Apache Maven vs Bazel: What are the differences?

Introduction

In the world of software development, build systems play a crucial role in automating the process of compiling and packaging code. Two popular build systems widely used are Apache Maven and Bazel. Although both serve the purpose of building software, there are several key differences between them.

1. Language Support: Apache Maven primarily focuses on Java projects, making it an ideal choice for Java developers. It provides a standardized way of managing dependencies and building Java applications. On the other hand, Bazel supports a wide range of programming languages including Java, C++, Objective-C, and Python. It provides a flexible and efficient build system for multi-language projects.

2. Build Speed: Maven's build process is known to be slower compared to Bazel. Maven follows a sequential build approach, where each module is built one after another. This can result in longer build times for larger projects. Bazel, on the other hand, uses a parallel and incremental build strategy. It intelligently analyzes the dependency graph and only builds the necessary targets, resulting in faster build times.

3. Scalability: While Maven works well for small to medium-sized projects, it may face challenges when dealing with large-scale projects or monorepos. Maven's centralized model doesn't scale well when there are numerous interdependent modules, leading to increased build times and complexity. Bazel, with its distributed caching and parallel build capabilities, handles large-scale projects more efficiently and enables better scalability.

4. Reproducible Builds: Bazel focuses heavily on reproducibility and hermetic builds. It guarantees that the build will be the same across different machines, ensuring consistent results. This is crucial for projects requiring high reliability and consistency. Maven, although it provides dependency management through its central repository, does not enforce hermetic builds by default, potentially leading to inconsistencies across different builds.

5. Incremental Builds: Bazel has built-in support for incremental builds, meaning it only rebuilds the necessary parts of the codebase when changes occur. This minimizes the overall build time, especially during iterative development and continuous integration workflows. Maven, while it can skip previously built modules, lacks the fine-grained incremental build capabilities of Bazel.

6. Ease of Configuration: Maven relies on XML configuration files for its build configuration, which can be verbose and complex for beginners. The XML-based syntax and the mandatory usage of plugins may create a steep learning curve for developers new to Maven. Bazel, on the other hand, uses a human-readable language called Starlark for build configurations, which offers more flexibility and simplicity.

In summary, Apache Maven and Bazel differ in terms of language support, build speed, scalability, reproducibility, incremental builds, and ease of configuration. These differences make each build system suitable for specific use cases, depending on the requirements of the project.