JEE6 Servlet 3.0

Notes from https://www.sun.com/offers/details/java_ee6_servlet.xml

• Added annotations for declarative programming and generics:

  /*
    You can use web.xml to override values
   */
  @WebServlet // defines a servlet
  @WebFilter // defines a filter
  @WebListener // defines a listener
  @WebInitParam // defines an init param
  @ServletSecurity // security constraints
  @MultipartConfig // file upload

• @WebServlet
  • MUST specifiy url mapping
  • Default name of servlet is full qualified class name
  • Must still extend HttpServlet
  • Example:

    package com.foo;
    @WebServlet(name="MyServlet", urlPattern="/myApp/*")
    public class MyServlet extends HttpServlet {
      public void doGet(HttpServletRequest req, HttpServletResponse res) { ... }
    }

• Enable use of frameworks without alot of boiler plate configuration. Modularize web.xml
  • Dynamic registration of Servlets and Filters
    • Performed during ServletContext intialization;
      • ServletContext.add<Servlet|Filter>
      • ServletContext.create<Servlet|Filter>
      • ServletContext.find<Servlet|Filter>
  • Example:

    // Registration
    ServletRegistration.Dynamic dynamic = 
        servletContext.addServlet("DynamicServlet", "com.foo.MyServlet");
    dynamic.addMapping("/dynamicServlet");
    dynamic.setAsyncSupported(true);
    
    // Lookup
    ServletRegistration declared = servletContext.getServletRegistration("DeclaredServlet");
    declared.addMapping("/declaredServlet");
    declared.setInitParameter("param", "value");

• Modularized web.xml
  • web-fragment.xml
  • bundled in framework jar fil in META-INF
  • Almost identical to web.xml
  • Only jars in WEB-INF/lib will be scanned for web-fragment.xml files
  • Example:

    <web-fragment>
      <servlet>
        <servlet-name>welcome</servlet-name>
        ...
    </web-fragment>

  • Ordering is from JSF.
    • web.xml may declare ordering of fragments via <absolute-ordering>
    • fragments can specify ordering with <before> and <after>
• ServletContainerInitializer
  • Expresses interest in classes via @HandleTypes
  • Container scans webapp for classes that match @HandleTypes and passes them to ServletContainerIntializer
• Resource sharing
  • Static (e.g. images) and JSP resources no longer confined to document root of web application
  • May be place in WEB-INF/lib/<*.jar>/META-INF/resources
  • Resources in document root take precedence over those in bundled jars
• Asynch support
  • Must declare @WebServlet(asyncSupported=true)
  • Then call AsyncContext ctx = ServletRequest.startAsync(req, res)
  • AsyncContext can then either:

    dispatch(String path)
    start(Runnable action)

  • Then paired with complete()
  • ServletRequest.isAsyncSupported()
    • True if all <filter|servlet> support async in the filter chain and the request dispatch chain
    • Can be configured in web.xml, Annotation, or API
• Security
  • Added support for:

    // Declared using https contraints with @ServletSecurity
    HttpServletRequest.authenticate
    HttpServletRequest.login
    HttpServletRequest.logout