| <html><head><META http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Chapter 3. GreenPages Highlights</title><meta content="DocBook XSL Stylesheets V1.76.0" name="generator"><link rel="home" href="index.html" title="A Guide to the GreenPages Sample"><link rel="up" href="index.html" title="A Guide to the GreenPages Sample"><link rel="prev" href="ch02s05.html" title="Running GreenPages from Eclipse"><link rel="next" href="ch03s02.html" title="Middle Tier Highlights"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table summary="Navigation header" width="100%"><tr><td align="left" width="20%"><a accesskey="p" href="ch02s05.html">Prev</a> </td><th align="center" width="60%"> </th><td align="right" width="20%"> <a accesskey="n" href="ch03s02.html">Next</a></td></tr></table><hr></div><div class="chapter" title="Chapter 3. GreenPages Highlights"><div class="titlepage"><div><div><h2 class="title"><a name="highlights"></a>Chapter 3. GreenPages Highlights</h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="ch03.html#highlights.wab">Web Application Bundle Highlights</a></span></dt><dd><dl><dt><span class="section"><a href="ch03.html#N10421">web.xml</a></span></dt><dt><span class="section"><a href="ch03.html#N10451">Controller Class</a></span></dt><dt><span class="section"><a href="ch03.html#N1047C">Component Scanning</a></span></dt><dt><span class="section"><a href="ch03.html#N104A6">Bundle Manifest</a></span></dt><dt><span class="section"><a href="ch03.html#N104C5">Service Injection</a></span></dt></dl></dd><dt><span class="section"><a href="ch03s02.html">Middle Tier Highlights</a></span></dt><dd><dl><dt><span class="section"><a href="ch03s02.html#N104EE">DataSource</a></span></dt><dt><span class="section"><a href="ch03s02.html#N10513">EntityManager</a></span></dt><dt><span class="section"><a href="ch03s02.html#N10575">Transaction Management</a></span></dt></dl></dd><dt><span class="section"><a href="ch03s03.html">Testing Highlights</a></span></dt><dd><dl><dt><span class="section"><a href="ch03s03.html#N105B1">Single Bundle Integration Test</a></span></dt><dt><span class="section"><a href="ch03s03.html#N105F5">Multi Bundle Integration Test</a></span></dt></dl></dd><dt><span class="section"><a href="ch03s04.html">Automated Build Highlights</a></span></dt><dd><dl><dt><span class="section"><a href="ch03s04.html#N10642">Building the PAR</a></span></dt><dt><span class="section"><a href="ch03s04.html#N10679">Obtaining Dependencies</a></span></dt><dt><span class="section"><a href="ch03s04.html#N106A0">Automatically Running the Tests</a></span></dt></dl></dd></dl></div><p> |
| This chapter picks out some notable features of the GreenPages sample code from the <code class="literal">greenpages.*</code> folders. |
| </p><div class="section" title="Web Application Bundle Highlights"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="highlights.wab"></a>Web Application Bundle Highlights</h2></div></div></div><p> |
| The GreenPages Web Application Bundle (WAB) is built using Spring MVC configured with Spring annotations and component |
| scanning. The Bundlor tool is used to generate the bundle manifest of the WAB and a service is injected into the code |
| using Spring DM in combination with Spring autowiring. |
| </p><p> |
| For more information on Spring, Spring MVC, Bundlor and Spring DM, please see <a class="link" href="apa.html#further.resources.projects" title="Projects">Projects</a>.. |
| </p><div class="section" title="web.xml"><div class="titlepage"><div><div><h3 class="title"><a name="N10421"></a>web.xml</h3></div></div></div><p> |
| The web deployment descriptor file <code class="literal">web.xml</code> is in the <code class="literal">src/main/webapp/WEB_INF</code> folder of the |
| <code class="literal">greenpages.web</code> project. |
| It defines a servlet, a servlet context parameter, and a servlet context listener. |
| </p><p> |
| Spring's dispatcher servlet is used to dispatch web requests to handlers. |
| </p><pre class="programlisting"> <servlet> |
| <servlet-name>greenpages</servlet-name> |
| <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class> |
| </servlet> |
| </pre><p> |
| </p><p> |
| The <code class="literal">contextClass</code> servlet parameter declares the implementation of <code class="interfacename">WebApplicationContext</code> |
| that Spring instantiates. |
| The application context acts as a root application context and each servlet in the web application, which in the case of GreenPages is |
| just the dispatcher servlet, has its own application context which is a child of the root application context. |
| <code class="classname">ServerOsgiBundleXmlWebApplicationContext</code> is provided by Virgo and will hold beans created by Spring DM, which |
| are then available in child application contexts. |
| </p><pre class="programlisting"> <context-param> |
| <param-name>contextClass</param-name> |
| <param-value>org.eclipse.virgo.web.dm.ServerOsgiBundleXmlWebApplicationContext</param-value> |
| </context-param> |
| |
| </pre><p> |
| </p><p> |
| A servlet context listener is defined which will start up the root application context for the web application when the servlet context |
| is initialised. |
