无法在Java 7中添加/更新注释

编程问答 2022-06-09

问题描述

我正在尝试在Java 7中动态添加注释。但是这样做没有成功。可以使用一些帮助。

以下是我采取的两种方法。在这两种方法中，当我检查时添加新的注释后，类/字段都不会立即反映出来。

1。使用javaassist创建新的注释 

    public void javaassist(String className,List<String> props) throws Exception{
         //pool creation 
         Classpool pool = Classpool.getDefault();
         //extracting the class
         CtClass cc = pool.getCtClass(className);
         // create the annotation
         ClassFile ccFile = cc.getClassFile();
         ConstPool constpool = ccFile.getConstPool();
         
         AnnotationsAttribute attr = new AnnotationsAttribute(constpool,AnnotationsAttribute.visibleTag);
         
         for(String propName: props) {
             javassist.bytecode.annotation.Annotation annot = 
                     new javassist.bytecode.annotation.Annotation("org.hibernate.annotations.ColumnTransformer",constpool);
             annot.addMemberValue("read",new StringMemberValue("aes_decrypt("+propName+",'mysecret')",ccFile.getConstPool()));
             annot.addMemberValue("write",new StringMemberValue("aes_encrypt(?,ccFile.getConstPool()));
             
             attr.addAnnotation(annot);
             
             //looking for the method to apply the annotation on
             CtField propField = cc.getDeclaredField(propName);
             // add the annotation to the method descriptor
             List<AnnotationsAttribute> atts= propField.getFieldInfo().getAttributes();
             System.out.println(atts);
             // propField.getFieldInfo().addAttribute(attr);             
             atts.add(attr);
             System.out.println(atts);
         }
    }

2。使用Class.class.getDeclaredField（“ annotations”）

创建新的注释 
    @SuppressWarnings({ "unchecked","rawtypes" })
    private void withNew(Class clazz,List<String> props) throws NoSuchFieldException,SecurityException,IllegalArgumentException,illegalaccessexception {
        Field fieldAnnotations = Class.class.getDeclaredField("annotations");
        fieldAnnotations.setAccessible(true);
        Map<Class<? extends Annotation>,Annotation> annotations = (Map<Class<? extends Annotation>,Annotation>) fieldAnnotations.get(clazz);
        for(String prop: props) {
            annotations.put(ColumnTransformer.class,this.buildColTransfAnnotation(prop,key));
        }
    }
    
    private Annotation buildColTransfAnnotation(final String propName,final String key) {
        return new ColumnTransformer() {
            @Override
            public Class<? extends Annotation> annotationType() {
                return ColumnTransformer.class;
            }
            
            @Override
            public String write() {
                return "aes_encrypt(?,'"+key+"')";
            }
            
            @Override
            public String read() {
                return "aes_decrypt("+propName+",'"+key+"')";
            }
            
            @Override
            public String forColumn() {
                return null;
            }
        };
    }

以下是我的验证方式 

    private void print(List<String> props) throws NoSuchFieldException,SecurityException {
        for(String propName: props) {
            Field field = Partner.class.getDeclaredField(propName);
            
            for(Annotation an: field.getAnnotations()) {
                System.out.println(an);
            }
        }
    }

似乎与Java 7有关。

解决方法

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annotationsannotationsjavajavajava-7javassistreflection