| a 发行版的完整最终代码。
基本的系统
我将从 一 个基本的面向方面的性能监视系统开始。这个系统可以捕捉处理 Web 请求的不 同 servlet 的时间和计数。清单 1 显示了一个捕捉这个性能信息的简单方面：
AOP@Work: 用AspectJ进行性能监视，第1部分(3)
时间:2011-09-07 IBM Ron Bodkin
清单 1. 捕捉 servlet 时间和计数的方面
/**
* Monitors performance timing and execution counts for
* <code>HttpServlet</code> operations
*/
public aspect HttpServletMonitor {
/** Execution of any Servlet request methods. */
public pointcut monitoredOperation(Object operation) :
execution(void HttpServlet.do*(..)) && this (operation);
/** Advice that records statistics for each monitored operation. */
void around(Object operation) : monitoredOperation(operation) {
long start = getTime();
proceed(operation);
PerfStats stats = lookupStats (operation);
stats.recordExecution(getTime(), start);
}
/**
* Find the appropriate statistics collector object for this
* operation.
*
* @param operation
* the instance of the operation being monitored
*/
protected PerfStats lookupStats(Object operation) {
Class keyClass = operation.getClass();
synchronized(operations) {
stats = (PerfStats) operations.get(keyClass);
if (stats == null) {
stats = perfStatsFactory.
createTopLevelOperationStats(HttpServlet.class,
keyClass);
operations.put(keyClass, stats);
}
}
return stats;
}
/**
* Helper method to collect time in milliseconds. Could plug in
* nanotimer.
*/
public long getTime() {
return System.currentTimeMillis();
}
public void setPerfStatsFactory(PerfStatsFactory
perfStatsFactory) {
this.perfStatsFactory = perfStatsFactory;
}
public PerfStatsFactory getPerfStatsFactory() {
return perfStatsFactory;
}
/** Track top-level operations. */
private Map/*<Class,PerfStats>*/ operations =
new WeakIdentityHashMap();
private PerfStatsFactory perfStatsFactory;
}
/**
* Holds summary performance statistics for a
* given topic of interest
* (e.g., a subclass of Servlet).
*/
public interface PerfStats {
/**
* Record that a single execution occurred.
*
* @param start time in milliseconds
* @param end time in milliseconds
*/
void recordExecution(long start, long end);
/**
* Reset these statistics back to zero. Useful to track statistics
* during an interval.
*/
void reset();
/**
* @return total accumulated time in milliseconds from all
* executions (since last reset).
*/
int getAccumulatedTime();
/**
* @return the largest time for any single execution, in
* milliseconds (since last reset).
*/
int getMaxTime ();
/**
* @return the number of executions recorded (since last reset).
*/
int getCount();
}
/**
* Implementation of the
*
* @link
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