程序执行中哪些特定的事件或方法调用顺序导致在系统启动、线程启动和输出日志中的类型加载消息之前打印静态变量的值？
"main", "1", "Main.java:4", "Field Write", "staticVariable is updated to 1"
"main", "2", "SYSTEM", "System Start", " "
AspectJAspect.aj
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.aspectj.lang.annotation.After;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.aspectj.lang.JoinPoint;
@Aspect
public class AspectJAspect
{
private static long aspectStartTime; // Variable to store the start time of the aspect
private static int serialNumber = 1;
// Pointcut to capture the main method of any class across any package
@Pointcut("execution(public static void main(String[]))")
public void mainMethod() {}
// Advice triggered before entering the main method
@Before("mainMethod()")
public void beforeMainMethodExecution(JoinPoint joinPoint)
{
// Capture start time of the aspect
aspectStartTime = System.currentTimeMillis();
// Print system start and thread start messages
System.out.println("\"main\"" + ", \"" + serialNumber++ + "\"" + ", \"SYSTEM\"" + ", \"System Start\", \" \"");
System.out.println("\"main\"" + ", \"" + serialNumber++ + "\"" + ", \"SYSTEM\"" + ", \"Thread Start\", \"main\"");
// Print type load messages for Object class and the declaring class of the main method
System.out.println("\"main\"" + ", \"" + serialNumber++ + "\"" + ", \"SYSTEM\"" + ", \"Type Load\", \"class=java.lang.Object\"");
System.out.println("\"main\"" + ", \"" + serialNumber++ + "\"" + ", \"SYSTEM\"" + ", \"Type Load\", \"class=" + joinPoint.getSignature().getDeclaringType().getName() + "\"");
}
// Pointcut to capture any method execution
@Pointcut("execution(* *(..))")
public void anyMethod() {}
// Pointcut to capture any constructor execution
@Pointcut("call(*.new(..))")
public void anyConstructor() {}
// Pointcut to capture field updates within methods
@Pointcut("set(* *) && !within(AspectJAspect)")
public void fieldUpdate() {}
// Advice triggered before any method execution
@Before("anyMethod()")
public void beforeMethodExecution(JoinPoint joinPoint)
{
// Get thread name, method name, and source information
String threadName = Thread.currentThread().getName();
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
String methodName = signature.getName();
String sourceInfo = joinPoint.getSourceLocation().getFileName() + ":" + joinPoint.getSourceLocation().getLine();
// Print method entry message
System.out.println("\"" + threadName + "\"" + ", \"" + serialNumber++ + "\"" + ", \"" + sourceInfo + "\"" + ", \"Method Entry\", \"" + methodName + "\"");
}
// Advice triggered after a field update within a method
@After("fieldUpdate()")
public void afterFieldUpdate(JoinPoint joinPoint)
{
// Get field name, new value, thread name, and source information
String fieldName = joinPoint.getSignature().getName();
Object newValue = joinPoint.getArgs()[0];
String threadName = Thread.currentThread().getName();
String sourceInfo = joinPoint.getSourceLocation().getFileName() + ":" + joinPoint.getSourceLocation().getLine();
// Check if the method signature represents a constructor
boolean isConstructor = joinPoint.getSignature() instanceof MethodSignature &&
((MethodSignature) joinPoint.getSignature()).getMethod().getName().equals("<init>");
// Print field write message
if (isConstructor)
{
System.out.println("\"" + threadName + "\"" + ", \"" + serialNumber++ + "\"" + ", \"" + sourceInfo + "\"" + ", \"Field Write\", \"" + fieldName + " is updated to " + newValue + "\"");
}
else
{
System.out.println("\"" + threadName + "\"" + ", \"" + serialNumber++ + "\"" + ", \"" + sourceInfo + "\"" + ", \"Field Write\", \"" + fieldName + " is updated to " + newValue + "\"");
}
}
// Advice triggered after any method execution
@After("anyMethod()")
public void afterMethodExecution(JoinPoint joinPoint)
{
// Get thread name, method name, and source information
String threadName = Thread.currentThread().getName();
MethodSignature signature = (MethodSignature) joinPoint.getSignature();
String methodName = signature.getName();
String sourceInfo = joinPoint.getSourceLocation().getFileName() + ":" + joinPoint.getSourceLocation().getLine();
// Print method exit message
System.out.println("\"" + threadName + "\"" + ", \"" + serialNumber++ + "\"" + ", \"" + sourceInfo + "\"" + ", \"Method Exit\", \"" + methodName + "\"");
}
// Advice triggered before any constructor execution
@Before("anyConstructor()")
public void beforeConstructorExecution(JoinPoint joinPoint)
{
// Get thread name, constructor name, and source information
String threadName = Thread.currentThread().getName();
String constructorName = joinPoint.getSignature().getName();
