关于使用AspectJ执行策略 [英] About Policy Enforcement with AspectJ

问题描述

我正在使用Aspectj来实施整个项目的政策.

I am using Aspectj for project-wide policy enforcement.

我现在要实现的一件事是，除了使用Guava的Preconditions.check*方法进行简单验证之外，任何设置方法中都应该没有逻辑.

One thing I am trying to implement now is that there should be no logic in any setter methods except simple validation with Guava's Preconditions.check* methods.

public pointcut withinSetter() :
    withincode(public void set*(*));
public pointcut inputValidation() :
    call(public void Preconditions.check*(*));
public pointcut setFieldValue() : set(* *);
public pointcut entity() : within(com.mycompany.BaseEntity+);

declare warning :
entity() && withinSetter() && !setFieldValue() && !inputValidation():
"Please don't use Logic in Setters";

这可以按预期工作，对任何未设置的代码生成警告.但是，对于这样的构造，它会失败:

This works as expected, generating warnings for any non-setter code. However, it fails for constructs like this:

public void setFoo(final String newFoo) {
    Preconditions.checkNotNull(newFoo); // this is OK
    Preconditions.checkArgument(
                 newFoo.matches("\\p{Alpha}{3}"), // this generates a warning
                                                  // because String.matches()
                                                  // is called
                "Foo must have exactly 3 characters!");
    this.foo = newFoo;
}

所以我要寻找的是一个允许任何代码的结构，只要它发生在Preconditions.check*调用的参数内即可.有这样的切入点吗?

So what I am looking for is a construct that would allow any code, as long as it happens inside the parameters to a Preconditions.check* call. Is there such a pointcut?

推荐答案

我知道这是一个老问题，但是我在寻找其他东西时偶然发现了它.

答案是否定的，因为在JVM字节码中没有诸如"check*调用内的逻辑"之类的东西.例如，newFoo.matches(..)在 之前被评估，结果被传递给Preconditions.checkArgument(..)，非常像这样:

The answer is no, because in JVM bytecode there is no such thing as "logic inside a check* call". For example, newFoo.matches(..) is evaluated before the result is passed to Preconditions.checkArgument(..), very much like this:

boolean match = newFoo.matches("\\p{Alpha}{3}");
Preconditions.checkArgument(match, "Foo must have exactly 3 characters!");

如果代码是这样编写的，那么您将发出警告，那么为什么不将相同的Java代码(可能导致相似或相同的字节代码)编写为嵌套调用呢? ;-)

If the code was written like this, you would issue a warning anway, so why not if the same Java code, possibly resulting in similar or identical byte code, is written as a nested call? ;-)

更新:我创建了一个小示例:

Update: I have created a little example:

public class Application {
    public static void main(String[] args) {
        String newFoo = "Scrum";
        boolean match = newFoo.matches("\\p{Alpha}{3}");
        checkArgument(
            match,
            "Foo must have exactly 3 characters!"
        );
        checkArgument(
            newFoo.matches("\\p{Alpha}{3}"),
            "Foo must have exactly 3 characters!"
        );
    }

    private static void checkArgument(boolean status, String errorMessage) {
        if (!status)
            System.out.println(errorMessage);
    }
}

如果使用javap -c Application转储字节码，则会看到以下内容:

If you dump the byte code using javap -c Application you see this:

Compiled from "Application.java"
public class Application extends java.lang.Object{
public Application();
  Code:
   0:   aload_0
   1:   invokespecial   #8; //Method java/lang/Object."<init>":()V
   4:   return

public static void main(java.lang.String[]);
  Code:
   0:   ldc #16; //String Scrum
   2:   astore_1
   3:   aload_1
   4:   ldc #18; //String \p{Alpha}{3}
   6:   invokevirtual   #20; //Method java/lang/String.matches:(Ljava/lang/String;)Z
   9:   istore_2
   10:  iload_2
   11:  ldc #26; //String Foo must have exactly 3 characters!
   13:  invokestatic    #28; //Method checkArgument:(ZLjava/lang/String;)V
   16:  aload_1
   17:  ldc #18; //String \p{Alpha}{3}
   19:  invokevirtual   #20; //Method java/lang/String.matches:(Ljava/lang/String;)Z
   22:  ldc #26; //String Foo must have exactly 3 characters!
   24:  invokestatic    #28; //Method checkArgument:(ZLjava/lang/String;)V
   27:  return

}

如您所见，转储中第3-13行和第16-24行的字节码相同，除了存储和重新加载布尔值.也许这说明了我之前说过的话.

As you can see, the byte code of lines 3-13 versus 16-24 in the dump is identical except for the storing and re-loading of the boolean value. Maybe this illustrates what I have said before.

这篇关于关于使用AspectJ执行策略的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！