https://github.com/salesforce/bazel-jdt-java-toolchain
Eclipse Java Compiler (ECJ) for Bazel
https://github.com/salesforce/bazel-jdt-java-toolchain
bazel compile ecj eclipse java
Last synced: about 1 year ago
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Eclipse Java Compiler (ECJ) for Bazel
- Host: GitHub
- URL: https://github.com/salesforce/bazel-jdt-java-toolchain
- Owner: salesforce
- License: apache-2.0
- Created: 2021-10-13T08:11:05.000Z (over 4 years ago)
- Default Branch: main
- Last Pushed: 2024-08-02T15:26:46.000Z (almost 2 years ago)
- Last Synced: 2024-08-03T13:54:17.296Z (almost 2 years ago)
- Topics: bazel, compile, ecj, eclipse, java
- Language: Java
- Homepage:
- Size: 19.1 MB
- Stars: 9
- Watchers: 6
- Forks: 6
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE
- Code of conduct: CODE_OF_CONDUCT.md
- Codeowners: CODEOWNERS
Awesome Lists containing this project
README
# jdt-java-toolchain
A Java Toolchain for Bazel that uses ECJ (Eclipse Compiler for Java) for compilation.
## Why ECJ?
The Eclipse Compiler for Java is much (much, much) faster than javac.
It's even faster than Bazel's Java header compiler, i.e. with this toolchain you can disable Turbine header compilation and still have a faster build time.
Additionally, we included a few optimizations to further improve the compilation performance.
For example, it's possible to disable transitive dependencies and only compile with directly declared dependencies.
## Usage
See [releases](https://github.com/salesforce/bazel-jdt-java-toolchain/releases/) for the release
specific notes and instructions what to add to your `WORKSPACE` file.
Once this is completed, add this to your `.bazelrc`:
```
build --extra_toolchains=@bazel_jdt_java_toolchain//jdt:all
```
By default the `jdt_java_toolchain` is using `rules_java` default for compilation.
Please create your own `default_java_toolchain` if this doesn't work for your use case.
Have a look at `jdt/BUILD` to see which JDKs are supported.
## ECJ Notes
Read [ECJ README](compiler/src/main/ecj/README.md) for details about updating JDT.
## Current Limitations
Currently, there are some issues with clients that try to access use this toolchain
by compiling the builder from source. Many of the Bazel macros depend on the current
java toolchain, and because that toolchain has not been built yet, we run into a circular
dependency.
The solution is for `bazel-jdt-java-toolchain` developers to build the toolchain and then
copy the deploy jar into the repository. Clients can then use the `override_repository` command
and point directly at the source of this repo for development and testing.
Unfortunately this means additional steps are required for developers. This script can be
used to facilitate the steps.
```
#!/bin/bash
bazel build :JdtJavaBuilder_deploy.jar
cp -fv bazel-bin/JdtJavaBuilder_deploy.jar compiler/export/
bazel build //compiler/third_party/turbine:turbine_direct_binary_deploy.jar
cp -fv bazel-bin/compiler/third_party/turbine/turbine_direct_binary_deploy.jar compiler/tools/
```
For your convenience, the `build-toolchain` script is provided in this repository.
## Debugging
For debugging the toolchain's Java code (including ECJ compiler) here are a few notes:
Override repository in your project's `.bazelrc` (or via command line) and add debug statements as follows:
```
build --override_repository=jdt_java_toolchain=/Users/.../bazel-jdt-java-toolchain/
common --subcommands=pretty_print
common --verbose_failures
```
This will give output during the build how Bazel is invoking JDT compiler:
```
bazel build //some-java-target:target
INFO: Analyzed target //some-java-target:target (...).
INFO: Found 1 target...
SUBCOMMAND: # //ome-java-target:target [action 'Building some-java-target/libtarget-class.jar ...]
(cd /private/var/tmp/_bazel_username/hash/execroot/core && \
exec env - \
LC_CTYPE=en_US.UTF-8 \
LD_LIBRARY_PATH='' \
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
/Users/username/tools/Darwin/jdk/bin/java \
-jar \
external/jdt_java_toolchain/builder/export/JdtJavaBuilder_deploy.jar \
@bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-0.params \
@bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-1.params)
ERROR: /Users/username/app/main/core/some-java-target/BUILD.bazel:4:13: Building some-java-target/libtarget-class.jar ... failed: (Exit 1): java failed: error executing command
(cd /private/var/tmp/_bazel_username/hash/execroot/core && \
exec env - \
LC_CTYPE=en_US.UTF-8 \
LD_LIBRARY_PATH='' \
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
/Users/username/tools/Darwin/jdk/bin/java -jar external/jdt_java_toolchain/builder/export/JdtJavaBuilder_deploy.jar @bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-0.params @bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-1.params)
```
Either take the *SUBCOMMAND* or *ERROR* command.
You can ignore the `exec env` part.
The interesting two steps are:
```
cd /private/var/tmp/_bazel_username/hash/execroot/core
```
```
/Users/username/tools/Darwin/jdk/bin/java -jar external/jdt_java_toolchain/builder/export/JdtJavaBuilder_deploy.jar @bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-0.params @bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-1.params
```
The first is the execution directory and the latter the command.
You need to `cd` into the execution directory and then run the command yourself.
But this time add the remote debug arguments (before `-jar`) as follows:
```
/Users/username/tools/Darwin/jdk/bin/java -agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000 -jar external/jdt_java_toolchain/builder/export/JdtJavaBuilder_deploy.jar @bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-0.params @bazel-out/darwin-fastbuild/bin/some-java-target/libtarget-class.jar-1.params
```
The important part is `suspend=y`.
Without it the compiler would be finished before you are able to connect.
Once you run the command, connect to the waiting process with your IDE's remote debugger.
# Development Guide
This project can be loaded with the Bazel Eclipse Feature.
The VS Code Bazel Java extension should also work.
## Releasing
See [RELEASING README](dist/README.md).