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Spring-related knowledge of what, many novices are not very clear about this, in order to help you solve this problem, the following editor will explain in detail for you, people with this need can come to learn, I hope you can gain something.

Ioc through reflection (dependency injection)

There are two ways to inject through constructor injection and set method injection

1: through the set get method

2: by annotating

Circular dependency of spring and three-level cache

I would like to make a simple summary of the above source code: first, spring gets x from the singleton pool, which is not available as mentioned earlier, and then determines whether it is in the collection in which bean is being created. It was analyzed earlier that this collection now exists x, and y; so if sets up to enter the branch; enter the branch spring to get x directly from the tertiary cache; according to the previous analysis, there is nothing in the tertiary cache, so nll is returned. Go to the next if branch and get an ObjectFactory factory object from the second-level cache; according to the previous analysis, there is x in the second-level cache, so you can get it; then call singletonFactory.getObject (); get a semi-finished x bean object; then put the x object into the third-level cache and clear x from the second-level cache (at this time, there is only one y in the second-level cache, but there is one more x in the third-tier cache)

Question 1. Why is it taken from the third-tier cache in the first place? It's mainly for performance, because what's stored in the third-level cache is an x object, so if you can get it, you won't go to the second level; who would ask what's the use of the second level? Why save the factory in the first place? Why not directly save the three-level cache in the first place? It's a little complicated here. If you save it directly to the third-level cache, you can only store one object, assuming that the state of the object was xa, but the x that we want to inject here is xc, then it cannot be satisfied; but if you save a factory, the factory produces any xa or xb or xc according to the situation; for example, in the case of aop, x is injected into y, and x is also injected into x The x injected in y needs to add an aop, but the logic of adding a proxy is not a proxy object after the injection of the attribute, that is, when the life cycle of x is thoughtful to inject the attribute, then save x and then inject y, get and create yrecoery y to inject x and get x; the x taken out is an object without a proxy; but it is different if it is a factory. First, save a factory that can generate x, and then inject y. When you inject y, you get and create yQuery to inject x, get x, get it from the third-level cache as null, and then get a factory from the secondary cache and call the factory's getObject (); spring determines in the getObject method that x is configured by aop at this time, so you need to return a proxy x to inject it into y. Of course, some readers will ask you, didn't you say earlier that getObject will return a xbean in its current state? The premise of this is that I don't care about the specific source code of getObject, because this piece of thing is more complicated, and we need to understand the post-processor function of spring. Let's not discuss it here. Anyway, getObject will return an x according to the situation, but what is the status of x? spring will return it according to the situation.

Question 2. Why cache remove from Tier 2? Because if there are more complex circular dependencies that can improve performance; for example, if x is cyclically dependent on each other, then the first time y injects x, it returns an x from the secondary cache through the factory and puts it into the tertiary cache, while the second time z injects x, you no longer need to get the x object through the factory. Because the first thing in the if branch is to access the third-level cache; as for remove, it is for gc.

Original link: https://blog.csdn.net/java_lyvee/article/details/101793774

The underlying implementation principle of AOP

Several ways of obtaining bean by spring

By adding @ Bean to the configuration file and then getting the

You can also get it by adding @ component

Complete the creation of the object in the following ways

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