Spring ASM framework for AOP function in the Java library
Spring ASM framework for AOP function in the Java library
introduction:
Facing surface programming (AOP) is a widely used programming idea in software development. It can provide a decoupled way to handle the cross-cutting point (Cross-Cutting Concerns), such as log records, performance monitoring, transaction managementwait.In Java, the Spring framework provides a powerful AOP implementation, and ASM is one of the core technologies of Spring AOP. It is used to modify and enhance the class at the Java bytecode level.This article will introduce how to use the Spring ASM framework to implement the AOP function in the Java library.
1. What is the Spring ASM framework?
Spring ASM is a module based on ASM bytecode operation technology used in the Spring framework to implement AOP.ASM is a lightweight Java bytecode editing library that can directly operate the byte code and can modify and enhance class behavior by defining and registered visitor (VISITOR).Spring uses ASM to generate proxy classes and weave enhanced code to achieve AOP function.
Second, the working principle of the Spring ASM framework
The Spring ASM framework mainly implements the AOP function through the following steps:
1. Configure cut surface: Define the cut surface in the Spring configuration file, and the cut surface usually contains two parts: PointCut and enhanced logic.
-Stitting point is an expression, which methods for specifying which classes should be woven into enhancement logic.
-An enhanced logic is the operation that must be performed after the cut point matching, such as log records, transaction management, etc.
2. Generate proxy class: Spring will use ASM to generate a proxy class. The proxy class will integrate the target class and woven the enhancement logic for all methods of the target class.
3. Execution of enhanced logic: When the method of the target class is called, the agent class will execute enhanced logic before, during or after execution.
3. Example demonstration
The following is a simple example to demonstrate how to use the Spring ASM framework to implement the AOP function.
1. Create Maven project: First create a new Java Maven project, or use existing projects.
2. Add dependencies: Add Spring ASM to the project's pom.xml file:
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context</artifactId>
<version>5.3.10</version>
</dependency>
3. Create a target class: Create a target class containing business logic, such as a simple calculator class:
public class Calculator {
public int add(int a, int b) {
return a + b;
}
}
4. Configure cut surface: Define the cut surface in the Spring configuration file, such as a simple log cut:
<bean id="loggingAspect" class="com.example.LoggingAspect">
5. Realize the logic of cutting surface: Create a cut -off class to achieve the corresponding enhancement logic, such as the log record:
public class LoggingAspect {
public void beforeMethod(JoinPoint joinPoint) {
// Record logs before the method execution
System.out.println("Before method: " + joinPoint.getSignature().getName());
}
}
6. Start the application: Create a simple test class, load the Spring configuration file, and call the target class:
public class Application {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("spring-config.xml");
Calculator calculator = context.getBean(Calculator.class);
int result = calculator.add(1, 2);
System.out.println("Result: " + result);
}
}
Through the above steps, we successfully use the Spring ASM framework to implement the AOP function.When executing the `Calculator.add (1, 2)`, the log cut will record the log before the method execution.
in conclusion:
The Spring ASM framework is one of the core technologies of the Spring AOP function. It realizes the AOP function by directly operating bytecode to help us realize the horizontal focusing point such as log records and transaction management.By configuration, generate agency classes, and enhancement logic, we can easily use the Spring framework to achieve AOP programming.
