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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">5.3 Building the JPA module</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch05s02.html">Prev</a> </td><th width="60%" align="center">5. The Middle Tier</th><td width="20%" align="right"> <a accesskey="n" href="ch05s04.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.building-jpa-module"></a>5.3 Building the JPA module</h2></div></div></div><p> |
| In this section the JPA module in GreenPages is created, building upon an existing skeleton. |
| JPA and its metadata are configured, and a JPA-based Directory service implementation |
| is published which is then consumed by the application’s Web bundle. |
| </p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.building-jpa-module.completing-jpadirectory"></a>Completing the JPA-based Directory implementation</h3></div></div></div><p> |
| The <code class="literal">greenpages.jpa</code> starter project provides the beginnings of a JPA-based implementation of |
| <code class="literal">Directory</code> named <code class="literal">JpaDirectory</code>. Import the <code class="literal">greenpages.jpa</code> project |
| from the <code class="literal">$GREENPAGES_HOME/start</code> directory. |
| </p><p> |
| Open the <code class="code">JpaDirectory.java</code> source file |
| in the <code class="literal">greenpages.jpa</code> package of <code class="literal">greenpages.jpa</code> project (under <code class="code">src/main/java</code>). |
| </p><p> |
| The source file |
| contains a Java Persistence Query Language (JPQL) search query that will be used to retrieve |
| listings from the database, and empty |
| implementations of the <code class="literal">search</code> and <code class="literal">findListing</code> methods. |
| </p><p> |
| First add an <code class="literal">EntityManager</code> to it. |
| Before the new field |
| can be added, <code class="literal">EntityManager</code> must be available on the classpath. |
| Open the pom for |
| <code class="literal">greenpages.jpa</code> and add the following dependency: |
| </p><pre class="programlisting"> <<span class="hl-tag">dependency</span>> |
| <<span class="hl-tag">groupId</span>>javax.persistence<<span class="hl-tag">/groupId</span>> |
| <<span class="hl-tag">artifactId</span>>com.springsource.javax.persistence<<span class="hl-tag">/artifactId</span>> |
| <<span class="hl-tag">/dependency</span>> |
| </pre><p> |
| </p><p> |
| Now return to <code class="literal">JpaDirectory</code> and add the following field to the class along with an |
| import for <code class="literal">javax.persistence.EntityManager</code> (which should be suggested by Eclipse): |
| </p><pre class="programlisting"> <span class="hl-keyword">private</span> EntityManager em; |
| </pre><p> |
| </p><p> |
| This <code class="literal">EntityManager</code> can now be used to implement the <code class="literal">search</code> and |
| <code class="literal">findListing</code> methods. Update the implementations of these two methods to match the |
| following implementations and then save the updated class: |
| </p><pre class="programlisting"> <span class="hl-keyword">public</span> Listing findListing(<span class="hl-keyword">int</span> id) { |
| <span class="hl-keyword">return</span> em.find(JpaListing.<span class="hl-keyword">class</span>, id); |
| } |
| |
| @SuppressWarnings(<span class="hl-string">"unchecked"</span>) |
| <span class="hl-keyword">public</span> List<Listing> search(String term) { |
| <span class="hl-keyword">return</span> em.createQuery(SEARCH_QUERY).setParameter(<span class="hl-string">"term"</span>, |
| <span class="hl-string">"%"</span> + term.toUpperCase() + <span class="hl-string">"%"</span>).getResultList(); |
| } |
| </pre><p> |
| (Warnings from Eclipse should now be absent.) |
| </p><p> |
| The application context now needs to be updated to create <code class="literal">JpaDirectory</code> and to create |
