Maven Plugin

The critter-maven plugin generates Morphia entity models and property accessors at build time (AOT — ahead of time), so they are ready on the classpath before your application starts. Without the plugin, Morphia generates the same models at each JVM startup.

The plugin is entirely optional; the runtime fallback produces identical results. It is recommended to use the plugin, however.

Why use it?

Without plugin (runtime generation) With plugin (AOT generation)

Without plugin (runtime generation)	With plugin (AOT generation)
Models generated at JVM startup	Models generated once at build time, loaded instantly
Startup cost proportional to number of mapped entities	Zero startup cost — models are regular `.class` files on the classpath
No build-time dependency on the plugin	Build-time dependency, no runtime overhead
Good for development and smaller applications	Recommended for production deployments and fast-start environments (e.g., serverless, containers)

Models generated at JVM startup

Models generated once at build time, loaded instantly

Startup cost proportional to number of mapped entities

Zero startup cost — models are regular .class files on the classpath

No build-time dependency on the plugin

Build-time dependency, no runtime overhead

Good for development and smaller applications

Recommended for production deployments and fast-start environments (e.g., serverless, containers)

Both paths generate the bytecode necessary to manage your entities. The plugin simply moves the generation work from JVM startup to build time.

Setup

Add the plugin to your pom.xml and set morphia.mapper=critter in your config:

<plugin>
    <groupId>dev.morphia.morphia</groupId>
    <artifactId>critter-maven</artifactId>
    <version>${morphia.version}</version>
    <executions>
        <execution>
            <id>generate-critter</id>
            <goals>
                <goal>generate-models</goal>
            </goals>
        </execution>
    </executions>
</plugin>

# META-INF/morphia-config.properties
morphia.mapper=critter

When morphia.mapper=critter is active and the plugin has run, Morphia loads the pre-generated models automatically — no code changes required.

Goals

`generate-models` (default phase: `process-classes`)

Reads compiled .class files from ${project.build.outputDirectory} and writes generated entity model and accessor classes to target/generated-classes/critter. This is the standard goal for most projects. It has no user-configurable parameters.

How it fits together

Maven build
  └─ compile phase          → your entity .class files
  └─ process-classes phase  → critter-maven:generate-models
       reads entity .class files
       writes generated entity model class files
  └─ package phase          → all .class files bundled in JAR

Runtime (morphia.mapper=critter)
  └─ CritterMapper.mapEntity(Hotel.class)
       1. tryLoadPregenerated()  → finds HotelEntityModel on classpath ✓
       2. (skipped)              → no runtime generation needed
       3. (skipped)              → no reflection fallback needed

If the plugin was not run (e.g., during a quick mvn test-compile without the full lifecycle), step 1 finds nothing and Morphia transparently falls back to runtime generation at step 2.