Introduction and Motivation

circe (pronounced SUR-see, or KEER-kee in classical Greek, or CHEER-chay in Ecclesiastical Latin) is a JSON library for Scala (and Scala.js).

Why?

Dependencies and modularity

circe depends on cats, and the core project has only one dependency (cats-core).

Other subprojects bring in dependencies on Jawn (for parsing in the jawn subproject), Shapeless (for automatic codec derivation in generic), but it would be possible to replace the functionality provided by these subprojects with alternative implementations that use other libraries.

Parsing

circe doesn't include a JSON parser in the core project, which is focused on the JSON AST, zippers, and codecs. The jawn subproject provides support for parsing JSON via a Jawn facade. Jawn is fast, cross-platform, and offers asynchronous parsing. The circe-jackson project supports using Jackson for both parsing and printing.

circe also provides a parser subproject that provides parsing support for Scala.js, with JVM parsing provided by io.circe.jawn and JavaScript parsing from scalajs.js.JSON.

See the Parsing page for more details.

Lenses

circe doesn't use or provide lenses in the core project. This is related to the first point above, since Monocle has a Scalaz dependency, but we also feel that it simplifies the API. The 0.3.0 release added an experimental optics subproject that provides Monocle lenses.

See the Optics page for more details.

Codec derivation

circe does not use macros or provide any kind of automatic derivation in the core project. Instead circe includes a subproject (generic) that provides generic codec derivation using Shapeless.

This subproject provides fully automatic derivation of instances for case classes and sealed trait hierarchies. It also includes derivation of "incomplete" case class instances (see my recent blog post for details). Note that if you use -Ypartial-unification and auto, incomplete decoders will not work (see #724).

See the Encoding and Decoding page for more details.

Aliases

circe aims to simplify its API by using no operator aliases. This is largely a matter of personal taste, and may change in the future.

Testing

I'd like to provide more complete test coverage (in part via Discipline), but it's early days for this.

Performance

circe is developed with a focus on performance. See the Performance page for details.

License

circe is licensed under the Apache License, Version 2.0 (the "License"); you may not use this software except in compliance with the License.

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.