| an <code class="literal">EntityManager</code> that can be injected into <code class="literal">JpaDirectory</code>. |
| </p><p> |
| Open |
| <code class="literal">module-context.xml</code> in the <code class="literal">META-INF/spring</code> folder of the |
| <code class="literal">greenpages.jpa</code>. Add the following beans that will create <code class="literal">JpaDirectory</code> |
| and an <code class="literal">EntityManager</code>, enable load-time weaving that is required by JPA, and enable |
| annotation-based configuration that will allow the <code class="literal">EntityManager</code> to be injected into |
| <code class="literal">JpaDirectory</code>: |
| </p><pre class="programlisting"> <<span class="hl-comment">!-- |
| Activates a load-time weaver for the context. Any bean within the |
| context that implements LoadTimeWeaverAware (such as |
| LocalContainerEntityManagerFactoryBean) will receive a reference to |
| the autodetected load-time weaver. |
| --</span>> |
| <<span class="hl-tag">context:load-time-weaver</span> <span class="hl-attribute">aspectj-weaving</span>=<span class="hl-value">"on"</span> /> |
| |
| <<span class="hl-comment">!-- JPA EntityManagerFactory --</span>> |
| <<span class="hl-tag">bean</span> <span class="hl-attribute">id</span>=<span class="hl-value">"entityManagerFactory"</span> |
| <span class="hl-attribute">class</span>=<span class="hl-value">"org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"</span> |
| <span class="hl-attribute">p:dataSource-ref</span>=<span class="hl-value">"dataSource"</span>> |
| <<span class="hl-tag">property</span> <span class="hl-attribute">name</span>=<span class="hl-value">"jpaVendorAdapter"</span>> |
| <<span class="hl-tag">bean</span> <span class="hl-attribute">id</span>=<span class="hl-value">"jpaVendorAdapter"</span> |
| <span class="hl-attribute">class</span>=<span class="hl-value">"org.springframework.orm.jpa.vendor.EclipseLinkJpaVendorAdapter"</span> |
| <span class="hl-attribute">p:databasePlatform</span>=<span class="hl-value">"org.eclipse.persistence.platform.database.HSQLPlatform"</span> |
| <span class="hl-attribute">p:showSql</span>=<span class="hl-value">"true"</span> /> |
| <<span class="hl-tag">/property</span>> |
| <<span class="hl-tag">/bean</span>> |
| |
| <<span class="hl-comment">!-- |
| Activates various annotations to be detected in bean classes: Spring's |
| @Required and @Autowired, as well as JSR 250's @PostConstruct, |
| @PreDestroy and @Resource (if available) and JPA's @PersistenceContext |
| and @PersistenceUnit (if available). |
| --</span>> |
| <<span class="hl-tag">context:annotation-config</span> /> |
| |
| <<span class="hl-tag">bean</span> <span class="hl-attribute">id</span>=<span class="hl-value">"directory"</span> <span class="hl-attribute">class</span>=<span class="hl-value">"greenpages.jpa.JpaDirectory"</span> /> |
| </pre><p> |
| </p><p> |
| The addition of the new beans to the context has introduced a new dependency upon Spring’s ORM support and upon |
| EclipseLink and its JPA implementation. Add the following dependencies to the pom file for |
| <code class="literal">greenpages.jpa</code> and save it: |
| </p><pre class="programlisting"> <<span class="hl-tag">dependency</span>> |
| <<span class="hl-tag">groupId</span>>org.springframework<<span class="hl-tag">/groupId</span>> |
| <<span class="hl-tag">artifactId</span>>org.springframework.spring-library<<span class="hl-tag">/artifactId</span>> |
| <<span class="hl-tag">type</span>>libd<<span class="hl-tag">/type</span>> |
| <<span class="hl-tag">/dependency</span>> |
| <<span class="hl-tag">dependency</span>> |
| <<span class="hl-tag">groupId</span>>org.eclipse.persistence<<span class="hl-tag">/groupId</span>> |
| <<span class="hl-tag">artifactId</span>>com.springsource.org.eclipse.persistence<<span class="hl-tag">/artifactId</span>> |
| <<span class="hl-tag">/dependency</span>> |
| <<span class="hl-tag">dependency</span>> |
