etdl-target-java

The Java developer API for ETDL. Generates a Java record/interface/orchestration-class surface from a validated .etdl document, bound to the compiled Rust ETDL runtime via Java 21's java.lang.foreign (the Foreign Function & Memory API) — no JNI glue code, no per-language native crate. This crate is pure Rust: it never re-implements branch/SLA accounting, retry backoff, or ECEL evaluation in Java — every one of those calls through to etdl-runtime-ffi, the same implementation the Rust target itself uses.

Building this crate never needs a JDK

etdl-target-java only emits Java source text — it's a plain Rust library used by etdl-cli (etdl compile --target java) or directly via its JavaCodeGenerator. A JDK 21+ is needed only to compile/run the generated Java, and a built etdl-runtime-ffi is needed only to run anything that touches BranchMonitor/RetryPolicy/Condition.

What it generates

etdl/runtime/
    EtdlNative.java        # java.lang.foreign MethodHandle bindings to libetdl_runtime_ffi
    BranchMonitor.java      # thin facade — delegates to the native runtime
    RetryPolicy.java        # thin facade — native attempt/backoff loop via an upcall stub
    Condition.java          # thin facade — native regex/set-membership evaluation
    WorkflowError.java
    Publisher.java           # developer-implemented interface (consequence: send)
    BackoffStrategy.java
<package>/
    <Type>.java              # one record per referenced AsyncAPI message
    <Tree>Handlers.java       # generated interface — implement this, don't edit it
    <Stem>Workflow.java        # generated orchestration + fault-tree probability constants

The etdl/runtime/*.java and <Stem>Workflow.java/<Tree>Handlers.java files are regenerated on every compile and marked DO NOT EDIT DIRECTLY. Your own code implements the generated <Tree>Handlers interface and Publisher in separate, hand-written classes that are never touched by regeneration.

Usage

etdl compile order-fulfillment.etdl --target java --out-dir ./generated
cargo build -p etdl-runtime-ffi --release   # the native runtime the generated code binds to

javac --release 21 --enable-preview -d out $(find ./generated -name '*.java')
java --enable-preview --enable-native-access=ALL-UNNAMED \
     -Detdl.runtime.library=/path/to/libetdl_runtime_ffi.so \
     -cp out your.package.Main

--enable-preview is only required on JDK 21 (the FFM API is finalized, flag-free, from JDK 22 onward).

Verified, not just generated

This crate's own test suite compiles hand-authored Handlers/Publisher implementations against generated output and runs it against a real, compiled etdl-runtime-ffi — including the native retry callback and RE2 regex evaluation through etdl_core::condition::matches. See tests/java_runtime_integration.rs.

Full architecture: docs/architecture/targets.md.

License

Apache-2.0