JVM shutdown hook (Surviving abrupt shotdown)

Project I am working currently requires the ability to detect shutdown on JVM. Its basically required to be detected so that active connections to the JMS server to be destroyed. I wrote code to destroy connection on ServletContextListener which worked fine for some scenario, but failed if I kill web server processes explicitly.


The solution is a little known feature of the language that lets you register JVM shut down hooks. A shut down hook is simply a Thread that is registered with the JVM and run just before the JVM shuts down.

Here is code snippet to register shutdown hook with JVM:

Runtime.getRuntime().addShutdownHook(new Thread()
  {
   public void run()
   {
    // your code here which needs be executed before shutdown
   }
  });

Runtime.getRuntime().addShutdownHook(new Thread()
  {
   public void run()
   {
    try
    {
     Thread.sleep(10000);
    }
    catch (InterruptedException ex)
    {
    }
    // halt will bail out without calling further shutdown hooks or
    // finalizers

    Runtime.getRuntime().halt(1);
   }
  });

Database encryption using Jasypt (Java Simplified Encryption)

Here are required jars for using Jasypt

commons-lang

commons-codec

jasypt

Here is example of string encryptor with Spring and Hibernate.

Define encryptor in spring configuration file:

    
    
        PBEWithSHA1AndDESede
    
  
    
        jasypt
    
    
        4
    
 
  
  
    
        strongHibernateStringEncryptor
    
    
        
    
 

In hibernate mapping file define type as follows:

@TypeDef(
        name="encryptedString", 
        typeClass=EncryptedStringType.class, 
        parameters={@Parameter(name="encryptorRegisteredName",
                               value="strongHibernateStringEncryptor")}
    )

And then specify type as encryptedString for the columns you want to encrypt.

e.g.

@Column(name = "QO_OPTION", length = 4000, nullable = false)
 @Type(type="encryptedString")
 private String optionText;

Here hibernate will take care of encrypting while saving string to database and decrypting while loading object from database.