动态修改字段注释值

是否可以在运行时更改字段注释值？

我可以访问这些值，但无法找到更改它们的方法。

可以访问：

Article.class.declaredFields.find {it.name="annotatedField"}.declaredAnnotations 

Answer 1

我认为除了Field（或Object）之外，最好保持对Annotation对象的引用，并在更改其值时更新Annotation引用。 这样，当Class.java中的注释实现发生更改时，您的代码就不太可能中断。

问题注释中链接的答案对于处理包含单个元素的注释很有用，但如果您需要设置多个元素，则这是一个使用代理的更通用的解决方案：

 import java.lang.annotation.Annotation; import java.lang.annotation.Retention; import java.lang.annotation.RetentionPolicy; import java.lang.reflect.Field; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; public class Test { public static void main(String[] args) throws Exception { Foo foo = new Foo(); Field field = foo.getClass().getDeclaredFields()[0]; Anno anno = field.getAnnotation(Anno.class); System.out.println(String.format("Old properties: %s, %s, %s", anno.value(), anno.bar(), anno.barr())); Anno anno2 = (Anno) setAttrValue(anno, Anno.class, "value", "new"); System.out.println(String.format("New properties: %s, %s, %s", anno2.value(), anno2.bar(), anno2.barr())); Anno anno3 = (Anno) setAttrValue(anno2, Anno.class, "bar", "new bar"); System.out.println(String.format("New properties: %s, %s, %s", anno3.value(), anno3.bar(), anno3.barr())); } public static Annotation setAttrValue(Annotation anno, Class type, String attrName, Object newValue) throws Exception { InvocationHandler handler = new AnnotationInvocationHandler(anno, attrName, newValue); Annotation proxy = (Annotation) Proxy.newProxyInstance(anno.getClass().getClassLoader(), new Class[]{type}, handler); return proxy; } } class AnnotationInvocationHandler implements InvocationHandler { private Annotation orig; private String attrName; private Object newValue; public AnnotationInvocationHandler(Annotation orig, String attrName, Object newValue) throws Exception { this.orig = orig; this.attrName = attrName; this.newValue = newValue; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { // "override" the return value for the property we want if (method.getName().equals(attrName) && args == null) return newValue; // keep other properties and methods we want like equals() and hashCode() else { Class[] paramTypes = toClassArray(args); return orig.getClass().getMethod(method.getName(), paramTypes).invoke(orig, args); } } private static Class[] toClassArray(Object[] arr) { if (arr == null) return null; Class[] classArr = new Class[arr.length]; for (int i=0; i 

节目输出：

 Old properties: old, bar, barr New properties: new, bar, barr New properties: new, new bar, barr