Creating Container-managed Entity Beans with JBoss : Page 5

The JBoss CMP Descriptor File
The JBoss CMP descriptor file, jbosscmp-jdbc.xml, contains database and relationship mapping information for the entity beans in an EJB jar. For each entity defined in the EJB jar descriptor, the JBoss CMP descriptor must contain one <entity> child element in the <enterprise-beans> element. The <entity> element contains:

• <ejb-name> (required). Entity bean name, which must match an <ejb-name> element in the EJB jar descriptor.
• <datasource>. JNDI name of data source where entity bean is persisted. This element is required unless specified in the <defaults> element. (See the JBoss documentation for more information.)
• <datasource-mapping>. Name of data source type mapping. (Default is "Hypersonic SQL".)
• <table-name> (required). Name of table where entity data is stored.
• <create-table>. Indicator that the table should be created when the entity bean is deployed.
• <remove-table>. Indicator that the table should be removed when the entity bean is undeployed.
• <pk-constraint>. Indicator that a primary key constraint should be added to the table when it is created.
• <read-only>. Indicator that the table cannot be updated.
• <read-time-out>. Amount of time (milliseconds) that a read on a read-only field is valid.
• <row-locking>. Indicator that row locking should be used in transactions.
• <read-ahead>. Indicator that read-ahead caching should be used for queries.
• <list-cache-max>. Number of read lists that can be tracked by the entity.

For each container managed field in the entity bean, the <entity> element must contain one <cmp-field>, which includes:

• <field-name> (required). Container managed field name. The value should match the <field-name> of a <cmp-field> in the corresponding <entity> in the EJB jar descriptor.
• <column-name>. Name of the column that corresponds to the field in the table. The default is the value of <field-name>.
• - Indicator that null is not an allowed value. The default for primary key fields and fields with primitive data types is "true".
• <jdbc-type>. JDBC type of the field. This element is required only when you include an <sql-type> element. Valid values are the types defined in java.sql.Types. The data source mapping determines the default value.
• <sql-type>. SQL type of the table column. This element is required only when <jdbc-type> is specified. Valid values are the types defined by the database. The data source mapping determines the default value.

JBlog's JBoss CMP descriptor contains two <entity> elements, one for Author and one for Story.

   // Author entity element in JBoss CMP descriptor
   
   <entity>
      <ejb-name>Author</ejb-name>
      <table-name>author</table-name>
   
      <cmp-field>
         <field-name>username</field-name>
         <not-null/>
      </cmp-field>
      <cmp-field>
         <field-name>password</field-name>
         <not-null/>
      </cmp-field>
      <cmp-field>
         <field-name>name</field-name>
      </cmp-field>
   </entity>
   
   // Listing 10: Story entity element in JBoss CMP descriptor
   
   <entity>
      <ejb-name>Story</ejb-name>
      <table-name>story</table-name>
   
      <cmp-field>
         <field-name>storyId</field-name>
         <column-name>story_id</column-name>
         <not-null/>
      </cmp-field>
      <cmp-field>
         <field-name>pubDate</field-name>
         <column-name>pub_date</column-name>
         <not-null/>
      </cmp-field>
      <cmp-field>
         <field-name>title</field-name>
         <not-null/>
      </cmp-field>
      <cmp-field>
         <field-name>text</field-name>
         <not-null/>
      </cmp-field>
      <cmp-field>
         <field-name>username</field-name>
      </cmp-field>
   </entity>

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