@Transactional annotation on interface or concrete class?

The Spring team's recommendation is that you only annotate concrete classes with the @Transactional annotation, as opposed to annotating interfaces. You certainly can place the @Transactional annotation on an interface (or an interface method), but this will only work as you would expect it to if you are using interface-based proxies. The fact that annotations are not inherited means that if you are using class-based proxies (proxy-target-class="true") or the weaving-based aspect (mode="aspectj") then the transaction settings will not be recognised by the proxying/weaving infrastructure and the object will not be wrapped in a transactional proxy (which would be decidedly bad). So please do take the Spring team's advice and only annotate concrete classes (and the methods of concrete classes) with the @Transactional annotation.

Note: In proxy mode (which is the default), only 'external' method calls coming in through the proxy will be intercepted. This means that 'self-invocation', i.e. a method within the target object calling some other method of the target object, won't lead to an actual transaction at runtime even if the invoked method is marked with @Transactional!

Consider the use of AspectJ mode if you expect self-invocations to be wrapped with transactions as well. In this case, there won't be a proxy in the first place; instead, the target class will be 'weaved' (i.e. its byte code will be modified) in order to turn @Transactional into runtime behavior on any kind of method.

Writing a JVM shutdown hook

Following is the class which exits on some condition. So before exit, if we need to carry out some task, register a shutdown hook(TestShutdownHook.java) with JVM

public class Test {
 
 public static void main(String args[]){
  
  Test test = new Test();
  TestShutdownHook testshutdownHook = new TestShutdownHook(test);
  Runtime.getRuntime().addShutdownHook(testshutdownHook);
  test.startTest();

 }

 private void startTest() {
  
  int counter = 0;
  while(true){
   if(counter == 100){
    System.exit(0);
   }
   System.out.println("Running..");
   counter++;
  }
 }

 public void beforeShutdownDothis() {
  System.out.println("Doing somethig before shutdown");
 }
}

package com.my;

public class TestShutdownHook extends Thread {
 
 private Test test;

 public TestShutdownHook(Test test){
  this.test = test;
 }
 
 public void run(){
  test.beforeShutdownDothis();
 }
}

Useful tips for Spring beans initialization

Referring to Constants in the bean initilization

Using the static factory for creating NON singleton beans. Even though, parameters are in 'constructor-arg' element, those are treated as normal parameters to method call.

  
   0
  
  
   test
  
  
   0
  
 

Write the following code in the class which implements BeanFactoryAware , InitializingBean interfaces.

String testFileSystemNames[] = {"/","/usr","/exports"};
  Object args[] = new Object[3];
  List fileSystemObjects = new ArrayList();
  for(int i=0; i< testFileSystemNames.length; i++ ){
   args[0]=i+1;
   args[1]=testFileSystemNames[i];
   args[2]=i;
   FileSystem fileSystem = (FileSystem)beanFactory.getBean("fileSystem", args);
   fileSystemObjects.add(fileSystem);
  }

Quick Tip for using SimpleJdbcTemplate

When using SimpleJdbcTemplte.queryForMap method, remember that the results returned as Map has keys in all capital letters. e.g

Map results = template.queryForMap("select id, balance from Account where id=?", account.getId());

In above case, to retrieve the value of id and balance use results.get("ID") and results.get("BALANCE") instead of results.get("id") and results.get("balance");

:)

Spring Dynamic Modules - Integration Testing

While installing Simple Service demo, I realised that some of the dependencies are missing from POM. Add the following dependencies in POM.xml under simple-service-integration-test folder and it should work fine. Happy OSGIng!!




Cheers !!

RIA - Flex with BlazeDS and Spring Integration

1. Create a new Flex Project with following selections :
Project name: HelloWorld
Application server type: J2EE
Select 'Use remote object access service with LiveCycle data Service'
Select 'Create combined Java/Flex project using WTP'
On Next screen -> Select the appropriate Target runtime.
Flex WAR File - point to blazeds.war file.
On Next screen -> select serverport as configured on your system.
Click, Finish.

2. Under src folder, create a new java class 'HelloWorld' with method signature as follows :
public String sayHello(String name)


3. Declare the spring dispatcher servlet in web.xml file as shown in following fig. All the spring beans will be defined in file 'web-application-config.xml'.



4. Create spring configuration file (helloworldservlet.xml) under WEB-INF folder. Do not declare any spring beans in this file.

5. Create web-application-config.xml under WEB-INF/config directory. Declare the HelloWorld bean and expose it as mentioned below.



6. Add the necessary libraries in lib folder in WEB-INF .

7. Add the default channel in service-config.xml file. This is very important. Enable the channels by providing server name, port name and content root.

8. Add the following code to HelloWorld.mxml file between mx:Application elements.


9. Start the server. Ensure that application is deployed properly.

10. Run the HelloWorld.html file under bin-debug by right click -> Run as -> Run On server by selecting proper server.

11. Enter your name and click the Submit button. Application should respond with Greetings to you !



Hope this helps you !