Servlet 3.0. Alexis Moussine-Pouchkine. mercredi 13 avril 2011

Transcription

1 Servlet 3.0 Alexis Moussine-Pouchkine 1

2 Overview Java Servlet 3.0 API JSR members Good mix of representation from major Java EE vendors, web container developers and web framework authors 2

3 Overview Main areas of focus Ease of Development Extensibility Asynchronous support Security Final release available now as part of Java EE 6 and GlassFish v3 3

4 Ease of Development Enhance API using new language features in introduced since Java SE 5.0 Annotations for declarative style of programming Generics for type safety in API without breaking backwards compatibility Better defaults and convention over configuration 4

5 Ease of Development Annotations to declare Servlets, Filters, Listeners and Security Defines a Defines a Defines a Defines an init security file upload Use web.xml to override values 5

6 Ease of - For defining a Servlet MUST specify url mapping All other attributes optional with reasonable defaults For example, the default name of a Servlet is the fully qualified class name Must still extend HttpServlet to derive method contracts for doget, dopost and other methods

7 Ease of Development Servlet 2.5 example /* Code in Java Class */ package com.foo; public class MyServlet extends HttpServlet { public void doget (HttpServletRequest req, HttpServletResponse res) {... }... } <!--Deployment descriptor web.xml --> <web-app> <servlet> <servlet-name>myservlet </servlet-name> <servlet-class> com.foo.myservlet </servlet-class> </servlet> <servlet-mapping> <servlet-name>myservlet </servlet-name> <url-pattern>/myapp/* </url-pattern> </servlet-mapping>... </web-app> 7

8 Ease of Development package urlpattern="/myapp/*") public class MyServlet extends HttpServlet {! public void doget(httpservletrequest req,!!!!! HttpServletResponse res) {!!... }! 8

9 Extensibility Enable use of frameworks without boiler plate configuration in deployment descriptors Put the burden on framework developer Dynamic registration of Servlets and Filters using programmatic configuration APIs Modularize web.xml to allow frameworks to be self-contained Use of annotations enables extensibility as well 9

10 Extensibility web-fragment.xml partial web.xml Bundled in framework jar file in META-INF directory Container discovers and assembles the effective descriptor Almost identical to web.xml a few ordering related elements are different Only JAR files in WEB-INF/lib are considered 10

11 Extensibility <web-fragment> <servlet> <servlet-name>welcome</servlet-name> <servlet-class> WelcomeServlet </servlet-class> </servlet> <servlet-mapping> <servlet-name>welcome</servlet-name> <url-pattern>/welcome</url-pattern> </servlet-mapping>... </web-fragment> 11

12 metadata-complete The spontaneous assembly of fragments can be scary to some If metadata-complete is set to "true", the deployment tool must ignore any annotations that specify deployment information If metadata-complete is not specified or is set to "false", the deployment tool must examine the class files of the application for annotations 12

13 Programmatic Registration and lookup ServletRegistration.Dynamic dynamic = servletcontext.addservlet ("DynamicServlet","com.mycom.MyServlet"); dynamic.addmapping("/dynamicservlet"); dynamic.setasyncsupported(true); ServletRegistration declared = servletcontext.getservletregistration ("DeclaredServlet"); declared.addmapping("/declaredservlet"); declared.setinitparameter("param", "value"); 13

14 ServletContainerInitializer Provided by apps or the container Discovered using the service provider API in the Java runtime Expresses interest in classes Container scans webapp for classes that and passes them to the ServletContainerInitializer, along with ServletContext 14

15 Resource JARs WEB-INF/lib/{*.jar}/META-INF/resources Modular web applications static content Images, CSS, JavaScript (think dojo, jquery,...) a JAR placed in WEB-INF/lib has static content from its META-INF/resource directory served from the application webcontext root : WEB-INF/lib/pictures.jar/META-INF/resources/foo.png WEB-INF/lib/styles.jar/META-INF/resources/foo.css WEB-INF/lib/scripts.jar/META-INF/resources/foo.js

16 Asynchronous Support Useful for Comet, long waits Must (asyncsupported=true) Then Call AsyncContext ctx = ServletRequest.startAsync(req, res) AsyncContext can then either: dispatch(string path) start(runnable action) Then paired with complete() 16

17 Asynchronous API ServletRequest ServletRequest.isAsyncSupported() > True if ALL [Filter Servlet]s support async in The Filter chain The Request dispatch chain Can be configured > web.xml > Annotation > API 17

18 Asynchronous API ServletRequest AsyncContext ServletRequest.startAsync > Called by Servlet Filter > Response not committed on return of Service method Filter chain 18

19 Asynchronous API AsyncContext AsyncContext.dispatch > Called by asynchronous handler > Schedule async dispatch DispatcherType.ASYNC > Response generated by [Servlet Filter] using Container thread pool JSP, JSF or other frameworks 19

20 Asynchronous API AsyncContext AsyncContext.complete > Called by asynchronous handler or container > Signals Response has been generated 20

21 Asynchronous urlpatterns={"/myapp"}) public class MyServlet extends HttpServlet { } public void doget (HttpServletRequest req, HttpServletResponse res){... AsyncContext ctx = req.startasync();... } 21

22 ChatServlet (1/2) import javax.servlet.asynccontext; import javax.servlet.asyncevent; import javax.servlet.asynclistener; Queue<AsyncContext> queue; BlockingQueue<String> = {"/chat"}, asyncsupported = true) public class ChatServlet extends HttpServlet { doget(...) { AsyncContext ac = req.startasync(); ac.settimeout(10 * 60 * 1000); ac.addlistener(new AsyncListener() { public void oncomplete(asyncevent event) { queue.remove(ac); }... }); queue.add(ac); }... 22

23 ChatServlet (2/2) init(...) { while (true) { String message = messagequeue.take(); for (AsyncContext ac : queue) { PrintWriter acwriter = ac.getresponse().getwriter(); acwriter.println(message); } } } dopost(...) { String action = req.getparameter("action"); String name = req.getparameter("name"); String message = req.getparameter("message"); if ("login".equals(action)) { messagequeue.put(name + " has joined."); } else if ("post".equals(action)) { messagequeue.put(message); } 23

24 Security Programmatic login / logout Support for programmatic authentication, login and logout > HttpServletRequest.authenticate > HttpservletRequest.login > HttpServletRequest.logout Annotations for declaring http constraints for resources 24

25 Servlet 3.0 Annotations for ease of development Optional web.xml Better defaults Web Framework pluggability Asynchronous Processing Security enhancements 25

26 Q & A Alexis.Moussine-Pouchkine@Oracle.COM 26