Migrate a Gradle Project

This tutorial walks through migrating a Gradle Java/Kotlin project to Bazel.

What You’ll Learn

How to analyze a Gradle project
How to handle multi-module projects
How to map Gradle dependencies to Bazel

Prerequisites

A Gradle project with build.gradle or build.gradle.kts
Bazel 9.x installed
rebaze binary

Project Structure

Consider a typical Gradle project:

Directorymyapp/
- build.gradle.kts
- settings.gradle.kts
- Directoryapp/
  - build.gradle.kts
  - src/main/java/…
- Directorylib/
  - build.gradle.kts
  - src/main/java/…

With settings.gradle.kts:

rootProject.name = "myapp"
include("app", "lib")

Analyze the project

rebaze analyze myapp/

Output:

Detected build systems: gradle

Preview the migration

rebaze migrate myapp/ --dry-run

Shows generated files:

module(name = "myapp", version = "0.1.0")
bazel_dep(name = "rules_java", version = "...")

java_binary(
    name = "app",
    srcs = glob(["src/main/java/**/*.java"]),
    deps = ["//lib"],
)

java_library(
    name = "lib",
    srcs = glob(["src/main/java/**/*.java"]),
    visibility = ["//visibility:public"],
)

Run the migration
Terminal window
```
rebaze migrate myapp/
```

Validate

rebaze validate myapp/

Or:

cd myapp
bazel build //...
bazel test //...

External Dependencies

Gradle dependencies are mapped to rules_jvm_external:

dependencies {
    implementation("com.google.guava:guava:32.1.3-jre")
    testImplementation("junit:junit:4.13.2")
}

Generates:

maven = use_extension("@rules_jvm_external//:extensions.bzl", "maven")
maven.install(
    artifacts = [
        "com.google.guava:guava:32.1.3-jre",
        "junit:junit:4.13.2",
    ],
)
use_repo(maven, "maven")

java_library(
    name = "lib",
    srcs = glob(["src/main/java/**/*.java"]),
    deps = ["@maven//:com_google_guava_guava"],
)

Gradle to Bazel Mapping

Gradle	Bazel
`implementation`	`deps`
`api`	`deps` + `exports`
`testImplementation`	test target `deps`
`compileOnly`	`neverlink = True`
`runtimeOnly`	`runtime_deps`

Current Limitations

Next Steps

CLI Reference - All migration options
Dependency Strategies - Resolution options