Skip to main content

Creating Spring Bean dynamically in the Runtime

In my training someone asked me whether it is possible to create an object (a Spring Bean) dynamically so you can choose which implementation you want to have in the runtime. So at the compile time you don't know what object actually should be created yet. The application should decide what object to be created based on a property file.

1. We create an annotation so we can mark the method which should be able to create the object dynamically:

...
package your.package;
...
@Retention(RetentionPolicy.RUNTIME)
public @interface InjectDynamicObject {
}
...

2. Use the new created annotation in your method which should be able to create the object dynamically:

...
@Named("customerBo")
public class CustomerBoImpl implements CustomerBo {
...
    @Override
  @InjectDynamicObject
  public Customer getDynamicCustomer() {
        return this.dynamicCustomer;
}
...

3. Write an aspect with Pointcut and Advise which change the object returned by the method in the step 2:

...
@Named
@Aspect
public class DynamicObjectAspect {

    // This comes from the property file 
@Value("#{objects.object}")
private String object;

@Inject
private ApplicationContext applicationContext;

@Pointcut("execution(@your.package.InjectDynamicObject * *(..))")
public void beanAnnotatedWithInjectDynamicObject() {
}

@Around("beanAnnotatedWithInjectDynamicObject()")
public Object adviceBeanAnnotatedWithInjectDynamicObject(
ProceedingJoinPoint pjp) throws Throwable {
Object returnResult = pjp.proceed();
       // Create the bean or object depends on the property file
Object createdObject = applicationContext.getBean(object);
return createdObject;
}
}
...

4. Write your unit test to test the method:

...
    @Test
public void testCustomerOnlineOrOffline() {
// Dynamic object creation
System.out.println("DYNAMIC CUSTOMER: "
+ customerBo.getDynamicCustomer().getName());
}
...

OK, there is another easier way to do this ;-) Without Aspects and AspectJ, just pure Spring:

Just inject all your component implementations into a Map and get the correct implementation out of it. Just like what we have done in eXTra Client application. Please take a look at our implementation of PluginsLocatorManager as an example: http://goo.gl/itpcb. Spring injects the Map with Bean name as String and the Bean itself automagically. "... Even typed Maps can be autowired as long as the expected key type is String. The Map values will contain all beans of the expected type, and the keys will contain the corresponding bean names" (see Spring documentation for details).

...
@Named("customerBo")
public class CustomerBoImpl implements CustomerBo {
...
    // We inject the customer implementations into a Map
    @Inject
    private Map<String, Customer> customerDynamicMap;


    // This comes from the property file as a key for the Map
@Value("#{objects.object}")
private String object;
    
    @Override
  public Customer getDynamicCustomer() {
        return this.customerDynamicMap.get(object);
}
...

Have fun!
Lofi

Comments

roman said…

SEM SERVICES
I am fully satisfied with the information you have posted. Good job. Keep posting:)
CUSTOMIZED ERP SOLUTIONS

Popular posts from this blog

Software Development Macro and Micro Process

If you think that in year 2012 all companies which produce software and IT divisions in our world have already their optimized software development process, you are wrong. It seems that we - software architects, software developers or whatever your title is - still need to optimize the software development process in many software companies and IT divisions.

So what do you do if you enter a software company or IT division and you see following things:

1. There is a perfect project management process to handle all those development of software butit is a pure project management without a context to software development. So basically you only take care of cost, time, budget and quality factors. In the software development you still use the old fashioned waterfall process.

2. From the tooling point of view: you have a project management planning and controlling tool but you are still in the beginning of Wiki (almost no collaboration tool) andyou don't use issues tracking system to han…

Smart Home Sweet Home with Gigaset Elements?

Introduction
Last week I had a chance to try the Smart Home solution from Gigaset Elements. I read some articles about this product which said how easy to install this product for dummy users. Those articles woke my interest and I began to google products for Smart Home solutions.

In this article (German language) you will find a nice overview about some products for Smart Home, which can be bought in Germany. The Nest product from Google is still not available in Germany. Although it seems that RWE will offer Nest products in Germany in couple of months.

The installation of Gigaset Elements was really easy. The problem I encountered was to add the sirensensor. I had to push hard the button on the siren sensor at the same time with the button on the base, so that they can communicate with each other. After about one hour I managed to install everything properly.

Points to mention
Generally the idea is very nice. Gigaset Elements try to push KISS (Keep it Simple Stupid) principle. Howev…