| <<span class="hl-tag">groupId</span>>org.eclipse.persistence<<span class="hl-tag">/groupId</span>> |
| <<span class="hl-tag">artifactId</span>>com.springsource.org.eclipse.persistence.jpa<<span class="hl-tag">/artifactId</span>> |
| <<span class="hl-tag">/dependency</span>> |
| </pre><p> |
| </p><p> |
| Now switch back to <code class="literal">module-context.xml</code> for <code class="literal">greenpages.jpa</code> and observe |
| that the errors relating to Spring’s ORM types have now been resolved. |
| Save <code class="literal">module-context.xml</code>. |
| </p><p> |
| The application context now contains a factory that will create an <code class="literal">EntityManager</code> and is |
| configured for annotation-based configuration. |
| The last step in completing <code class="literal">JpaDirectory</code> |
| is to annotate the <code class="literal">EntityManager</code> field so that Spring will inject the |
| <code class="literal">EntityManager</code> created by the factory into the field. |
| </p><p> |
| Open <code class="literal">JpaDirectory.java</code> again and add an annotation <code class="literal">@PersistenceContext</code> to the |
| <code class="literal">EntityManager</code> field. |
| </p><pre class="programlisting">@PersistenceContext |
| <span class="hl-keyword">private</span> EntityManager em; |
| </pre><p> |
| Eclipse will suggest an import for |
| <code class="literal">javax.persistence.PersistenceContext</code>; accept this and save the file. |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.building-jpa-module.providing-jpa-metadata"></a>Providing the JPA metadata</h3></div></div></div><p> |
| JPA uses a file named <code class="literal">META-INF/persistence.xml</code> to describe persistence units. |
| <code class="literal">persistence.xml</code> refers to a second file, typically named |
| <code class="literal">META-INF/orm.xml</code>, to define entity mappings. |
| In the case of GreenPages the |
| <code class="literal">persistence.xml</code> file specifies a single persistence unit that points to the |
| <code class="literal">greenpages.JpaListing</code> class. |
| The specified mapping file |
| (<code class="literal">META-INF/orm.xml</code>) tells the JPA implementation how to map |
| <code class="literal">JpaListing</code> to the <code class="literal">LISTING</code> database table described above. |
| (For more information on JPA consult the Documentation section in the appendix.) |
| </p><p> |
| Create a new file named <code class="literal">persistence.xml</code> in the <code class="literal">META-INF</code> folder of |
| the <code class="literal">greenpages.jpa</code> project. Add the following contents to the new file and then save it: |
| </p><pre class="programlisting"><<span class="hl-tag">?xml version="1.0" encoding="UTF-8" ?</span>> |
| <<span class="hl-tag">persistence</span> <span class="hl-attribute">xmlns</span>=<span class="hl-value">"http://java.sun.com/xml/ns/persistence"</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://java.sun.com/xml/ns/persistence |
| http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd"</span> |
| <span class="hl-attribute">version</span>=<span class="hl-value">"1.0"</span>> |
| |
| <<span class="hl-tag">persistence-unit</span> <span class="hl-attribute">name</span>=<span class="hl-value">"GreenPages"</span> <span class="hl-attribute">transaction-type</span>=<span class="hl-value">"RESOURCE_LOCAL"</span>> |
| <<span class="hl-tag">class</span>>greenpages.jpa.JpaListing<<span class="hl-tag">/class</span>> |
| <<span class="hl-tag">/persistence-unit</span>> |
| |
| <<span class="hl-tag">/persistence</span>> |
| </pre><p> |
| </p><p> |
| Now create a new file named <code class="literal">orm.xml</code> also in the <code class="literal">META-INF</code> folder |
| alongside <code class="literal">persistence.xml</code>. Add the following contents to the new file and then save it: |
