Developing with Apache Droids in your spring based project.

Once you have created the droids.jar, place it in your classpath and you are ready to develope your own components and robots. Droids is completly Spring driven, if you never have seen Spring at all you need to check out their documentation otherwise you will be lost.

We will develope a SIMPLE robot that will crawl a web page and send the data to an Apache Solr server (poor man's approach of Apache Nutch crawling) and will call it "indexer".

The resulting classes can be found in $DROIDS_HOME/src/example/java and can be compiled with ant droids.compile-example. This target compiles the examples, creates a jar and copy the resulting jar into the lib directory.

In your principal spring configuration you need to import the default spring configuration files from droids. A typical file would look something like the following.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN 2.0//EN"
    "http://www.springframework.org/dtd/spring-beans-2.0.dtd">
<beans>
  <import resource="classpath:/org/apache/droids/droids-core-factories-context.xml"/>
  <import resource="classpath:/org/apache/droids/droids-core-context.xml"/>
<!-- ... -->
</beans>

Then we need to configure the org.apache.droids.helper.factories.DroidFactory bean to add our new droid.

<bean id="org.apache.droids.helper.factories.DroidFactory"
  class="org.apache.droids.helper.factories.DroidFactory">
  <property name="map">
    <map>
      <entry key="indexer" value-ref="indexer"/>
      <!-- Referencing as well the Hello crawler 
         that is configured by the Droids core -->
      <entry key="hello" value-ref="hello"/>
    </map>
  </property>
</bean>

Then we need to configure our indexer.

<!-- Indexer -->
<bean id="indexer" class="org.apache.droids.examples.IndexerCrawler">
  <property name="core" ref="org.apache.droids.Core"/>
  <property name="queue" ref="org.apache.droids.queue.Simple"/>
  <property name="maxThreads" value="@droids.maxThreads@"/>
  <property name="url" value="@droids.initial.url@"/>
  <property name="updateUrl" value="http://localhost:8983/solr/update"/>
</bean>

The variables within @@ are replaced while building the jar with ant. The actual value is defiened either by the properties in your build.properties or the default.properties.

Now we need to wrap up our droid in defining our new handler.

<bean id="org.apache.droids.helper.factories.HandlerFactory"
  class="org.apache.droids.helper.factories.HandlerFactory">
  <property name="map">
    <map>
      <entry key="solr" value-ref="org.apache.droids.handle.Solr"/>
    </map>
  </property>
</bean>

<!-- Handler -->
<bean id="org.apache.droids.handle.Solr" class="org.apache.droids.handle.Solr">
  <property name="updateUrl" value="http://localhost:8983/solr/update"/>
</bean>