javaassist动态修改注解

Posted on | In |

JavaassistAnno ob变量加上了注解A，需要改成B。

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package vm;

import vm.anno.A;

public class JavaassistAnno {
    @A
    private Object ob;
}


public @interface A {
}

public @interface B {
}

直接修改field的属性就可以

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ClassPool classPool = ClassPool.getDefault();
CtClass ctClass = classPool.getCtClass("vm.JavaassistAnno");
for(CtField ctField : ctClass.getDeclaredFields()){
    FieldInfo fieldInfo = ctField.getFieldInfo();
    ConstPool cp = fieldInfo.getConstPool();
    AnnotationsAttribute att = (AnnotationsAttribute) fieldInfo.getAttribute(AnnotationsAttribute.visibleTag);
    AnnotationsAttribute attribute = new AnnotationsAttribute(cp, AnnotationsAttribute.visibleTag);
    for (Annotation ann : att.getAnnotations()){
        if(ann.getTypeName().equals("vm.anno.A")){
            Annotation annotation = new Annotation("vm.anno.B", cp);
            attribute.addAnnotation(annotation);
        } else {
            attribute.addAnnotation(ann);
        }
    }
    fieldInfo.addAttribute(attribute);
}
//这个默认是调用了Thread.currentThread().getContextClassLoader()的defineClass方法，也有api可以指定classloader，或许取到了hibernate的classloader就可以输出过去。
ctClass.toClass();
Class clz = JavaassistAnno.class;
Field field = clz.getDeclaredField("ob");
for (java.lang.annotation.Annotation annotation : field.getAnnotations()){
    //可以看到能成功输出@vm.anno.B
    System.out.println(annotation);
}