servletutilities.java

来自「JfreeChart 常用图表例子」· Java 代码 · 共 445 行 · 第 1/2 页

     * Saves the chart as a JPEG format file in the temporary directory and
     * populates the ChartRenderingInfo object which can be used to generate
     * an HTML image map.
     *
     * @param chart  the chart to be saved (<code>null</code> not permitted).
     * @param width  the width of the chart
     * @param height  the height of the chart
     * @param info  the ChartRenderingInfo object to be populated
     * @param session  the HttpSession of the client (if <code>null</code>, the
     *                 temporary file is marked as "one-time" and deleted by 
     *                 the {@link DisplayChart} servlet right after it is
     *                 streamed to the client).
     *
     * @return The filename of the chart saved in the temporary directory
     *
     * @throws IOException if there is a problem saving the file.
     */
    public static String saveChartAsJPEG(JFreeChart chart, int width, 
                                         int height, ChartRenderingInfo info, 
                                         HttpSession session)
            throws IOException {

        if (chart == null) {
            throw new IllegalArgumentException("Null 'chart' argument.");   
        }
        
        ServletUtilities.createTempDir();
        String prefix = ServletUtilities.tempFilePrefix;
        if (session == null) {
            prefix = ServletUtilities.tempOneTimeFilePrefix;   
        }
        File tempFile = File.createTempFile(
            prefix, ".jpeg", new File(System.getProperty("java.io.tmpdir"))
        );
        ChartUtilities.saveChartAsJPEG(tempFile, chart, width, height, info);
        if (session != null) {
            ServletUtilities.registerChartForDeletion(tempFile, session);
        }
        return tempFile.getName();

    }

    /**
     * Creates the temporary directory if it does not exist.  Throws a 
     * <code>RuntimeException</code> if the temporary directory is 
     * <code>null</code>.  Uses the system property <code>java.io.tmpdir</code> 
     * as the temporary directory.  This sounds like a strange thing to do but 
     * my temporary directory was not created on my default Tomcat 4.0.3 
     * installation.  Could save some questions on the forum if it is created 
     * when not present.
     */
    protected static void createTempDir() {
        String tempDirName = System.getProperty("java.io.tmpdir");
        if (tempDirName == null) {
            throw new RuntimeException(
                "Temporary directory system property (java.io.tmpdir) is null."
            );
        }

        // create the temporary directory if it doesn't exist
        File tempDir = new File(tempDirName);
        if (!tempDir.exists()) {
            tempDir.mkdirs();
        }
    }

    /**
     * Adds a {@link ChartDeleter} object to the session object with the name 
     * <code>JFreeChart_Deleter</code> if there is not already one bound to the 
     * session and adds the filename to the list of charts to be deleted.
     *
     * @param tempFile  the file to be deleted.
     * @param session  the HTTP session of the client.
     */
    protected static void registerChartForDeletion(File tempFile, 
                                                   HttpSession session) {

        //  Add chart to deletion list in session
        if (session != null) {
            ChartDeleter chartDeleter 
                = (ChartDeleter) session.getAttribute("JFreeChart_Deleter");
            if (chartDeleter == null) {
                chartDeleter = new ChartDeleter();
                session.setAttribute("JFreeChart_Deleter", chartDeleter);
            }
            chartDeleter.addChart(tempFile.getName());
        }
        else {
            System.out.println("Session is null - chart will not be deleted");
        }
    }

    /**
     * Binary streams the specified file in the temporary directory to the
     * HTTP response in 1KB chunks.
     * 
     * @param filename  the name of the file in the temporary directory.
     * @param response  the HTTP response object.
     * 
     * @throws IOException  if there is an I/O problem.
     */
    public static void sendTempFile(String filename, 
                                    HttpServletResponse response)
        throws IOException {

        File file = new File(System.getProperty("java.io.tmpdir"), filename);
        ServletUtilities.sendTempFile(file, response);
    }

    /**
     * Binary streams the specified file to the HTTP response in 1KB chunks.
     *
     * @param file  the file to be streamed.
     * @param response  the HTTP response object.
     *
     * @throws IOException if there is an I/O problem.
     */
    public static void sendTempFile(File file, HttpServletResponse response)
            throws IOException {

        String mimeType = null;
        String filename = file.getName();
        if (filename.length() > 5) {
            if (filename.substring(filename.length() - 5, 
                    filename.length()).equals(".jpeg")) {
                mimeType = "image/jpeg";
            } 
            else if (filename.substring(filename.length() - 4, 
                    filename.length()).equals(".png")) {
                mimeType = "image/png";
            }
        }
        ServletUtilities.sendTempFile(file, response, mimeType);
    }

    /**
     * Binary streams the specified file to the HTTP response in 1KB chunks.
     *
     * @param file  the file to be streamed.
     * @param response  the HTTP response object.
     * @param mimeType  the mime type of the file, null allowed.
     *
     * @throws IOException if there is an I/O problem.
     */
    public static void sendTempFile(File file, HttpServletResponse response,
                                    String mimeType) throws IOException {

        if (file.exists()) {
            BufferedInputStream bis = new BufferedInputStream(
                new FileInputStream(file)
            );

            //  Set HTTP headers
            if (mimeType != null) {
                response.setHeader("Content-Type", mimeType);
            }
            response.setHeader("Content-Length", String.valueOf(file.length()));
            SimpleDateFormat sdf = new SimpleDateFormat(
                "EEE, dd MMM yyyy HH:mm:ss z"
            );
            sdf.setTimeZone(TimeZone.getTimeZone("GMT"));
            response.setHeader(
                "Last-Modified", sdf.format(new Date(file.lastModified()))
            );

            BufferedOutputStream bos = new BufferedOutputStream(
                response.getOutputStream()
            );
            byte[] input = new byte[1024];
            boolean eof = false;
            while (!eof) {
                int length = bis.read(input);
                if (length == -1) {
                    eof = true;
                } 
                else {
                    bos.write(input, 0, length);
                }
            }
            bos.flush();
            bis.close();
            bos.close();
        }
        else {
            throw new FileNotFoundException(file.getAbsolutePath());
        }
        return;
    }

    /**
     * Perform a search/replace operation on a String
     * There are String methods to do this since (JDK 1.4)
     *
     * @param inputString  the String to have the search/replace operation.
     * @param searchString  the search String.
     * @param replaceString  the replace String.
     *
     * @return The String with the replacements made.
     */
    public static String searchReplace(String inputString,
                                       String searchString,
                                       String replaceString) {

        int i = inputString.indexOf(searchString);
        if (i == -1) {
            return inputString;
        }

        String r = "";
        r += inputString.substring(0, i) + replaceString;
        if (i + searchString.length() < inputString.length()) {
            r += searchReplace(
                inputString.substring(i + searchString.length()),
                searchString, replaceString
            );
        }

        return r;
    }

}