com.objectplanet.chart
Class ChartServlet

java.lang.Object
  javax.servlet.GenericServlet
      com.objectplanet.chart.ChartServlet

All Implemented Interfaces:

java.io.Serializable, javax.servlet.Servlet, javax.servlet.ServletConfig

public class ChartServlet
extends javax.servlet.GenericServlet

This servlet generates a chart as a PNG image.

Author:

Bjorn J. Kvande.

See Also:

Serialized Form

Field Summary

protected Chart	chart The chart component used.
protected ChartDataLoader	dataLoader The data loader used to load chart parameters.
protected java.lang.String	encoding The encoding used to read data from an URL.
protected java.lang.String	format The image format to use.
protected GaugeChart	gaugeChart The gauge chart component used.
protected java.util.Hashtable	imageList The list of image parameters read.
protected int	jpegQuality The quality of the returned jpeg image.
protected PlotterChart	plotterChart The plotter chart component used.
protected PngEncoder	pngEncoder The png encoder used to encode the charts as png images.
protected java.lang.String	type The chart may be of "bar", "line", "pie", "time_line", "spline", "plotter" type.
protected java.util.Hashtable	urlList The list of url parameters read.
protected java.util.Hashtable	urlTargetList The list of url target parameters read.

Constructor Summary

ChartServlet()

Method Summary

protected static java.lang.String	convertLineBreaks(java.lang.String label) Converts '\n' to .
protected java.lang.String	convertURL(java.lang.String url, javax.servlet.ServletRequest req, java.lang.String separator, java.lang.String equals) Converts the data URL to use the standard parameter separator (&) instead of the one the servlet tag has to use (¤).
protected void	encodeChartImage(java.awt.Image image, int width, int height, java.io.OutputStream out, javax.servlet.ServletResponse res) Encodes the specified java image to a jpeg/png bytestream.
protected void	generateChartImage(javax.servlet.ServletRequest req, javax.servlet.ServletResponse res, java.util.Hashtable parameters, java.lang.String error) Generates a chart image based on the given parameters
void	generateImagemap(java.lang.String type, javax.servlet.ServletRequest req, javax.servlet.ServletResponse res) Generates and prints out an imagemap to implement drilldown functionality for the chart.
protected java.awt.Image	getImage(java.awt.Component chart, int width, int height, boolean antialias) Returns the current chart as an image.
void	init(javax.servlet.ServletConfig config) This method is called when the servlet is placed into service.
protected void	loadInputParameters(java.io.InputStream input, java.util.Hashtable parameters, java.util.Hashtable urlList, java.util.Hashtable urlTargetList, java.util.Hashtable imageList) Loads the parameters from the given data input stream.
protected void	loadURLParameters(java.lang.String urlString, java.util.Hashtable parameters, java.util.Hashtable urlList, java.util.Hashtable urlTargetList, java.util.Hashtable imageList) Loads the parameters from the specified url.
protected void	paintError(java.awt.Graphics g, java.lang.String label) Paints a multiline label broken with \n.
protected void	paintLabel(java.awt.Graphics g, java.lang.String label, int label_x, int label_y) Paints a multiline label broken with \n.
void	service(javax.servlet.ServletRequest req, javax.servlet.ServletResponse res) The 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

chart

protected Chart chart

The chart component used.

dataLoader

protected ChartDataLoader dataLoader

The data loader used to load chart parameters.

encoding

protected java.lang.String encoding

The encoding used to read data from an URL.

format

protected java.lang.String format

The image format to use.

gaugeChart

protected GaugeChart gaugeChart

The gauge chart component used.

imageList

protected java.util.Hashtable imageList

The list of image parameters read.

jpegQuality

protected int jpegQuality

The quality of the returned jpeg image.

plotterChart

protected PlotterChart plotterChart

The plotter chart component used.

pngEncoder

protected PngEncoder pngEncoder

The png encoder used to encode the charts as png images.

type

protected java.lang.String type

The chart may be of "bar", "line", "pie", "time_line", "spline", "plotter" type.

urlList

protected java.util.Hashtable urlList

The list of url parameters read.

urlTargetList

protected java.util.Hashtable urlTargetList

The list of url target parameters read.

Constructor Detail

ChartServlet

public ChartServlet()

Method Detail

convertLineBreaks

protected static java.lang.String convertLineBreaks(java.lang.String label)

Converts '\n' to
. Converts also the Unicode char sequences and uxxxx to valid chars.

Parameters:

label - The label with the \ and n.

convertURL

protected java.lang.String convertURL(java.lang.String url,
                                      javax.servlet.ServletRequest req,
                                      java.lang.String separator,
                                      java.lang.String equals)

Converts the data URL to use the standard parameter separator (&) instead of the one the servlet tag has to use (¤).

