JavaScript is a Revolutionize myths

Frankly speaking, I personally feel that JavaScript is a toy language?

No, not that way. JavaScript has make a lot of improvement due to the brain from the Safari, Firefox, and Chrome, it has already become a lot more faster now. And getting more fun and interesting.

This programming language is a design fault.

Before JavaScript, there are HTML and CSS. HTML is responsible for the structure of the web content; CSS is responsible for adding in style to bring some color and life to the content. Whereas JavaScript is like a controller that could control the behavior of the content, and it works together with HTML and CSS.

Programming JavaScript is a real fun.

Since it doesn't need any fancy tool, just a simple notepad to do the coding and then load it up into the browser and it just run. Thus it should be the first programming language teach to the student. But during my time, although I did attend to this class but I don't find my interest on it as C++ is my interest during that time.

 

Connecting Derby...

This is a real annoying every time I come to connecting Derby, I just can't remember the command. After few hours searching, this command is the most friendly to remember.

connect 'jdbc:derby:mydb' user 'username' password 'abcd1234';

Grant read permission to spring.security.strategy to Tomcat 6

I have a Spring project initially was developed on computer A, it is working fine and no error. When I transfer it to computer B, I got this error during the Tomcat start up:

SEVERE: Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.security.web.context.HttpSessionSecurityContextRepository#0': Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.security.web.context.HttpSessionSecurityContextRepository]: Constructor threw exception; nested exception is java.lang.ExceptionInInitializerError
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:964)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:910)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:484)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:455)
 at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:293)
 at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:290)
 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:192)
 at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:585)
 at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
 at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
 at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:282)
 at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:204)
 at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47)
 at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4205)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4704)
 at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
 at org.apache.catalina.core.StandardHost.start(StandardHost.java:840)
 at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
 at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)
 at org.apache.catalina.core.StandardService.start(StandardService.java:525)
 at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)
 at org.apache.catalina.startup.Catalina.start(Catalina.java:595)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
 at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.security.web.context.HttpSessionSecurityContextRepository]: Constructor threw exception; nested exception is java.lang.ExceptionInInitializerError
 at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:141)
 at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:74)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$3.run(AbstractAutowireCapableBeanFactory.java:952)
 at java.security.AccessController.doPrivileged(Native Method)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:950)
 ... 28 more
Caused by: java.lang.ExceptionInInitializerError
 at org.springframework.security.web.context.HttpSessionSecurityContextRepository.(HttpSessionSecurityContextRepository.java:62)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
 at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:126)
 ... 32 more
Caused by: java.security.AccessControlException: access denied (java.util.PropertyPermission spring.security.strategy read)
 at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
 at java.security.AccessController.checkPermission(AccessController.java:549)
 at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
 at java.lang.SecurityManager.checkPropertyAccess(SecurityManager.java:1285)
 at java.lang.System.getProperty(System.java:650)
 at org.springframework.security.core.context.SecurityContextHolder.(SecurityContextHolder.java:53)
 ... 38 more
May 24, 2013 9:52:10 PM org.apache.catalina.core.StandardContext listenerStart
SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'org.springframework.security.web.context.HttpSessionSecurityContextRepository#0': Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.security.web.context.HttpSessionSecurityContextRepository]: Constructor threw exception; nested exception is java.lang.ExceptionInInitializerError
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:964)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:910)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:484)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:455)
 at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:293)
 at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222)
 at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:290)
 at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:192)
 at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:585)
 at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:895)
 at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:425)
 at org.springframework.web.context.ContextLoader.createWebApplicationContext(ContextLoader.java:282)
 at org.springframework.web.context.ContextLoader.initWebApplicationContext(ContextLoader.java:204)
 at org.springframework.web.context.ContextLoaderListener.contextInitialized(ContextLoaderListener.java:47)
 at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4205)
 at org.apache.catalina.core.StandardContext.start(StandardContext.java:4704)
 at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
 at org.apache.catalina.core.StandardHost.start(StandardHost.java:840)
 at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1053)
 at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:463)
 at org.apache.catalina.core.StandardService.start(StandardService.java:525)
 at org.apache.catalina.core.StandardServer.start(StandardServer.java:754)
 at org.apache.catalina.startup.Catalina.start(Catalina.java:595)
 at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
 at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
 at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
 at java.lang.reflect.Method.invoke(Method.java:597)
 at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:289)
 at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:414)
Caused by: org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.security.web.context.HttpSessionSecurityContextRepository]: Constructor threw exception; nested exception is java.lang.ExceptionInInitializerError
 at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:141)
 at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:74)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$3.run(AbstractAutowireCapableBeanFactory.java:952)
 at java.security.AccessController.doPrivileged(Native Method)
 at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.instantiateBean(AbstractAutowireCapableBeanFactory.java:950)
 ... 28 more
Caused by: java.lang.ExceptionInInitializerError
 at org.springframework.security.web.context.HttpSessionSecurityContextRepository.(HttpSessionSecurityContextRepository.java:62)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
 at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
 at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
 at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
 at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:126)
 ... 32 more
Caused by: java.security.AccessControlException: access denied (java.util.PropertyPermission spring.security.strategy read)
 at java.security.AccessControlContext.checkPermission(AccessControlContext.java:374)
 at java.security.AccessController.checkPermission(AccessController.java:549)
 at java.lang.SecurityManager.checkPermission(SecurityManager.java:532)
 at java.lang.SecurityManager.checkPropertyAccess(SecurityManager.java:1285)
 at java.lang.System.getProperty(System.java:650)
 at org.springframework.security.core.context.SecurityContextHolder.(SecurityContextHolder.java:53)
 ... 38 more

