使用 Javassist 向运行时生成的方法/类添加注释 [英] Adding an annotation to a runtime generated method/class using Javassist

问题描述

我正在使用 Javassist 生成一个类 foo，使用方法 bar，但我似乎找不到向方法添加注释(注释本身不是运行时生成的)的方法.我试过的代码是这样的:

I'm using Javassist to generate a class foo, with method bar, but I can't seem to find a way to add an annotation (the annotation itself isn't runtime generated) to the method. The code I tried looks like this:

ClassPool pool = ClassPool.getDefault();

// create the class
CtClass cc = pool.makeClass("foo");

// create the method
CtMethod mthd = CtNewMethod.make("public Integer getInteger() { return null; }", cc);
cc.addMethod(mthd);

ClassFile ccFile = cc.getClassFile();
ConstPool constpool = ccFile.getConstPool();

// create the annotation
AnnotationsAttribute attr = new AnnotationsAttribute(constpool, AnnotationsAttribute.visibleTag);
Annotation annot = new Annotation("MyAnnotation", constpool);
annot.addMemberValue("value", new IntegerMemberValue(ccFile.getConstPool(), 0));
attr.addAnnotation(annot);
ccFile.addAttribute(attr);

// generate the class
clazz = cc.toClass();

// length is zero
java.lang.annotation.Annotation[] annots = clazz.getAnnotations();

显然我做错了什么，因为 annots 是一个空数组.

And obviously I'm doing something wrong since annots is an empty array.

这是注释的样子:

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyAnnotation {
    int value();
}

推荐答案

最终解决了，我在错误的地方添加了注释.我想将它添加到方法中，但我将它添加到类中.

Solved it eventually, I was adding the annotation to the wrong place. I wanted to add it to the method, but I was adding it to the class.

这是固定代码的样子:

// wrong
ccFile.addAttribute(attr);

// right
mthd.getMethodInfo().addAttribute(attr);

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