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:
<model xmlns="http://codehaus-plexus.github.io/MODELLO/2.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://codehaus-plexus.github.io/MODELLO/2.0.0 https://codehaus-plexus.github.io/modello/xsd/modello-2.0.0.xsd" xml.namespace="https://maven.apache.org/plugins/maven-archetype-plugin/archetype-descriptor/${version}" xml.schemaLocation="https://maven.apache.org/xsd/archetype-descriptor-${version}.xsd"> <id>archetype-descriptor</id> <name>ArchetypeDescriptor</name> <description> <![CDATA[ <p>This is a reference for the Archetype descriptor used to describe archetypes's metadata.</p> <p>The metadata about an archetype is stored in the <code>archetype-metadata.xml</code> file located in the <code>META-INF/maven</code> directory of its jar file.</p>]]> </description> <defaults> <default> <key>package</key> <value>org.apache.maven.archetype.metadata</value> </default> </defaults> <classes> <class rootElement="true" xml.tagName="archetype-descriptor"> <name>ArchetypeDescriptor</name> <version>1.0.0+</version> <superClass>AbstractArchetypeDescriptor</superClass> <fields> <field xml.attribute="true"> <name>name</name> <version>1.0.0+</version> <type>String</type> <required>true</required> <description>Name of the Archetype, that will be displayed to the user when choosing an archetype.</description> </field> <field xml.attribute="true"> <name>partial</name> <version>1.0.0+</version> <type>boolean</type> <required>false</required> <description>Is this archetype representing a full Maven project or only parts?</description> </field> <field> <name>requiredProperties</name> <version>1.0.0+</version> <description>List of required properties to generate a project from this archetype.</description> <association> <type>RequiredProperty</type> <multiplicity>*</multiplicity> </association> </field> </fields> </class> <class> <name>ModuleDescriptor</name> <version>1.0.0+</version> <superClass>AbstractArchetypeDescriptor</superClass> <fields> <field xml.attribute="true"> <name>id</name> <version>1.0.0+</version> <type>String</type> <required>true</required> <description>The module's artifactId.</description> </field> <field xml.attribute="true"> <name>dir</name> <version>1.0.0+</version> <type>String</type> <required>true</required> <description>The module's directory.</description> </field> <field xml.attribute="true"> <name>name</name> <version>1.0.0+</version> <type>String</type> <required>true</required> <description>The module's name.</description> </field> </fields> </class> <class> <name>AbstractArchetypeDescriptor</name> <version>1.0.0+</version> <fields> <field xdoc.separator="blank"> <name>fileSets</name> <version>1.0.0+</version> <association> <type>FileSet</type> <multiplicity>*</multiplicity> </association> <required>true</required> <description>File sets definition.</description> </field> <field xdoc.separator="blank"> <name>modules</name> <version>1.0.0+</version> <association> <type>ModuleDescriptor</type> <multiplicity>*</multiplicity> </association> <required>false</required> <description>Modules definition.</description> </field> </fields> </class> <class> <name>FileSet</name> <version>1.0.0+</version> <description><![CDATA[ A fileset defines the way the project's files located in the jar file are used by the Archetype Plugin to generate a project. If file or directory name contains <code>__<i>property</i>__</code> pattern, it is replaced with corresponding property value. ]]></description> <fields> <field xml.attribute="true"> <name>filtered</name> <version>1.0.0+</version> <type>boolean</type> <required>false</required> <description><![CDATA[ Filesets can be filtered, which means the selected files will be used as <a href="https://velocity.apache.org/engine/1.5/user-guide.html">Velocity templates</a>. They can be non-filtered, which means the selected files will be copied without modification. ]]></description> </field> <field xml.attribute="true"> <name>packaged</name> <version>1.0.0+</version> <type>boolean</type> <required>false</required> <description>Filesets can be packaged, which means the selected files will be generated/copied in a directory structure that is prepended by the package property. They can be non-packaged, which means that the selected files will be generated/copied without that prepend.</description> </field> <field xml.attribute="true"> <name>encoding</name> <version>1.0.0+</version> <type>String</type> <required>false</required> <description>Encoding to use when filtering content.</description> </field> <field> <name>directory</name> <version>1.0.0+</version> <type>String</type> <required>false</required> <defaultValue/> <description>The directory where the files will be searched for, which is also the directory where the project's files will be generated.</description> </field> <field> <name>includes</name> <version>1.0.0+</version> <association> <type>String</type> <multiplicity>*</multiplicity> </association> <required>false</required> <description>Inclusion definition "à la" Ant.</description> </field> <field> <name>excludes</name> <version>1.0.0+</version> <association> <type>String</type> <multiplicity>*</multiplicity> </association> <required>false</required> <description>Exclusion definition "à la" Ant.</description> </field> </fields> <codeSegments> <codeSegment> <code><![CDATA[ public String toString() { return getDirectory() + " (" + ( isFiltered() ? "Filtered" : "Copied" ) + "-" + ( isPackaged() ? "Packaged" : "Flat" ) + ") [" + org.codehaus.plexus.util.StringUtils.join( getIncludes().iterator(), ", " ) + " -- " + org.codehaus.plexus.util.StringUtils.join( getExcludes().iterator(), ", " ) + "]"; } ]]></code> </codeSegment> </codeSegments> </class> <class> <name>RequiredProperty</name> <version>1.0.0+</version> <description>Definition of a property required when generating a project from this archetype.</description> <fields> <field xml.attribute="true"> <name>key</name> <version>1.0.0+</version> <type>String</type> <required>true</required> <description>Key value of the property.</description> </field> <field> <name>defaultValue</name> <type>String</type> <required>false</required> <description>Default value of the property.</description> </field> <field> <name>validationRegex</name> <version>1.1.0+</version> <type>String</type> <required>false</required> <description>A regular expression used to validate the property.</description> </field> </fields> </class> </classes> </model>
To utilize Modello, you would configure the modello-maven-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 (see modello-plugin-xpp3 for more details):
<project> ... <build> <plugins> <plugin> <groupId>org.codehaus.modello</groupId> <artifactId>modello-maven-plugin</artifactId> <version>1.8.3</version> <executions> <execution> <goals> <!-- Generate the xpp3 reader code --> <goal>xpp3-reader</goal> <!-- Generate the xpp3 writer code --> <goal>xpp3-writer</goal> <!-- Generate the Java sources for the model itself --> <goal>java</goal> </goals> </execution> </executions> <configuration> <models> <model>src/main/mdo/archetype-descriptor.mdo</model> </models> <version>1.0.0</version> <useJava5>true</useJava5> </configuration> </plugin> </plugins> </build> ... </project>