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Converting an Array to a Collection

Ravi Nallakukkala — Thu, 29 Nov 2007 06:35:42 +0000

Sometimes the common problems seems to be we don’t remember the API, one such scenario I recently faced was how to convert a Array to a collection? Following seems to decent ways

// Fixed-size list
List list = Arrays.asList(array);

// Growable list
list = new LinkedList(Arrays.asList(array));

// Duplicate elements are discarded
Set set = new HashSet(Arrays.asList(array));

java.lang.NoSuchMethodError: weblogic.servlet.jsp.StandardTagLib.fakeEmptyBodyTag( Ljavax/servlet/jsp/PageContext; Ljavax/servlet/jsp/tagext/BodyTag;IZ

Ravi Nallakukkala — Wed, 18 Apr 2007 23:15:08 +0000

I was trying to deploy my Ear containing a war file in Weblogic 8.1, got the following exception

java.lang.NoSuchMethodError: weblogic.servlet.jsp.StandardTagLib.fakeEmptyBodyTag(Ljavax/servlet/jsp/PageContext;Ljavax/servlet/jsp/tagext/BodyTag;IZ)V
	at jsp_servlet._login.__login._jspService(__login.java:1016)
	at weblogic.servlet.jsp.JspBase.service(JspBase.java:33)
	at weblogic.servlet.internal.ServletStubImpl$ServletInvocationAction.run(ServletStubImpl.java:1053)
	at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:387)
	at weblogic.servlet.internal.ServletStubImpl.invokeServlet(ServletStubImpl.java:431)
	at weblogic.servlet.internal.TailFilter.doFilter(TailFilter.java:28)
	at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
	at com.pearson.ph.phcore.presentation.servlets.CheckLoginFilter.doFilter(CheckLoginFilter.java:76)
	at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
	at com.pearson.ph.phcore.presentation.servlets.CheckLoginFilter.doFilter(CheckLoginFilter.java:76)
	at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
	at com.pearson.ph.itext.presentation.servlets.SessionFilter.doFilter(SessionFilter.java:87)
	at weblogic.servlet.internal.FilterChainImpl.doFilter(FilterChainImpl.java:27)
	at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:6297)
	at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:317)
	at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:97)
	at weblogic.servlet.internal.WebAppServletContext.invokeServlet(WebAppServletContext.java:3575)
	at weblogic.servlet.internal.ServletRequestImpl.execute(ServletRequestImpl.java:2573)
	at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:178)
	at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:151)

Solution
Seems this is an issue with Weblogic server 8.1, when upgraded to Weblogic 8.1 sp4 the problem goes away.

Java Serialization impact of unused variables

Ravi Nallakukkala — Wed, 04 Apr 2007 06:01:42 +0000

Java serialization is a process of saving an object’s state to a byte stream and rebuilding the bytes into a Java object (may be at some future time).

As serialization is a concept based on maintaining the state of the object, so every attribute inside the object will have an impact on the amount of data serialized.

To explain the impact of unused variables on Java serialization lets take an example.

(more…)

Java 5 For each syntax for arrays

Ravi Nallakukkala — Sun, 25 Mar 2007 05:41:12 +0000

You can use “for each” java syntax for iterating through the arrays, probably you are already aware you can definitely use for each syntax for iterating over classes implementing iterator.

here’s an example for iterating a array using for each syntax

public class test{

public static void main(String[]arg){

String []arr = new String[]{”one”,”two”};

for(String each: arr) System.out.println(each);
}

}

Output:

one
two

Hibernate Vs EJB

Ravi Nallakukkala — Sun, 25 Mar 2007 03:26:34 +0000

Advantages:
- Hibernate Beans are easier to implement since you don’t need any interface coding.
- Queries can be dynamic and perform faster (at least on WebLogic and JBoss)
- Hibernate offers a more object-oriented approach. You can map is-a relationships as subclasses.
- For data transfer you can use Hibernate Beans as DTOs if you want (and if it’s applicable). You can even fill ‘custom’ DTOs with query results just with one line of code using the select-new construct.

Disadvantages:
- Hibernate Beans are not automatically ‘locked’ for others while used during a transaction. This can lead to inconsistent data when more clients concurrently modify the same data.
-Object Pooling is an Issue