String sourceInfo = joinPoint.getSourceLocation().getFileName() + ":" + joinPoint.getSourceLocation().getLine();
// Print constructor entry message
System.out.println("\"" + threadName + "\"" + ", \"" + serialNumber++ + "\"" + ", \"" + sourceInfo + "\"" + ", \"Constructor Entry\", \"" + constructorName + "\"");
}
// Advice triggered after any constructor execution
@After("anyConstructor()")
public void afterConstructorExecution(JoinPoint joinPoint)
{
// Get thread name, constructor name, and source information
String threadName = Thread.currentThread().getName();
String constructorName = joinPoint.getSignature().getName();
String sourceInfo = joinPoint.getSourceLocation().getFileName() + ":" + joinPoint.getSourceLocation().getLine();
// Print constructor exit message
System.out.println("\"" + threadName + "\"" + ", \"" + serialNumber++ + "\"" + ", \"" + sourceInfo + "\"" + ", \"Constructor Exit\", \"" + constructorName + "\"");
}
// Advice triggered after the main method exits of any class across any package
@After("execution(public static void main(String[]))")
public void afterMainMethod(JoinPoint joinPoint)
{
// Capture end time of the aspect
long aspectEndTime = System.currentTimeMillis();
// Calculate aspect execution time
long aspectExecutionTime = aspectEndTime - aspectStartTime;
// Print aspect execution time
System.out.println("Aspect execution time: " + aspectExecutionTime + " milliseconds");
}
}
Main.java
public class Main
{
public static int staticVariable = 1;
public int a;
public int b;
public int c;
public int d;
public int e;
public Main(int d, int e)
{
this.d = d;
this.e = e;
}
public static void main(String[] args)
{
Main aop = new Main(5, 10);
aop.methodA(5);
aop.methodB(6);
aop.methodC(7);
Main.updateStaticVariable(8);
}
public void methodA(int value)
{
a = value;
a = 20;
}
public void methodB(int value)
{
b = value;
c = 15;
}
public void methodC(int value)
{
d = value;
e = 25;
}
public static void updateStaticVariable(int value)
{
staticVariable = value;
}
}
输出
"main", "1", "Main.java:4", "Field Write", "staticVariable is updated to 1"
"main", "2", "SYSTEM", "System Start", " "
"main", "3", "SYSTEM", "Thread Start", "main"
"main", "4", "SYSTEM", "Type Load", "class=java.lang.Object"
"main", "5", "SYSTEM", "Type Load", "class=org.mazouz.aop.Main"
"main", "6", "Main.java:16", "Method Entry", "main"
"main", "7", "Main.java:17", "Constructor Entry", "<init>"
"main", "8", "Main.java:12", "Field Write", "d is updated to 5"
"main", "9", "Main.java:13", "Field Write", "e is updated to 10"
"main", "10", "Main.java:17", "Constructor Exit", "<init>"
"main", "11", "Main.java:24", "Method Entry", "methodA"
"main", "12", "Main.java:25", "Field Write", "a is updated to 5"
"main", "13", "Main.java:26", "Field Write", "a is updated to 20"
"main", "14", "Main.java:24", "Method Exit", "methodA"
"main", "15", "Main.java:29", "Method Entry", "methodB"
"main", "16", "Main.java:30", "Field Write", "b is updated to 6"
"main", "17", "Main.java:31", "Field Write", "c is updated to 15"
"main", "18", "Main.java:29", "Method Exit", "methodB"
"main", "19", "Main.java:34", "Method Entry", "methodC"
"main", "20", "Main.java:35", "Field Write", "d is updated to 7"
"main", "21", "Main.java:36", "Field Write", "e is updated to 25"
"main", "22", "Main.java:34", "Method Exit", "methodC"
"main", "23", "Main.java:39", "Method Entry", "updateStaticVariable"
"main", "24", "Main.java:40", "Field Write", "staticVariable is updated to 8"
"main", "25", "Main.java:39", "Method Exit", "updateStaticVariable"
"main", "26", "Main.java:16", "Method Exit", "main"
Aspect execution time: 45 milliseconds
是什么让静态变量值出现在输出日志中系统启动消息之前
"main", "1", "Main.java:4", "Field Write", "staticVariable is updated to 1"
"main", "2", "SYSTEM", "System Start", " "
在输出中加载类型后，有什么方法可以捕获 Main 类中静态变量的值分配吗？
你所说的“系统启动”就是静态方法的执行。在此之前，包含该方法的目标类已经初始化，如 user85421 所解释的。
你要拦截的是静态类初始化：
@Before("staticinitialization(Main)")
然后，日志输出将是这样的：
"main", "1", "SYSTEM", "System Start", " "
"main", "2", "SYSTEM", "Thread Start", "main"
"main", "3", "SYSTEM", "Type Load", "class=java.lang.Object"
"main", "4", "SYSTEM", "Type Load", "class=Main"
"main", "5", "Main.java:2", "Field Write", "staticVariable is updated to 1"
"main", "6", "Main.java:14", "Method Entry", "main"
"main", "7", "Main.java:15", "Constructor Entry", "<init>"
"main", "8", "Main.java:10", "Field Write", "d is updated to 5"
"main", "9", "Main.java:11", "Field Write", "e is updated to 10"
...
请参阅 https://eclipse.dev/aspectj/doc/latest/progguide/progguide.html#quick-pointcuts。我已经在您上一个问题的这个答案中向您指出了编程指南。