AOP与AspectJ5的详细介绍

// using a dedicated syntax
// that compliments the Java language
public aspect Foo {

pointcut someListOperation() : call(* List+.add(..));

pointcut userScope() : within(com.biz..*);

before() : someListOperation() && userScope() {
System.out.println("called: "
+ thisJoinPoint.getSignature()
);
}
}
上面的代码使用了AspectJ专用的语法，你可以用Java Annotations写出等效的代码，如下：
// the Java 5 annotations approach
@Aspect
public class Foo {

@Pointcut("call(* java.util.List+.add(..))")
public void someListOperation() {}

@Pointcut("within(com.biz..*)")
public void userScope() {}

@Before("someListOperation() && userScope()")
public void before(JoinPoint thisJoinPoint) {
System.out.println("called: "
+ thisJoinPoint.getSignature()
);
}
}

// say this is the original user code
void businessMethod() {
userCode.do();
}

//---- Case 1
// say the AOP weaver was applied BEFORE the
// performance management weaver
// the woven code will behave like:
void businessMethod() {
try {
performanceEnter();
aopBeforeExecuting();//hypothetical advice
userCode.do()
} finally {
performanceExit();
}
}
// ie the AOP code affect the measure


//---- Case 2
// say the AOP weaver was applied AFTER the
// performance management weaver
// the woven code will behave like:
void businessMethod() {
aopBeforeExecuting();//hypothetical advice
try {
performanceEnter();
userCode.do()
} finally {
performanceExit();
}
}
// ie the AOP code will NOT affect the measure

public void invokeA(Object foo) throws Throwable {
Method mA = foo.getClass().getDeclaredMethod("doA", new Class[0]);
mA.invoke(foo, new Object[0]);
}

public class Hello {

// -- the sample method to intercept
public void sayHello() {
System.out.println("Hello World");
}

// -- using the JRockit JVM support for AOP
static void weave() throws Throwable {
// match on method name
StringFilter methodName = new StringFilter(
"sayHello",
StringFilter.Type.EXACT
);

// match on callee type
ClassFilter klass = new ClassFilter(
Hello.class,
false,
null
);

// advice is a regular method dispatch
Method advice = Aspect.class.getDeclaredMethod(
"advice",
new Class[0]
);

// get a JRockit weaver and subscribe the
// advice to the join point picked out by the filter
Weaver w = WeaverFactory.createWeaver();

w.addSubscription(new MethodSubscription(
new MethodFilter(
0,
null,
klass,
methodName,
null,
null
),
MethodSubscription.InsertionType.BEFORE,
advice
));
}

// -- sample code

static void test() {
new Hello().sayHello();
}

public static void main(String a[])
throws Throwable {
weave();
test();
}

// -- the sample aspect

public static class Aspect {

public static void advice() {
System.out.println("About to say:");
}
}
}