scopes

A little library for resource scopes.

When used with Java 7, scopes will take advantage of the java.lang.AutoCloseable interface and the suppressed exception features of java.lang.Throwable.

When used with Java 6, if—in response to an exception from the body of the with-resource-scope macro—an exception occurs trying to close a resource, then it will be swallowed up.

For example:

(with-resource-scope
  (scoped-thunk! #(throw (Exception. "bar")))
  (throw (Exception. "foo")))

The “foo” exception will propagate from the body of the with-resource-scope. In the case of Java 7, you will be able to access the “bar” exception with .getSuppressed. In the case of Java 6, there will be no way to access the “bar” exception as it will have been thrown away.

Usage

To use this for a Leiningen project

[pjstadig/scopes "0.3.0"]

Or for a Maven project

<dependency>
  <groupId>pjstadig</groupId>
  <artifactId>scopes</artifactId>
  <version>0.3.0</version>
</dependency>

A resource scope is established using the with-resource-scope macro, and objects are registered with the closest dynamic scope using scoped! or scoped-thunk!. For example:

(require '[pjstadig.scopes :refer [scoped! with-resource-scope]])

(defn use-a-resource [f]
  (line-seq (scoped! (io/input-stream (io/file f)))))

(with-resource-scope
  (use-a-resource "/etc/hosts"))

The closeable? function can be used to determine if an object satisfies the ScopedCloseable protocol.

user=> (closeable? 1)
false

License

Copyright © 2013, 2014 Paul Stadig and contributors. All rights reserved.

This Source Code Form is subject to the terms of the Mozilla Public License,
v. 2.0. If a copy of the MPL was not distributed with this file, You can
obtain one at http://mozilla.org/MPL/2.0/.

This Source Code Form is "Incompatible With Secondary Licenses", as defined
by the Mozilla Public License, v. 2.0.