net.sourceforge.stripes.controller.NameBasedActionResolver Maven / Gradle / Ivy
/* Copyright 2005-2006 Tim Fennell
*
* 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 net.sourceforge.stripes.controller;
import net.sourceforge.stripes.action.ActionBean;
import net.sourceforge.stripes.action.ActionBeanContext;
import net.sourceforge.stripes.action.Resolution;
import net.sourceforge.stripes.action.ForwardResolution;
import net.sourceforge.stripes.config.Configuration;
import net.sourceforge.stripes.exception.StripesServletException;
import net.sourceforge.stripes.util.Literal;
import net.sourceforge.stripes.util.Log;
import javax.servlet.ServletContext;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.net.MalformedURLException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Set;
/**
* An ActionResolver that uses the names of classes and methods to generate sensible default
* URL bindings and event names respectively. Extends the default
* {@link AnnotatedClassActionResolver}, and is fully backward compatible. Any classes and
* methods that are annotated with {@link net.sourceforge.stripes.action.UrlBinding} and
* {@link net.sourceforge.stripes.action.HandlesEvent} will retain the bindings specified in
* those annotations. In the case when an annotation is absent then a default binding is
* generated.
*
* The generation of ActionBean URL bindings is done by taking the class name and removing
* any extraneous packages at the front of the name, removing the strings "Action" and "Bean"
* from the end of the name, substituting slashes for periods and appending a suffix (.action by
* default). The set of packages that are trimmed is specified by the
* {@code getBasePackages()} method. By default this method returns the set
* [web, www, stripes, action]. These packages (and their parents) are removed from the
* class name. E.g. {@code com.myco.web.foo.BarActionBean} would become {@code foo.BarActionBean}.
* Continuing on, the list of Action Bean suffixes, specified by the {@code getActionBeanSuffixes()}
* method, are trimmed from the end of the Action Bean class name. With the defaults,
* [Bean, Action], we would trim {@code foo.BarActionBean} further to {@code foo.Bar}, and then
* translate it to {@code /foo/Bar}. Lastly the suffix returned by {@code getBindingSuffix()}
* is appended, giving the binding {@code /foo/Bar.action}.
*
* The translation of class names into URL bindings is designed to be easy to override and
* customize. To that end you can easily change how this translation is done by overriding
* {@code getBasePackages()} and/or {@code getBindingSuffix()}, or completely customize the
* behaviour by overriding {@code getUrlBinding(String)}.
*
* Mapping of method names to event names is simpler. Again the parent class is delegated to
* in case the method is annotated. If it is not, and the method is a concrete public method that
* returns a Resolution (or subclass thereof) it is mapped to an event of the same name as the
* method. So an un-annotated method "{@code public Resolution view()}" is mapped to an event
* called "view". It should be noted that there is no special method name that signifies the
* default handler. If there is more than one handler and you require a default handler you
* must still mark the default method with {@code @DefaultHandler}.
*
* Another useful feature of the NameBasedActionResolver is that when a request arrives for a
* URL that is not bound to an ActionBean the resolver will attempt to map the request to a view
* and return a 'dummy' ActionBean that will take the user to the view. The exact behaviour is
* modifiable by overriding one or more of
* {@link #handleActionBeanNotFound(ActionBeanContext, String)}, {@link #findView(String)} or
* {@link #getFindViewAttempts(String)}. The default behaviour is to map the URL being requested
* to three potential JSP names/paths, check for the existence of a JSP at those locations and if
* one exists then to return an ActionBean that will render the view. For example if a user
* requested '/account/ViewAccount.action' but an ActionBean does not yet exist bound to that URL,
* the resolver will check for JSPs in the following order:
*
*
* - /account/ViewAccount.jsp
* - /account/viewAccount.jsp
* - /account/view_account.jsp
*
*
* The value of this approach comes from the fact that by default all pages can appear to have
* a pre-action whether they actually have one or not. In the above can you might chose to link
* to {@code /account/ViewAccount.action} even though you know that no action exists and you want
* to navigate directly to a page. This way, if you later decide you do need a pre-action for any
* reason you can simply code the ActionBean and be done. No URLs or links need to be modified
* and all requests to {@code /account/ViewAccount.action} will flow through the ActionBean.
*
* @author Tim Fennell
* @since Stripes 1.2
*/
public class NameBasedActionResolver extends AnnotatedClassActionResolver {
/**
* Default set of packages (web, www, stripes, action) to be removed from the front
* of class names when translating them to URL bindings.
