package org.nanocontainer.nanowar.nanoweb;
import ognl.Ognl;
import ognl.OgnlException;
import org.nanocontainer.nanowar.ApplicationScopeObjectReference;
import org.nanocontainer.nanowar.KeyConstants;
import org.nanocontainer.nanowar.RequestScopeObjectReference;
import org.nanocontainer.nanowar.ServletRequestContainerLauncher;
import org.picocontainer.MutablePicoContainer;
import org.picocontainer.defaults.ObjectReference;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.net.URL;
import java.util.Enumeration;
/**
* Dispatcher servlet for NanoWeb.
* NanoWeb is an ultra simple MVC framework inspired from WebWork It is based on ScriptedContainerBuilderFactory,
* PicoContainer, Ognl, Groovy and Velocity.
* Design goals:
* <ul>
* <li>One-file configuration (all in an embedded ScriptedContainerBuilderFactory script in web.xml)</li>
* <li>Sensible defaults with the goal to reduce the need for complex configuration</li>
* <li>Non intrusiveness. Actions are PicoComponents/POJOs that extend nothing</li>
* <li>Actions can be written in a compilable scripting language like Groovy</li>
* <li>Actions must implement a String execute() method</li>
* <li>The result from execute will be used to determine the view path. Example: /something.nano + "success" -> /something_success.vm</li>
* </ul>
* Other things:
* <ul>
* <li>Map action paths to action classes in nanocontainer servlet script (using groovy)</li>
* <li>Views can set values in actions with Ognl expressions</li>
* </ul>
*
* @author Aslak Hellesøy
* @author Kouhei Mori
* @version $Revision: 2528 $
*/
public class NanoWebServlet extends HttpServlet implements KeyConstants {
private Dispatcher dispatcher;
// TODO make this configurable from web.xml
private final CachingScriptClassLoader cachingScriptClassLoader = new CachingScriptClassLoader();
public void init() throws ServletException {
ServletContext servletContext = getServletContext();
MutablePicoContainer applicationContainer = getApplicationContainer(servletContext);
initDispatcher(applicationContainer);
}
private void initDispatcher(MutablePicoContainer applicationContainer) {
dispatcher = (Dispatcher) applicationContainer.getComponentInstanceOfType(Dispatcher.class);
if (dispatcher == null) {
dispatcher = new ChainingDispatcher(".vm");
}
}
protected void service(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws ServletException, IOException {
ServletRequestContainerLauncher containerLauncher = new ServletRequestContainerLauncher(getServletContext(), httpServletRequest);
try {
containerLauncher.startContainer();
String servletPath = getServletPath(httpServletRequest);
String scriptPathWithoutExtension = servletPath.substring(0, servletPath.lastIndexOf('/'));
Object action = getActionObject(scriptPathWithoutExtension, httpServletRequest);
setPropertiesWithOgnl(httpServletRequest, action);
int dot = servletPath.lastIndexOf('.');
String actionMethod = servletPath.substring(servletPath.lastIndexOf('/') + 1, dot);
String result = execute(action, actionMethod);
httpServletRequest.setAttribute("action", action);
ServletContext servletContext = getServletContext();
dispatcher.dispatch(servletContext, httpServletRequest, httpServletResponse, scriptPathWithoutExtension, actionMethod, result);
} catch (ScriptException e) {
handleServiceScriptException(e, httpServletResponse, httpServletRequest);
} finally {
containerLauncher.killContainer();
}
}
/**
* This overridable method contains the default behavior for the catching of ScriptException during the
* service call. Because different containers suck at handling exceptions, this default behavior displays
* a simple page. Teams deploying NanoWebServlet may want to extend and replace this functionality. This
* servlet may be participating with some larger model-2 design.
*
* @param e the script exception
* @param httpServletResponse the servlet response
* @param httpServletRequest the servlet request
* @throws IOException if for some bizarre reason the outgoing page cannot be written to.
