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

<Insert Picture Here>Servlets 3.0Asynchronous, Extensiblity, Ease-of-useArun Gupta, Java EE & GlassFish Guyblogs.sun.com/arungupta, @arungupta

Beijing 2010December 13–16, 2010 2

The following is intended to outline our generalproduct direction. It is intended for informationpurposes only, and may not be incorporated into anycontract. It is not a commitment to deliver anymaterial, code, or functionality, and should not berelied upon in making purchasing decisions.The development, release, and timing of anyfeatures or functionality described for Oracle’sproducts remains at the sole discretion of Oracle. 3

Agenda• Overview• Ease of Development• Dynamic Registration of Servlets and Filters• Pluggability• Asynchronous Support• Security Enhancements• Miscellaneous 4

Overviewl Java Servlet 3.0 done as part of JSR 315 – Final release done in December 2009.l ~20 members in the expert group – Major Java EE vendors, open source web container developers, framework authorsl Main areas of focus – Ease of Development – Pluggability – Asynchronous support – Security 5

Ease of Developmentl Enhanced APIs to use new Java SE language features introduced since J2SE 5.0 – Generics for type safety in API where possiblel Annotations for declarative style of programming – web.xml optionall Convention over configuration 6

Ease of Development Use of annotationsl 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 constraintsl Can override using “web.xml” 7

Servlet 2.5 example At least 2 files<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> 8

@WebServlet – Sample Code@WebServlet(urlPatterns={“/myApp”})public class SimpleSample extends HttpServlet{ public void doGet(HttpServletRequest req,HttpServletResponse res) { }} 9

@WebServlet Async – Sample Code@WebServlet(urlPatterns=“/myApp”,name=”MyServlet”, asyncSupported=true)public class SimpleSample extends HttpServlet{ public void doGet(HttpServletRequest req,HttpServletResponse res) { }} 10

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]l 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 11

Dynamic Registration Lookupl 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 12

Dynamic Registration Register exampleServletRegistration.Dynamic dynamic = servletContext.addServlet( "DynamicServlet", "com.mycom.MyServlet");dynamic.addMapping("/dynamicServlet");dynamic.setAsyncSupported(true); 13

Dynamic Registration Lookup exampleServletRegistration declared =servletContext.getServletRegistration("DeclaredServlet");declared.addMapping("/declaredServlet");declared.setInitParameter("param", "value"); 14

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 15

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 16

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 17

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” 18

Dynamic RegistrationJava 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(); 19

Dynamic RegistrationJava 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 were // 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); 20

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] 21

Resource Sharing – Sample Codemyapp.war WEB-INF/lib/catalog.jar /META-INF/resources/catalog/books.htmlhttp://localhost:8080/myapp/catalog/books.html 22

Why Asynchronous Servlets?l Not for Async IO – Requests mostly small (single packet) – Hard to asynchronously produce large responses – Async IO support waiting for NIO2l Async Servlets are for: – Waiting for resources (eg JDBC connection) – Waiting for events (eg Chat) – Waiting for responses (eg web services) 23

Blocking waiting consumes resourcesl Web Application using remote web services – Handling 1000 requests / sec – 50% requests call remote web service – 500 threads in container thread pooll If remote web service is slow (1000ms) – Thread starvation in 1 second! – 50% of requests use all 500 threads 24

Asynchronous APIEnable asynchronous supportl Configured in – web.xml: <async-supported>true</asyncsupported> – With annotation: @WebServlet(asyncSupported=true) – Programmatic: registration.setAsyncSupported(true) 25

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 26

Security Annotations to define security constraintsl @ServletSecurity used to define access control constraintsl @HttpConstraint for all HTTP methodsl @HttpMethodConstraint for specific HTTP methodsl More specific wins 27

Security – Sample Code@ServletSecurity( httpMethodConstraints = { @HttpMethodConstraint(value = "GET", rolesAllowed = "R1"), @HttpMethodConstraint(value = "POST", rolesAllowed = "R2") })public class MyServlet extends HttpServlet { // Servlet methods} 28

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 29

Miscellaneous Featuresl Session tracking cookie configuration – Via web.xml – Programmatic via javax.servlet.SessionCookieConfigl Support for HttpOnly cookie attribute – Example: servletContext.getSessionCookieConfig().setHttpOnly (true)l Default error page <error-page> <error-code>...</error-code> <exception-type>...</exception-type> <location>/404.html</location> </error-page> 30

Miscellaneous Features / API (contd)ServletRequest#getServletContextServletRequest#getDispatcherTypeServlet[Request|Response]Wrapper#isWrapperForHttpServletResponse#getStatusHttpServletResponse#getHeaderHttpServletResponse#getHeadersHttpServletResponse#getHeaderNames 31

Miscellaneous Features / API (contd)File uploadServletRequest#getPartsServletRequest#getPart@MultipartConfigChanges to web.xml 32

Summaryl Major revision since Servlet 2.5l Comprehensive set of new features enable modern style of web applications and greatly increases developer productivityl Simplifies assembly of large applications from reusable components 33

References• glassfish.org• blogs.sun.com/theaquarium• youtube.com/user/GlassFishVideos• facebook.com/glassfish• Follow @glassfish 34

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

by Arun Gupta on Dec 10, 2010

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