Understand the design ideas of the framework when the life cycle is runtime in the Java library
The design ideas of the framework when the life cycle of the Java class library is running
In the development of Java applications, the life cycle of the object is often required, that is, the process of creation, initialization, use, and destruction of objects.In order to simplify the management of the life cycle of the object and improve the maintenance and reuse of code, the Java class library introduces the design ideas of the framework of the life cycle.
The design ideas of the framework when the life cycle runtime is based on the observer mode and the callback mechanism. By defining specific interfaces, classes, and annotations, developers can easily manage and control the life cycle of objects.Here are several common designs of the framework when runtime of life cycle.
1. IOC container (Inversion of Control)
The IOC container is an overturning of the traditional object creation method. It is separated from the application code of the object's creation and dependency injection, and the container is responsible for the life cycle management and dependencies injection by the container.The Spring framework is a typical IOC container that defines the creation and dependencies of the object through configuration files or annotations. The container creates the life cycle of and manages the objects of managing objects based on these configurations.
Example code:
// Define a service interface
public interface Service {
void doSomething();
}
// Define a implementation class
public class ServiceImpl implements Service {
@Override
public void doSomething() {
System.out.println("Doing something...");
}
}
// Configure the life cycle of the object in the Spring configuration file
<bean id="service" class="com.example.ServiceImpl" scope="singleton">
<!-Define dependence injection->
</bean>
// Use IOC container creation and management objects in the application
public class MainClass {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
Service service = context.getBean("service", Service.class);
service.doSomething();
}
}
2. Life cycle annotation
The Java class library provides some special annotations, which are used to mark the life cycle stage and related operations.For example,@PostConStruct Annotation is used to mark one method immediately after the object is created, and@predestroy annotations are used to mark one method before the object is destroyed.These annotations can be integrated with IOC containers or other frameworks to achieve the initialization and destruction logic of objects.
Example code:
public class MyService {
@PostConstruct
public void init() {
// Object initialization logic
}
@PreDestroy
public void cleanup() {
// Object destruction logic
}
}
3. Life cycle callback interface
The Java class library defines some life cycle callback interfaces, allowing developers to insert custom logic in different stages of the object's life cycle.For example, the ServiceContextListener interface defines some callback methods to perform some initialization and destruction operations when web applications start and close.
Example code:
public class MyServletContextListener implements ServletContextListener {
@Override
public void contextInitialized(ServletContextEvent event) {
// Web application initialization logic
}
@Override
public void contextDestroyed(ServletContextEvent event) {
// Web application destruction logic
}
}
The design ideas of the framework of the life cycle are widely used in the Java class library to help developers manage and control the life cycle of objects.By using IOC container, life cycle annotation, and callback interface, developers can more flexibly manage the creation, initialization, use, and destruction process of the objects to improve the maintenance and reusability of the code.
