org.directwebremoting.Browser Maven / Gradle / Ivy
package org.directwebremoting;
import java.util.ArrayList;
import java.util.Collection;
import org.directwebremoting.extend.AllScriptSessionFilter;
import org.directwebremoting.extend.AndScriptSessionFilter;
import org.directwebremoting.extend.IdScriptSessionFilter;
import org.directwebremoting.extend.PageScriptSessionFilter;
import org.directwebremoting.extend.TaskDispatcher;
import org.directwebremoting.extend.TaskDispatcherFactory;
import org.directwebremoting.io.JavascriptObject;
/**
* A collection of APIs that manage reverse ajax APIs.
* See {@link #withAllSessions} for a menu of the various different with*
* methods.
*
The {@link Runnable}s that are passed to the with* methods may be executed
* any number of times between 0 (nothing passes the filter) 1 (where
* {@link Browser#getTargetSessions()} returns all the matching ScriptSessions)
* and X (where X is the number of matching ScriptSessions, with
* {@link Browser#getTargetSessions()} returning one of the ScriptSessions on
* each invocation).
* @author Joe Walker [joe at getahead dot ltd dot uk]
*/
public class Browser
{
/**
* Execute some task (represented by a {@link Runnable}) and aim the output
* at all browser window open at all pages in this web application.
* It is likely that a more fine-grained broadcast method will be applicable
* to most situations. The other with* methods in this class provide extra
* ways to filter the set of pages to broadcast to. This option could be
* useful if all pages contain an 'update' area, or to broadcast status
* information: Window.alert("System reboot in 20mins. Please log off");
* To send UI code to browser windows looking at a specific page, see the
* {@link #withPage} method. To send to a custom set of browser windows,
* see the {@link #withAllSessionsFiltered} method. To send to a specific
* session, use {@link #withSession}.
* @param task A code block to execute
*/
public static void withAllSessions(Runnable task)
{
withAllSessions(getServerContext(), task);
}
/**
* As {@link #withAllSessions(Runnable)}, but for use when there is more
* than one copy of DWR in the ServletContext.
*
* For 99% of cases the former method will be much simpler to use.
* @param serverContext The specific DWR context in which to execute
* @param task ...
*/
public static void withAllSessions(ServerContext serverContext, Runnable task)
{
currentServerContext.set(serverContext);
try {
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(serverContext);
taskDispatcher.dispatchTask(new AllScriptSessionFilter(), task);
} finally {
currentServerContext.remove();
}
}
/**
* Execute a task an send the output to a subset of the total list of users.
* The {@link ScriptSessionFilter} defines which subset.
* This method could be used to alert administrators wherever they are on a
* site about urgent action that need attention.
* @param filter Used to define the set of browser windows which should
* receive the update.
* @param task A code block to execute
*/
public static void withAllSessionsFiltered(ScriptSessionFilter filter, Runnable task)
{
withAllSessionsFiltered(getServerContext(), filter, task);
}
/**
* As {@link #withAllSessionsFiltered(ScriptSessionFilter, Runnable)}, but
* for use when there is more than one copy of DWR in the ServletContext.
*
* For 99% of cases the former method will be much simpler to use.
* @param serverContext The specific DWR context in which to execute
* @param filter ...
* @param task ...
*/
public static void withAllSessionsFiltered(ServerContext serverContext, ScriptSessionFilter filter, Runnable task)
{
currentServerContext.set(serverContext);
try {
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(serverContext);
taskDispatcher.dispatchTask(filter, task);
} finally {
currentServerContext.remove();
}
}
/**
* Execute a task and aim the output at all the browser windows open at the
* same page as the current request. No further filtering is performed.
* This implies that this method is only of use from a DWR created thread.
* To send to a subset of the browser windows viewing a page, see the
* {@link #withCurrentPageFiltered} method.
* @param task A code block to execute
*/
public static void withCurrentPage(Runnable task)
{
WebContext webContext = WebContextFactory.get();
currentServerContext.set(webContext);
try {
String page = webContext.getCurrentPage();
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(webContext);
taskDispatcher.dispatchTask(new PageScriptSessionFilter(webContext, page), task);
} finally {
currentServerContext.remove();
}
}
/**
* Execute a task and aim the output at all the browser windows open at a
* given page in this web application. No further filtering is performed.
* To send to a subset of the browser windows viewing a page, see the
* {@link #withPageFiltered} method.
* @param page The page to send to, excluding protocol/host/port specifiers
* but including context path and servlet path. For example to send to
* http://example.com:8080/webapp/controller/path/index.html,
* you should use "/webapp/controller/path/index.html" or since the default
* PageNormalizer understands default pages, this is the same as sending to
* browsers viewing "/webapp/controller/path/".
* To discover the contextPath at runtime you can use
* javax.servlet.ServletContext#getContextPath with servlet 2.5, or before
* version 2.5 you can also use {@link ServerContext#getContextPath} or
* {@link javax.servlet.http.HttpServletRequest#getContextPath}.
* @param task A code block to execute
*/
public static void withPage(String page, Runnable task)
{
withPage(getServerContext(), page, task);
}
/**
* As {@link #withPage(String, Runnable)}, but for use when there is more
* than one copy of DWR in the ServletContext.
