沿續上篇的AspectJ 5 for Spring annotation的疑問，也讓我首次去檢驗Open Source的程式碼。其實Open Source的code以前都不看，就有一種怕改到不能用的自卑心作祟。而OOP的好處不在於改，可以繼承，所以我寫了MyDispatchAction繼承MappingDispatchAction的class，讓原本protected的getMethodName，變成public探出頭來呼吸一下，而業務Action再繼承我寫的。
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import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.struts.action.ActionForm;
import org.apache.struts.action.ActionForward;
import org.apache.struts.action.ActionMapping;
import org.apache.struts.actions.MappingDispatchAction;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class MyDispactionAction extends MappingDispatchAction {
private static Logger logger = LoggerFactory.getLogger(MyDispactionAction.class);
private String methodName;
@Override
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
if (isCancelled(request)) {
ActionForward af = cancelled(mapping, form, request, response);
if (af != null) {
return af;
}
}
// Get the parameter. This could be overridden in subclasses.
String parameter = getParameter(mapping, form, request, response);
// Get the method's name. This could be overridden in subclasses.
String name = getMethodName(mapping, form, request, response, parameter);
this.methodName = name;
// Prevent recursive calls
if ("execute".equals(name) || "perform".equals(name)){
String message = messages.getMessage("dispatch.recursive", mapping.getPath());
logger.error(message);
throw new ServletException(message);
}
// Invoke the named method, and return the result
return dispatchMethod(mapping, form, request, response, name);
}
public String getMethodName() {
return this.methodName;
}
} |
上述程式碼中，粗體字是原MappingDispatchAction的execute method內容，加了紅色一行this.methodName = name。而在AOP程式，可以透過getMethodName取得資訊，但需在JointPoint.proceed執行之後才會有值，所以理論上也適於@After、@AfterReturn等annotation，如下：
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import org.apache.commons.lang.time.StopWatch;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import com.mycompany.actions.MyDispactionAction;
@Aspect
@Component
public class WebLogger {
private static Logger logger = LoggerFactory.getLogger(WebLogger.class);
@Pointcut("target(com.foo.bar.action.ILoginAction)")
public void timer() {
logger.info("call timer!!");
}
@Around("timer()")
public Object time(ProceedingJoinPoint joinPoint) throws Throwable {
String clazzName = joinPoint.getTarget().getClass().getSimpleName();
String methodName = joinPoint.getSignature().getName();
MyDispactionAction action = null;
try {
action = (MyDispactionAction) joinPoint.getTarget(); // 將target強制轉型為MyDispatchAction
} catch (Exception e) {
logger.warn("Cast Error", e);
}
StopWatch clock = new StopWatch();
clock.start();
Object result = joinPoint.proceed();
clock.stop();
if (action != null) methodName = action.getMethodName(); // 必須在jointPoint.proceed之後
String[] params = new String[] { clazzName, methodName, clock.getTime() + "" };
logger.info("[{}] Run [{}] method spent [{}] ms", params);
return result;
}
}
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如此一來，業務Action繼承MyDispatchAction和實作ILoginAction，就可被AOP WebLogger攔截到ILoginAction的實作品的method name，如下：
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public class LoginAction extends MyDispactionAction implements ILoginAction {
private static Logger logger = LoggerFactory.getLogger(LoginAction.class);
public ActionForward login(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response) {
// 略...
}
} |
當然，別忽略在application-context.xml裡的設定，要設成proxy-target-class="true"
最後在WebLogger程式如願攔截到login method name了，Log如下：
2010/03/14 15:34:37 INFO [WebLogger.java:51] : [LoginAction] Run [login] method spent [163] ms
附帶一提，ILoginAction可以是一個什麼method都沒定的interface，照樣能運行。更聰明的作法，是MyDispatchAction去實作一個介面，便於被AOP的target取得^^。
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