| # Java compilers in Bazel |
| |
| Bazel compiles Java code using a custom builder. This builder is called |
| JavaBuilder and its code lies in //src/java_tools/buildjar. To build Java |
| code, JavaBuilder use the Java compiler from the JDK. To support |
| [ErrorProne](http://errorprone.info) checks, we vendor a custom build |
| of the Java compiler code. This is the raw version of the Java compiler |
| from [OpenJDK](https://openjdk.java.net) but compiled for a lower |
| version of the JRE. Those builds are vendored in |
| //third_party/java/jdk/langtools. |
| |
| Currently Bazel supports running on a JRE 8 only because the default Java |
| compiler used (//third_party/java/jdk/langtools/javac-9-dev-r4023-2.jar) is the |
| Java compiler of OpenJDK 9 compiled to run on a JRE 8. This cannot |
| be built to run on a JRE 7 because of code incompatibility. Bazel's |
| JavaBuilder at HEAD cannot be linked with earlier version of the |
| Java compiler (it depends on some internals of the Java compiler). |
| |
| To build a version of Bazel that can run on a JRE 7, we need to rely |
| on the version of JavaBuilder provided with Bazel 0.1.0 |
| (//third_party/java/jdk/javabuilder/JavaBuilder_0.1.0_deploy.jar) which works |
| with a Java compiler of OpenJDK 8 compiled to run on a JRE 7 |
| (//third_party/java/jdk/langtools/javac7.jar). |
