncoding();
                    element = createTextMultipartElement(encoding);
                }
                this.inputStream.resetForNextBoundary();
            }
        }
        return element;
    }

    /**
     * Get the character encoding used for this current multipart element.
     */
    protected String getElementEncoding()
    {
        String encoding = this.inputStream.getElementCharset();
        if (encoding == null)
        {
            encoding = this.request.getCharacterEncoding();
            if (encoding == null)
            {
                encoding = DEFAULT_ENCODING;
            }
        }
        return encoding;
    }

    /**
     * Create a text element from the data in the body of the element.
     * @param encoding The character encoding of the string.
     */
    protected MultipartElement createTextMultipartElement(String encoding) throws IOException
    {
        MultipartElement element;

        int read = 0;
        byte[] buffer = new byte[TEXT_BUFFER_SIZE];
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        while ((read = this.inputStream.read(buffer, 0, TEXT_BUFFER_SIZE)) > 0)
        {
            baos.write(buffer, 0, read);
        }
        //create the element
        String value = baos.toString(encoding);
        element = new MultipartElement(this.inputStream.getElementName(), value);
        return element;
    }

    /**
     * Create a multipart element instance representing the file in the stream.
     */
    protected MultipartElement createFileMultipartElement() throws IOException
    {
        MultipartElement element;
        //create a local file on disk representing the element
        File elementFile = createLocalFile();
        element = new MultipartElement(this.inputStream.getElementName(), this.inputStream.getElementFileName(),
                                       this.inputStream.getElementContentType(), elementFile);
        return element;
    }

    /**
     * Set the maximum amount of bytes read from a line at one time
     *
     * @see javax.servlet.ServletInputStream#readLine(byte[], int, int)
     */
    public void setBufferSize(int bufferSize) {
        this.bufferSize = bufferSize;
    }

    /**
     * Get the maximum amount of bytes read from a line at one time
     *
     * @see javax.servlet.ServletInputStream#readLine(byte[], int, int)
     */
    public int getBufferSize() {
        return bufferSize;
    }

    /**
     * Set the maximum post data size allowed for a multipart request
     * @param maxSize The maximum post data size in bytes, set to <code>-1</code>
     *                for no limit
     */
    public void setMaxSize(long maxSize) {
        this.maxSize = maxSize;
    }

    /**
     * Get the maximum post data size allowed for a multipart request
     * @return The maximum post data size in bytes
     */
    public long getMaxSize()
    {
        return this.maxSize;
    }

    /**
     * Whether or not the maximum length has been exceeded by the client.
     */
    public boolean isMaxLengthExceeded()
    {
        return (this.maxLengthExceeded || this.inputStream.isMaxLengthMet());
    }


    /**
     * Parses a content-type String for the boundary.
     */
    private final void getBoundaryFromContentType() throws IOException
    {
        if (this.contentType.lastIndexOf(PARAMETER_BOUNDARY) != -1)
        {
            String _boundary = this.contentType.substring(this.contentType.lastIndexOf(PARAMETER_BOUNDARY) + 9);
            if (_boundary.endsWith("\n"))
            {
                //strip it off
                this.boundary = _boundary.substring(0, _boundary.length()-1);
            }
            this.boundary = _boundary;
        }
        else
        {
            this.boundary = null;
        }
        //throw an exception if we're unable to obtain a boundary at this point
        if ((this.boundary == null) || (this.boundary.length() < 1))
        {
            throw new IOException(MESSAGE_CANNOT_RETRIEVE_BOUNDARY);
        }
    }
    /**
     * Gets the value of the Content-Type header of the request.
     */
    private final void getContentTypeOfRequest()
    {
        this.contentType = request.getContentType();
        if (this.contentType == null)
        {
            this.contentType = this.request.getHeader(HEADER_CONTENT_TYPE);
        }
    }

    /**
     * Creates a file on disk from the current mulitpart element.
     */
    protected File createLocalFile() throws IOException
    {
        File tempFile = File.createTempFile(FILE_PREFIX, null, new File(this.tempDir));
        BufferedOutputStream fos = new BufferedOutputStream(new FileOutputStream(tempFile), this.diskBufferSize);
        int read = 0;
        byte buffer[] = new byte[this.diskBufferSize];
        while ((read = this.inputStream.read(buffer, 0, this.diskBufferSize)) > 0)
        {
            fos.write(buffer, 0, read);
        }
        fos.flush();
        fos.close();
        return tempFile;
    }
}