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| </script><!--End Google Analytics code--></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">5.2 Creating the DataSource project</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch05.html">Prev</a> </td><th width="60%" align="center">5. The Middle Tier</th><td width="20%" align="right"> <a accesskey="n" href="ch05s03.html">Next</a></td></tr></table><hr></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="middle-tier.create-db-project"></a>5.2 Creating the DataSource project</h2></div></div></div><p> |
| This section describes how to use |
| the bundle project creation wizard to create a new <code class="literal">Bundle Project</code>. The project’s Spring bean |
| definition files will also be created using the Spring bean configuration file creation wizard. |
| </p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.create-db-project.new-bundle-project"></a>Creating a new Bundle Project</h3></div></div></div><p> |
| Create a new project by right-clicking in the <span class="emphasis"><em>Package Explorer</em></span> view and selecting |
| <span class="guimenu">New</span> → <span class="guimenuitem">Project…</span>. In the resulting |
| dialog select <span class="guimenu">EclipseRT</span> → <span class="guimenuitem">Bundle |
| Project</span> and press <span class="emphasis"><em>Next</em></span>: |
| </p><div class="mediaobject" align="center"><img src="images/middle-tier/new-bundle-project.png" align="middle"></div><p> |
| </p><p> |
| In the <span class="emphasis"><em>New Bundle Project</em></span> dialog, name the project <code class="literal">greenpages.db</code>. |
| Choose the create the project from an existing source location and specify a location that will place the new |
| <code class="literal">greenpages.db</code> alongside the project skeletons that were imported into the workspace |
| earlier. If the <code class="literal">start</code> directory of the GreenPages sample is being used this will |
| be <code class="literal">$GREENPAGES_HOME/start/greenpages.db</code> (and, <span class="emphasis"><em>mutatis mutandis</em></span> on Windows). |
| Click <span class="emphasis"><em>Next</em></span>. |
| </p><div class="mediaobject" align="center"><img src="images/middle-tier/create-bundle-project.png" align="middle"></div><p> |
| </p><p> |
| In this page of the wizard, many of the <span class="emphasis"><em>Bundle Properties</em></span> are already populated. The |
| <code class="literal">Bundle-SymbolicName</code> is the name of the project. The <code class="literal">Bundle-Name</code> is |
| derived from the <code class="literal">Bundle-SymbolicName</code>. The <code class="literal">Bundle-Version</code> is |
| set, and there is no <code class="literal">Bundle-Description</code>. |
| </p><p> |
| Change the <code class="literal">Bundle-Name</code> to “<span class="quote"><code class="literal">GreenPages DataSource</code></span>” to more accurately |
| describe the bundle’s purpose. An option to ‘Enable Bundle Classpath Container’ is already selected. It should |
| be <span class="emphasis"><em>de</em></span>-selected, as a Maven Classpath container will be configured later. |
| Ensure that the <span class="emphasis"><em>Target Runtime</em></span> |
| is set to <span class="emphasis"><em>Virgo Web Server (Runtime) v2.1</em></span>. |
| Click <span class="emphasis"><em>Finish</em></span>. |
| </p><div class="mediaobject" align="center"><img src="images/middle-tier/config-bundle-project.png" align="middle"></div><p> |
| The <code class="literal">greenpages.db</code> project appears in the <span class="emphasis"><em>Package Explorer</em></span> view. |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.create-db-project.configuring-classpath"></a>Configuring the project’s classpath container</h3></div></div></div><p> |
| Before a Maven Classpath Container can be added to the project, a <code class="literal">pom.xml</code> file must |
| be created. |
| Create a new file in the root of the <code class="literal">greenpages.db</code> project named |
| <code class="literal">pom.xml</code> and add the following contents to it: |
| </p><pre class="programlisting"><<span class="hl-tag">?xml version="1.0" encoding="UTF-8"?</span>> |
| <<span class="hl-tag">project</span> |
| <span class="hl-attribute">xmlns</span>=<span class="hl-value">"http://maven.apache.org/POM/4.0.0"</span> |
| <span class="hl-attribute">xmlns:xsi</span>=<span class="hl-value">"http://www.w3.org/2001/XMLSchema-instance"</span> |
| <span class="hl-attribute">xsi:schemaLocation</span>=<span class="hl-value">"http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd"</span>> |
| |
| <<span class="hl-tag">parent</span>> |
| <<span class="hl-tag">groupId</span>>com.springsource.dmserver<<span class="hl-tag">/groupId</span>> |
| <<span class="hl-tag">artifactId</span>>greenpages.parent<<span class="hl-tag">/artifactId</span>> |
