动态给class加注解

package vine.common;

import com.alibaba.fastjson.JSONObject;
import com.alibaba.fastjson.serializer.SerializerFeature;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtField;
import javassist.bytecode.AnnotationsAttribute;
import javassist.bytecode.AttributeInfo;
import javassist.bytecode.annotation.Annotation;
import javassist.bytecode.annotation.IntegerMemberValue;
import lombok.SneakyThrows;

import java.lang.reflect.Field;
import java.util.List;

public class AssistUtil {

    @SneakyThrows
    public static Class<?> addAnnotation(String clzName,String annotationName) {
        ClassPool classPool = ClassPool.getDefault();
        CtClass clz = classPool.get(clzName);

        CtField[] fields = clz.getDeclaredFields();
        int i = 0;
        for (CtField field : fields) {
            List<AttributeInfo> attributes = field.getFieldInfo().getAttributes();
            AnnotationsAttribute annotationsAttribute;
            if (!attributes.isEmpty()) {
                annotationsAttribute = (AnnotationsAttribute) attributes.get(0);
            }else {
                annotationsAttribute = new AnnotationsAttribute(field.getFieldInfo().getConstPool(), AnnotationsAttribute.visibleTag);
            }
            Annotation annotation = new Annotation(annotationName, field.getFieldInfo().getConstPool());
            annotation.addMemberValue("ordinal",new IntegerMemberValue(field.getFieldInfo().getConstPool(),i++));
//            annotation.addMemberValue("ordinal",new IntegerMemberValue(i++,field.getFieldInfo().getConstPool()));
            annotationsAttribute.addAnnotation(annotation);
            field.getFieldInfo().addAttribute(annotationsAttribute);
        }
        Class<?> afterClass = clz.toClass();
        for (Field field : afterClass.getDeclaredFields()) {
            for (java.lang.annotation.Annotation annotation : field.getAnnotations()) {
                System.out.println(annotation);
            }
        }
        return afterClass;
    }

    @SneakyThrows
    public static String toJsonString(Class<?> type) {
        SerializerFeature[] serializer = {SerializerFeature.WriteMapNullValue, SerializerFeature.WriteNullNumberAsZero,
                SerializerFeature.WriteNullListAsEmpty, SerializerFeature.WriteNullStringAsEmpty,
                SerializerFeature.WriteNullBooleanAsFalse};
        Object o = type.newInstance();
        return JSONObject.toJSONString(o,serializer);
    }


    public static void main(String[] args) {
        Class<?> aClass = addAnnotation("vine.base.Prepare", "com.alibaba.fastjson.annotation.JSONField");
        System.out.println(toJsonString(aClass));

    }
}