Creating spring beans in dynamically generated classes

Question

I am dynamically creating classes containing spring beans, however the beans do not get an instance or are not initialized, leaving them as null.

How to make sure that a dynamically created class correctly creates all its spring beans?

This is how I dynamically create the class:

Class ctransform; try { ctransform = Class.forName(strClassName); Method handleRequestMethod = findHandleRequestMethod(ctransform); if (handleRequestMethod != null) { return (Message<?>) handleRequestMethod.invoke(ctransform.newInstance(), message); } } 

This leaves all spring bean objects inside ctransform (of type strClassName) equal to zero.

Answer 1

Whenever you create classes, they are not controlled by spring. Spring needs to instantiate classes so that it can inject its dependencies. This is, unless you use @Configurable and <context:load-time-weaver/> , but it's more of a hack, and I suggest against it.

Instead

• make a bean prototype
• get ApplicationContext (in a web application this is done through WebApplicationContextUtils.getRequiredWebApplicationContext(servletContext) )
• If the classes are not registered (and I assume that this is not the case), try casting to a StaticApplicationContext (I'm not sure if this will work) and call registerPrototype(..) to register your classes in context. If this does not work, use GenericContext and registerBeanDefinition(..)
• Get all instances matching your type using appContext.getBeansOfType(yourclass) ; or if you just registered it and know its name - use only appContext.getBean(name)
• Choose which one is applicable. Usually you will have only one entry in the Map , so use it.

But I would generally avoid reflecting on Spring beans - there must be another way to achieve the goal.

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Update: I just thought of an easier solution that would work if you don't need to register beans - that is, your dynamically generated classes will not be inserted into any other dynamically generated class:

 // using WebApplicationContextUtils, for example ApplicationContext appContext = getApplicationContext(); Object dynamicBeanInstance = createDyamicBeanInstance(); // your method here appContext.getAutowireCapableBeanFactory().autowireBean(dynamicBeanInsatnce); 

And you will have your dependencies installed if your new class is not registered as a bean.

Answer 2

You need a Spring container to instantiate the class than using reflection to instantiate. To make a prototype bean for the prototype, use the following syntax:

 <bean id="prototypeBean" class="xyz.PrototypeBean" scope="prototype"> <!-- inject dependencies here as required --> </bean> 

Then create a prototype bean using the following code:

 ApplicationContext applicationContext = new ClassPathXmlApplicationContext ( "applicationContext.xml" ); PrototypeBean prototypeBean = ( PrototypeBean ) applicationContext.getBean ( "prototypeBean" );