| </p><pre class="programlisting"> <listener> |
| <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> |
| </listener> |
| |
| </pre><p> |
| </p></div><div class="section" title="Controller Class"><div class="titlepage"><div><div><h3 class="title"><a name="N10451"></a>Controller Class</h3></div></div></div><p> |
| In the <code class="literal">src/main/java</code> source folder of the <code class="literal">greenpages.web</code> project |
| the package <code class="classname">greenpages.web</code> |
| contains the controller class <code class="classname">GreenPagesController</code>. |
| </p><p> |
| Spring annotations are used to add web behaviour to the class. |
| The <code class="classname">@Controller</code> annotation tells Spring that the class serves the role of a controller and that the |
| class should be scanned for <span class="emphasis"><em>request mappings</em></span>. |
| Request mappings are defined using the <code class="classname">@RequestMapping</code> annotation. |
| For instance, the URL <code class="literal">/home.htm</code> is mapped to the handler method <code class="literal">home</code>. |
| </p><pre class="programlisting">@Controller |
| public class GreenPagesController { |
| ??? |
| @RequestMapping("/home.htm") |
| public void home() { |
| } |
| ??? |
| </pre><p> |
| Note that request mappings can also be specified at the class level. |
| </p></div><div class="section" title="Component Scanning"><div class="titlepage"><div><div><h3 class="title"><a name="N1047C"></a>Component Scanning</h3></div></div></div><p> |
| Spring will detect the <code class="classname">@Controller</code> annotation and create a bean of type controller, |
| <span class="emphasis"><em>provided that</em></span> it scans the classpath for these. |
| Spring’s component scanning is enabled by the presence of a <code class="literal">context</code> tag |
| in one of the Spring bean definition files. |
| </p><p> |
| The <code class="filename">WEB-INF/greenpages-servlet.xml</code> file in the |
| <code class="literal">src/main/webapp</code> folder contains the following lines: |
| </p><pre class="programlisting"><!-- enable classpath scanning --> |
| <context:component-scan base-package="greenpages.web" /> |
| </pre><p> |
| Notice the convention embodied in the filename <code class="filename">WEB-INF/greenpages-servlet.xml</code>. |
| During dispatcher servlet initialisation, Spring looks for a file named <code class="literal">[servlet-name]-servlet.xml</code> |
| in the <code class="literal">WEB-INF</code> directory of the web application and creates the beans defined there. |
| </p></div><div class="section" title="Bundle Manifest"><div class="titlepage"><div><div><h3 class="title"><a name="N104A6"></a>Bundle Manifest</h3></div></div></div><p> |
| The Virgo Tomcat Server has special support for WABs. |
| To take advantage of this support, the <code class="literal">greenpages.web</code> bundle must be declared to be a WAB and a |
| context path must be defined. |
| </p><p> |
| The Bundlor template (the file <code class="filename">template.mf</code> at the top level under the <code class="literal">greenpages.web</code> project) |
| is input to the Bundlor tool which generates the manifest of the bundle. |
| </p><p> |
| The Bundlor template defines the context path as follows (and this is what declares the bundle to be a WAB): |
| </p><pre class="programlisting">Web-ContextPath: greenpages |
| </pre><p> |
| </p><p> |
| The Bundlor template also ensures Spring packages and greenpages packages from other bundles are imported with suitable version ranges: |
| </p><pre class="programlisting">Import-Template: |
| org.springframework.*;version="[3.0, 3.1)", |
| greenpages.*;version="[2.3, 2.4)" |
| </pre><p> |
| </p></div><div class="section" title="Service Injection"><div class="titlepage"><div><div><h3 class="title"><a name="N104C5"></a>Service Injection</h3></div></div></div><p> |
| The file <code class="filename">webapp/WEB-INF/applicationContext.xml</code> declares a reference to a |
| <code class="interfacename">greenpages.Directory</code> service in the service registry using Spring DM as follows: |
| </p><pre class="programlisting"><osgi:reference id="directory" interface="greenpages.Directory"/> |
| </pre><p> |
| The resultant bean resides in the root web application context. |
| </p><p> |
| The <code class="classname">GreenPagesController</code> class uses Spring autowiring to inject the service: |
| </p><pre class="programlisting">@Autowired |
| private Directory directory; |
| </pre><p> |
| The controller's bean resides in the web application context associated with the Spring dispatcher servlet and so has |
| access to the directory service bean in the root web application context. |
| </p></div></div></div><div class="navfooter"><hr><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="ch02s05.html">Prev</a> </td><td align="center" width="20%"> </td><td align="right" width="40%"> <a accesskey="n" href="ch03s02.html">Next</a></td></tr><tr><td valign="top" align="left" width="40%"> </td><td align="center" width="20%"><a accesskey="h" href="index.html">Home</a></td><td valign="top" align="right" width="40%"> </td></tr></table></div></body></html> |
