Common Annotations 1.2 API framework in the technical principles and applications in the Java class library

Common Annotations 1.2 API framework (that is, the JSR-250 specification) is an important part of the Java EE class library. It provides developers with a series of annotations to simplify code and improve the readability and maintenance of codeEssenceThis article will introduce the technical principles and applications of Common Annotations 1.2 API framework in the Java class library. Common Annotations 1.2 API framework includes some commonly used annotations, such as@PostConStruct,@predestroy,@resource,@ejb, etc.These annotations can be applied to classes and methods. By using these annotations in the code, the corresponding processing logic can be automatically triggered at a specific time. @PostConStruct Annotation is used to perform corresponding logic after the object is initialized, and it is usually used to do some initialization operations; @Predestroy annotations are used to perform corresponding logic before the object destroy, and it is usually used to release resources.@Resource annotations are used to obtain external resources, such as database connection, JMS connection, etc.; @EJB annotations are used to obtain EJB components. The following is a simple example code that demonstrates how to use @PostConStruct and @predestroy annotations in the Java class: import javax.annotation.PostConstruct; import javax.annotation.PreDestroy; public class ExampleService { @PostConstruct public void init() { // Initialize operation System.out.println("Initializing ExampleService"); } public void doSomething() { // Business logic operation System.out.println("Doing something"); } @PreDestroy public void destroy() { // Destruction operation System.out.println("Destroying ExampleService"); } } In the above code, the method of@PostConStruct annotations will be executed after initialization of the ExampleService object, and the@predestroy annotation mark will be executed before the ExampleService object is destroyed.In this way, developers can easily manage the life cycle of the object through these annotations. In addition to the above annotations, the Common Annotations 1.2 API framework also provides some other annotations, such as @Resource and @EJB, which can easily obtain external resources and EJB components. In short, the Common Annitations 1.2 API framework has a wide range of applications in the Java library, which can help developers simplify code and improve the readability and maintenance of code.Through reasonable use of these annotations, developers can easily achieve some common development tasks and improve development efficiency.