Thread: [Andromdaplugins-cvs] CVS update: cartridges/andromda-ejb3/src/site/xdoc howto19.xml

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  User: vancek  
  Date: 06/05/01 19:27:00

  Added:       andromda-ejb3/src/site/xdoc howto19.xml
  Log:
  initial revision DAO
  
  Revision  Changes    Path
  1.1                  cartridges/andromda-ejb3/src/site/xdoc/howto19.xml
  
  Index: howto19.xml
  ===================================================================
  <?xml version="1.0" encoding="iso-8859-1"?>
  <document>
      <properties>
          <author email="va...@us...">Vance Karimi</author>
          <title>AndroMDA - EJB3 - HowTo DAO</title>
      </properties>
      <body>
          <section name="Data Access Objects (DAO)">
              <p>
                  The Data Access Layer provides an API for accessing and manipulating data in the persistence tier 
                  and abstracts or hides much of this complexity from the session bean business logic tier.
                  To find out more about the different tiers on an enterprise application and where DAO object
                  typically fit in the stack, you can read the 
                  <a href="http://galaxy.andromda.org/docs/getting-started/java/index.html">getting started
                  guide</a>.
              </p>
              <p>
                  For every entity class, modelled with the <![CDATA[<<Entity>>]]> stereotype, 3 DAO related
                  objects are created.  This provdes the typical CRUD API and finder method accessability for a 
                  specific entity.
              </p>
              <p>
                  DAO's are just stateless session beans with a local interface.  The presentation layer wouldn't
                  use the DAO local interface directly.  Instead, your session beans in the business layer
                  would utilise the DAO interface for all persistence related tasks.
              </p>
              <p>
                  By modelling dependencies from the service to the entities the cartridge will inject the local interface
                  of the DAO of the target entities in to the session bean.  You are then free to use this DAO
                  instance variable when CRUD features available in the API are required.
              </p>
              <p>
                  The following example, illustrates a typical entity POJO and its generated DAO components.
              </p>
              <p>
                  <img src="images/org/andromda/test/19/a/uml.gif"/>
              </p>
              <p>
                  <ul>
                      <li class="gen">Auto-generated source that does not need manual editing</li>
                      <li class="impl">Auto-generated source that should be edited manually</li>
                      <li class="changed">File that is affected by the modifications applied in this section</li>
                  </ul>
              </p>
              <p>
                  <ul>
                      <li class="gen"><a class="changed" href="src/org/andromda/test/howto19/a/Person.java"><code>Person.java</code></a></li>
                      <li class="gen"><a class="changed" href="src/org/andromda/test/howto19/a/PersonDao.java"><code>PersonDao.java</code></a></li>
                      <li class="gen"><a class="changed" href="src/org/andromda/test/howto19/a/PersonDaoBase.java"><code>PersonDaoBase.java</code></a></li>
                      <li class="impl"><a class="changed" href="src/org/andromda/test/howto19/a/PersonDaoImpl.java"><code>PersonDaoImpl.java</code></a></li>
                      <li class="gen"><a class="changed" href="src/org/andromda/test/howto19/a/PersonDaoException.java"><code>PersonDaoException.java</code></a></li>
                  </ul>
              </p>
              <p>
                  Since the <code>Person</code> entity contains finder methods, the <code>PersonDaoImpl</code>
                  is generated once only to <code>core/src/main/java</code>. You can override or add any method 
                  implementation to this file.
              </p>
              <p>
                  The <code>PersonDaoBase.java</code> injects the <code>javax.ejb.SessionContext</code> by
                  default and makes this available for use in the subclass via the <code>context</code> protected
                  property.  This base DAO class contains the bulk of the CRUD API implementation.  It injects
                  the default <code>PersistenceContext</code> and provides the finder method implementations
                  modelled on the entity.
              </p>
              <a name="Queries"/>
              <subsection name="Queries">
                  <p>
                      The <code>Person</code> entity contains the <code>@NamedQueries</code> annotation with
                      the array of <code>@NamedQuery</code> annotations defining the query logic.  The corresponding
                      <code>findBy</code> methods in the <code>PersonDaoBase</code> provide the ability to either
                      specify a query string or use the named query defined in the application at deploy-time.
                  </p>
              </subsection>
              <a name="View_Interface"/>
              <subsection name="View Interface">
                  <p>
                      The DAO stateless session bean is accessed via the local interface. This means that you
                      cannot access DAO from a remote container, but this isn't a concern since your session 
                      facade exposes the remote interface and contains your business logic.
                  </p>
              </subsection>
              <a name="Transactions"/>
              <subsection name="Transactions">
                  <p>
                      All DAO base abstract classes define the <code>@TransactionAttribute</code> annotation,
                      setting the transaction type to <code>REQUIRED</code>.  Typically, you would start your
                      transactions in your business logic within your session facades.
                  </p>
              </subsection>
              <a name="Security"/>
              <subsection name="Security">
                  <p>
                      The EJB3 cartridge provides the ability to set basic security constraints to allow
                      role based security when accessing and invoking CRUD operations in the DAO session beans.
                      To find out how to enable JAAS security, click on <a href="howto8.html">Security</a>.
                  </p>
                  <p>
                      If you enable security and do not model actor dependencies on the entities to limit 
                      roles permitted to access to your DAO, the EJB3 cartridge will add the
                      <code>@javax.annotation.security.PermitAll</code> annotation at the class level of your
                      base DAO class.  This implies that all methods of the DAO are not checked for
                      security constraints.
                  </p>
              </subsection>
          </section>
          <section name="Next">
              <p>
                  In the next section we'll learn about entity relationships, click
                  <a href="howto2.html">here</a> to continue.
              </p>
          </section>
      </body>
  </document>

Thread: [Andromdaplugins-cvs] CVS update: cartridges/andromda-ejb3/src/site/xdoc howto19.xml

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