Spring transaction management example8/16/2023 ![]() ![]() It's transparent to the client code.Īs for the "external method" thing, if your bean invokes one of its own methods, then it will not be doing so via the proxy. When the invocation finishes, the TransactionInterceptor commits/rolls back the transaction. So when you call the method from client code, you're calling the method on the proxy object, which first invokes the TransactionInterceptor (which begins a transaction), which in turn invokes the method on your target bean. For target beans annotated with Spring will create a TransactionInterceptor, and pass it to the generated proxy object. However, the proxies can also be supplied with interceptors, and when present these interceptors will be invoked by the proxy before it invokes your target bean's method. The default behaviour of these proxy objects when a method is invoked is just to invoke the same method on the "target" bean (i.e. ![]() These proxy objects are instances of classes that are auto-generated at runtime. When Spring loads your bean definitions, and has been configured to look for annotations, it will create these proxy objects around your actual bean. I have an updated version that I could probably make available. Note that the BeanFactoryPostProcessor code would be a little different now, as it was written back in the Spring 1.x timeframe. me.someMethod().) The forum post explains in more detail. Then if I need to make internal calls that require a change in the transaction status of the thread, I direct the call through the proxy (e.g. I save this reference to a member variable called me. I explain one approach in this forum post in which I use a BeanFactoryPostProcessor to inject an instance of the proxy into "self-referencing" classes at runtime. There are ways of working around that problem, however. When you make an internal call within the object, you're really making a call through the this reference, which bypasses the proxy. Transactions in EJB work similarly, by the way.Īs you observed, through, the proxy mechanism only works when calls come in from some external object. And when clients make calls into your object, the calls are intercepted and the behaviors injected via the proxy mechanism. So when you annotate a method with Spring dynamically creates a proxy that implements the same interface(s) as the class you're annotating. And you can provide your own, too, for things like logging. Transaction management is just one example of the behaviors that can be hooked in. It provides a way for Spring to inject behaviors before, after, or around method calls into the object being proxied. The proxy is mostly invisible at runtime. I recommend reading the ones on Aspect-Oriented Programming and Transactions, as Spring's declarative transaction support uses AOP at its foundation.īut at a very high level, Spring creates proxies for classes that declare on the class itself or on members. The Spring reference doc devotes multiple chapters to it.
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