스프링 AOP(3) - Before 어드바이스 만들기

Before 어드바이스는 스프링이 제공하는 가장 유용한 어드바이스 중 하나다. Before 어드바이스는 메서드로 넘겨주는 인자를 수정할 수 있으며 메서드를 실행하기 전에 예외를 발생시켜서 실행을 막을 수도 있다.

import org.springframework.aop.MethodBeforeAdvice;
import org.springframework.aop.framework.ProxyFactory;

import java.lang.reflect.Method;

public class SimpleBeforeAdvice  implements MethodBeforeAdvice {

    public static void main(String[] args) {
        MessageWriter target = new MessageWriter();

        // create the proxy
        ProxyFactory pf = new ProxyFactory();

        pf.addAdvice(new SimpleBeforeAdvice());
        pf.setTarget(target);

        MessageWriter proxy = (MessageWriter) pf.getProxy();

        // write the messages
        proxy.writeMessage();
    }

    public void before(Method method, Object[] args, Object target)
            throws Throwable {
        System.out.println("Before method: " + method.getName());
    }

}

결과

Before method : writeMessage
World

Before 어드바이스를 사용하여 메서드 접근 보안하기

SecureBean클래스 - 보안처리를 할 클래스

package com.lastjava.spring.ch05.security;

public class SecureBean {
 public void writeSecureMessage() {
        System.out.println("Every time I learn something new, "
                + "it pushes some old stuff out of my brain");
    }
}

UserInfo클래스 - 사용자 정보를 저장

package com.lastjava.spring.ch05.security;

public class UserInfo {
 private String username;
    private String password;
   
    public UserInfo(String username, String password) {
        this.username = username;
        this.password = password;
    }
   
    public String getPassword() {
        return password;
    }

    public String getUsername() {
        return username;
    }
}

SecurityManager클래스 - 사용자 인증을 담당하고 그들의 계정 정보를 담아뒸더가 나중에 참조

package com.lastjava.spring.ch05.security;

public class SecurityManager {

    private static ThreadLocal<UserInfo> threadLocal = new ThreadLocal<UserInfo>();

    public void login(String username, String password) {
        // assumes that all credentials
        // are valid for a login
        threadLocal.set(new UserInfo(username, password));
    }

    public void logout() {
        threadLocal.set(null);
    }
   
    public UserInfo getLoggedOnUser() {
        return threadLocal.get();
    }
}

SecurityAdvice클래스 - 해당 메서드 접근전에 실행 메서드실행을 예외처리로 방지한다.

package com.lastjava.spring.ch05.security;

import java.lang.reflect.Method;

import org.springframework.aop.MethodBeforeAdvice;

public class SecurityAdvice implements MethodBeforeAdvice {

    private SecurityManager securityManager;

    public SecurityAdvice() {
        this.securityManager = new SecurityManager();
    }

    public void before(Method method, Object[] args, Object target)
            throws Throwable {
        UserInfo user = securityManager.getLoggedOnUser();

        if (user == null) {
            System.out.println("No user authenticated");
            throw new SecurityException(
                    "You must login before attempting to invoke the method: "
                            + method.getName());
        } else if ("janm".equals(user.getUsername())) {
            System.out.println("Logged in user is janm - OKAY!");
        } else {
            System.out.println("Logged in user is " + user.getUsername()
                    + " NOT GOOD :(");
            throw new SecurityException("User " + user.getUsername()
                    + " is not allowed access to method " + method.getName());
        }

    }
}

SecurityExample 클래스

package com.lastjava.spring.ch05.security;

import org.springframework.aop.framework.ProxyFactory;

public class SecurityExample {
 public static void main(String[] args) {
        // get the security manager
        SecurityManager mgr = new SecurityManager();

        // get the bean
        SecureBean bean = getSecureBean();

        // try as robh
        mgr.login("janm", "*****");
        bean.writeSecureMessage();
        mgr.logout();

        // try as janm
        try {
            mgr.login("mallory", "****");
            bean.writeSecureMessage();
        } catch(SecurityException ex) {
            System.out.println("Exception Caught: " + ex.getMessage());
        } finally {
            mgr.logout();
        }

        // try with no credentials
        try {
            bean.writeSecureMessage();
        } catch(SecurityException ex) {
            System.out.println("Exception Caught: " + ex.getMessage());
        }

    }

     private static SecureBean getSecureBean() {
        // create the target
        SecureBean target = new SecureBean();

        // create the advice
        SecurityAdvice advice = new SecurityAdvice();

        // get the proxy
        ProxyFactory factory = new ProxyFactory();
        factory.setTarget(target);
        factory.addAdvice(advice);

        return (SecureBean)factory.getProxy();

    }
}

결과

Logged in user is janm - OKAY!
Every time I learn something new, it pushes some old stuff out of my brain
Logged in user is mallory NOT GOOD :(
Exception Caught: User mallory is not allowed access to method writeSecureMessage
No user authenticated
Exception Caught: You must login before attempting to invoke the method: writeSecureMessage