Introduction of common functions and practical skills of CDI API

CDI (Contexts and Dependency Injection) is a dependent injection specification of the Java platform. It provides a standard mechanism to manage the life cycle of life and resolve dependence.The CDI API provides a series of common functions and practical skills that enable developers to use dependency injection and achieve efficient Java development. 1. Common function introduction of CDI API: 1. Dependency Injection: CDI API can automatically inject the required dependencies into the target object, avoiding the dependence relationship between manual processing objects.For example, by using @inject annotations on the member variables of the target class, the CDI container will automatically inject the appropriate instance into the variable. Example code: public class ExampleBean { @Inject private AnotherBean anotherBean; // ... } 2. Context Management: CDI API provides several contexts to manage the life cycle of the object, including Request Context, Session Context, and Application Context.Use the corresponding annotation to specify the required context.For example, using @RequestScoped annotations can make a bean's life cycle associated with HTTP requests. Example code: @RequestScoped public class RequestScopedBean { // ... } 3. Event Management: CDI API allows to communicate between events in each part of the application. This loose coupling method can improve the maintenance and scalability of the code.Developers can use @ObServes annotations to monitor the specified type of events and perform corresponding logic when triggering the event. Example code: public class EventListener { public void onEvent(@Observes EventType event) { // Treatment event logic } } 4. Qualifiers: CDI API can solve the ambiguity between multiple instances by using limited character, thereby determining the object to be injected more accurately.Developers can customize the limited character and use the corresponding annotation to specify the instance to be injected at the injection point. Example code: @Qualifier @Retention(RetentionPolicy.RUNTIME) @Target({ElementType.FIELD, ElementType.PARAMETER}) public @interface CustomQualifier { // ... } @Inject @CustomQualifier private ExampleBean exampleBean; 2. Introduction to CDI API Practice Skills: 1. Create scalable CDI assembly: CDI API supports behaviors that define CDI containers through expansion SPI interfaces.Developers can use this feature to achieve customized assembly rules and life cycle management to meet specific business needs. 2. Integrate integration with other Java EE specifications: CDI API and other Java EE specifications (such as the Java Persistence API, Javaseerver Faces, etc.) can be seamlessly integrated and strengthened the development efficiency and maintenance of the application.Developers can use these integration points to achieve more elegant and unified application architecture. 3. Unit test: CDI API provides some auxiliary tools for developers to write CDI -related unit tests.For example, you can use the cdi.current () method to obtain the current CDI container instance, and then obtain the required Bean instance through the container. Example code: public class ExampleTest { @Test public void testExample() { ExampleBean exampleBean = CDI.current().select(ExampleBean.class).get(); // Execute test logic } } Summarize: As the JAVA platform's dependency injection specification, CDI API provides many useful functions and practical skills, enabling developers to more easily use dependency injection and achieve efficient Java development.By being proficient and flexible to apply the CDI API, developers can improve the maintenance, scalability and testability of code, and bring more convenience to the development and maintenance of applications.