How to set root password on Amazon EC2 instance

The default Amazon Linux EC2 instance does not allow root user login.
Use this first:
-sudo !!

or the traditional way
-sudo passwd root
and set the root password, then su - to get to root.

How to add xml resources in package using maven

By default maven does not include any files from "src/main/java" (${sourceDirectory} variable). You have two possibilities (choose one of them):

• put all your resource files (different than java files) to "src/main/resources" - recomended

http://stackoverflow.com/questions/9798955/with-maven-clean-package-xml-source-files-are-not-included-in-classpath

String pool management summary

package testPackage;
class Test {
       public static void main(String[] args) {
               String hello = "Hello", lo = "lo";
               System.out.print((hello == "Hello") + " ");
               System.out.print((Other.hello == hello) + " ");
               System.out.print((other.Other.hello == hello) + " ");
               System.out.print((hello == ("Hel"+"lo")) + " ");
               System.out.print((hello == ("Hel"+lo)) + " ");
               System.out.println(hello == ("Hel"+lo).intern());
       }
}
class Other { static String hello = "Hello"; }

and the compilation unit:

package other;
public class Other { static String hello = "Hello"; }

produces the output:

true true true true false true

This example illustrates six points:

• Literal strings within the same class in the same package represent references to the same String object.
• Literal strings within different classes in the same package represent references to the same String object.
• Literal strings within different classes in different packages likewise represent references to the same String object.
• Strings computed by constant expressions are computed at compile time and then treated as if they were literals.
• Strings computed by concatenation at run time are newly created and therefore distinct.

Ant reset property value

Ant works with "first setter wins principle"  Ant properties accept the FIRST setting of the property as the definitive one. Thereafter, future attempts to set the property will be ignored. Properties therefore are not variables, but more like manifest constant definitions.

Jboss Logger

If you want to add a new category to your Jboss Log4j logger, you need to define a log variable in your code like:

>LogFactory.getLog("application-name");

and you should add a new category in jboss-log4j.xml file like:






and may be you can define a appender for log management :

Maven quick tips

mvn ant:ant                     ==> generate build.xml
mvn archtype:generate   ==> generate maven project ---->'generate archtype.goal'
mvn help:effective-pom ==> parent pom included

maven ====> has  3 lifecycle (1=clean 2=default 3=site)
               
clean has 3 phases
                1.1 pre-clean
                1.2 clean
                1.3 post clean

                       
mvn help:system variables can be accessed via ${env.key}

Oracle XE: Changing the default http port

Need to run following command only:

SQL>connect user/pass@xe

SQL> -- set http port and ftp port
SQL> begin
2    dbms_xdb.sethttpport('80');
3    dbms_xdb.setftpport('2100');
4  end;
5  /

http://daust.blogspot.com/2006/01/xe-changing-default-http-port.html