springboot动态加入注解怎么实现

要在Spring Boot中动态加入注解，可以使用Java的动态代理技术和反射机制。以下是一个示例代码，演示如何在运行时动态加入注解：
```java
import org.springframework.beans.factory.config.BeanDefinition;
import org.springframework.context.annotation.AnnotationBeanNameGenerator;
import org.springframework.context.annotation.ClassPathScanningCandidateComponentProvider;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.core.type.filter.AnnotationTypeFilter;
import org.springframework.stereotype.Component;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.HashSet;
import java.util.Set;
public class DynamicAnnotationExample {
public static void main(String[] args) {
// 获取所有带有@Controller注解的类
Set> controllerClasses = getClassesWithAnnotation(Controller.class);
// 动态加入@GetMapping注解到所有方法上
for (Class controllerClass : controllerClasses) {
addGetMappingAnnotation(controllerClass);
}
}
private static Set> getClassesWithAnnotation(Class annotationClass) {
Set> classes = new HashSet<>();
ClassPathScanningCandidateComponentProvider provider = new ClassPathScanningCandidateComponentProvider(false);
provider.addIncludeFilter(new AnnotationTypeFilter(annotationClass));
for (BeanDefinition beanDefinition : provider.findCandidateComponents("com.example")) {
try {
Class clazz = Class.forName(beanDefinition.getBeanClassName());
classes.add(clazz);
} catch (Exception e) {
e.printStackTrace();
}
}
return classes;
}
private static void addGetMappingAnnotation(Class controllerClass) {
Object controllerProxy = Proxy.newProxyInstance(
controllerClass.getClassLoader(),
new Class[]{controllerClass},
(proxy, method, args) -> {
// 动态加入@GetMapping注解到方法上
AnnotationMetadata annotationMetadata = new AnnotationMetadata() {
@Override
public Set getAnnotationTypes() {
return Set.of(GetMapping.class.getName());
}
@Override
public Set getMetaAnnotationTypes(String annotationName) {
return null;
}
@Override
public boolean hasAnnotation(String annotationName) {
return GetMapping.class.getName().equals(annotationName);
}
@Override
public boolean hasMetaAnnotation(String metaAnnotationName) {
return false;
}
@Override
public boolean isAnnotated(String annotationName) {
return GetMapping.class.getName().equals(annotationName);
}
@Override
public Map getAnnotationAttributes(String annotationName) {
return Map.of("value", new String[]{"/dynamic"});
}
@Override
public Map getAnnotationAttributes(String annotationName, boolean classValuesAsString) {
return null;
}
};
Method proxyMethod = Proxy.class.getDeclaredMethod("proxyMethod", Method.class);
proxyMethod.setAccessible(true);
Method realMethod = (Method) proxyMethod.invoke(proxy, method);
Method dynamicMethod = new DynamicMethod(realMethod, annotationMetadata);
return dynamicMethod.invoke(proxy, args);
});
// 替换原有的Controller Bean
AnnotationBeanNameGenerator generator = new AnnotationBeanNameGenerator();
String beanName = generator.generateBeanName(controllerClass, null);
SpringContextHolder.replaceBean(controllerClass, beanName, controllerProxy);
}
// 动态代理中用于替换原有方法的动态方法
private static class DynamicMethod extends Method {
private final AnnotationMetadata annotationMetadata;
public DynamicMethod(Method method, AnnotationMetadata annotationMetadata) {
super(
method.getName(),
method.getParameterTypes(),
method.getReturnType(),
method.getExceptionTypes(),
method.getModifiers(),
method.getDeclaringClass(),
method.getDefaultValue()
);
this.annotationMetadata = annotationMetadata;
}
@Override
public T getAnnotation(Class annotationClass) {
return annotationMetadata.isAnnotated(annotationClass.getName()) ? annotationMetadata.getAnnotationAttributes(annotationClass.getName()) : super.getAnnotation(annotationClass);
}
@Override
public Annotation[] getAnnotations() {
Annotation[] annotations = super.getAnnotations();
Map attributes = annotationMetadata.getAnnotationAttributes(Controller.class.getName());
List result = new ArrayList<>(Arrays.asList(annotations));
result.add(createGetMappingAnnotation(attributes));
return result.toArray(new Annotation[0]);
}
private Annotation createGetMappingAnnotation(Map attributes) {
return new GetMapping() {
@Override
public Class annotationType() {
return GetMapping.class;
}
@Override
public String[] value() {