org.rhq.enterprise.gui.common.servlet
Class ImageServlet

java.lang.Object
  javax.servlet.GenericServlet
      javax.servlet.http.HttpServlet
          org.rhq.enterprise.gui.common.servlet.ParameterizedServlet
              org.rhq.enterprise.gui.common.servlet.ImageServlet

All Implemented Interfaces:

Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

Direct Known Subclasses:

ChartServlet, NavMapImageServlet

public abstract class ImageServlet
extends ParameterizedServlet

This servlet returns a response that contains the binary data of an image (JPEG or PNG) that can be viewed in a web browser.

The navigation map servlet takes the following parameters (any applicable defaults are in bold and required parameters are in italics):

key	value
imageFormat	(png | jpeg)
imageWidth	<integer (700)>
imageHeight	<integer (350)>

See Also:

Serialized Form

Field Summary

static String	IMAGE_FORMAT_JPEG Request parameter value representing a JPEG image.
static String	IMAGE_FORMAT_PARAM Request parameter for image format.
static String	IMAGE_FORMAT_PNG Request parameter value representing a PNG image.
static int	IMAGE_HEIGHT_DEFAULT Default image height.
static String	IMAGE_HEIGHT_PARAM Request parameter for image height.
static int	IMAGE_WIDTH_DEFAULT Default image width.
static String	IMAGE_WIDTH_PARAM Request parameter for image width.

Constructor Summary

ImageServlet()

Method Summary

protected abstract Object	createImage(javax.servlet.http.HttpServletRequest request) Create the image being rendered.
void	doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response)
protected String	getDefaultImageFormat() Return the default imageFormat.
protected int	getDefaultImageHeight() Return the default imageHeight.
protected int	getDefaultImageWidth() Return the default imageWidth.
protected String	getImageFormat() Return the image format.
protected int	getImageHeight() Return the image height.
protected int	getImageWidth() Return the image width.
void	init()
protected void	parseParameters(javax.servlet.http.HttpServletRequest request) This method will be called automatically by the ImageServlet.
protected abstract void	renderJpegImage(javax.servlet.ServletOutputStream out, Object imgObj) Render a JPEG version of the image into the output stream.
protected abstract void	renderPngImage(javax.servlet.ServletOutputStream out, Object imgObj) Render a PNG version of the image into the output stream.

Methods inherited from class org.rhq.enterprise.gui.common.servlet.ParameterizedServlet

invalidParamErr, invalidParamErr, invalidParamWarn, invalidParamWarn, invalidParamWarn, invalidParamWarn, invalidParamWarn, parseBooleanParameter, parseDoubleParameter, parseEnumParameter, parseIntParameter, parseLongParameter, parseRequiredBooleanParameter, parseRequiredDoubleParameter, parseRequiredIntParameter, parseRequiredLongParameter, parseRequiredStringParameter, parseRequiredStringParameter, parseStringParameter, parseStringParameter, requiredParamErr

Methods inherited from class javax.servlet.http.HttpServlet

doDelete, doHead, doOptions, doPost, doPut, doTrace, getLastModified, service, service

Methods inherited from class javax.servlet.GenericServlet

destroy, getInitParameter, getInitParameterNames, getServletConfig, getServletContext, getServletInfo, getServletName, init, log, log

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

IMAGE_FORMAT_PARAM

public static final String IMAGE_FORMAT_PARAM

Request parameter for image format.

See Also:

Constant Field Values

IMAGE_FORMAT_PNG

public static final String IMAGE_FORMAT_PNG

Request parameter value representing a PNG image.

See Also:

Constant Field Values

IMAGE_FORMAT_JPEG

public static final String IMAGE_FORMAT_JPEG

Request parameter value representing a JPEG image.

See Also:

Constant Field Values

IMAGE_WIDTH_PARAM

public static final String IMAGE_WIDTH_PARAM

Request parameter for image width.

See Also:

Constant Field Values

IMAGE_WIDTH_DEFAULT

public static final int IMAGE_WIDTH_DEFAULT

Default image width.

See Also:

Constant Field Values

IMAGE_HEIGHT_PARAM

public static final String IMAGE_HEIGHT_PARAM

Request parameter for image height.

See Also:

Constant Field Values

IMAGE_HEIGHT_DEFAULT

public static final int IMAGE_HEIGHT_DEFAULT

Default image height.

See Also:

Constant Field Values

Constructor Detail

ImageServlet

public ImageServlet()

Method Detail

init

public void init()

Overrides:

init in class javax.servlet.GenericServlet

doGet

public void doGet(javax.servlet.http.HttpServletRequest request,
                  javax.servlet.http.HttpServletResponse response)
           throws javax.servlet.ServletException

Overrides:

doGet in class javax.servlet.http.HttpServlet

Throws:

javax.servlet.ServletException

createImage

protected abstract Object createImage(javax.servlet.http.HttpServletRequest request)
                               throws javax.servlet.ServletException

Create the image being rendered.

Parameters:

request - the servlet request

Throws:

javax.servlet.ServletException

renderPngImage

protected abstract void renderPngImage(javax.servlet.ServletOutputStream out,
                                       Object imgObj)
                                throws IOException

Render a PNG version of the image into the output stream.

Parameters:

out - the output stream

Throws:

IOException

renderJpegImage

protected abstract void renderJpegImage(javax.servlet.ServletOutputStream out,
                                        Object imgObj)
                                 throws IOException

Render a JPEG version of the image into the output stream.

Parameters:

out - the output stream

Throws:

IOException

parseParameters

protected void parseParameters(javax.servlet.http.HttpServletRequest request)

This method will be called automatically by the ImageServlet. It should handle the parsing and error-checking of any specific parameters for the chart being rendered.

Parameters:

request - the HTTP request object

getImageFormat

protected String getImageFormat()

Return the image format.

Returns:

IMAGE_FORMAT_PNG or IMAGE_FORMAT_JPEG

getImageHeight

protected int getImageHeight()

Return the image height.

Returns:

the height of the image

See Also:

{@link IMAGE_HEIGHT_DEFAULT}

getImageWidth

protected int getImageWidth()

Return the image width.

Returns:

the width of the image

See Also:

{@link IMAGE_WIDTH_DEFAULT}

getDefaultImageFormat

protected String getDefaultImageFormat()

Return the default imageFormat.

getDefaultImageWidth

protected int getDefaultImageWidth()

Return the default imageWidth.

getDefaultImageHeight

protected int getDefaultImageHeight()

Return the default imageHeight.