Several versions of Jackson are still in widespread use, and
io.circe.jackson is cross-published with support for Jackson 2.5, 2.6, 2.7, and 2.8. Each module has a two-digit suffix indicating its Jackson version (
circe-jackson28 supports Jackson 2.8, etc.).
The project source is mostly shared, with version-specific code in separate source trees. Note that the source supporting Jackson 2.6 and 2.7 is identical, so these version share a source tree.
There's not a lot of documentation, but the API is fairly minimal, and we do publish the API docs.
Until the 0.6.2 release, the circe-jackson module lived in the main circe project, so if you're interested in finding the source for earlier releases, please check the release tags there.
Jackson vs. Jawn
The primary purpose of this module is to support circe adopters who already have a Jackson dependency and would like to avoid adding a dependency on Jawn.
In general new projects or projects that aren't currently using Jackson should prefer circe-jawn to circe-jackson. Not all guarantees that hold for Jawn-based parsing and the default printer will hold for the Jackson-based versions. Jackson's handling of numbers in particular differs significantly: it doesn't distinguish positive and negative zeros, it may truncate large JSON numbers or simply fail to parse them, it may print large numbers as strings, etc.
In our benchmarks circe-jawn outperforms circe-jackson on parsing that involves a lot of JSON objects, but the default circe printer is not as fast as circe-jackson's:
Benchmark Mode Cnt Score Error Units ParsingBenchmark.parseFoosC thrpt 100 3421.718 ± 17.133 ops/s ParsingBenchmark.parseFoosCJ thrpt 100 2230.284 ± 20.305 ops/s ParsingBenchmark.parseIntsC thrpt 100 16894.760 ± 70.032 ops/s ParsingBenchmark.parseIntsCJ thrpt 100 17093.963 ± 125.049 ops/s Benchmark Mode Cnt Score Error Units PrintingBenchmark.printFoosC thrpt 100 4173.857 ± 18.818 ops/s PrintingBenchmark.printFoosCJ thrpt 100 4997.025 ± 22.633 ops/s PrintingBenchmark.printIntsC thrpt 100 25834.763 ± 92.639 ops/s PrintingBenchmark.printIntsCJ thrpt 100 56459.382 ± 182.105 ops/s
If your project needs JSON printing to be as fast as possible, it may be worth evaluating circe-jackson in your own benchmarks (especially since it's essentially a drop-in replacement—simply add the appropriate version to your build, import
io.circe.jackson.syntax._, and call
doc.jacksonPrint on your
Json values instead of e.g.
Contributors and participation
This project is adapted from the Jackson-based parsing code in Play JSON (another excellent Scala JSON library).
Please see the circe contributors' guide for details on how to submit a pull request.
circe-jackson 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.