*/
public static final Set BASE_PACKAGES =
Collections.unmodifiableSet(Literal.set("web", "www", "stripes", "action"));
/** Default suffix (.action) to add to URL bindings.*/
public static final String DEFAULT_BINDING_SUFFIX = ".action";
/**
* Default list of suffixes (Bean, Action) to remove to the end of the Action Bean class name.
*/
public static final List DEFAULT_ACTION_BEAN_SUFFIXES =
Collections.unmodifiableList(Literal.list("Bean", "Action"));
/** Log instance used to log information from this class. */
private static final Log log = Log.getInstance(NameBasedActionResolver.class);
/**
* First invokes the parent classes init() method and then quietly adds a specialized
* ActionBean to the set of ActionBeans the resolver is managing. The "specialized" bean
* is one that is used when a bean is not bound to a URL, to then forward the user to
* an appropriate view if one exists.
*/
@Override
public void init(Configuration configuration) throws Exception {
super.init(configuration);
addActionBean(DefaultViewActionBean.class);
}
/**
* Finds or generates the URL binding for the class supplied. First delegates to the parent
* class to see if an annotated url binding is present. If not, the class name is taken
* and translated into a URL binding using {@code getUrlBinding(String name)}.
*
* @param clazz a Class representing an ActionBean
* @return the String URL binding for the ActionBean
*/
@Override
public String getUrlBinding(Class clazz) {
String binding = super.getUrlBinding(clazz);
// If there's no annotated binding, and the class is concrete
if (binding == null && !Modifier.isAbstract(clazz.getModifiers())) {
binding = getUrlBinding(clazz.getName());
}
return binding;
}
/**
* Takes a class name and translates it into a URL binding by removing extraneous package names,
* removing Action, Bean, or ActionBean from the end of the class name if present, replacing
* periods with slashes, and appending a standard suffix as supplied by
* {@link net.sourceforge.stripes.controller.NameBasedActionResolver#getBindingSuffix()}.
*
* For example the class {@code com.myco.web.action.user.RegisterActionBean} would be
* translated to {@code /user/Register.action}. The behaviour of this method can be
* overridden either directly or by overriding the methods {@code getBindingSuffix()} and
* {@code getBasePackages()} which are used by this method.
*
* @param name the name of the class to create a binding for
* @return a String URL binding for the class
*
*/
protected String getUrlBinding(String name) {
// Chop off the packages up until (and including) any base package
for (String base : getBasePackages()) {
int i = name.indexOf("." + base + ".");
if (i != -1) {
name = name.substring(i + base.length() + 1);
}
else if (name.startsWith(base + ".")) {
name = name.substring(base.length());
}
}
// If it ends in any of the Action Bean suffixes, remove them
for (String suffix : getActionBeanSuffixes()) {
if (name.endsWith(suffix)) {
name = name.substring(0, name.length() - suffix.length());
}
}
// Replace periods with slashes and make sure it starts with one
name = name.replace('.', '/');
if (!name.startsWith("/")) {
name = "/" + name;
}
// Lastly add the suffix
name += getBindingSuffix();
return name;
}
/**
* Returns a set of package names (fully qualified or not) that should be removed
* from the start of a classname before translating the name into a URL Binding. By default
* returns "web", "www", "stripes" and "action".
*
* @return a non-null set of String package names.
*/
protected Set getBasePackages() {
return BASE_PACKAGES;
}
/**
* Returns a non-null String suffix to be used when constructing URL bindings. The
* default is ".action".
*/
protected String getBindingSuffix() {
return DEFAULT_BINDING_SUFFIX;
}
/**
* Returns a list of suffixes to be removed from the end of the Action Bean class name, if present.
* The defaults are ["Bean", "Action"].
*
* @since Stripes 1.5
*/
protected List getActionBeanSuffixes() {
return DEFAULT_ACTION_BEAN_SUFFIXES;
}
/**
* First checks with the super class to see if an annotated event name is present, and if
* not then returns the name of the handler method itself. Will return null for methods
* that do not return a resolution or are non-public or abstract.
*
* @param handler a method which may or may not be a handler method
* @return the name of the event handled, or null
*/
@Override
public String getHandledEvent(Method handler) {
String name = super.getHandledEvent(handler);
// If the method isn't annotated, but does return a resolution and is
// not abstract (we already know it's public) then use the method name
if ( name == null
&& !Modifier.isAbstract(handler.getModifiers())
&& Resolution.class.isAssignableFrom(handler.getReturnType())
&& handler.getParameterTypes().length == 0) {
name = handler.getName();
}
return name;
}
/**
* Overridden to trap the exception that is thrown when a URL cannot be mapped to an
* ActionBean and then attempt to construct a dummy ActionBean that will forward the
* user to an appropriate view. In an exception is caught then the method
* {@link #handleActionBeanNotFound(ActionBeanContext, String)} is invoked to handle
* the exception.
