Spring：如何手动注入不受实际应用程序管理的bean？

Question

Here the context :

• we have a java library, which is a factory code.
• this library is deployed directly on Tomcat
• Application "A", "B" & "C" use this library (jar) to compile, and it is the deployed version on Tomcat which is used when an application call it.

In the library, we have these packages : - old.service - old.service.impl - new.service - new.service.impl

The old services are some classic classes with setters. It is a spring bean declared in XML configuration of application "A".

In the new services, we have an annotated class (@Service) with some @Autowired attributes in order to be managed by application "B" & "C" which have an autoscan in XML configuration.

We would like to change the implementation of a old services, in order to use the new one without changing anything in application "A". For that, we can call the new class from the older. But the pb is Spring......

How can we instanciate the new class, and the @autowired attributes ? Can we instanciate manually the new class in older class, and instanciate attributes by reflection ?

Thank you.

ps: there is no XML configuration in the java library.

Answer 1

Two ways:

1. In app A where you instantiate old.service.impl Spring bean inject reference to new.service.impl into it

   < bean class="old.service.impl"> < property name="newService" ref="newServiceBean"/> < /bean> < bean class="new.service.impl" id="newServiceBean" />

Obviously this means you will have to modify your old.service.impl to add setter for "newService", then use it in old service impl code

1. Get "new.service.impl" reference directly from web application context:

   WebApplicationContextUtils.getWebApplicationContext(servletContext).getBean(newServiceImpl.class);

You will need to obtain ServletContext in this case. One way to do it is to get it from HttpRequest

Option 1 is preferred - you are not relying on running inside a servlet then, and requires very few changes in your code.