Tutorials : Smoothing Out Graphics Functioning Wrinkles in Linux and Unix :

Exploring the Solutions

#1: Using Sun JDK 1.4 Headless Mode

java -Djava.awt.headless=true

This project attempted to set the java.awt.headless system property value to "true," with surprising results—the following exception was thrown and when I requested the registration page (with the embedded, dynamic visual image), it was not generated properly:

[21/04/06 11:33:00:388 EDT] 456af8da WebGroup      E SRVE0026E: [Servlet Error]-[Captcha]: java.awt.HeadlessException
	at sun.java2d.HeadlessGraphicsEnvironment.getDefaultScreenDevice(HeadlessGraphicsEnvironment.java:98)
	at nl.captcha.text.imp.DefaultWordRenderer.renderWord(DefaultWordRenderer.java:59)
	at nl.captcha.servlet.DefaultCaptchaIml.createImage(DefaultCaptchaIml.java:103)
	at nl.captcha.servlet.CaptchaServlet.doGet(CaptchaServlet.java:44)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
	at com.ibm.ws.webcontainer.servlet.StrictServletInstance.doService(StrictServletInstance.java:110)
	at com.ibm.ws.webcontainer.servlet.StrictLifecycleServlet._service(StrictLifecycleServlet.java:174)
	at com.ibm.ws.webcontainer.servlet.IdleServletState.service(StrictLifecycleServlet.java:313)
	at com.ibm.ws.webcontainer.servlet.StrictLifecycleServlet.service(StrictLifecycleServlet.java:116)
	at com.ibm.ws.webcontainer.servlet.ServletInstance.service(ServletInstance.java:283)
	at com.ibm.ws.webcontainer.servlet.ValidServletReferenceState.dispatch(ValidServletReferenceState.java:42)
	at com.ibm.ws.webcontainer.servlet.ServletInstanceReference.dispatch(ServletInstanceReference.java:40)
	at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.handleWebAppDispatch(WebAppRequestDispatcher.java:974)
	at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.dispatch(WebAppRequestDispatcher.java:555)
	at com.ibm.ws.webcontainer.webapp.WebAppRequestDispatcher.forward(WebAppRequestDispatcher.java:200)
	at com.ibm.ws.webcontainer.srt.WebAppInvoker.doForward(WebAppInvoker.java:119)
	at com.ibm.ws.webcontainer.srt.WebAppInvoker.handleInvocationHook(WebAppInvoker.java:276)
	at com.ibm.ws.webcontainer.cache.invocation.CachedInvocation.handleInvocation(CachedInvocation.java:71)
	at com.ibm.ws.webcontainer.srp.ServletRequestProcessor.dispatchByURI(ServletRequestProcessor.java:182)
	at com.ibm.ws.webcontainer.oselistener.OSEListenerDispatcher.service(OSEListener.java:334)
	at com.ibm.ws.webcontainer.http.HttpConnection.handleRequest(HttpConnection.java:56)
	at com.ibm.ws.http.HttpConnection.readAndHandleRequest(HttpConnection.java:618)
	at com.ibm.ws.http.HttpConnection.run(HttpConnection.java:443)
	at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:593)

As you can see, the exception was thrown at the line 59 from the method of renderWord (String word, int width, int height) inside the nl.captcha.text.imp.DefaultWordRenderer.java class in SimpleCaptcha library:

Line 58 ………………GraphicsEnvironment ge =   
                            GraphicsEnvironment.getLocalGraphicsEnvironment();

Line 59 ………………GraphicsDevice gd = ge.getDefaultScreenDevice();

Line 59 ………………GraphicsConfiguration gc = gd.getDefaultConfiguration();

The corresponding code change, along with the recompiled SimpleCaptcha source code, can be found in the source code: lsimplecaptcha-20060421.jar under the $PROJECT_ROOT$/dist ("$PROJECT_ROOT$ = C:\aolWebRegAdmin\SimpleCaptchaWeb, which is the SimpleCaptcha open source project root. Please see the details in Figures 1 and 2. The SimpleCaptcha project source code can be downloaded here.

Figure 1: The SimpleCaptcha project directory structure within the IBM WSAD5.1 IDE.

Figure 2: Recompiling the SimpleCaptcha source code and generating the .jar file.

Note: In order to use the Ant build.xml file for the auto build, you'll need to modify the builld.properties file to your corresponding J2EE .jar file path:

 
j2ee.jar=C:/Program Files/IBM/WebSphere Studio/
                          Application  Developer/v5.1.1/runtimes/aes_v4_jar/lib/j2ee.jar

Figure 3: The Random text image does not show up on the test page.

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