Using Clojure Inside Java Applications

Some teams adopt Clojure by embedding it inside an existing Java application: keep the JVM, keep the deployment pipeline, and introduce Clojure where it reduces complexity.

The safest model is “library boundary”:

• expose a small set of Clojure functions as your public API
• keep most Clojure code pure and data-oriented
• call into it from Java through a thin adapter (load the namespace, resolve a var, invoke it)

This section focuses on boundary design so you get the benefits of Clojure without turning your Java codebase into a dynamic, hard-to-debug mix of runtime loading and evaluation.

In this section

• Compiling Clojure for Java Use
  Compile Clojure namespaces when Java callers need bytecode, named classes, or packaged artifacts, and keep ahead-of-time compilation limited to integration requirements.
• Invoking Clojure Functions from Java
  Call Clojure vars from Java through the Clojure Java API or through generated classes while keeping the exposed surface small, stable, and data-oriented.
• Managing Classpaths and Dependencies in Clojure and Java Integration
  Align Java and Clojure dependencies, classpaths, and packaging so both sides load the same classes without version drift, hidden transitive conflicts, or environment-specific surprises.