*
* For 99% of cases the former method will be much simpler to use.
* @param serverContext The specific DWR context in which to execute
* @param page ...
* @param task ...
*/
public static void withPage(ServerContext serverContext, String page, Runnable task)
{
currentServerContext.set(serverContext);
try {
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(serverContext);
taskDispatcher.dispatchTask(new PageScriptSessionFilter(serverContext, page), task);
} finally {
currentServerContext.remove();
}
}
/**
* Execute a task and aim the output at a subset of the browser windows open
* at the same page as the current request. The filter allows you to select
* the set of users that will be interested in the update.
* This implies that this method is only of use from a DWR created thread.
* @param filter Used to define the set of browser windows which should
* receive the update.
* @param task A code block to execute
*/
public static void withCurrentPageFiltered(ScriptSessionFilter filter, Runnable task)
{
WebContext webContext = WebContextFactory.get();
String page = webContext.getCurrentPage();
ScriptSessionFilter pageFilter = new PageScriptSessionFilter(webContext, page);
ScriptSessionFilter realFilter = new AndScriptSessionFilter(pageFilter, filter);
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(webContext);
taskDispatcher.dispatchTask(realFilter, task);
}
/**
* Execute a task and aim the output at a subset of the users on a page.
* This method is useful when you have a small number of pages that each
* have a significant number of functions on them. The filter allows you to
* select the set of users that will be interested in the update.
* @param page The page to send to. See {@link #withPage} for details
* @param filter Used to define the set of browser windows which should
* receive the update.
* @param task A code block to execute
*/
public static void withPageFiltered(String page, ScriptSessionFilter filter, Runnable task)
{
withPageFiltered(getServerContext(), page, filter, task);
}
/**
* As {@link #withPageFiltered}, but for use when there is more than one copy of DWR
* in a ServletContext.
*
* For 99% of cases the former method will be much simpler to use.
* @param serverContext The specific DWR context in which to execute
* @param page ...
* @param filter ...
* @param task ...
*/
public static void withPageFiltered(ServerContext serverContext, String page, ScriptSessionFilter filter, Runnable task)
{
currentServerContext.set(serverContext);
try {
ScriptSessionFilter pageFilter = new PageScriptSessionFilter(serverContext, page);
ScriptSessionFilter realFilter = new AndScriptSessionFilter(pageFilter, filter);
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(serverContext);
taskDispatcher.dispatchTask(realFilter, task);
} finally {
currentServerContext.remove();
}
}
/**
* Execute a task and aim the output at a specific script session. This
* method is likely to be useful for directed updates that originate away
* from a thread started by the browser window in question. Examples include
* an instant message, or the results of a slow method invocation.
* This method is implicit in anything called from a DWR thread, so should
* not need to be used to send UI updates back to an originating browser.
* @param sessionId The {@link ScriptSession}.id of the browser window
* @param task A code block to execute
*/
public static void withSession(String sessionId, Runnable task)
{
withSession(getServerContext(), sessionId, task);
}
/**
* As {@link #withSession(String, Runnable)}, but for use when there is more
* than one copy of DWR in a ServletContext.
*
* For 99% of cases the former method will be much simpler to use.
* @param serverContext The specific DWR context in which to execute
* @param sessionId ...
* @param task ...
*/
public static void withSession(ServerContext serverContext, String sessionId, Runnable task)
{
currentServerContext.set(serverContext);
try {
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(serverContext);
taskDispatcher.dispatchTask(new IdScriptSessionFilter(sessionId), task);
} finally {
currentServerContext.remove();
}
}
/**
* If a browser passes an object or function to DWR then DWR may need to
* release the reference that DWR keeps. If the server-side manifestation of
* this object is a proxy implemented interface, then there is no place for
* a close method, so this function allows you to close proxy implemented
* interfaces.
* @param proxy An proxy created interface implementation from a browser
* that we no longer need.
*/
public static void close(Object proxy)
{
if (proxy instanceof JavascriptObject)
{
JavascriptObject dproxy = (JavascriptObject) proxy;
dproxy.close();
}
}
/**
* This method discovers the sessions that are currently being targeted
* by browser updates.
*
* It will generally only be useful to authors of reverse ajax UI proxy
* APIs. Using it directly may cause scaling problems
* @return The list of current browser windows.
*/
public static Collection getTargetSessions()
{
TaskDispatcher taskDispatcher = TaskDispatcherFactory.get(getServerContext());
Collection sessions = taskDispatcher.getTargetSessions();
if (sessions != null)
{
return sessions;
}
WebContext webContext = WebContextFactory.get();
if (webContext != null)
{
sessions = new ArrayList();
sessions.add(webContext.getScriptSession());
return sessions;
}
throw new IllegalStateException("No current UI to manipulate. See org.directwebremoting.Browser to set one.");
}
private static ServerContext getServerContext()
{
ServerContext servCtx = currentServerContext.get();
if (servCtx != null)
{
return servCtx;
}
else
{
return ServerContextFactory.get();
}
}
/**
* ThreadLocal in which the current ServerContext is stored.
*/
private static final ThreadLocal currentServerContext = new ThreadLocal();
}