Introduction and use guide for CDI API framework
Introduction and use guide for CDI API framework
CDI (Contexts and Dependency Injection) is a lightweight dependency injection framework provided by Java Ee to manage the dependency of Java applications.It provides a simple and powerful mechanism that automatically solves dependencies in the application and provides context management for various components.
The CDI API framework provides a set of annotations and classes to achieve dependent injection and context management in applications.Here are some commonly used CDI API annotations:
1. @Inject: The field, constructing function or method for marking the fields that need to inject dependencies.Using this annotation, you can inject the dependent object into other objects.
2. @qualifier: Limited conclusion solutions used to mark customized.By customized limited conclusion solutions, you can provide different limited characters for multiple instances with the same type, so as to specify the required instance when injected.
3. @Named: Used to mark an instance and give it a readable name.This is usually used to distinguish specific instances from other examples.
4. @producess: Used to mark a method, this method produces an instance of a specific type.By using @produces annotations, you can create methods that are responsible for generating specific types of objects. These methods usually include some complex initial logic.
In addition to the above annotations, the CDI API also provides some categories of management contexts, such as Beanmanager, Event, Instance, etc., which can perform various context management tasks in the application.
The following is an example code using CDI API:
1. Define a dependent object:
public class Dependency {
public String getMessage() {
return "Hello CDI!";
}
}
2. Use @inject annotation to inject the dependent object in another class:
public class MyBean {
@Inject
private Dependency dependency;
public void printMessage() {
System.out.println(dependency.getMessage());
}
}
3. Use the CDI API to create an instance in the application and call the method:
public static void main(String[] args) {
Weld weld = new Weld();
WeldContainer container = weld.initialize();
MyBean bean = container.select(MyBean.class).get();
bean.printMessage();
weld.shutdown();
}
In the above code, we use the @Inject annotation to inject the Dependency object into the Mybean class.Then, we use the CDI API's WELD container to initialize the CDI environment and call the PrintMessage () method through the instance of the Mybean class.
This is just a simple example of the CDI API framework. CDI also provides more functions, such as the release and subscription, life cycle management of the incident.By using the CDI API, you can easily manage the dependencies in the Java application and achieve more efficient and maintainable code.