*
* @param context the ActionBeanContext of the current request
* @param urlBinding the urlBinding determined for the current request
* @return an ActionBean if there is an appropriate way to handle the request
* @throws StripesServletException if no ActionBean or alternate strategy can be found
*/
@Override
public ActionBean getActionBean(ActionBeanContext context,
String urlBinding) throws StripesServletException {
try {
return super.getActionBean(context, urlBinding);
}
catch (StripesServletException sse) {
ActionBean bean = handleActionBeanNotFound(context, urlBinding);
if (bean != null) {
setActionBeanContext(bean, context);
assertGetContextWorks(bean);
return bean;
}
else {
throw sse;
}
}
}
/**
* Invoked when no appropriate ActionBean can be located. Attempts to locate a view that is
* appropriate for this request by calling {@link #findView(String)}. If a view is found
* then a dummy ActionBean is constructed that will send the user to the view. If no appropriate
* view is found then null is returned.
*
* @param context the ActionBeanContext of the current request
* @param urlBinding the urlBinding determined for the current request
* @return an ActionBean that will render a view for the user, or null
* @since Stripes 1.3
*/
protected ActionBean handleActionBeanNotFound(ActionBeanContext context, String urlBinding) {
ActionBean bean = null;
Resolution view = findView(urlBinding);
if (view != null) {
log.debug("Could not find an ActionBean bound to '", urlBinding, "', but found a view ",
"at '", view, "'. Forwarding the user there instead.");
bean = new DefaultViewActionBean(view);
}
return bean;
}
/**
* Attempts to locate a default view for the urlBinding provided and return a
* ForwardResolution that will take the user to the view. Looks for views by using the
* list of attempts returned by {@link #getFindViewAttempts(String)}.
*
*
For each view name derived a check is performed using
* {@link ServletContext#getResource(String)} to see if there is a file located at that URL.
* Only if a file actually exists will a Resolution be returned.
*
* Can be overridden to provide a different kind of resolution. It is strongly recommended
* when overriding this method to check for the actual existence of views prior to manufacturing
* a resolution in order not to cause confusion when URLs are mistyped.
*
* @param urlBinding the url being accessed by the client in the current request
* @return a Resolution if a default view can be found, or null otherwise
* @since Stripes 1.3
*/
protected Resolution findView(String urlBinding) {
List attempts = getFindViewAttempts(urlBinding);
ServletContext ctx = StripesFilter.getConfiguration()
.getBootstrapPropertyResolver().getFilterConfig().getServletContext();
for (String jsp : attempts) {
try {
// This will try /account/ViewAccount.jsp
if (ctx.getResource(jsp) != null) {
return new ForwardResolution(jsp);
}
}
catch (MalformedURLException mue) {
}
}
return null;
}
/**
* Returns the list of attempts to locate a default view for the urlBinding provided.
* Generates attempts for views by converting the incoming urlBinding with the following rules.
* For example if the urlBinding is '/account/ViewAccount.action' the following views will be
* returned in order:
*
*
* - /account/ViewAccount.jsp
* - /account/viewAccount.jsp
* - /account/view_account.jsp
*
*
* Can be overridden to look for views with a different pattern.
*
* @param urlBinding the url being accessed by the client in the current request
* @since Stripes 1.5
*/
protected List getFindViewAttempts(String urlBinding) {
List attempts = new ArrayList(3);
int lastPeriod = urlBinding.lastIndexOf('.');
String path = urlBinding.substring(0, urlBinding.lastIndexOf("/") + 1);
String name = (lastPeriod >= path.length()) ? urlBinding.substring(path.length(), lastPeriod)
: urlBinding.substring(path.length());
if (name.length() > 0) {
// This will try /account/ViewAccount.jsp
attempts.add(path + name + ".jsp");
// This will try /account/viewAccount.jsp
name = Character.toLowerCase(name.charAt(0)) + name.substring(1);
attempts.add(path + name + ".jsp");
// And finally this will try /account/view_account.jsp
StringBuilder builder = new StringBuilder();
for (int i = 0; i < name.length(); ++i) {
char ch = name.charAt(i);
if (Character.isUpperCase(ch)) {
builder.append("_");
builder.append(Character.toLowerCase(ch));
}
else {
builder.append(ch);
}
}
attempts.add(path + builder.toString() + ".jsp");
}
return attempts;
}
}