memo from the small room

Table of contents [ hide ] Design pattern Annotations are an implementation of the decorator design pattern. The decorator pattern is a design pattern that allows behavior to be added to an individual object, dynamically, without affecting the behavior of other objects from the same class. Annotations in Java Annotations, a form of metadata, provide data about a program that is not part of the program itself. Annotations have no direct effect on the operation of the code they annotate. Annotations have a number of uses: Information for the compiler:  Annotations can be used by the compiler to detect errors or suppress warnings Compile-time and deployment-time processing:  Software tools can process annotation information to generate code, XML files, and so forth. Runtime processing:   Some annotations are available to be examined at runtime. Annotations in Spring Spring uses annotations extensively as a core feature, especially Spring AOP, and almost all the fu...

Table of contents [ hide ] Proxy in design pattern The proxy pattern is a software design pattern, as a wrapper or agent object that is being called by the client to access the real serving object behind the scene. There are two advantages: Provides access control for real objects. Provides additional functionality when accessing real objects. And there are two types of proxy: Static proxy: proxies are created manually. Java example on  GitHub . Dynamic proxy: proxies are created by JDK Proxy or CGLib Proxy with reflection. JDK proxy Before the proxy object is created, it must implement the invoke method of the InvocationHandler, which is invasive to the target object. JDK Dynamic proxy can only proxy by the interface (so your target class needs to implement an interface, which is then also implemented by the proxy class) CGLib proxy The proxy object is created by implementing the intercept method of MethodInterceptor, and the target object does not need to implement this m...

Table of contents [ hide ] The famous two features of Spring are IOC and AOP. Inversion of Control It uses the Spring's container to help us get objects, and the Spring manages these objects. There are two main types: Dependency Lookup: The Inversion of Control is limited to the container invoking callback methods that the application code can use to obtain resources. Dependency Injection:  The container is wholly responsible for wiring up components, and passing resolved objects into JavaBean properties or constructors for application. Aspect-Oriented Programming It helps to add new business logic across different modules without modifying the current code. reference: https://zhuanlan.zhihu.com/p/136474190 https://www.jianshu.com/p/7a1c0bad2708