Parameters:

url - The data url to convert.

req - The servlet request.

separator - The separator used in the servlet tag.

equals - The equals sign.

Returns:

The converted URL.

encodeChartImage

protected void encodeChartImage(java.awt.Image image,
                                int width,
                                int height,
                                java.io.OutputStream out,
                                javax.servlet.ServletResponse res)
                         throws java.io.IOException

Encodes the specified java image to a jpeg/png bytestream. Make a subclass and override this method to support other image formats. The content type has to be set before the image is written to the output stream; res.setContentType("image/jpeg").

Parameters:

image - The image to encode.

width - The width of the image.

height - The height of the image.

out - The output stream to encode it to.

res - The servlet response.

Throws:

java.io.IOException

generateChartImage

protected void generateChartImage(javax.servlet.ServletRequest req,
                                  javax.servlet.ServletResponse res,
                                  java.util.Hashtable parameters,
                                  java.lang.String error)
                           throws java.io.IOException

Generates a chart image based on the given parameters

Parameters:

req - The servlet request.

res - The servlet response.

parameters - Paramters passed to the servlet.

error - Message to display on the image if an error happens.

Throws:

java.io.IOException - If an I/O exception has occurred.

generateImagemap

public void generateImagemap(java.lang.String type,
                             javax.servlet.ServletRequest req,
                             javax.servlet.ServletResponse res)
                      throws java.io.IOException

Generates and prints out an imagemap to implement drilldown functionality for the chart.

Parameters:

type - The type of the chart.

req - The servlet request.

res - The servlet response.

Throws:

java.io.IOException

getImage

protected java.awt.Image getImage(java.awt.Component chart,
                                  int width,
                                  int height,
                                  boolean antialias)

Returns the current chart as an image.

Parameters:

chart - The chart to get the image from.

width - The width of the chart in pixels.

height - The height of the chart in pixels.

antialias - True if antialiased, falst otherwise.

Returns:

The chart as an image object.

init

public void init(javax.servlet.ServletConfig config)

This method is called when the servlet is placed into service. It creates the bar/line/pie charts to be used for generating the chart images.

Specified by:

init in interface javax.servlet.Servlet

Overrides:

init in class javax.servlet.GenericServlet

loadInputParameters

protected void loadInputParameters(java.io.InputStream input,
                                   java.util.Hashtable parameters,
                                   java.util.Hashtable urlList,
                                   java.util.Hashtable urlTargetList,
                                   java.util.Hashtable imageList)
                            throws java.lang.Exception

Loads the parameters from the given data input stream. The input stream is usually gotten from a valid URL or is forwarded by another component in this web application.

Parameters:

input - The input stream to read the data from.

parameters - Read the parameters into this hashtable.

urlList - Read the drilldown parameters into this hashtable.

urlTargetList - Read the url target parameters into this hashtable.

imageList - Read the image parameters into this hashtable.

Throws:

java.lang.Exception

loadURLParameters

protected void loadURLParameters(java.lang.String urlString,
                                 java.util.Hashtable parameters,
                                 java.util.Hashtable urlList,
                                 java.util.Hashtable urlTargetList,
                                 java.util.Hashtable imageList)
                          throws java.lang.Exception

Loads the parameters from the specified url. The URL must be a valid absolute URL, since this is a servlet running on some kind of server and does not have a document base or code base.

Parameters:

urlString - The url to load the data from.

parameters - Read the parameters into this hashtable.

urlList - Read the drilldown parameters into this hashtable.

urlTargetList - Read the url target parameters into this hashtable.

imageList - Read the image parameters into this hashtable.

Throws:

java.lang.Exception

paintError

protected void paintError(java.awt.Graphics g,
                          java.lang.String label)

Paints a multiline label broken with \n.

Parameters:

g - The graphics context used to paint with.

label - The label to paint.

paintLabel

protected void paintLabel(java.awt.Graphics g,
                          java.lang.String label,
                          int label_x,
                          int label_y)

Paints a multiline label broken with \n.

Parameters:

g - The graphics context used to paint with.

label - The label to paint.

label_x - The x position of the label.

label_y - The y position of the label.

service

public void service(javax.servlet.ServletRequest req,
                    javax.servlet.ServletResponse res)
             throws javax.servlet.ServletException,
                    java.io.IOException

The service.

Specified by:

service in interface javax.servlet.Servlet

Specified by:

service in class javax.servlet.GenericServlet

Throws:

javax.servlet.ServletException - If the call could not be processed.

java.io.IOException