jbeats

Java port of beats — parses Java source files and emits per-method structural metadata as JSON.

What it does

For each method and constructor in a .java file, jbeats extracts:

• Token sequence — structural control-flow tokens (if, for, try/catch, lambda, etc.) encoded as integers
• Call targets — fully-qualified names of imported classes called by the method (e.g. java.util.Collections.sort)
• Direct imports — imports actually referenced in the method body
• Metadata — name, receiver class, line range, parameters, return type, visibility, and flags for generated/test/trivial-constructor code

Output is written as pretty-printed JSON to $TMPDIR/beats/<repo>/<relative-path>-beats.json.

Build

Requires GraalVM JDK 21 with native-image.

# Fat JAR only
mvn clean package -DskipTests

# Fat JAR + native binary (outputs to target/jbeats)
mvn -Pnative package -DskipTests

# Run tests
mvn test

Usage

./target/jbeats --inp=/path/to/MyClass.java --repo=myrepo

The path to the output file is printed to stdout on success. Errors go to stderr.

Output format

{
  "functions": [
    {
      "name": "processHints",
      "package_name": "org.apache.cassandra.hints",
      "file_name": "HintsDescriptor.java",
      "file_path": "src/java/org/apache/cassandra/hints/HintsDescriptor.java",
      "start_line": 42,
      "end_line": 67,
      "line_count": 26,
      "is_method": true,
      "is_exported": true,
      "receiver": "HintsDescriptor",
      "params": [
        { "type_name": "List<Hint>", "is_func_type": false, "is_interface": false }
      ],
      "returns": [
        { "type_name": "int", "is_error": false }
      ],
      "token_seq": [0, 14, 16, 1, 18, 7],
      "call_targets": ["java.util.Collections.sort"],
      "direct_imports": ["java.util.Collections"],
      "generated_code": false,
      "test_code": false,
      "is_constructor": false,
      "body": "public int processHints(...) { ... }"
    }
  ]
}