Spring interceptor for conditional access to a request action

AccessCondition.java

package net.caoticode.spring.interceptors.conditional;

import javax.servlet.http.HttpServletRequest;
import org.springframework.context.ApplicationContext;

public interface AccessCondition {
	boolean test(HttpServletRequest request, ApplicationContext context);
}

ConditionalAccess.java

package net.caoticode.spring.interceptors.conditional;

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

import javax.servlet.http.HttpServletRequest;

import org.springframework.context.ApplicationContext;

@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
public @interface ConditionalAccess {
	Class<? extends AccessCondition> testClass() default DefaultAccessCondition.class;

	String testScript() default "";

	String action() default "";

	public static class DefaultAccessCondition implements AccessCondition {

		@Override
		public boolean test(HttpServletRequest request, ApplicationContext context) {
			return true;
		}

	}
}

ConditionalAccessInterceptor.java

package net.caoticode.spring.interceptors.conditional;

import java.io.IOException;

import javax.script.Bindings;
import javax.script.ScriptEngine;
import javax.script.ScriptEngineManager;
import javax.script.ScriptException;
import javax.script.SimpleBindings;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import com.regesta.opac.asc.interceptors.conditional.ConditionalAccess.DefaultAccessCondition;

public class ConditionalAccessInterceptor implements HandlerInterceptor, ApplicationContextAware {

    ApplicationContext applicationContext;
	ScriptEngineManager manager = new ScriptEngineManager();
	ScriptEngine engine = manager.getEngineByName("JavaScript");

	@Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
		this.applicationContext = applicationContext;
	}

    @Override
	public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex3) throws Exception {
	}

	@Override
	public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView model) throws Exception {
	}

	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
		if (handler instanceof HandlerMethod) {
			HandlerMethod handlerMethod = (HandlerMethod) handler;

			ConditionalAccess ca = getAnnotation(handlerMethod);
			if (ca != null) {
				boolean result = true;
				if (!ca.testScript().isEmpty()) {
					result = evalScript(ca.testScript(), request);
				}
				if (!ca.testClass().equals(DefaultAccessCondition.class)) {
					AccessCondition cond = ca.testClass().newInstance();
					result = result && cond.test(request, applicationContext);
				}

				if (!result) {
					invokeAction(ca.action(), request, response);
					return false;
				}
			}
		}

		return true;
	}

	private ConditionalAccess getAnnotation(HandlerMethod handler) {
		ConditionalAccess annotation = handler.getMethodAnnotation(ConditionalAccess.class);

		if (annotation == null) {
			Class<?> beanType = handler.getBeanType();
			annotation = beanType.getAnnotation(ConditionalAccess.class);
		}

		return annotation;
	}

	private boolean evalScript(String script, HttpServletRequest request) throws ScriptException {
		Bindings bindings = new SimpleBindings();
		bindings.put("request", request);
		bindings.put("session", request.getSession());
		bindings.put("context", applicationContext);

		return ((Boolean) engine.eval(script, bindings)).booleanValue();
	}

	private void invokeAction(String action, HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
		String actionType = action.substring(0, action.indexOf(':'));
		String url = action.substring(actionType.length() + 1);

		if (actionType.equals("redirect")) {
			response.sendRedirect(request.getContextPath() + url);
		} else if (actionType.equals("forward")) {
			request.getRequestDispatcher(request.getContextPath() + url).forward(request, response);
		}
	}
}

gistfile1.xml

<!-- add ConditionalAccessInterceptor to the Spring configuration -->
<interceptors>
    <beans:bean class="net.caoticode.spring.interceptors.conditional.ConditionalAccessInterceptor" />
</interceptors>