如何在运行时记录传递给方法的参数?是否有任何Java库可用于此或任何可以引发以监视它的异常?
答案 0 :(得分:5)
您可以使用javassist的ProxyFactory
或Translator
来更改以在运行时打印参数:
Translator
(使用新的ClassLoader
):public static class PrintArgumentsTranslator implements Translator {
public void start(ClassPool pool) {}
@Override
public void onLoad(ClassPool pool, String cname)
throws NotFoundException, CannotCompileException {
CtClass c = pool.get(cname);
for (CtMethod m : c.getDeclaredMethods())
insertLogStatement(c, m);
for (CtConstructor m : c.getConstructors())
insertLogStatement(c, m);
}
private void insertLogStatement(CtClass c, CtBehavior m) {
try {
List<String> args = new LinkedList<String>();
for (int i = 0; i < m.getParameterTypes().length; i++)
args.add("$" + (i + 1));
String toPrint =
"\"----- calling: "+c.getName() +"." + m.getName()
+ args.toString()
.replace("[", "(\" + ")
.replace(",", " + \", \" + ")
.replace("]", "+\")\"");
m.insertBefore("System.out.println("+toPrint+");");
} catch (Exception e) {
// ignore any exception (we cannot insert log statement)
}
}
}
*请注意,您需要更改默认ClassLoader
,以便可以对类进行检测,因此在调用main
之前,您需要插入以下代码:
public static void main(String[] args) throws Throwable {
ClassPool cp = ClassPool.getDefault();
Loader cl = new Loader(cp);
cl.addTranslator(cp, new PrintArgumentsTranslator());
cl.run("test.Test$MyApp", args); // or whatever class you want to start with
}
public class MyApp {
public MyApp() {
System.out.println("Inside: MyApp constructor");
}
public static void main(String[] args) {
System.out.println("Inside: main method");
new MyApp().method("Hello World!", 4711);
}
public void method(String string, int i) {
System.out.println("Inside: MyApp method");
}
}
输出:
----- calling: test.Test$MyApp.main([Ljava.lang.String;@145e044)
Inside: main method
----- calling: test.Test$MyApp.Test$MyApp()
Inside: MyApp constructor
----- calling: test.Test$MyApp.method(Hello World!, 4711)
Inside: MyApp method
ProxyFactory
public class Test {
public String method(String string, int integer) {
return String.format("%s %d", string, integer);
}
public static void main(String[] args) throws Exception {
ProxyFactory f = new ProxyFactory();
f.setSuperclass(Test.class);
Class<?> c = f.createClass();
MethodHandler mi = new MethodHandler() {
public Object invoke(
Object self, Method m, Method proceed, Object[] args)
throws Throwable {
System.out.printf("Method %s called with %s%n",
m.getName(), Arrays.toString(args));
// call the original method
return proceed.invoke(self, args);
}
};
Test foo = (Test) c.newInstance();
((Proxy) foo).setHandler(mi);
foo.method("Hello", 4711);
}
}
输出:
Method method called with [Hello, 4711]
答案 1 :(得分:3)
你应该尝试使用AOP。以下示例可以或多或少地执行您想要的操作:How to use AOP with AspectJ for logging?
答案 2 :(得分:1)
我认为您可以注册MBean
,然后才能使用JMX进行检查。
链接: http://docs.oracle.com/cd/E19159-01/819-7758/gcitp/index.html