Servlets 3.0 - Asynchronous, Extensibility, Ease-of-use @ JavaOne Brazil 2010

1. <Insert Picture Here>
Servlets 3.0
Asynchronous, Extensiblity, Ease-of-use
Arun Gupta, Java EE & GlassFish Guy
blogs.sun.com/arungupta, @arungupta

2. Beijing 2010
December 13–16, 2010
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3. The following is intended to outline our general
product direction. It is intended for information
purposes only, and may not be incorporated into any
contract. It is not a commitment to deliver any
material, code, or functionality, and should not be
relied upon in making purchasing decisions.
The development, release, and timing of any
features or functionality described for Oracle’s
products remains at the sole discretion of Oracle.
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4. Agenda
• Overview
• Ease of Development
• Dynamic Registration of Servlets and
Filters
• Pluggability
• Asynchronous Support
• Security Enhancements
• Miscellaneous
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5. Overview
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Java Servlet 3.0 done as part of JSR 315
– Final release done in December 2009.
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~20 members in the expert group
– Major Java EE vendors, open source web container
developers, framework authors
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Main areas of focus
– Ease of Development
– Pluggability
– Asynchronous support
– Security
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6. Ease of Development
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Enhanced APIs to use new Java SE
language features introduced since J2SE 5.0
– Generics for type safety in API where possible
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Annotations for declarative style of
programming
– web.xml optional
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Convention over configuration
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7. Ease of Development
Use of annotations
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Annotations to declare Servlets, Filters,
Listeners and servlet security
– @WebServlet – Define a Servlet
– @WebFilter – Define a Filter
– @WebListener – Define a Listener
– @WebInitParam – Define init param
– @MultipartConfig – Define file upload properties
– @ServletSecurity – Define security constraints
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Can override using “web.xml”
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8. Servlet 2.5 example
At least 2 files
<!--Deployment descriptor web.xml /* Code in Java Class */
-->
<web-app> package com.sun;
<servlet> public class MyServlet extends
<servlet-name>MyServlet HttpServlet
</servlet-name> {
<servlet-class> public void
com.sun.MyServlet doGet(HttpServletRequest
</servlet-class> req,HttpServletResponse res)
</servlet> {
<servlet-mapping> ...
<servlet-name>MyServlet
</servlet-name> }
<url-pattern>/myApp/* ...
</url-pattern> }
</servlet-mapping>
...
</web-app>
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9. @WebServlet – Sample Code
@WebServlet(urlPatterns={“/myApp”})
public class SimpleSample extends HttpServlet
{
public void doGet(HttpServletRequest
req,HttpServletResponse res)
{
}
}
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10. @WebServlet Async – Sample Code
@WebServlet(urlPatterns=“/myApp”,
name=”MyServlet”, asyncSupported=true)
public class SimpleSample extends HttpServlet
{
public void doGet(HttpServletRequest
req,HttpServletResponse res)
{
}
}
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11. Dynamic Registration
Create and/or register
• ServletContext#add[Servlet | Filter]
• Overloaded versions take [Servlet | Filter] name and
– Fully qualified [Servlet | Filter] class name or
– Class <? extends [Servlet | Filter]> or
– [Servlet | Filter] instance
• User returned Registration handle to configure all aspects of
[Servlet | Filter]
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ServletContext#create[Servlet | Filter]
– Takes Class<? Extends [Servlet | Filter]> argument
– Supports resource injection by container
– Returned [Servlet | Filter] instance may be fully customized before it
is registered
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12. Dynamic Registration
Lookup
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ServletContext#find[Servlet |
Filter]Registration
– Takes [Servlet | Filter] name as argument
– Returned Registration handle provides subset of configuration
methods
– May only be used to add initialization parameters and mappings
– Conflict returned as java.util.Set
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13. Dynamic Registration
Register example
ServletRegistration.Dynamic dynamic =
servletContext.addServlet(
"DynamicServlet",
"com.mycom.MyServlet");
dynamic.addMapping("/dynamicServlet");
dynamic.setAsyncSupported(true);
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14. Dynamic Registration
Lookup example
ServletRegistration declared =
servletContext.getServletRegistration("Declare
dServlet");
declared.addMapping("/declaredServlet");
declared.setInitParameter("param", "value");
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15. Pluggability
• Plugin libraries using web fragments
– Modular web.xml
– Absolute ordering: <absolute-ordering>
– Relative ordering: <ordering>, <before>, <after>
• Bundled in framework *.jar/META-INF
• Zero-configuration, drag-and-drop for web
frameworks
– Servlets, servlet filters, context listeners for a framework
get discovered and registered by the container
• Only JAR files in WEB-INF/lib are used
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16. Pluggability – Sample Code
<web-fragment>
<filter>
<filter-name>wicket.helloworld</filter-name>
<filter-class>org.apache.wicket.protocol.http.WicketFilter</filter-class>
<init-param>
<param-name>applicationClassName</param-name>
<param-value>...</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>wicket.helloworld</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-fragment>
http://blogs.sun.com/arungupta/entry/totd_91_applying_java_ee
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17. Pluggability – Sample Code
<web-fragment>
<filter>
<filter-name>LiftFilter</filter-name>
<display-name>Lift Filter</display-name>
<description>The Filter that intercepts lift calls</description>
<filter-class>net.liftweb.http.LiftFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>LiftFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
</web-fragment>
http://blogs.sun.com/arungupta/entry/totd_101_applying_servlet_3
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18. Extensibility
ServletContainerInitializer
• Container installed JARs
– App or Library
• Discovered using the service provider API
• Expresses interest in classes via
@HandlesTypes
• Who uses it ?
