Java Build Tool Comparison

Three build tools dominate modern Java: Maven, Gradle, and Bazel. They make different trade-offs between configuration cost, build speed, and flexibility. Most teams pick Maven by default; some pick Gradle for specific reasons; few pick Bazel without a specific scaling need. This page covers what each is good at and how to decide.

Maven

Declarative XML, convention-over-configuration, decades of ecosystem.

Strengths

- **Declarative**: the POM describes what, not how. Predictable behavior across teams.

- **Ecosystem**: every Java library publishes Maven artifacts; every IDE supports Maven natively.

- **Consistency**: the conventions (directory layout, lifecycle phases) are nearly universal.

- **Tooling**: extensive plugin ecosystem.

Weaknesses

- **XML verbosity**: large POMs are hard to read.

- **Build performance**: slower than alternatives at scale.

- **Customization friction**: non-standard build steps require plugins or workarounds.

- **Limited incrementality**: Maven re-runs phases more often than Gradle.

When Maven is right

- Standard Java application, no exotic build needs

- Team familiar with Maven

- Heavy use of mainstream Java libraries

- Multi-module project with conventional structure

This describes most Java projects.

Gradle

Configuration-as-code (Groovy or Kotlin DSL), build caching, incremental compilation.

Strengths

- **Speed**: incremental builds, build caching, daemon process — significantly faster than Maven on large projects

- **Flexibility**: full programming language for build configuration

- **Customization**: easy to add custom build steps without plugins

- **Multi-language support**: Java, Kotlin, Scala, Android, native — all in one build system

- **Dependency configuration**: more powerful than Maven for complex cases

Weaknesses

- **Complexity**: full programming language is more powerful and more confusing

- **Reproducibility**: build configuration can do unexpected things; harder to reason about

- **Documentation**: improved over time but still less consistent than Maven

- **Plugin quality**: variable; Maven plugins are generally more polished

- **Steep learning curve** for the configuration model

When Gradle is right

- Android development (Gradle is the standard)

- Large multi-module project where build performance matters

- Mixed-language project (Kotlin + Java + native)

- Custom build needs that don't fit Maven plugins

Bazel

Hermetic, content-addressed, designed for very large monorepos.

Strengths

- **Hermetic builds**: every build dependency declared explicitly; results reproducible across machines

- **Caching**: aggressive remote caching; same output always produces same hash

- **Speed at scale**: builds with thousands of modules are tractable

- **Multi-language**: Java, C++, Python, Go, Rust, etc. — all in one build

- **Determinism**: build outputs are bit-identical given identical inputs

Weaknesses

- **Setup cost**: high initial complexity

- **Ecosystem friction**: Bazel doesn't natively understand Maven artifacts; need rules_jvm_external

- **Less common**: smaller community, fewer learning resources

- **Tooling**: IDE integration historically weaker than Maven/Gradle

When Bazel is right

- Large monorepo (thousands of modules)

- Multi-language code with shared build infrastructure

- Strong reproducibility requirements

- Engineering culture willing to invest in build infrastructure

This describes Google, Uber, Stripe, etc. For typical applications, Bazel is overkill.

Side-by-side

|---------|-------|--------|-------|

| Reproducibility | OK | OK | Excellent |

Migration considerations

Maven → Gradle

Gradle has Maven import that converts most POM files. The result is functional but often non-idiomatic Gradle. Migration usually requires manual cleanup; the speedup is real on large projects.

Maven → Bazel

A real undertaking. Maven artifacts have to be exposed via `rules_jvm_external` or similar; build dependencies have to be declared explicitly per target. For most projects, not worth the effort unless build performance is genuinely a bottleneck.

Multi-tool

Some organizations use Maven for libraries (ecosystem compatibility) and Gradle/Bazel for applications (build performance). Possible but adds complexity.

A reasonable default

For new Java projects:

- **Default**: Maven. Standard tooling, good IDE support, large ecosystem.

- **If build speed becomes a real bottleneck**: switch to Gradle, accepting the complexity.

- **If you're building a monorepo with multiple languages**: consider Bazel from the start, accepting the setup cost.

The migration path is one direction usually: Maven → Gradle is feasible; Maven → Bazel is heavy. Plan accordingly.

Common failure patterns

- **Picking Bazel for a small project.** Setup cost dominates; benefits don't materialize.

- **Picking Gradle "for performance" without measuring.** Maven is fast enough for many projects; the migration cost may exceed the speedup.

- **Custom Maven plugins to do what Gradle does naturally.** The complexity creep suggests Gradle may be the better tool.

- **Mixing build tools without a plan.** Each tool's conventions conflict; cognitive load multiplies.