When to use MultiActionController in Spring framework

Generally we have mapping file for dispatcher servlet to decide which controller to use as per URL mapping but if we have to take decision on basis of request parameters then MultiActionController can be used.

Reset System date and Time through Java API

How to reset the Windows system date and time through Java ?

Java API for reset the Windows System date & time
--------------------------------------------
However you can execute any Windows command by using the Runtime class. So you should be able to invoke the Time and Date command. This piece of code will be used to update the date and time using java.

try
{

String newDate = "01-06-04";
String newTime = "8:30";
Runtime.getRuntime().exec("CMD /c \"DATE " + newDate + "\"");
Runtime.getRuntime().exec("CMD /c \"TIME " + newTime + "\"");
}
catch(Exception e){
// Unable to change the date and time
}

Java Performance Tips

Using shift operator for faster division and multiplication

Multiplications
              12 * 2     = 12 << 1
              12 * 4     = 12 << 2
              12 * 8     = 12 << 3
              12 * 16   = 12 << 4
              12 * 32   = 12 << 5
              12 * 64   = 12 << 6
              12 * 128 = 12 << 7
              12 * 256 = 12 << 8
Divisions
             12 / 2     = 12 >> 1
             12 / 4     = 12 >> 2
             12 / 8     = 12 >> 3
             12 / 16   = 12 >> 4
             12 / 32   = 12 >> 5
             12 / 64   = 12 >> 6
             12 / 128 = 12 >> 7
             12 / 256 = 12 >> 8

Classpath

Setting the classpath

For example If I have the class
/home/user01/Test.java
/home/user01/f1/TestA .java
/home/user01/f2/TestB .java
/home/user01/f3/TestC .java

TestA {
     public void show() {
           System.out.println("Show from TestA");
     }
} 

TestB {
     public void show() {
           System.out.println("Show from TestB");
     }
}


TestC {
     public void show() {
           System.out.println("Show from TestC");
     }
}

Test {
     public static void main(Stirng atr[]) {
               TestA ta = new TestA();
               TestB tb = new TestB();
               TestC tc = new TestC();
               ta.show();
               tb.show();
               tc.show();

     }
}

If each class reside in different folder we need to set the classpath for all the file, then only the file got compile

[user01@localhost user01] java Test.java
the above command will lead you with error messages

Test.java4: cannot find symbol
symbol : class TestB
location: class TestB
...................

To Compile the above class
javac -classpath /home/user01/f1:/home/user01/f2:/home/user01/f3 Test.java
To Execute the above class
java -classpath /home/user01/f1:/home/user01/f2:/home/user01/f3 Test

Java Script Tips

How can I pass a JavaScript array to the next page when a form is submitted?

When submitting a form, only the named form fields get passed onwards with their contents. The JavaScript code, and the objects you create are lost.

If you need to pass the data held within an array as part of the form, you need to place the data in a form field - a hidden form field is best.

Once the target page has loaded you need to parse the search data to extract the data to build another array.

On the first page, use something like:

Unix File Permissions

Unix File Permissions

Unix File Permissions Unix, as a multi-user system, has security measures built in. Files contain information such as the owner of the file and which groups are allowed access, the file size, the last date of modification, etc. The reason for permissions is to limit the scope of what can be done with a file and by who. It would not be a good idea for everyone to be able to delete your files or create executable programs in your private directories. You can examine the permissions of a file by typing: ls -l filename. This command will show you the permissions, the ownership, the size, and the modification date of the file. ex. ls -l testfile.txt will return something like this:   -rw-rw-rw   1username   username   3425   Jan 23 08:55   testfile.txt This file has read/write permission for the owner, the group, and others (everyone). This is known as a world writable file. (Remember, write also means delete!) Unless you specifically need everyone to be able to write to your file, like a CGI guestbook, this should be avoided. You want to give your files the minimum permissions that they require for best security. To change a file's permissions you use the chmod program. We can tighten up the permissions on testfile.txt by typing: chmod 664 testfile.txt. What does is allows others to read the file but denies them write permission. Owner and group are given read/write permission. Now testfile.txt looks like this:   -rw-rw-r--   1username   username   3425   Jan 23 08:55   testfile.txt Here are the settings that can be used for file permissions Number Letters Permissions 0 ---   no permissions 1 --x   executable only 2 -w-   write only 3 -wx   write/execute 4 r--   read only 5 r-x   read/execute 6 rw-   read/write 7 rwx   read/write/execute As you can see there are three numbers in the chmod 665 command. They correspond to the owner, group, and others. Here are some common examples: chmod 666 - read/write for the owner, group, and everyone. (Common for a guestbook type text file) chmod 644 - read/write for the owner, read only for group and everyone. chmod 755 - read/write/execute for the owner, read/execute for group and everyone (common for CGI scripts) chmod 622 - read/write for owner, writable for group and everyone (perhaps a log file or questionnaire) chmod 711 - read/write/execute for owner, execute only for group and everyone (allows webserver to execute but only the owner can read/write - no snoops) Unix treats everything as a file. Directories also use the same permission scheme. A little more information about using numbers for permissions: The number scheme actually uses Octal numbers. These numbers are added together to construct the number which corresponds to the table above. No Permissions: 0 Execute is: 1 Write is: 2 Read is: 4 By adding up these three numbers you get the permissions above. Read/Write permission = 6 (2 + 4) Read/Execute permission = 5 (1 + 4) Read/Write/Execute permission = 7 (1 + 2 + 4) etc. Another method of setting permissions In addition to using the Octal system for setting permissions, you can use letters combined with the (+, -, =) operators. For this system you identify owner as u (user), group as g, and other as o. To set permissions you can add a permission +, subtract a permission -, or declare a permission with =. Here are some examples: chmod u+rwx,g+rx,o+x filename.txt  (owner read/write/execute group read/execute others execute only) chmod u+rwx,g-rx,o-x filename.txt  (owner unchanged, group remove read/execute others remove execute) chmod u=rwx filename.txt  (The owner can read/write/execute, others remain with what they had.) chmod u=rw,g=r,o=r filename.txt  (owner can read/write, group and other read only.) The method you use is up to you. The results are the same, however, to me it seems clearer to use the Octal system since each time you use it you are reseting all of the permissions so you won't accidentally overlook anything. That concludes this discussion of file permissions. You can find out more information by researching the ls and the chmod programs.

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