Understand the basic knowledge of the Java core JVM framework
Understand the basic knowledge of the Java core JVM framework
JVM (Java virtual machine) is the operating environment of the Java language, which is responsible for explaining and executing the Java bytecode.JVM is a core component of Java and is also the key to making Java cross -platform characteristics.
1. JVM basic knowledge
JVM is a virtual computer that can run the Java program on different operating systems.It has three main subsystems: ClassLoader, Runtime Data Area, and Execution Engine.
-ClassLoader loaded files and converts it into Java bytecodes that can be run.
-Runtime Data Area is the memory area of JVM, including method areas, piles, virtual machine stacks, local method stacks, and programmeters.These areas store data and intermediate results.
-Execution Engine executes the Java bytecode and translates it into executable machine code.
2. JVM function
JVM provides many important functions, making the Java language a powerful and highly safe programming language.
-D memory management: JVM is responsible for the memory of the management program, and automatically distributes and recycle memory.It cleans up the objects that are no longer used through the garbage recovery mechanism to avoid memory leakage and collapse.
-D multi -threaded support: JVM supports multi -threaded operation. It is responsible for allocating threads to processors, coordinating shared resources and communication between threads.
-S safety management: JVM provides a security mechanism to restrict the Java program's access to the operating system.It uses security strategy and permissions to ensure that the program can only perform trusted operations.
-Clene processing: JVM has an abnormal processing mechanism, which can capture and process abnormalities in the program.It provides an abnormal class and anomalous processor that can be used to write a strong program.
-D dynamic loading: JVM can dynamically load class and libraries at runtime.This makes the Java program more flexible, and can load and uninstall the module as needed to achieve a loose coupling architecture.
3. JVM framework
The JVM framework is a software framework built on JVM to simplify the development and deployment of Java applications.The following are several common JVM frameworks:
-Spring Framework: Spring is a full -featured application framework that provides functions such as IOC container, AOP support, transaction management, and web development.It makes Java development simple and provides a more modular architecture style.
-Hibernate: Hibernate is a powerful ORM (object relationship mapping) framework that is used to mappore the Java object with the database table.It provides simple API and query language, making the database operation simple and efficient.
-Apache Struts: Struts is a MVC framework for developing Java Web applications.It separates the application of different layers (models, views, and controllers) of the application, and provides rich functions, such as form verification and data binding.
Below is an example code using the Spring framework:
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
public class MyApp {
public static void main(String[] args) {
ApplicationContext context = new AnnotationConfigApplicationContext(AppConfig.class);
MyService service = context.getBean(MyService.class);
service.doSomething();
}
}
public class AppConfig {
// Define the dependency of bean in the configuration class
@Bean
public MyService myService() {
return new MyServiceImpl();
}
}
public interface MyService {
void doSomething();
}
public class MyServiceImpl implements MyService {
@Override
public void doSomething() {
System.out.println("Doing something...");
}
}
In this example, we use the Spring framework to manage and assemble the MyService object.By configured AppConfig, we define Bean's dependence and obtain and use Bean through ApplicationContext.
Summarize:
Understanding the basic knowledge of the Java core JVM framework is very important for Java developers.JVM, as the running environment of the Java language, is responsible for explaining and executing the Java program.It provides important functions such as multi -threaded support, security management, and memory management.On top of JVM, there are many excellent frameworks, such as Spring, Hibernate, and Struts. They simplify the development and deployment process of Java applications and improve development efficiency.Through learning and mastering these knowledge, Java developers can develop more powerful and high -performance applications.
