Hibernate Example

Available as of Camel 2.11

This example is located in the examples/camel-example-hibernate directory of the Camel Extras project.
There is a README.txt file with instructions how to run it.

The source code for this example can be viewed online at this link

If you use maven then you can easily compile and install the example from the command line:

mvn install

About

This example shows how to exchange data using a shared database table.

The example has two Camel routes. The first route insert new data into the table, triggered by a timer to run every 5th second.
The second route pickup the newly inserted rows from the table, process the row(s), and mark the row(s) as processed when done; to avoid picking up the same rows again.

Implementation

In the camel-context.xml file in the src/main/resources/META-INF/spring folder we have the Spring XML file to setup and configure the database and Hibernate, as well the CamelContext.

Setting up database
<!-- this is the JDBC data source which uses an in-memory only Apache Derby database -->
  <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
    <property name="driverClassName" value="org.apache.derby.jdbc.EmbeddedDriver"/>
    <property name="url" value="jdbc:derby:memory:orders;create=true"/>
    <property name="username" value=""/>
    <property name="password" value=""/>
  </bean>

And in the same file we setup Hibernate. At first we have the Camel Hibernate component, and then a number of beans to setup transactions. And then the last bean setup the Hibernate session factory where we refer to the data source and the hibernate mapping files, and any other hibernate configurations we may need.

Setting up Hibernate
  <!-- setup the Camel hibernate component -->
  <bean id="hibernate" class="org.apacheextras.camel.component.hibernate.HibernateComponent">
    <property name="sessionFactory" ref="sessionFactory"/>
    <property name="transactionStrategy" ref="springTransactionStrategy"/>
  </bean>

  <!-- setup hibernate and spring to use transaction -->
  <bean id="springTransactionStrategy" class="org.apacheextras.camel.component.hibernate.SpringTransactionStrategy">
    <constructor-arg ref="sessionFactory"/>
    <constructor-arg ref="transactionTemplate"/>
  </bean>
  <bean id="transactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager">
    <property name="sessionFactory" ref="sessionFactory"/>
  </bean>
  <bean id="transactionTemplate" class="org.springframework.transaction.support.TransactionTemplate">
    <property name="transactionManager" ref="transactionManager"/>
  </bean>

  <!-- setup Hibernate session factory -->
  <bean id="sessionFactory" class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <!-- here we define the hibernate mapping files we use -->
    <property name="mappingResources">
      <list>
        <value>Order.hbm.xml</value>
      </list>
    </property>
    <!-- and here we have additional hibernate options -->
    <property name="hibernateProperties">
      <value>
        hibernate.dialect=org.hibernate.dialect.DerbyTenSevenDialect
        hibernate.hbm2ddl.auto=create
      </value>
    </property>
  </bean>

And then in the same file we setup our Camel application. At first we have a orderBean that we use in the routes to generate new orders and process orders as well.

Camel application
  <!-- order bean is our business logic bean that creates new orders -->
  <bean id="orderBean" class="org.apacheextras.camel.examples.hibernate.OrderBean"/>

  <camelContext xmlns="http://camel.apache.org/schema/spring">

    <!-- route that generate new orders and insert them in the database -->
    <route id="generateOrder-route">
      <from uri="timer:foo?period=5s"/>
      <transform>
        <method ref="orderBean" method="generateOrder"/>
      </transform>
      <to uri="hibernate:org.apacheextras.camel.examples.hibernate.Order"/>
      <log message="Inserted new order ${body.id}"/>
    </route>


    <!-- route that process the orders by picking up new rows from the database
         and when done processing then update the row to mark it as processed -->
    <route id="processOrder-route">
      <from uri="hibernate:org.apacheextras.camel.examples.hibernate.Order?delay=1s"/>
      <to uri="bean:orderBean?method=processOrder"/>
      <log message="${body}"/>
    </route>

  </camelContext>

Hibernate mapping and POJO beans

In this example we have a Order POJO in the class org.apacheextras.camel.examples.hibernate.Order which we use Hibernate to map to/from the database. The Order pojo is just a bean with the following attributes with getter/setter

Order pojo
public class Order {

    private int id;
    private int item;
    private int amount;
    private String description;

    // getter/setter here
    ...
}

The Order pojo is mapped to Hibernate using the mapping file Order.hbm.xml which is located in the src/main/resources directory of the example

Hibernate mapping file to Order pojo
<hibernate-mapping>

	<class name="org.apacheextras.camel.examples.hibernate.Order" schema="orders" table="incoming_order">

		<id name="id">
			<generator class="native"/>
		</id>

		<property name="item" length="8"/>
		<property name="amount" length="4"/>
		<property name="description" length="50"/>
	</class>

</hibernate-mapping>

Running the example

This example can be run from the command line

mvn camel:run

Press ctrl + c to stop the example.

When running this example you should see logging in the console about orders being processed, for example as shown below:

[pache.camel.spring.Main.main()] SpringCamelContext             INFO  Apache Camel 2.11.0 (CamelContext: camel-1) started in 0.836 seconds
[mel-1) thread #0 - timer://foo] generateOrder-route            INFO  Inserted new order 1
[camel.examples.hibernate.Order] processOrder-route             INFO  Processed order id 1 item 222 of 2 copies of ActiveMQ in Action
[mel-1) thread #0 - timer://foo] generateOrder-route            INFO  Inserted new order 2
[camel.examples.hibernate.Order] processOrder-route             INFO  Processed order id 2 item 111 of 2 copies of Camel in Action
...

See Also

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