Apache Servicemix :: Bundles :: Spring Aop's dynamic agency mechanism in the Java library analysis
Apache Servicemix :: Bundles :: Spring Aop's dynamic agency mechanism in the Java library analysis
Apache Servicemix is a Java -based open source enterprise service bus (ESB) framework. It provides a strong set of tools and components for construction, management and integration of various enterprise applications and services.
Spring Aop (facing surface programming) is a key feature of the Spring framework. It allows developers to separate the cross-sectional attention point through the dynamic agency mechanism through the dynamic agency mechanism.In the target object.Dynamic proxy is one of the core mechanisms of Spring AOP. It allows agents to generate target objects during runtime so that specific cross -cut logic can be applied when the proxy object is called.
The dynamic proxy mechanism in the Java library is a technology that implements AOP. It injects cross -logic logic into the target object by generating an agent object during runtime.The dynamic proxy mechanism in the Java class library uses two main proxy classes: interface -based proxy and class -based proxy.
Interface -based proxy uses the Java Proxy class to create proxy objects.Developers need to define an interface, the method of the target object is defined in the interface, and then the proxy object is generated through the static method of the Proxy class.The generated proxy object implements the target interface, can intercept the call of the target object method, and apply cross -section logic before and after calling.The following is an example code:
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
public interface UserService {
void addUser(String username, String password);
void deleteUser(String username);
}
public class UserServiceImpl implements UserService {
public void addUser(String username, String password) {
System.out.println("Adding user: " + username);
}
public void deleteUser(String username) {
System.out.println("Deleting user: " + username);
}
}
public class UserServiceProxy implements InvocationHandler {
private Object target;
public Object bind(Object target) {
this.target = target;
return Proxy.newProxyInstance(target.getClass().getClassLoader(), target.getClass().getInterfaces(), this);
}
public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
Object result;
System.out.println("Before method: " + method.getName());
result = method.invoke(target, args);
System.out.println("After method: " + method.getName());
return result;
}
}
public class Main {
public static void main(String[] args) {
UserService userService = new UserServiceImpl();
UserService proxy = (UserService) new UserServiceProxy().bind(userService);
proxy.addUser("John Doe", "password");
proxy.deleteUser("Jane Smith");
}
}
In the above example, the userService interface defines the method of the target object, and the UserServiceIMPL implements the interface.UserServiceProxy implements the Invocationhandler interface and defines horizontal cutting logic in the Invoke () method.In the Main class, the UserService instance is first created, and then the proxy object Proxy is generated by using UserServiceProxy.When calling the proxy object proxy, the horizontal section logic is executed first, and then the method of calling the target object.
Another dynamic agency mechanism is based on class proxy, which is usually implemented using the CGLIB library.The CGLIB library creates a proxy object by generating subclasses of the target class.Different from interface -based proxy, class -based agents can directly proxy classes without relying on interfaces.The following is a CGLIB -based example code:
import org.springframework.cglib.proxy.MethodInterceptor;
import org.springframework.cglib.proxy.MethodProxy;
import org.springframework.cglib.proxy.Enhancer;
public class UserServiceInterceptor implements MethodInterceptor {
public Object intercept(Object obj, Method method, Object[] args, MethodProxy proxy) throws Throwable {
Object result;
System.out.println("Before method: " + method.getName());
result = proxy.invokeSuper(obj, args);
System.out.println("After method: " + method.getName());
return result;
}
}
public class Main {
public static void main(String[] args) {
Enhancer enhancer = new Enhancer();
enhancer.setSuperclass(UserService.class);
enhancer.setCallback(new UserServiceInterceptor());
UserService userService = (UserService) enhancer.create();
userService.addUser("John Doe", "password");
userService.deleteUser("Jane Smith");
}
}
In the above example, the userServiceInterceptor implements the MethodInterceptor interface and defines horizontal cutting logic in the intercept () method.In the main class, set the target class and interceptor through the Enhancer class, and then use the enhancer.create () method to generate proxy objects.When the user used UserService call method, the cross -cut logic will be executed first, and then the method of the target object is called.
The dynamic agency mechanism is an important tool for achieving AOP in the Java class library. It can achieve modularization and reuse of cross -section logic, and improve the maintenance of code and flexibility.In Apache ServiceMix, using the Spring AOP binding dynamic agency mechanism can easily achieve the separation and injection of cross -sectional attention points, providing better integration and expansion capabilities.
