AspectJ+Javasist记录日志

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在项目中碰到这样一个需求，对一个服务类的每一个方法，在方法开始和结束的时候分别记录一条日志，内容包括方法名，参数名+参数值以及方法执行的时间。

 

@Override
public String get(String key) {
//	long start = System.currentTimeMillis();
//	System.out.println("Begin Method = get, Args = [key=" + key + "]");
	String value = props.getProperty(key);
//	System.out.println("End Method = get, Args = [key=" + key + "], Cost=" + (System.currentTimeMillis() - start)+ "ms");
	return value;
}

 以上注释的代码能够满足要求，但是如果类中的方法比较多得时候，会有大量的冗余代码，不利于维护。这个时候可以用AspectJ实现日志代码的嵌入，但是JointPoint只能拿到参数值，无法拿到参数名。因此考虑用Javasist在初始化的时候先把参数名保存到内存中。以下是代码：

 

 

服务实现类（接口略）：

 

package test;

import java.util.Properties;

public class ServiceImpl implements Service {
	private Properties props = new Properties();

	@Override
	public String get(String key) {
		return props.getProperty(key);
	}

	@Override
	public void put(String key, String value) {
		props.put(key, value);
	}

	@Override
	public void putAll(Properties props) {
		this.props.putAll(props);
	}
}

 

 

Aspect类：

 

package test;

import java.util.Map;

import javassist.ClassClassPath;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.Modifier;
import javassist.NotFoundException;
import javassist.bytecode.CodeAttribute;
import javassist.bytecode.LocalVariableAttribute;
import javassist.bytecode.MethodInfo;

import org.apache.log4j.Logger;
import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;

import com.google.common.collect.Maps;

@Aspect
public class LogHelper {
	final static private Logger logger = Logger.getLogger(ServiceImpl.class);
	private static final String DELIMITER = " | ";

	private Map paraMap = Maps.newHashMap();

	public void init() throws NotFoundException {
		reflectGetParamName(ServiceImpl.class);
	}

	@Pointcut("execution(* (test.*+).*(..))")
	public void aspectjMethod() {
	}

	@Around("aspectjMethod()")
	public Object around(ProceedingJoinPoint call) throws Throwable {
		long startTime = System.nanoTime();
		String methodName = call.getSignature().getName();
		String className = call.getTarget().getClass().getSimpleName();
		Object[] args = call.getArgs();
		StringBuilder begin = new StringBuilder("Begin ").append("Method=").append(methodName).append(", Args=[")
				.append(argsToString(className, methodName, args)).append("]");
		logger.info(begin);

		Object result = call.proceed(args);
		long costTime = (System.nanoTime() - startTime) / 1000;// μs
		StringBuilder end = new StringBuilder("End ").append("Method=").append(methodName).append(", Args=[")
				.append(argsToString(className, methodName, args)).append("], Cost=").append(costTime).append("μs");
		logger.info(end);
		return result;
	}

	private String argsToString(String className, String methodName, Object[] args) {
		String[] paraNames = paraMap.get(className + methodName);
		boolean appendParaName = true;
		if (paraNames == null || paraNames.length != args.length) {
			logger.warn("Fail to get parameter(s)' name. ClassName = " + className + ", MethodName = " + methodName
					+ ", Expected ParaNum = " + args.length);
			appendParaName = false;
		}
		StringBuilder sb = new StringBuilder();
		for (int i = 0; i < args.length; i++) {
			Object obj = args[i];
			String paraName = paraNames[i];
			if (sb.length() != 0) {
				sb.append(DELIMITER);
			}
			if (appendParaName) {
				sb.append(paraName).append("=");
			}
			sb.append(String.valueOf(obj));
		}
		return sb.toString();
	}

	private void reflectGetParamName(Class clazz) throws NotFoundException {
		ClassPool pool = ClassPool.getDefault();
		pool.insertClassPath(new ClassClassPath(clazz));
		CtClass cc = pool.get(clazz.getName());
		for (CtMethod cm : cc.getDeclaredMethods()) {
			String methodName = cm.getName();
			// 使用javaassist的反射方法获取方法的参数名
			MethodInfo methodInfo = cm.getMethodInfo();
			CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
			LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute
					.getAttribute(LocalVariableAttribute.tag);
			if (attr == null) {
				throw new NotFoundException("CodeAttribute Not Found. ClassName = " + clazz.getName()
						+ ", MethodName = " + methodName);
			}
			String[] paramNames = new String[cm.getParameterTypes().length];
			int pos = Modifier.isStatic(cm.getModifiers()) ? 0 : 1;
			for (int i = 0; i < paramNames.length; i++)
				paramNames[i] = attr.variableName(i + pos);
			paraMap.put(clazz.getSimpleName() + methodName, paramNames);
		}
	}
}

 

1. 首先初始化的时候调用reflectGetParamName，运用反射获取所有方法的参数名，并保存到paraMap中。
2. 在方法执行的前后分别打印日志并计算执行时间，方法名和参数值从JoinPoint中获取，参数名从paraMap中获取

配置文件applicationContext.xml：

 

测试代码：

package test;

import java.util.Properties;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

	public static void main(String[] args) {
		ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");
		Service service = (Service) context.getBean("service");
		service.put("1", "one");
		service.putAll(new Properties());
		System.out.println(service.get("1"));
	}

}

 

测试结果：

 

15/07/16 10:19:38 INFO test.ServiceImpl: Begin Method=put, Args=[key=1 | value=one]
15/07/16 10:19:38 INFO test.ServiceImpl: End Method=put, Args=[key=1 | value=one], Cost=1539μs
15/07/16 10:19:38 INFO test.ServiceImpl: Begin Method=putAll, Args=[props={}]
15/07/16 10:19:38 INFO test.ServiceImpl: End Method=putAll, Args=[props={}], Cost=148μs
15/07/16 10:19:38 INFO test.ServiceImpl: Begin Method=get, Args=[key=1]
15/07/16 10:19:38 INFO test.ServiceImpl: End Method=get, Args=[key=1], Cost=86μs