– Mojarra (JSF2) is bootstrapped into GlassFish
• No “faces-config.xml” or “web.xml”
– Jersey (JAX-RS) registers root Application
• No (or portable) “web.xml”
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19. Dynamic Registration
Java Server Faces
@SuppressWarnings({"UnusedDeclaration"})
@HandlesTypes({
ManagedBean.class,
FacesComponent.class,
FacesValidator.class,
FacesConverter.class,
FacesBehaviorRenderer.class,
ResourceDependency.class,
ResourceDependencies.class,
ListenerFor.class,
ListenersFor.class,
UIComponent.class,
Validator.class,
Converter.class,
Renderer.class
})
public class FacesInitializer implements ServletContainerInitializer {
// NOTE: Loggins should not be used with this class.
private static final String FACES_SERVLET_CLASS =
FacesServlet.class.getName();
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20. Dynamic Registration
Java Server Faces
public void onStartup(Set<Class<?>> classes, ServletContext servletContext)
throws ServletException {
if (shouldCheckMappings(classes, servletContext)) {
Map<String,? extends ServletRegistration> existing =
servletContext.getServletRegistrations();
for (ServletRegistration registration : existing.values()) {
if (FACES_SERVLET_CLASS.equals(registration.getClassName())) {
// FacesServlet has already been defined, so we're
// not going to add additional mappings;
return;
}
}
ServletRegistration reg =
servletContext.addServlet("FacesServlet",
"javax.faces.webapp.FacesServlet");
reg.addMapping("/faces/*", "*.jsf", "*.faces");
servletContext.setAttribute(RIConstants.FACES_INITIALIZER_MAPPINGS_ADDED,
Boolean.TRUE);
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21. Resource Sharing
• Static and JSP not confined to document root
of the web application
• May be placed in WEB-INF/lib/
[*.jar]/META-INF/resources
• Resources in root take precedence over
those in bundled JAR
• Container must honor this new location when
– Processing HTTP requests
– Calls to ServletContext#getResource[AsStream]
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22. Resource Sharing – Sample Code
myapp.war
WEB-INF/lib/catalog.jar
/META-INF/resources/catalog/books.html
http://localhost:8080/myapp/catalog/books.html
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23. Why Asynchronous Servlets?
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Not for Async IO
– Requests mostly small (single packet)
– Hard to asynchronously produce large responses
– Async IO support waiting for NIO2
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Async Servlets are for:
– Waiting for resources (eg JDBC connection)
– Waiting for events (eg Chat)
– Waiting for responses (eg web services)
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24. Blocking waiting consumes resources
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Web Application using remote web services
– Handling 1000 requests / sec
– 50% requests call remote web service
– 500 threads in container thread pool
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If remote web service is slow (1000ms)
– Thread starvation in 1 second!
– 50% of requests use all 500 threads
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25. Asynchronous API
Enable asynchronous support
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Configured in
– web.xml:
<async-supported>true</async-
supported>
– With annotation:
@WebServlet(asyncSupported=true)
– Programmatic:
registration.setAsyncSupported(true)
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26. Asynchronous Servlets – Sample Code
AsyncContext context = request.startAsync();
context.addListener(new AsyncListener() { … });
context.dispatch(“/request.jsp”);
//context.start(Runnable action);
. . .
context.complete();
http://blogs.sun.com/arungupta/entry/totd_139_asynchronous_request_processing
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27. Security
Annotations to define security constraints
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@ServletSecurity used to define access
control constraints
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@HttpConstraint for all HTTP methods
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@HttpMethodConstraint for specific HTTP
methods
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More specific wins
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28. Security – Sample Code
@ServletSecurity(
httpMethodConstraints = {
@HttpMethodConstraint(value = "GET", rolesAllowed = "R1"),
@HttpMethodConstraint(value = "POST", rolesAllowed = "R2")
}
)
public class MyServlet extends HttpServlet {
// Servlet methods
}
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29. Security
Programmatic container authentication and logout
> HttpServletRequest#login(String username,
String password)
– Replacement for FBL
– Application supervises credential collection
> HttpServletRequest#authenticate(HttpServletR
esponse)
– Application initiates container mediated authentication from a
resource that is not covered by any authentication constraints
– Application decides when authentication must occur
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30. Miscellaneous Features
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Session tracking cookie configuration
– Via web.xml
– Programmatic via javax.servlet.SessionCookieConfig
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Support for HttpOnly cookie attribute
– Example:
servletContext.getSessionCookieConfig().setHttpOnly
(true)
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Default error page
<error-page>
<error-code>...</error-code>
<exception-type>...</exception-type>
<location>/404.html</location>
</error-page>
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31. Miscellaneous Features / API (contd)
ServletRequest#getServletContext
ServletRequest#getDispatcherType
Servlet[Request|
Response]Wrapper#isWrapperFor
HttpServletResponse#getStatus
HttpServletResponse#getHeader
HttpServletResponse#getHeaders
HttpServletResponse#getHeaderNames
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32. Miscellaneous Features / API (contd)
File upload
ServletRequest#getParts
ServletRequest#getPart
@MultipartConfig
Changes to web.xml
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33. Summary
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Major revision since Servlet 2.5
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Comprehensive set of new features enable
modern style of web applications and greatly
increases developer productivity
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Simplifies assembly of large applications
from reusable components
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34. References
• glassfish.org
• blogs.sun.com/theaquarium
• youtube.com/user/GlassFishVideos
• facebook.com/glassfish
• Follow @glassfish
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