Writing a Simple Module

This document describes how to create a trivial AntDepo module from scratch without the use of any special tools. Creating the module by hand, shows off the basic requirements to develop a module. AntDepo modules use a simple, standard file structure with a couple of required configuration property files.

Modules have the following directory layout:

module_name  |  |--- module.properties   // file containing module metadata  |--- commands.properties // file containing command metadata  |  +--- bin                 // optional binaries, shell scripts, etc.  |  +--- commands            // contains command handlers  |  +--- lib                 // optional module resource files 

Create a directory for the module in the module library:

mkdir $ANTDEPO_BASE/lib/ant/modules/HelloModulemkdir $ANTDEPO_BASE/lib/ant/modules/HelloModule/commandscd $ANTDEPO_BASE/lib/ant/modules/HelloModule

Create the module.properties file. The module.properties file is a standard configuration property file describing the module and its contents. Name and describe the module and define a command named Hello.

module.name=HelloModulemodule.description=My first modulemodule.commands=Hello 

With the module structure built, the next step is to create an implementation for the Hello command by supplying a command handler (ie., an Ant buildfile). Create a command handler file named Hello.xml and save it to $ANTDEPO_BASE/lib/ant/modules/HelloModule/commands.

Write Hello.xml

<project name="Hello" default="execute">  <property file="${module.dir}/module.properties"/>  <target name="execute">    <echo>Hi there</echo>  </target></project>      

AntDepo command handlers are Ant buildfiles that follow a few conventions. The primary requirement is that the handler has a target named execute and that target should be declared default for the project.

Run the command by specifying module name and command name.

ad -m HelloModule -c HelloHi there

This section describes how to define a command that uses a shell command type. A shell command type uses configuration data to define the script code to run. Declaring the script code in a property file allows you to define a generic handler template.

1. Add the command to the module.properties file

module.name=HelloModulemodule.description=My first modulemodule.commands=Hello, Echo

2. Define the command in the commands.properties file

The next step is to describe the shell command in the commands.properties file in the module base directory. Define the four properties as shown below.

command.Echo.command-type=shellcommand.Echo.execution-string=bashcommand.Echo.argument-string=echo Hi therecommand.Echo.doc=Says hello

3. Write Echo.xml

Create the handler for the Echo command using the ant-contrib shellscript task as shown below. Note the commands.properties file is now read.

<project name="Echo" default="execute">  <property file="${module.dir}/module.properties"/>  <property file="${module.dir}/commands.properties"/>  <target name="execute">    <shellscript shell="${command.Echo.execution-string}">       ${command.Echo.argument-string}    </shellscript>  </target></project>      

4. Run the command

ad -m HelloModule -c EchoHi there