Configure SQL datasource through properties in Camel Blueprint (within Karaf)

Question

Given a very simple Camel bundle for Karaf, generated with the camel-archetype-blueprint, I want to add a datasource that is configured via properties and not within the blueprint.xml.

I tried configuring a PropertiesComponent and accessing the property within the property value for the MySQL datasource in various ways, but none seems to work. When logging a message though, the properties are accessible.

How can a datasource be configured using parameter values from a properties file?

I especially need this to use the same datasource configuration for multiple bundles and distinguish between production/test environments. I thought about writing the properties with Maven during the build, depending on the target environment. Are there any other best practices on how to solve this datasource issue?

<?xml version="1.0" encoding="UTF-8"?>
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.osgi.org/xmlns/blueprint/v1.0.0 http://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd
       http://camel.apache.org/schema/blueprint http://camel.apache.org/schema/blueprint/camel-blueprint.xsd">

    <bean id="properties" class="org.apache.camel.component.properties.PropertiesComponent">
        <property name="location" value="classpath:config.properties" />
    </bean>

    <bean id="dataSourceMySQL" class="com.mysql.jdbc.jdbc2.optional.MysqlDataSource">
        <property name="url" value="jdbc:mysql://127.0.0.1/test_database" />
        <!-- This causes an error, as it tries to connect with
             `${mysqlUser}`@`localhost` without any evaluation -->
        <property name="user" value="${mysqlUser}" />
        <property name="password" value="${mysqlPassword}" />
    </bean>

    <service interface="javax.sql.DataSource" ref="dataSourceMySQL">
        <service-properties>
            <entry key="osgi.jndi.service.name" value="jdbc/mysqlDatasource" />
        </service-properties>
    </service>
    <bean id="sql" class="org.apache.camel.component.sql.SqlComponent">
        <property name="dataSource" ref="dataSourceMySQL" />
    </bean>

    <camelContext xmlns="http://camel.apache.org/schema/blueprint">
        <route id="messageQuery">
            <from uri="sql:SELECT * FROM messages" />
            <log message="The user property is: {{mysqlUser}}, the query result is: ${body}" />
        </route>
    </camelContext>

</blueprint>

Just for an overview, the project layout looks like this:

Answer 1

a) Datasource in bundle with xml and bundle properties

You could use bundle properties. The example below optionally uses a bundle configuration in etc/org.camel.demo.cfg:

<?xml version="1.0" encoding="UTF-8"?>
<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://www.osgi.org/xmlns/blueprint/v1.0.0 http://www.osgi.org/xmlns/blueprint/v1.0.0/blueprint.xsd
       http://camel.apache.org/schema/blueprint http://camel.apache.org/schema/blueprint/camel-blueprint.xsd">

    <!-- etc/org.camel.demo.cfg -->
    <cm:property-placeholder persistent-id="org.camel.demo" xmlns:cm="http://aries.apache.org/blueprint/xmlns/blueprint-cm/v1.0.0">
        <cm:default-properties>
            <cm:property name="mysqlUser" value="root"/>
            <cm:property name="mysqlPassword" value=""/>
        </cm:default-properties>
    </cm:property-placeholder>

    <bean id="properties" class="org.apache.camel.component.properties.PropertiesComponent">
        <property name="location" value="classpath:config.properties" />
    </bean>

    <bean id="dataSourceMySQL" class="com.mysql.jdbc.jdbc2.optional.MysqlDataSource">
        <property name="url" value="jdbc:mysql://127.0.0.1/test_database" />
        <property name="user" value="${mysqlUser}" />
        <property name="password" value="${mysqlPassword}" />
    </bean>
</blueprint>

b) Shared datasource

Another option would be to use a shared datasource. Just deploy a blueprint file containing only the datasource (example below uses postgres).

You can combine this also with config properties as shown above.

Providing the OSGi service

<blueprint xmlns="http://www.osgi.org/xmlns/blueprint/v1.0.0">

    <!-- use config properties if needed -->

    <bean id="dataSource" class="org.postgresql.ds.PGPoolingDataSource" destroy-method="close">
        <property name="serverName" value=":"/>
        <property name="user" value="postgres"/>
        <property name="password" value="postgres"/>
        <property name="dataSourceName" value="demo"/>
        <property name="initialConnections" value="2"/>
        <property name="maxConnections" value="4" />
    </bean>

    <service interface="javax.sql.DataSource" ref="dataSource">
        <service-properties>
            <entry key="osgi.jndi.service.name" value="jdbc/demo"/>
        </service-properties>
    </service>
</blueprint>

Referencing from another bundle

In your bundle you can then lookup the datasource osgi:service/javax.sql.DataSource/(osgi.jndi.service.name=jdbc/demo)

To use this datasource in a SqlComponent, a reference must be created like this:

<reference id="dataSource" interface="javax.sql.DataSource"
    filter="(osgi.jndi.service.name=jdbc/mysql)">
</reference>
<bean id="sql" class="org.apache.camel.component.sql.SqlComponent">
    <property name="dataSource" ref="dataSource" />
</bean>

Using the persistence.xml

Make sure you import org.demo.osgi.datasource.**. Here is a usage example with persistence.xml:

<persistence version="2.0"
             xmlns="http://java.sun.com/xml/ns/persistence" >

    <persistence-unit name="demo" transaction-type="JTA">
        <provider>org.hibernate.ejb.HibernatePersistence</provider>
        <jta-data-source>osgi:service/javax.sql.DataSource/(osgi.jndi.service.name=jdbc/demo)</jta-data-source>
        <mapping-file>META-INF/foo.xml</mapping-file>
    </persistence-unit>

</persistence>

c) Use jdbc-feature (optional)

The xml file from above can be created and managed using the jdbc feature. It depends a bit on your version if it is available or not:

JBossFuse:admin@545074693af1> features:install jdbc hibernate jndi
JBossFuse:admin@545074693af1> install mvn:org.postgresql/postgresql/9.4.1208
Bundle ID: 292
JBossFuse:admin@545074693af1> resolve 292
JBossFuse:admin@545074693af1> jdbc:create -t postgres -u postgres -p postgres  -url ${postgres.addr}:${postgres.port} demo

P.S.: If you want to remove the cleartext password from the config file use something like jasypt.