How to generate multiple classes from protoc in maven?

Question

I want to execute protoc (protobuffer compiler) from my maven file. I embeded an ant task in the pom.xml like the following

<executions>
  <execution>
      <id>generate-sources</id>
      <phase>generate-sources</phase>
      <configuration>
         <tasks>
           .... <!-- I have several of these blocks - how can I reduce them to one? -->
           <exec executable="protoc/protoc.exe">
              <arg value="--java_out=target/generated-sources"/>
              <arg value="src/main/protos/Proto1.proto"/>
              <arg value="--proto_path=src/main/protos"/>
           </exec>
           <exec executable="protoc/protoc.exe">
              <arg value="--java_out=target/generated-sources"/>
              <arg value="src/main/protos/Proto2.proto"/>
              <arg value="--proto_path=src/main/protos"/>
          </exec>
        .....
       </tasks>
       <sourceRoot>target/generated-sources</sourceRoot>
     </configuration>
     <goals>
       <goal>run</goal>
     </goals>
   </execution>

How can I define a loop or something so maven iterates all over the files in a directory?

I know there is a protobuffer maven plugin out there but I had to declare an external repository to use it and this is currently not an option.

Answer 1

The apply ant task should do you need. Replace the list of exec by :

<apply executable="protoc/protoc.exe" parallel="false">
  <arg value="--java_out=target/generated-sources"/>
  <srcfile/>
  <arg value="--proto_path=src/main/protos"/>
  <fileset dir="${basedir}/src/main/protos" includes="*.proto"/>
</apply>

http://ant.apache.org/manual/Tasks/apply.html