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Servlets 3.0 - JavaOne India 2011
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Servlets 3.0Asynchronous, Extensible, Ease-of-use
Arun Gupta, Java EE & GlassFish Guyblogs.oracle.com/arungupta, @arungupta
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The preceding 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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Agenda
•Overview•Ease of Development•Dynamic Registration of Servlets etc•Pluggability•Asynchronous Support•Security Enhancements•Miscellaneous
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Overview
lJava Servlet 3.0 done as part of JSR 315l~20 members in the expert group–Major Java EE vendors, open source web container developers, framework
authorslMain areas of focus–Ease of Development
–Pluggability–Asynchronous support
–Security
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Ease of Development
lEnhanced APIs to use new Java SE language features introduced since J2SE 5.0l Generics for type safety in API where possible
lAnnotations for declarative style of programmingl Optional web.xml
lConvention over configuration
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Ease of DevelopmentUse of annotations
lAnnotations 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 constraintslCan override using “web.xml”
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Servlet 2.5 exampleAt least 2 files
<!--Deployment descriptor web.xml -->
<web-app><servlet> <servlet-name>MyServlet
</servlet-name> <servlet-class> com.sun.MyServlet </servlet-class> </servlet> <servlet-mapping> <servlet-name>MyServlet </servlet-name> <url-pattern>/myApp/* </url-pattern> </servlet-mapping> ... </web-app>
/* Code in Java Class */
package com.sun;public class MyServlet extends HttpServlet { public void doGet(HttpServletRequest req,HttpServletResponse res)
{
...
}
...
}
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@WebServlet – Sample Code
@WebServlet(urlPatterns={“/myApp”})
public class SimpleSample extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse res) {
}
}
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@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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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]
lServletContext#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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Dynamic Registration Lookup
lServletContext#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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Dynamic Registration Register example
ServletRegistration.Dynamic dynamic =
servletContext.addServlet(
"DynamicServlet",
"com.mycom.MyServlet");
dynamic.addMapping("/dynamicServlet");
dynamic.setAsyncSupported(true);
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Dynamic Registration Lookup example
ServletRegistration declared =
servletContext.getServletRegistration("DeclaredServlet");
declared.addMapping("/declaredServlet");
declared.setInitParameter("param", "value");
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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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<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.oracle.com/arungupta/entry/totd_91_applying_java_ee
Pluggability – Sample Code
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<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.oracle.com/arungupta/entry/totd_101_applying_servlet_3
Pluggability – Sample Code
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ExtensibilityServletContainerInitializer
• Shared copies of frameworks• Container installed JARs– App or Library
• Discovered using the service provider API– META-INF/services/javax.servlet.ServletContainerInitializer
• Expresses interest in classes via @HandlesTypes
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ExtensibilityServletContainerInitializer
• 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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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();
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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);
Dynamic RegistrationJava Server Faces
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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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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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Why Asynchronous Servlets?
lNot for Async IO–Requests mostly small (single packet)–Hard to asynchronously produce large responses–Async IO support waiting for NIO2
lAsync Servlets are for:–Waiting for resources (eg JDBC connection)
–Waiting for events (eg Chat)–Waiting for responses (eg web services)
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Blocking waiting consumes resources
lWeb Application using remote web services–Handling 1000 requests / sec–50% requests call remote web service
–500 threads in container thread pool
l If remote web service is slow (1000ms)–Thread starvation in 1 second!
–50% of requests use all 500 threads
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Asynchronous APIEnable asynchronous support
lConfigured in–web.xml: <async-supported>true</async-supported>
–With annotation: @WebServlet(asyncSupported=true)–Programmatic: registration.setAsyncSupported(true)
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Asynchronous Servlets – Sample Code
AsyncContext context = request.startAsync();
context.addListener(new AsyncListener() { … });
context.dispatch(“/request.jsp”);
//context.start(Runnable action);
. . .
context.complete();
http://blogs.oracle.com/arungupta/entry/totd_139_asynchronous_request_processing
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SecurityAnnotations to define security constraints
l@ServletSecurity used to define access control constraintsl@HttpConstraint for all HTTP methodsl@HttpMethodConstraint for specific HTTP methodslMore specific wins
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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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SecurityProgrammatic container authentication and logout
>HttpServletRequest#login(String username, String password)–Replacement for FBL
–Application supervises credential collection
>HttpServletRequest#authenticate(HttpServletResponse)–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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Miscellaneous Features
lSession tracking cookie configuration–Via web.xml–Programmatic via javax.servlet.SessionCookieConfig
lSupport for HttpOnly cookie attribute–Example: servletContext.getSessionCookieConfig().setHttpOnly(true)
lDefault error page <error-page>
<error-code>...</error-code> <exception-type>...</exception-type>
<location>/404.html</location>
</error-page>
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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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Miscellaneous Features / API (contd)File upload
ServletRequest#getParts
ServletRequest#getPart
@MultipartConfig
Changes to web.xml
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Summary
lMajor revision since Servlet 2.5lComprehensive set of new features enable modern style of web applications and greatly increases developer productivity
lSimplifies assembly of large applications from reusable components
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Servlets 3.1 (JSR 340)http://jcp.org/en/jsr/detail?id=340
• Cloud support• Multi-tenancy– Security / Session state / Resources isolation
• Asynchronous IO based on NIO2• Simplified Asynchronous Servlets• Utilize Java EE concurrency utilities• Enable support for Web Sockets
NEW
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References
• oracle.com/javaee• glassfish.org• oracle.com/goto/glassfish• blogs.oracle.com/theaquarium• youtube.com/GlassFishVideos• Follow @glassfish
<Insert Picture Here>
Servlets 3.0Asynchronous, Extensible, Ease-of-use
Arun Gupta, Java EE & GlassFish Guyblogs.oracle.com/arungupta, @arungupta