| </p><pre class="programlisting"><<span class="hl-tag">?xml version="1.0" encoding="UTF-8" ?</span>> |
| <<span class="hl-tag">entity-mappings</span> <span class="hl-attribute">xmlns</span>=<span class="hl-value">"http://java.sun.com/xml/ns/persistence/orm"</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://java.sun.com/xml/ns/persistence/orm |
| http://java.sun.com/xml/ns/persistence/orm_1_0.xsd"</span> |
| <span class="hl-attribute">version</span>=<span class="hl-value">"1.0"</span>> |
| <<span class="hl-tag">package</span>>greenpages.jpa<<span class="hl-tag">/package</span>> |
| <<span class="hl-tag">entity</span> <span class="hl-attribute">class</span>=<span class="hl-value">"greenpages.jpa.JpaListing"</span> <span class="hl-attribute">name</span>=<span class="hl-value">"Listing"</span>> |
| <<span class="hl-tag">table</span> <span class="hl-attribute">name</span>=<span class="hl-value">"LISTING"</span> /> |
| <<span class="hl-tag">attributes</span>> |
| <<span class="hl-tag">id</span> <span class="hl-attribute">name</span>=<span class="hl-value">"listingNumber"</span>> |
| <<span class="hl-tag">column</span> <span class="hl-attribute">name</span>=<span class="hl-value">"LISTING_NUMBER"</span> /> |
| <<span class="hl-tag">generated-value</span> <span class="hl-attribute">strategy</span>=<span class="hl-value">"TABLE"</span> /> |
| <<span class="hl-tag">/id</span>> |
| <<span class="hl-tag">basic</span> <span class="hl-attribute">name</span>=<span class="hl-value">"firstName"</span>> |
| <<span class="hl-tag">column</span> <span class="hl-attribute">name</span>=<span class="hl-value">"FIRST_NAME"</span> /> |
| <<span class="hl-tag">/basic</span>> |
| <<span class="hl-tag">basic</span> <span class="hl-attribute">name</span>=<span class="hl-value">"lastName"</span>> |
| <<span class="hl-tag">column</span> <span class="hl-attribute">name</span>=<span class="hl-value">"LAST_NAME"</span> /> |
| <<span class="hl-tag">/basic</span>> |
| <<span class="hl-tag">basic</span> <span class="hl-attribute">name</span>=<span class="hl-value">"emailAddress"</span>> |
| <<span class="hl-tag">column</span> <span class="hl-attribute">name</span>=<span class="hl-value">"EMAIL_ADDRESS"</span> /> |
| <<span class="hl-tag">/basic</span>> |
| <<span class="hl-tag">/attributes</span>> |
| <<span class="hl-tag">/entity</span>> |
| <<span class="hl-tag">/entity-mappings</span>> |
| </pre><p> |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.building-jpa-module.consuming-datasource"></a>Consuming the DataSource from the service registry</h3></div></div></div><p> |
| The <code class="literal">entityManagerFactory</code> bean that was added earlier depends upon a bean named |
| <code class="literal">dataSource</code> which it will use to connect the <code class="literal">EntityManager</code> |
| to the GreenPages database. |
| The <code class="literal">greenpages.db</code> module already publishes a |
| <code class="literal">DataSource</code> to the service registry. |
| <code class="literal">greenpages.jpa</code> must now be |
| updated to consume this. |
| </p><p> |
| Open <code class="literal">osgi-context.xml</code> in the <code class="literal">META-INF/spring</code> folder of the |
| <code class="literal">greenpages.jpa</code> project and add the following: |
| </p><pre class="programlisting"> <<span class="hl-comment">!-- import the DataSource from OSGi --</span>> |
| <<span class="hl-tag">osgi:reference</span> <span class="hl-attribute">id</span>=<span class="hl-value">"dataSource"</span> <span class="hl-attribute">interface</span>=<span class="hl-value">"javax.sql.DataSource"</span> /> |
| </pre><p> |
| </p><p> |
| This will result in a bean being created in the application context that is named <code class="literal">dataSource</code>. |
| The bean will be of type <code class="literal">javax.sql.DataSource</code> and will be backed by a service found in the |
| OSGi service registry that implements the <code class="literal">javax.sql.DataSource</code> interface. |