This is so mysterious. But anyhow, I got the solution on this problem in Spring forum where I'm required to grant the read permission to spring.security.strategy. Do this in catalina.policy under the <tomcat_dir>/conf:

    permission java.util.PropertyPermission "spring.security.strategy", "read";
    permission java.lang.RuntimePermission "accessDeclaredMembers";
    permission java.net.SocketPermission "127.0.0.1:3306", "connect, accept";

Do take note that by adding the permission to spring.security.strategy is not enough. After this permission has been granted, there will subsequent permission error showing up. To avoid this, I also need to grant others permission as shown in the code above.

Alternative solution on PreRenderView

Usually when I want to determine whether the page is first loaded, I will put the following code in Facelet template.

Unfortunately that solution does not work under JSF 2.0 and below. The alternative is to add beforePhase attribute name right inside the <f:view> tag like this:

On the action class, add following code to perform the necessary task need to be complete before a page is render:

    public void doPreRenderView(PhaseEvent event) {
      
      if (event.getPhaseId() == PhaseId.RENDER_RESPONSE) {
        // do your stuff
      }
    }

Can not find Facelets taglib in JSP

This is an old project develop using JSP, my plan was to inject some new element into this project. I got the error Can not find the tag library descriptor for http://java.sun.com/jsf/facelets when the following line was included in this JSP page:

< %@ taglib uri="http://java.sun.com/jsf/facelets" prefix="ui"% >

This is impossible because Facelets is to replace JSP, it is a XML based view technology which is designed to be a successor of JSP. If I do this, this is definitely a brainless move. No choice, in order to use Facelets, I must have XHTML but not JSP.

Alias in Java

There is a very interesting question I got in the JAVA exam. Take a look at the following code, when does the object at line marked (0) will be the candidate for garbage collection?

String objA = “ABC”;  // (0)
String objB = a;

objA = “DEF”;  // (1)
objB = “GHI”;  // (2)

The answer is the line marked (2). Why not the line marked (1)? Because String objB is holding a reference of objA thus it will not get garbage collected. Until line marked (2), objB is assigned a new object, objA is no longer get reference by objB or no other objects are holding a reference of it, thus this is the great chance to dispose the object.

Bootstrap.jar was not found in classpath?

I was working on Tomcat 7 and I suspecting there are some problem with my existing Tomcat installation, thus I decided to re-download again to make sure a clean copy was use in my development. This time I download it into another folder name to ensure the old Tomcat directory is no longer using. Here is the problem, when I start the server, I get the following error:

The archive: D:/tool/Tomcat7/bin/bootstrap.jar which is referenced by the classpath, does not exist.

What a joke? My existing project (in Eclipse) was not reflected by the new Tomcat location? No, not that way. I mean take a look at the server classpath, goto Run -> Debug/Run Configuration -> Classpath tab, notice that the new bootstrap.jar path was there but the old path were still remain. Thus I have to manually remove the one and put the new one in exactly the same order as the existing one.