| <<span class="hl-tag">version</span>>2.3.0.RELEASE<<span class="hl-tag">/version</span>> |
| <<span class="hl-tag">relativePath</span>>../parent<<span class="hl-tag">/relativePath</span>> |
| <<span class="hl-tag">/parent</span>> |
| |
| <<span class="hl-tag">modelVersion</span>>4.0.0<<span class="hl-tag">/modelVersion</span>> |
| <<span class="hl-tag">groupId</span>>com.springsource.dmserver<<span class="hl-tag">/groupId</span>> |
| <<span class="hl-tag">artifactId</span>>greenpages.db<<span class="hl-tag">/artifactId</span>> |
| <<span class="hl-tag">name</span>>greenpages.db<<span class="hl-tag">/name</span>> |
| <<span class="hl-tag">packaging</span>>jar<<span class="hl-tag">/packaging</span>> |
| |
| <<span class="hl-tag">dependencies</span>> |
| <<span class="hl-tag">/dependencies</span>> |
| |
| <<span class="hl-tag">/project</span>> |
| </pre><p> |
| Save the file. |
| </p><p> |
| A Maven Classpath Container can now be added to the project. Right-click the |
| <code class="literal">greenpages.db</code> project in the Package Explorer and select |
| <span class="guimenu">Maven 2</span> → <span class="guimenuitem">Enable dependency management</span>. |
| Eclipse will perform some workspace building, and the <code class="literal">greenpages.db</code> project will now be marked as a Maven project. |
| (If the error <code class="literal">Cannot find artifact for parent POM</code> occurs check that the version is correct. |
| It may differ from the one given here.) |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.create-db-project.config-src-folders"></a>Configuring the source folders</h3></div></div></div><p> |
| The last part of the setup of the project is to configure its source folders. |
| Return to the <span class="emphasis"><em>Properties</em></span> dialog of |
| the <code class="literal">greenpages.db</code> project (from the <span class="emphasis"><em>Package Explorer</em></span> view). |
| Select <span class="emphasis"><em>Java Build Path</em></span> on the left-hand side and the <span class="emphasis"><em>Source</em></span> tab |
| on the right-hand side. |
| Remove any pre-configured source folders by selecting them and |
| clicking <span class="emphasis"><em>Remove</em></span>. |
| </p><p> |
| Now click <span class="emphasis"><em>Add folder</em></span> and then |
| <span class="emphasis"><em>Create new folder…</em></span>. |
| Specify <code class="literal">src/main/resources</code> as the folder |
| name and click <span class="emphasis"><em>Finish</em></span>, then <span class="emphasis"><em>OK</em></span> and <span class="emphasis"><em>OK</em></span> again. |
| </p><p> |
| The final change to be made is to drag the <code class="literal">META-INF</code> folder from <code class="literal">src</code> |
| to <code class="literal">src/main/resources</code>. |
| Once these changes have been made the project will appear |
| similar to the following in the <span class="emphasis"><em>Package Explorer</em></span> view: |
| </p><div class="mediaobject" align="center"><img src="images/middle-tier/db-project.png" align="middle"></div><p> |
| </p><p> |
| (It is useful to check that the Maven project just configured has the correct Java System library associated with it and that |
| the <code class="literal">MANIFEST.MF</code> file that we have just moved is correctly generated when necessary. |
| To ensure this, disable the dependency management (enabled in the previous section) and then re-enable it, saving the changes in between. |
| This step may also change the Java system libraries associated with the build (right-click on the <code class="literal">greenpages.db</code> project, under Properties, Java build path and Libraries). |
| If the Java system libraries look incorrect, simply remove them in the Libraries window and reset them.) |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.create-db-project.config-datasource"></a>Configuring the DataSource</h3></div></div></div><p> |
| The DataSource bundle’s main rôle is to configure and create a <code class="literal">DataSource</code> object and to |
| publish this to the OSGi service registry. This will be done by creating |
| a handful of Spring beans. |
| </p><p> |
| By default, Spring DM looks for application context files in a bundle’s <code class="literal">META-INF/spring</code> |
| directory. Create a new folder named <code class="literal">spring</code> in the <code class="literal">greenpages.db</code> |
| project’s <code class="literal">META-INF</code> folder. Having created the new folder, right-click it in the |
| Package Explorer and select |
| <span class="guimenu">New </span> → <span class="guimenuitem">Spring Bean Configuration File</span>. |
| This will open the wizard for creating Spring bean configuration files. |
| </p><p> |
| In the wizard enter a <code class="literal">File name</code> of <code class="literal">module-context.xml</code> and click |
| <span class="emphasis"><em>Next</em></span>: |
