Package clojure.java.api

Clojure interop from Java.

See: Description

Package clojure.java.api Description

Clojure interop from Java.

The clojure.java.api package provides a minimal interface to bootstrap Clojure access from other JVM languages. It does this by providing:

  1. The ability to use Clojure's namespaces to locate an arbitrary var, returning the var's clojure.lang.IFn interface.
  2. A convenience method read for reading data using Clojure's edn reader

IFns provide complete access to Clojure's APIs. You can also access any other library written in Clojure, after adding either its source or compiled form to the classpath.

The public Java API for Clojure consists of the following classes and interfaces:

  1. clojure.java.api.Clojure
  2. clojure.lang.IFn

All other Java classes should be treated as implementation details, and applications should avoid relying on them.

To lookup and call a Clojure function: 

IFn plus = Clojure.var("clojure.core", "+");
plus.invoke(1, 2);

Functions in clojure.core are automatically loaded. Other namespaces can be loaded via require: 

IFn require = Clojure.var("clojure.core", "require");
require.invoke(Clojure.read("clojure.set"));

IFns can be passed to higher order functions, e.g. the example below passes inc to map: 

IFn map = Clojure.var("clojure.core", "map");
IFn inc = Clojure.var("clojure.core", "inc");
map.invoke(inc, Clojure.read("[1 2 3]"));

Most IFns in Clojure refer to functions. A few, however, refer to non-function data values. To access these, use deref instead of fn:

IFn printLength = Clojure.var("clojure.core", "*print-length*");
IFn deref = Clojure.var("clojure.core", "deref");
deref.invoke(printLength);