*/
protected void handleServiceScriptException(ScriptException e, HttpServletResponse httpServletResponse, HttpServletRequest httpServletRequest) throws IOException {
e.printStackTrace();
// Print the stack trace and the script (for debugging)
PrintWriter writer = httpServletResponse.getWriter();
writer.println("<html>");
writer.println("<pre>");
e.printStackTrace(writer);
writer.println(httpServletRequest.getRequestURI());
URL scriptURL = e.getScriptURL();
InputStream in = scriptURL.openStream();
int c;
while ((c = in.read()) != -1) {
writer.write(c);
}
writer.println("</pre>");
writer.println("</html>");
}
private Object getActionObject(String path, HttpServletRequest request) throws ServletException, ScriptException {
MutablePicoContainer requestContainer = getRequestContainer(request);
// Try to get an action as specified in the configuration
Object action = requestContainer.getComponentInstance(path);
if (action == null) {
// Try to get an action from a script (groovy)
try {
action = getScriptAction(path + ".groovy", requestContainer);
} catch (IOException e) {
log("Failed to load action class", e);
throw new ServletException(e);
}
}
if (action == null) {
String msg = "No action found for '" + path + "'";
throw new ServletException(msg);
}
return action;
}
private Object getScriptAction(String scriptPath, MutablePicoContainer requestContainer) throws IOException, ScriptException {
URL scriptURL = getServletContext().getResource(scriptPath);
Object result = null;
if (scriptURL != null) {
Class scriptClass = cachingScriptClassLoader.getClass(scriptURL);
requestContainer.registerComponentImplementation(scriptPath, scriptClass);
result = requestContainer.getComponentInstance(scriptPath);
}
return result;
}
private void setPropertiesWithOgnl(HttpServletRequest servletRequest, Object action) throws ServletException {
Enumeration parameterNames = servletRequest.getParameterNames();
while (parameterNames.hasMoreElements()) {
String parameterName = (String) parameterNames.nextElement();
String parameterValue = servletRequest.getParameter(parameterName);
try {
Ognl.setValue(parameterName, action, parameterValue);
} catch (OgnlException e) {
log("Failed to set property with OGNL ('" + parameterName +"', '" + action + "', '" + parameterValue + "')", e);
throw new ServletException(e);
}
}
}
private String execute(Object actionObject, String actionMethodName) throws ServletException {
Method actionMethod = null;
try {
actionMethod = actionObject.getClass().getMethod(actionMethodName, (Class[])null);
} catch (NoSuchMethodException e) {
String message = "The " + actionObject.getClass().getName() + " doesn't have the method " + actionMethodName + "()";
log(message, e);
throw new ServletException(message, e);
}
try {
String view = (String) actionMethod.invoke(actionObject, (Object[])null);
return view;
} catch (IllegalAccessException e) {
String message = actionObject.getClass().getName() + "." + actionMethodName + "() isn't public";
log(message, e);
throw new ServletException(message, e);
} catch (InvocationTargetException e) {
String message = "Failed to actionMethod " + actionObject.getClass().getName() + "." + actionMethodName + "()";
log(message, e);
throw new ServletException(message, e);
}
}
static String getServletPath(HttpServletRequest httpServletRequest) {
String servletPath = (String) httpServletRequest.getAttribute("javax.servlet.include.servlet_path");
if (servletPath == null) {
servletPath = httpServletRequest.getServletPath();
}
return servletPath;
}
private MutablePicoContainer getApplicationContainer(ServletContext context) {
ObjectReference ref = new ApplicationScopeObjectReference(context, APPLICATION_CONTAINER);
return (MutablePicoContainer) ref.get();
}
private MutablePicoContainer getRequestContainer(ServletRequest request) {
ObjectReference ref = new RequestScopeObjectReference(request, REQUEST_CONTAINER);
return (MutablePicoContainer) ref.get();
}
}