| </p><div class="mediaobject" align="center"><img src="images/middle-tier/db-module-create-module-context.png" align="middle"></div><p> |
| </p><p> |
| Add the <span class="emphasis"><em>p - http://www.springframework.org/schema/p</em></span> namespace declaration to the pre-selected |
| <span class="emphasis"><em>beans</em></span> declaration and then click <span class="emphasis"><em>Finish</em></span>. |
| </p><div class="mediaobject" align="center"><img src="images/middle-tier/db-module-namespace-declaration-configuration.png" align="middle"></div><p> |
| </p><p> |
| Update the newly-created file (which is opened by Eclipse) to declare a bean that defines the <code class="literal">DataSource</code> |
| object that will be used to access the GreenPages database. |
| Do this by adding the following bean declaration: |
| </p><pre class="programlisting"> <<span class="hl-tag">bean</span> <span class="hl-attribute">id</span>=<span class="hl-value">"dataSource"</span> <span class="hl-attribute">class</span>=<span class="hl-value">"org.apache.commons.dbcp.BasicDataSource"</span> |
| <span class="hl-attribute">p:driverClassName</span>=<span class="hl-value">"org.h2.Driver"</span> <span class="hl-attribute">p:url</span>=<span class="hl-value">"jdbc:h2:~/greenpages-db/greenpages"</span> |
| <span class="hl-attribute">p:username</span>=<span class="hl-value">"greenpages"</span> <span class="hl-attribute">p:password</span>=<span class="hl-value">"pass"</span> |
| <span class="hl-attribute">init-method</span>=<span class="hl-value">"createDataSource"</span> <span class="hl-attribute">destroy-method</span>=<span class="hl-value">"close"</span> /> |
| </pre><p> |
| The new bean has introduced a dependency on Commons DBCP, which will cause an error to be reported by Eclipse. |
| </p><p> |
| This dependency must be recorded in the project’s pom file. Open the pom file for <code class="literal">greenpages.db</code> and add |
| the following dependency between the <code class="literal"><dependencies></code> tags: |
| </p><pre class="programlisting"> <<span class="hl-tag">dependency</span>> |
| <<span class="hl-tag">groupId</span>>org.apache.commons<<span class="hl-tag">/groupId</span>> |
| <<span class="hl-tag">artifactId</span>>com.springsource.org.apache.commons.dbcp<<span class="hl-tag">/artifactId</span>> |
| <<span class="hl-tag">/dependency</span>> |
| </pre><p> |
| Save the updated pom and then switch back to the editor for <code class="literal">module-context.xml</code>. |
| Save the updated file and |
| observe that the previously reported problem is now resolved as Commons DBCP is available on the classpath. |
| </p><p> |
| Now that the <code class="literal">DataSource</code> bean is available, it can be published into the OSGi service registry. |
| </p><p> |
| Right-click the <code class="literal">spring</code> folder and select |
| <span class="guimenu">New </span> → <span class="guimenuitem">Spring Bean Configuration File</span> again. |
| This time specify |
| a name of <code class="literal">osgi-context.xml</code>, click <span class="emphasis"><em>Next</em></span>, and add the <code class="literal">osgi</code> |
| namespace declaration |
| (ensure that the resultant schema location string contains the URL |
| <code class="literal">http://www.springframework.org/schema/osgi/spring-osgi-1.2.xsd</code> |
| as |
| <code class="literal">http://www.springframework.org/schema/osgi/spring-osgi-2.0-m1.xsd</code> |
| will result in an obscure deployment failure due to an invalid 'cacheTarget' property). |
| Click <span class="emphasis"><em>Finish</em></span> and then add the following to the new file to publish the |
| <code class="literal">DataSource</code> as a service: |
| </p><pre class="programlisting"> <<span class="hl-comment">!-- |
| export the dataSource bean to the OSGi service registry under the |
| DataSource interface |
| --</span>> |
| <<span class="hl-tag">osgi:service</span> <span class="hl-attribute">ref</span>=<span class="hl-value">"dataSource"</span> <span class="hl-attribute">interface</span>=<span class="hl-value">"javax.sql.DataSource"</span> /> |
| </pre><p> |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="id=middle-tier.create-db-project.config-bundlor-template"></a>Configuring Bundlor’s manifest template</h3></div></div></div><p> |
| Bundlor uses a manifest <span class="emphasis"><em>template</em></span> to control the contents of the generated manifest. |
| Create a new file named |
| <code class="literal">template.mf</code> in the root of the <code class="literal">greenpages.db</code> project. |
| Open the existing |
| <code class="literal">MANIFEST.MF</code> and switch to the <code class="literal">MANIFEST.MF</code> tab to view its source. Copy |
| the contents. Switch to the editor for <code class="literal">template.mf</code>, switch to the |
| <code class="literal">template.mf</code> tab and paste the contents from <code class="literal">MANIFEST.MF</code>. These entries |
| will tell Bundlor what the resulting manifest’s bundle symbolic name, bundle version, etc. should be. Save the |
