| Christopher Hunt | c908fdb | 2021-02-18 11:10:42 +1100 | [diff] [blame] | 1 | # Ahead Of Time (AOT) compilation for the Java Virtual Machine (JVM)" |
| 2 | |
| 3 | Ahead Of Time (AOT) compilation build tools such as those provided by [GraalVM's `native-image`](https://www.graalvm.org/reference-manual/native-image/) can require some configuration when using protobuf. |
| 4 | Protobuf for the JVM uses reflection and some of its target classes are not possible to determine in advance. |
| 5 | Historically, there were good reasons to use reflection based on APIs that were published effectively requiring them, and this situation is unlikely to change. |
| 6 | |
| 7 | [The Lite version of protobuf for the JVM](https://github.com/protocolbuffers/protobuf/blob/master/java/lite.md) |
| 8 | avoids reflection and may be better suited for use with AOT compilation tooling. This Lite version was originally targeted for use on Android which has similar AOT compilation |
| 9 | goals as GraalVM's native-image tool. |
| 10 | |
| 11 | ## GraalVM native-image |
| 12 | |
| 13 | This section addresses GraalVM's `native-image` configuration specifically as this AOT compilation tool due to its popularity. The `native-image` tool can be configured |
| 14 | with respect to: the [Java Native Interface](https://en.wikipedia.org/wiki/Java_Native_Interface) (JNI), http proxying, reflection, and other resources. While these |
| 15 | considerations can be manually declared as JSON files, we recommend that a JVM application is exercised along with |
| 16 | [the assisted configuration agent](https://www.graalvm.org/reference-manual/native-image/BuildConfiguration/#assisted-configuration-of-native-image-builds). The agent |
| 17 | will generate files that you can then subsequently point at when invoking `native-image`. We recommend that the generated files are retained with a project's source |
| 18 | code. |
