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Pax Wicket Service is an OSGi extension of the Wicket framework, allowing for dynamic loading and unloading of Wicket components and pageSources.
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/**
 * Copyright OPS4J
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License. You may obtain
 * a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.ops4j.pax.wicket.internal;

import static java.lang.reflect.Proxy.isProxyClass;
import static java.lang.reflect.Proxy.newProxyInstance;
import static org.ops4j.lang.NullArgumentException.validateNotNull;

import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;

import javax.servlet.Servlet;
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.apache.wicket.protocol.http.WicketFilter;
import org.apache.wicket.protocol.http.WicketServlet;

/**
 * @author [email protected]
 */
public class ServletProxy {

    private static final Class[] SERVLET_INTERFACES = new Class[]{
        Servlet.class
    };

    static Servlet newServletProxy(PaxWicketApplicationFactory applicationFactory) {
        ServletInvocationHandler ih = new ServletInvocationHandler(applicationFactory);
        return newServletProxy(ih);
    }

    private static Servlet newServletProxy(ServletInvocationHandler ih) {
        ClassLoader classLoader = ServletProxy.class.getClassLoader();
        return (Servlet) newProxyInstance(classLoader, SERVLET_INTERFACES, ih);
    }

    private static class ServletInvocationHandler implements InvocationHandler {

        private static final Class[] REQUEST_INTERFACES = new Class[]{
            HttpServletRequest.class
        };

        private final ServletDelegator delegator;
        private final PaxWicketApplicationFactory internalFactory;

        public ServletInvocationHandler(PaxWicketApplicationFactory internalFactory) {
            this.internalFactory = internalFactory;
            delegator = new ServletDelegator(internalFactory);
            internalFactory.getFilterDelegator().setServlet(delegator);
        }

        public Object invoke(Object proxy, Method method, Object[] args)
            throws Throwable {
            replaceHttpRequestArgument(args);
            if (internalFactory.getFilterDelegator() != null) {
                if (method.getName().equals("service")) {
                    internalFactory.getFilterDelegator().doFilter((HttpServletRequest) args[0],
                        (HttpServletResponse) args[1]);
                    return null;
                }
            }
            return method.invoke(delegator, args);
        }

        private void replaceHttpRequestArgument(Object[] args) {
            if (args == null || args.length == 0) {
                return;
            }

            for (int i = 0; i < args.length; i++) {
                Object arg = args[i];
                if (arg == null) {
                    continue;
                }

                Class argumentClass = arg.getClass();
                if (HttpServletRequest.class.isAssignableFrom(argumentClass) &&
                        !isProxyClass(argumentClass)) {
                    HttpServletRequest request = (HttpServletRequest) arg;
                    // Replace the request
                    args[i] = newProxyRequest(request);
                }
            }
        }

        private HttpServletRequest newProxyRequest(HttpServletRequest request) {
            ClassLoader loader = ServletProxy.class.getClassLoader();
            ServletRequestInvocationHandler ih =
                new ServletRequestInvocationHandler(request, internalFactory.getMountPoint());
            return (HttpServletRequest) newProxyInstance(loader, REQUEST_INTERFACES, ih);
        }

        private static final class ServletDelegator extends WicketServlet {

            private static final long serialVersionUID = 1L;

            private static final String WICKET_REQUIRED_ATTRIBUTE = "javax.servlet.context.tempdir";

            private final PaxWicketApplicationFactory appFactory;

            ServletDelegator(PaxWicketApplicationFactory applicationFactory) throws IllegalArgumentException {
                appFactory = applicationFactory;
            }

            @Override
            protected WicketFilter newWicketFilter() {
                ServletContext servletContext = getServletContext();
                if (servletContext.getAttribute(WICKET_REQUIRED_ATTRIBUTE) == null) {
                    servletContext.setAttribute(WICKET_REQUIRED_ATTRIBUTE, appFactory.getTmpDir());
                }
                return new PaxWicketFilter(appFactory);
            }

            @Override
            public String getServletName() {
                return appFactory.getApplicationName();
            }

            @Override
            public String toString() {
                return "Pax Wicket Servlet";
            }
        }

        private static class ServletRequestInvocationHandler
                implements InvocationHandler {

            private final HttpServletRequest m_request;
            private final String m_mountPoint;

            private ServletRequestInvocationHandler(HttpServletRequest request, String mountPoint)
                throws IllegalArgumentException {
                validateNotNull(request, "request");
                validateNotNull(mountPoint, "mountPoint");

                m_request = request;

                if (mountPoint.length() <= 1) {
                    if (mountPoint.startsWith("/")) {
                        mountPoint = mountPoint.substring(1);
                    }
                } else {
                    if (!mountPoint.startsWith("/")) {
                        mountPoint = "/" + mountPoint;
                    }
                }
                m_mountPoint = mountPoint;
            }

            public Object invoke(Object proxy, Method method, Object[] arguments)
                throws Throwable {
                String methodName = method.getName();

                Object returnValue;
                if (m_mountPoint.length() == 0) {
                    if ("getContextPath".equals(methodName) ||
                            "getServletPath".equals(methodName)) {
                        returnValue = "";
                    } else if ("getPathInfo".equals(methodName)) {
                        returnValue = m_request.getServletPath();
                    } else {
                        returnValue = method.invoke(m_request, arguments);
                    }
                } else {
                    returnValue = method.invoke(m_request, arguments);
                }

                return returnValue;
            }
        }
    }

}