如何在java中创建一个动态代理来保留方法上的参数注释?
2022-09-04 23:36:13
我目前正在尝试代理一些现有的 JAX/RS 资源,以便允许我使用休眠验证程序的方法验证支持。但是,当我代理我的类(当前使用 cglib 2.2)时,代理类中的参数上不存在 FormParam 注释,因此 JAX/RS 运行时(apache wink)不会填充参数。下面是一些演示此内容的测试代码:
import static java.lang.annotation.ElementType.*;
import static java.lang.annotation.RetentionPolicy.*;
import java.lang.annotation.Annotation;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import net.sf.cglib.proxy.Enhancer;
import net.sf.cglib.proxy.MethodInterceptor;
import net.sf.cglib.proxy.MethodProxy;
import javassist.util.proxy.ProxyFactory;
public class ProxyTester {
@Target( { PARAMETER })
@Retention(RUNTIME)
public static @interface TestAnnotation {
}
public static interface IProxyMe {
void aMethod(@TestAnnotation int param);
}
public static class ProxyMe implements IProxyMe {
public void aMethod(@TestAnnotation int param) {
}
}
static void dumpAnnotations(String type, Object proxy, Object forObject,
String forMethod) {
String className = forObject.getClass().getName();
System.err.println(type + " proxy for Class: " + className);
for (Method method : proxy.getClass().getMethods()) {
if (method.getName().equals(forMethod)) {
final int paramCount = method.getParameterTypes().length;
System.err.println(" Method: " + method.getName() + " has "
+ paramCount + " parameters");
int i = 0;
for (Annotation[] paramAnnotations : method
.getParameterAnnotations()) {
System.err.println(" Param " + (i++) + " has "
+ paramAnnotations.length + " annotations");
for (Annotation annotation : paramAnnotations) {
System.err.println(" Annotation "
+ annotation.toString());
}
}
}
}
}
static Object javassistProxy(IProxyMe in) throws Exception {
ProxyFactory pf = new ProxyFactory();
pf.setSuperclass(in.getClass());
Class c = pf.createClass();
return c.newInstance();
}
static Object cglibProxy(IProxyMe in) throws Exception {
Object p2 = Enhancer.create(in.getClass(), in.getClass()
.getInterfaces(), new MethodInterceptor() {
public Object intercept(Object arg0, Method arg1, Object[] arg2,
MethodProxy arg3) throws Throwable {
return arg3.invokeSuper(arg0, arg2);
}
});
return p2;
}
static Object jdkProxy(final IProxyMe in) throws Exception {
return java.lang.reflect.Proxy.newProxyInstance(in.getClass()
.getClassLoader(), in.getClass().getInterfaces(),
new InvocationHandler() {
public Object invoke(Object proxy, Method method,
Object[] args) throws Throwable {
return method.invoke(in, args);
}
});
}
public static void main(String[] args) throws Exception {
IProxyMe proxyMe = new ProxyMe();
dumpAnnotations("no", proxyMe, proxyMe, "aMethod");
dumpAnnotations("javassist", javassistProxy(proxyMe), proxyMe,
"aMethod");
dumpAnnotations("cglib", cglibProxy(proxyMe), proxyMe, "aMethod");
dumpAnnotations("jdk", jdkProxy(proxyMe), proxyMe, "aMethod");
}
}
这给了我以下输出:
no proxy for Class: ProxyTester$ProxyMe Method: aMethod has 1 parameters Param 0 has 1 annotations Annotation @ProxyTester.TestAnnotation() javassist proxy for Class: ProxyTester$ProxyMe Method: aMethod has 1 parameters Param 0 has 0 annotations cglib proxy for Class: ProxyTester$ProxyMe Method: aMethod has 1 parameters Param 0 has 0 annotations jdk proxy for Class: ProxyTester$ProxyMe Method: aMethod has 1 parameters Param 0 has 0 annotations
还有其他选择吗?