| updated template. |
| </p><p> |
| Still in the <code class="literal">template.mf</code> editor switch to the <span class="emphasis"><em>Overview</em></span> tab |
| and click <span class="emphasis"><em>Update MANIFEST.MF</em></span> which is under the “<span class="quote">Bundle Actions</span>” section. |
| </p><p> |
| At this point Bundlor will scan the project to determine its |
| dependencies. It will scan both <code class="literal">module-context.xml</code> and <code class="literal">osgi-context.xml</code> |
| looking for references to classes. For each class to which it finds a reference, an import for the class’s |
| package will be added to the resulting manifest. |
| </p><p> |
| In this case, Bundlor will generate imports for |
| both <code class="code">javax.sql</code> and <code class="code">org.apache.commons.dbcp</code>. |
| These imports may not be resolved. |
| The <code class="literal">greenpages.db</code> project needs to be associated with a Web Server instance which has the |
| Commons DBCP bundle in its repository to resolve them. |
| In any event the next step adds the <code class="literal">greenpages.db</code> |
| project to the GreenPages PAR and will result in it inheriting the PAR project’s targetted runtime |
| configuration. |
| </p><p> |
| Double-click the <code class="literal">MANIFEST.MF</code> file in the <code class="literal">greenpages</code> project in the |
| <span class="emphasis"><em>Package Explorer</em></span> view. |
| Switch to the <code class="literal">Dependencies</code> tab and click <span class="emphasis"><em>Add…</em></span>. |
| Select <code class="literal">greenpages.db</code> and click <span class="emphasis"><em>OK</em></span>. |
| Save the updated file. |
| A problem concerning the <code class="code">org.apache.commons.dbcp</code> dependency should now be resolved |
| (along with any other resolution errors) and (if the server is running) the |
| GreenPages application will be redeployed due to the addition of the <code class="literal">greenpages.db</code> |
| module. |
| Start the server if it is not already running and observe that this deployment fails. |
| </p><p> |
| The deployment will fail because the <code class="code">org.h2.Driver</code> class that is referenced in the |
| <code class="literal">DataSource</code> bean’s definition in <code class="literal">module-context.xml</code> is not available to |
| the bundle. |
| (Check for the exception <code class="code">org.springframework.beans.factory.BeanCreationException</code> with |
| text something like: |
| </p><pre class="programlisting">Error creating bean with name 'dataSource' |
| defined in URL [bundleentry://68.fwk504117357/META-INF/spring/ module-context.xml]: |
| Invocation of init method failed; |
| nested exception is org.apache.commons.dbcp.SQLNestedException: Cannot load JDBC driver class 'org.h2.Driver' |
| </pre><p> |
| though the numbers might be different.) |
| </p><p> |
| There are a few cases where Bundlor will not identify a dependency on a class and, at the moment, |
| this is one of them, although this is an area of Bundlor that is being improved all the time. |
| Thankfully, it is easy to add the required import by making a simple update to the template. |
| </p><p> |
| Open the editor for the |
| <code class="literal">template.mf</code> file in the <code class="literal">greenpages.db</code> project and add the following |
| <code class="literal">Import-Package</code> header and save the updated manifest: |
| </p><pre class="programlisting">Import-Package: org.h2;version="[1.0.71,1.0.71]" |
| </pre><p> |
| </p><p> |
| Saving the manifest will trigger a redeployment (or click on <span class="emphasis"><em>Update MANIFEST.MF</em></span> as before) |
| which will fail if the H2 database is not available. |
| (Refer to the section <a class="xref" href="ch03s03.html#installing.greenpages.building.db" title="Starting and configuring the database">the section called “Starting and configuring the database”</a> |
| in <a class="xref" href="ch03.html" title="3. Installing and exploring GreenPages">Chapter 3, <i>Installing and exploring GreenPages</i></a> to run and configure the database.) |
| </p><p> |
| If the database is running the GreenPages application should correctly deploy. |
| Although the application web front-end will run, the database contents is |
| not visible, of course, because we are still running with the <span class="emphasis"><em>stub</em></span> version of the <code class="code">search</code> method on the controller. |
| The implementation of the <code class="code">Directory</code> service needs to be changed to exploit the database.</p><p> |
| (One possible cause of failure here is the username and password on the <code class="literal">dataSource</code> |
| bean defined in <code class="literal">module-context.xml</code>. Check that these are exactly correct.) |
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