| (Some warnings concerning the <code class="literal">dataSource</code> bean will now disappear.) |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.building-jpa-module.publishing-directory"></a>Publishing the Directory implementation to the service registry</h3></div></div></div><p> |
| To make the JPA-based <code class="literal">Directory</code> implementation available to GreenPages’ |
| Web module it must be “<span class="quote">published</span>” to the OSGi service registry. |
| </p><p> |
| Open <code class="literal">osgi-context.xml</code> in the <code class="literal">META-INF/spring</code> folder of the |
| <code class="literal">greenpages.jpa</code> project, add the following and then save the updated file: |
| </p><pre class="programlisting"> <<span class="hl-comment">!-- export the directory bean to OSGi under the Directory interface --</span>> |
| <<span class="hl-tag">osgi:service</span> <span class="hl-attribute">ref</span>=<span class="hl-value">"directory"</span> <span class="hl-attribute">interface</span>=<span class="hl-value">"greenpages.Directory"</span> /> |
| </pre><p> |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="middle-tier.building-jpa-module.generating-manifest"></a>Generating greenpages.jpa’s manifest using Bundlor</h3></div></div></div><p> |
| Open the <code class="literal">template.mf</code> file in the root of the <code class="literal">greenpages.jpa</code> |
| project and switch to the <code class="literal">template.mf</code> tab. Add the following entries to the template |
| and save it. |
| </p><pre class="programlisting">Import-Bundle: com.springsource.org.eclipse.persistence;version="[1.0.0,1.0.0]", |
| com.springsource.org.eclipse.persistence.jpa;version="[1.0.0,1.0.0]" |
| Import-Package: org.springframework.context.weaving;version="[3.0,3.1)", |
| org.springframework.transaction.aspectj;version="[3.0,3.1)" |
| Excluded-Exports: greenpages.jpa |
| </pre><p> |
| </p><p> |
| The <code class="literal">Excluded-Exports</code> header tells Bundlor that the |
| <code class="literal">greenpages.jpa</code> should not be exported from the <code class="literal">greenpages.jpa</code> |
| bundle. |
| </p><p> |
| The <code class="literal">Import-Package</code> entries for |
| <code class="literal">org.springframework.context.weaving</code> and |
| <code class="literal">org.springframework.transaction.aspectj</code> are needed as Bundlor cannot, yet, |
| detect that these packages are required. |
| </p><p> |
| Lastly, the <code class="literal">Import-Bundle</code> entries for EclipseLink and its JPA implementation |
| are needed as Bundlor cannot, yet, detect that EclipseLink is the JPA implementation that is |
| being used by GreenPages. |
| </p><p> |
| Switch to the <span class="emphasis"><em>Overview</em></span> tab and click <span class="emphasis"><em>Update MANIFEST.MF</em></span>. |
| As with <code class="literal">greenpages.db</code> before, this update may result in some errors being |
| reported in the manifest as the project is not associated with a targetted runtime. Double-click the |
| <code class="literal">MANIFEST.MF</code> file in the <code class="literal">greenpages</code> project in the Package Explorer. |
| Switch to the <span class="emphasis"><em>Dependencies</em></span> tab and click <span class="emphasis"><em>Add…</em></span>. Select |
| <code class="literal">greenpages.jpa</code> and click <span class="emphasis"><em>OK</em></span>. Save the updated file. The |
| problems in the manifest should now be resolved and the GreenPages application should be redeployed |
| due to the addition of the <code class="literal">greenpages.jpa</code> module. This redeployment should succeed |
| and it’s now time to try the application again. |
| </p><p> |
| (A possible action if this fails is to Update (Maven) Dependencies on the project right-click menu in the Maven sub-menu.) |
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