Reputation: 68318
I'm converting a largish Ant build to Maven. As part of the Ant build, we have several steps which created Java classes by invoking one of the project's classes, simplified as:
javac SomeGenerator.java
java SomeGenerator generated # generate classes in generated/
javac generated/*.java
I've split each generator in its own Maven module, but I have the problem of not being able to run the generator since it's not yet compiled in the generate-sources
phase.
I've tried something similar to
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.1.1</version>
<executions>
<execution>
<id>generate-model</id>
<goals>
<goal>java</goal>
</goals>
<phase>generate-sources</phase>
<configuration>
<mainClass>DTOGenerator</mainClass>
<arguments>
<argument>${model.generated.dir}</argument>
</arguments>
</configuration>
</execution>
</executions>
</plugin>
Which sadly does not work, for the reasons outlined above. Splitting the code generators into two projects each, one for compiling the generator and another for generating the DTOs seems overkill.
What alternatives are there?
Using Maven 2.2.1.
Upvotes: 15
Views: 17972
Reputation: 152
Following is a minimal and well-commented pom.xml
that will allow code generation within the same project, while making sure to clean-up properly afterwards:
<build>
<plugins>
<!-- Compile XyzGenerator.java to XyzGenerator.class -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.11.0</version>
<executions>
<execution>
<id>code-generator</id>
<phase>generate-sources</phase>
<goals>
<goal>compile</goal>
</goals>
<configuration>
<includes>
<include>com/project/codegen/XyzGenerator.java</include>
</includes>
</configuration>
</execution>
</executions>
</plugin>
<!-- Execute XyzGenerator.class to generate Xyz.Java -->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>3.1.1</version>
<executions>
<execution>
<id>code-generator</id>
<phase>generate-sources</phase>
<goals>
<goal>java</goal>
</goals>
<configuration>
<classpathScope>compile</classpathScope>
<mainClass>com.project.codegen.CodeGenerator</mainClass>
<commandlineArgs>target/codegen/com/project/</commandlineArgs>
</configuration>
</execution>
</executions>
</plugin>
<!-- Include the path to Xyz.java for compilation -->
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>3.5.0</version>
<executions>
<execution>
<id>code-generator</id>
<phase>process-sources</phase>
<goals>
<goal>add-source</goal>
</goals>
<configuration>
<sources>
<source>target/codegen</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
<!-- Package the application in a JAR file -->
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.3.0</version>
<executions>
<execution>
<id>default-jar</id>
<phase>package</phase>
<goals>
<goal>jar</goal>
</goals>
<configuration>
<excludes>
<!-- Exclude the XyzGenerator.class file from the JAR -->
<exclude>com/project/codegen/*.*</exclude>
<exclude>com/project/codegen</exclude>
</excludes>
<archive>
<manifest>
<!-- Add the name of main class -->
<addClasspath>true</addClasspath>
<mainClass>com.project.Main</mainClass>
</manifest>
</archive>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
The main
function in CodeGenerator
class inside XyzGenerator.java
file takes the output directory as the first command line argument; above, this is passed in the <commandlineArgs>
tag.
The file structure is:
src
'- main
'- java
'- com
'- project
'- Main.class
'- codegen
'- XyzGenerator.java
target
'- codegen
'- com
'- project
Upvotes: 1
Reputation: 473
In order to do this in one project, there are 3 steps:
Compile generator code
We can do it in generate-sources
phase, using maven-compiler-plugin
. You can also exclude other source files.
Run generator to generate code
We can do it in process-sources
phase, using exec-maven-plugin
.
Compile project
Below is the key part of pom.xml
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.8.0</version>
<configuration>
<source>1.8</source>
<target>1.8</target>
</configuration>
<executions>
<execution>
<id>compile-generator</id>
<phase>generate-sources</phase>
<goals>
<goal>compile</goal>
</goals>
<configuration>
<includes>
<include>source/file/of/generator/*.java</include>
</includes>
<excludes>
<exclude>other/source/files/*.java</exclude>
</excludes>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.6.0</version>
<executions>
<execution>
<id>generate-codes</id>
<goals>
<goal>java</goal>
</goals>
<phase>process-sources</phase>
<configuration>
<mainClass>your.main.class.of.generator</mainClass>
</configuration>
</execution>
</executions>
</plugin>
Upvotes: 3
Reputation: 1216
I posted a minimal working setup here https://github.com/baloise/inlinesourcecodegenerator It uses build-helper compiler and exec plugins and has all code in the same project.
Upvotes: 1
Reputation: 2484
I didn't want to have 2 different projects, so I tried to setup Maven for adding the generated compiled code to the final jar package.
This is the working solution I've used:
process-classes
phase (executed just after the compile
phase):
exec-maven-plugin
for executing a main class able to generate my source files in target/generated-sources/java
folder (in my specific case I used the Roaster library for source code generation);build-helper-maven-plugin
for adding the generated sources in the correct locationprepare-package
phase:
maven-compiler-plugin
, in order to detect the changes and recompile the modulemaven-jar-plugin
for producing the jar packageThis is my pom.xml:
<build>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>exec-maven-plugin</artifactId>
<version>1.6.0</version>
<executions>
<execution>
<phase>process-classes</phase>
<goals>
<goal>java</goal>
</goals>
<configuration>
<mainClass>com.example.MyClassWriter</mainClass>
<arguments>
<argument>${project.basedir}</argument>
<argument>${project.build.directory}</argument>
</arguments>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>build-helper-maven-plugin</artifactId>
<version>3.0.0</version>
<executions>
<execution>
<phase>process-classes</phase>
<goals>
<goal>add-source</goal>
</goals>
<configuration>
<sources>
<source>${project.build.directory}/generated-sources/java</source>
</sources>
</configuration>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.6.1</version>
<executions>
<execution>
<phase>prepare-package</phase>
<goals>
<goal>compile</goal>
</goals>
</execution>
</executions>
</plugin>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-jar-plugin</artifactId>
<version>3.0.2</version>
<executions>
<execution>
<phase>prepare-package</phase>
</execution>
</executions>
</plugin>
</plugins>
</build>
Upvotes: 10
Reputation: 24169
We faced the same problem. We wanted to respect Maven's behavior as closely as possible, to have no problems with plugins and so on... Fighting Maven is just too expensive!
We realized that the update frequency of the generated code was usually very different from the one of the code that we manually write, so separating the code had very good performance characteristics for the build. So we accepted to have our generated classes as a dependency of the manually written.
We adopted the following structure, that had just one little change from a regular maven config, a change in the source directory.
We created a parent project for all our generations.
Note: if you want several generated results in the same jar, just put them in the same sub-directory.
It is a subdirectory of the Generations project.
It has a JAR type.
The source directory points to the sub-directory in the parent's target.
<sourceDirectory>../target/generated1</sourceDirectory>
It compiles normally in its own /target directory.
That structure allows us to :
<includes>
to handle only some of the classes).Upvotes: 1
Reputation: 114817
You can execute the maven-compile-plugin in the generate-sources phase. Just add another execution before the existing execution and configure it so that it just picks up the sources for the generator.
Or split the project in two: build the generator with a separate POM and include the generator library as a dependency to the POM that's generating the sources.
Personally I would split the project. Keeps the build files cleaner and easier to maintain.
Upvotes: 9