Guide to using Modello

Modello is a tool for generating resources from a simple model. From a simple model you can generate things like:

  • Java sources
  • XML serialization code for the model
  • XML deserialization code for model
  • Model documentation
  • XSD

A typical modello model looks like the following:

  1. <model xmlns="http://modello.codehaus.org/MODELLO/1.4.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  2.   xsi:schemaLocation="http://modello.codehaus.org/MODELLO/1.4.0 http://modello.codehaus.org/xsd/modello-1.4.0.xsd"
  3.   xml.namespace="http://maven.apache.org/plugins/maven-archetype-plugin/archetype/${version}"
  4.   xml.schemaLocation="http://maven.apache.org/xsd/archetype-${version}.xsd">
  5.   <id>archetype</id>
  6.   <name>Archetype</name>
  7.   <description>
  8.     <![CDATA[Maven's model for the old archetype descriptor (ie for Archetype 1.0.x).
  9.     <p>The metadata about an archetype is stored in the <code>archetype.xml</code> file located
  10.     in the <code>META-INF/maven</code> directory of its jar file.</p>]]>
  11.   </description>
  12.  
  13.   <defaults>
  14.     <default>
  15.       <key>package</key>
  16.       <value>org.apache.maven.archetype.model</value>
  17.     </default>
  18.   </defaults>
  19.  
  20.   <classes>
  21.     <class rootElement="true" xml.tagName="archetype">
  22.       <name>ArchetypeModel</name>
  23.       <description>Describes the assembly layout and packaging.</description>
  24.       <version>1.0.0</version>
  25.       <fields>
  26.         <field>
  27.           <name>id</name>
  28.           <version>1.0.0</version>
  29.           <required>true</required>
  30.           <type>String</type>
  31.           <description><![CDATA[The value should be the same as the artifactId in the archetype <code>pom.xml</code>.]]></description>
  32.         </field>
  33.         <field>
  34.           <name>allowPartial</name>
  35.           <version>1.0.0</version>
  36.           <type>boolean</type>
  37.           <description><![CDATA[Setting this option to <code>true</code> makes it possible to run the
  38.             <code>archetype:create</code> even on existing projects.]]></description>
  39.         </field>
  40.  
  41.         <field xdoc.separator="blank">
  42.           <name>sources</name>
  43.           <version>1.0.0</version>
  44.           <description><![CDATA[Files that will go into <code>src/main/java</code>.]]></description>
  45.           <association>
  46.             <type>Source</type>
  47.             <multiplicity>*</multiplicity>
  48.           </association>
  49.         </field>
  50.         <field>
  51.           <name>resources</name>
  52.           <version>1.0.0</version>
  53.           <description><![CDATA[Files that will go into <code>src/main/resources</code>.]]></description>
  54.           <association>
  55.             <type>Resource</type>
  56.             <multiplicity>*</multiplicity>
  57.           </association>
  58.         </field>
  59.  
  60.         <field xdoc.separator="blank">
  61.           <name>testSources</name>
  62.           <version>1.0.0</version>
  63.           <description><![CDATA[Files that will go into <code>src/test/java</code>.]]></description>
  64.           <association xml.tagName="source">
  65.             <type>Source</type>
  66.             <multiplicity>*</multiplicity>
  67.           </association>
  68.         </field>
  69.         <field>
  70.           <name>testResources</name>
  71.           <version>1.0.0</version>
  72.           <description><![CDATA[Files that will go into <code>src/test/resources</code>.]]></description>
  73.           <association xml.tagName="resource">
  74.             <type>Resource</type>
  75.             <multiplicity>*</multiplicity>
  76.           </association>
  77.         </field>
  78.  
  79.         <field xdoc.separator="blank">
  80.           <name>siteResources</name>
  81.           <version>1.0.0</version>
  82.           <description><![CDATA[Files that will go into <code>src/site</code>.]]></description>
  83.           <association xml.tagName="resource">
  84.             <type>Resource</type>
  85.             <multiplicity>*</multiplicity>
  86.           </association>
  87.         </field>
  88.       </fields>
  89.     </class>
  90.  
  91.     <class>
  92.       <name>Source</name>
  93.       <description>Describes a source file. Note that source files are always filtered, unlike resources that
  94.         can be non-filtered.</description>
  95.       <version>1.0.0</version>
  96.       <fields>
  97.         <field xml.content="true">
  98.           <name>file</name>
  99.           <version>1.0.0</version>
  100.           <type>String</type>
  101.           <description><![CDATA[The source file.]]></description>
  102.         </field>
  103.         <field xml.attribute="true">
  104.           <name>encoding</name>
  105.           <version>1.0.0</version>
  106.           <type>String</type>
  107.           <description><![CDATA[The encoding to be used when reading/writing this file.
  108.             Platform encoding is used by default, or ISO-8859-1 when filename ends in <code>.properties</code>]]></description>
  109.         </field>
  110.       </fields>
  111.     </class>
  112.     <class>
  113.       <name>Resource</name>
  114.       <description>Describes a resource file.</description>
  115.       <version>1.0.0</version>
  116.       <fields>
  117.         <field xml.content="true">
  118.           <name>file</name>
  119.           <version>1.0.0</version>
  120.           <type>String</type>
  121.           <description><![CDATA[The resource file.]]></description>
  122.         </field>
  123.         <field xml.attribute="true">
  124.           <name>encoding</name>
  125.           <version>1.0.0</version>
  126.           <type>String</type>
  127.           <description><![CDATA[The encoding to be used when reading/writing this file.
  128.             Platform encoding is used by default, or ISO-8859-1 when filename ends in <code>.properties</code>]]></description>
  129.         </field>
  130.         <field xml.attribute="true">
  131.           <name>filtered</name>
  132.           <version>1.0.0</version>
  133.           <type>boolean</type>
  134.           <defaultValue>true</defaultValue>
  135.           <description>A resource can be filtered, which means the file will be used as Velocity template.
  136.           It can be non-filtered, which means the file will be copied without modification.</description>
  137.         </field>
  138.       </fields>
  139.     </class>
  140.   </classes>
  141. </model>
  142.  

To utilize Modello you would configure the maven-modello-plugin something like the following where you want to generate the Java sources for the model, the xpp3 serialization code and the xpp3 deserialization code:

  1. <project>
  2.   ...
  3.   <build>
  4.     <plugins>
  5.       <plugin>
  6.         <groupId>org.codehaus.modello</groupId>
  7.         <artifactId>modello-maven-plugin</artifactId>
  8.         <version>1.8.3</version>
  9.         <executions>
  10.           <execution>
  11.             <goals>
  12.               <!-- Generate the xpp3 reader code -->
  13.               <goal>xpp3-reader</goal>
  14.               <!-- Generate the xpp3 writer code -->
  15.               <goal>xpp3-writer</goal>
  16.               <!-- Generate the Java sources for the model itself -->
  17.               <goal>java</goal>
  18.             </goals>
  19.           </execution>
  20.         </executions>
  21.         <configuration>
  22.           <models>
  23.             <model>src/main/mdo/descriptor.mdo</model>
  24.           </models>
  25.           <version>1.0.0</version>
  26.           <useJava5>true</useJava5>
  27.         </configuration>
  28.       </plugin>
  29.     </plugins>
  30.   </build>
  31.   ...
  32. </project>