The Java client workspace contains the MXAccess Gateway client library, generated protobuf/gRPC bindings, a Picocli test CLI project, and JUnit tests.

Layout

clients/java/
  settings.gradle
  build.gradle
  src/main/generated/
  zb-mom-ww-mxgateway-client/
  zb-mom-ww-mxgateway-cli/

zb-mom-ww-mxgateway-client generates Java protobuf and gRPC sources from ../../src/ZB.MOM.WW.MxGateway.Contracts/Protos. The Gradle protobuf plugin writes those generated sources under src/main/generated, which matches the client proto manifest in ../proto/proto-inputs.json. Do not edit generated files by hand.

zb-mom-ww-mxgateway-client exposes MxGatewayClientOptions, MxGatewayClient, MxGatewaySession, value/status helpers, typed gateway exceptions, raw generated stubs, and generated protobuf messages for parity tests.

zb-mom-ww-mxgateway-cli depends on zb-mom-ww-mxgateway-client and provides the mxgw-java application entry point. The CLI supports version, session, command, event streaming, write, and smoke-test commands with deterministic JSON output.

Regenerating Protobuf Bindings

Run generation from clients/java after the shared .proto files or Java output path changes:

gradle :zb-mom-ww-mxgateway-client:generateProto

Client Usage

Create a client with explicit transport and auth options:

MxGatewayClientOptions options = MxGatewayClientOptions.builder()
        .endpoint("localhost:5000")
        .apiKey(System.getenv("MXGATEWAY_API_KEY"))
        .plaintext(true)
        .build();

try (MxGatewayClient client = MxGatewayClient.connect(options);
        MxGatewaySession session = client.openSession("java-client")) {
    int serverHandle = session.register("java-client");
    int itemHandle = session.addItem(serverHandle, "TestObject.TestInt");
    session.advise(serverHandle, itemHandle);
    session.write(serverHandle, itemHandle, MxValues.int32Value(123), 0);
}

Use rawBlockingStub, rawFutureStub, rawAsyncStub, openSessionRaw, closeSessionRaw, invoke, and raw session helper methods when tests need the underlying protobuf messages. MxGatewayCommandException and MxAccessException preserve the raw MxCommandReply when the gateway returns a data-bearing MXAccess failure.

MxEventStream implements Iterator<MxEvent> and AutoCloseable. Closing it cancels the underlying gRPC stream. Canceling or timing out a Java client call only stops the client from waiting; it does not abort an in-flight MXAccess COM call on the worker STA.

For alarms, MxGatewayClient exposes queryActiveAlarms (one-shot snapshot), streamAlarms (returns an MxGatewayAlarmFeedSubscription whose iterator yields alarm-feed messages from the gateway's central monitor), and acknowledgeAlarm (ack by full alarm reference with an optional comment and ack target). Close the subscription to cancel the underlying gRPC stream.

Galaxy Repository Browse

The Galaxy Repository service is a separate metadata-only gRPC service exposed by the gateway. It lets clients enumerate the deployed Galaxy object hierarchy and the dynamic attributes on each object so they know which tag references to subscribe to via the MXAccess Gateway service. It uses the same API-key auth as the gateway and requires the metadata:read scope.

GalaxyRepositoryClient mirrors the MxGatewayClient pattern (caller-managed or owned channel, MxGatewayClientOptions, blocking + async variants). Three RPCs are exposed:

MxGatewayClientOptions options = MxGatewayClientOptions.builder()
        .endpoint("localhost:5000")
        .apiKey(System.getenv("MXGATEWAY_API_KEY"))
        .plaintext(true)
        .build();

try (GalaxyRepositoryClient galaxy = GalaxyRepositoryClient.connect(options)) {
    boolean ok = galaxy.testConnection();
    Optional<Instant> lastDeploy = galaxy.getLastDeployTime();
    List<GalaxyObject> hierarchy = galaxy.discoverHierarchy();
}

getLastDeployTime returns Optional.empty() when the server reports present=false. discoverHierarchy returns the generated GalaxyObject proto messages directly so callers can read all fields (including the nested GalaxyAttribute list) without an extra DTO layer.

The CLI exposes matching subcommands: galaxy-test, galaxy-deploy-time, galaxy-discover, and galaxy-watch. They take the same --endpoint, --api-key-env, --plaintext, --ca-file, --server-name-override, --timeout, and --json options as the gateway commands.

gradle :zb-mom-ww-mxgateway-cli:run --args="galaxy-test --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="galaxy-deploy-time --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="galaxy-discover --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --json"

Browsing lazily

For UI trees or OPC UA bridges, use browseChildren to walk one level at a time instead of loading the full hierarchy with discoverHierarchy. Pass a default request for root objects; subsequent calls set parentGobjectId, parentTagName, or parentContainedPath. Filter fields match DiscoverHierarchy. Each response pairs getChildrenList() with getChildHasChildrenList() so you know which nodes to expand. See Galaxy Repository for full request and filter semantics. This snippet documents the API as it appears once the Java client is regenerated on the Windows host.

BrowseChildrenReply reply = galaxy.browseChildren(
        BrowseChildrenRequest.newBuilder().build());

List<GalaxyObject> children = reply.getChildrenList();
List<Boolean> hasChildren = reply.getChildHasChildrenList();
for (int i = 0; i < children.size(); i++) {
    System.out.printf("%s expand=%b%n", children.get(i).getTagName(), hasChildren.get(i));
}

High-level walker

For UI trees, the client provides a LazyBrowseNode walker that handles sibling pagination and the child_has_children hint for you:

MxGatewayClientOptions options = MxGatewayClientOptions.builder()
        .endpoint("localhost:5000")
        .apiKey(System.getenv("MXGATEWAY_API_KEY"))
        .plaintext(true)
        .build();

try (GalaxyRepositoryClient galaxy = GalaxyRepositoryClient.connect(options)) {
    List<LazyBrowseNode> roots = galaxy.browse();
    for (LazyBrowseNode root : roots) {
        if (root.hasChildrenHint()) {
            root.expand();
        }
        for (LazyBrowseNode child : root.getChildren()) {
            String kind = child.hasChildrenHint() ? "has children" : "leaf";
            System.out.println(child.getObject().getTagName() + " (" + kind + ")");
        }
    }
}

expand is idempotent — calling it twice fires only one RPC, and is safe under concurrent callers. To refresh after a Galaxy redeploy, call browse again from the root.

Watching deploy events

GalaxyRepository.WatchDeployEvents is a server-streaming RPC: the gateway sends a bootstrap DeployEvent immediately on subscribe and then one event each time it observes a new galaxy.time_of_last_deploy. The sequence field is monotonic per server start; gaps mean the per-subscriber buffer dropped older events because the consumer was too slow.

The client exposes both an iterator-style adaptor over the async stub and an observer-callback variant. Both honour the channel-level streamTimeout.

try (GalaxyRepositoryClient galaxy = GalaxyRepositoryClient.connect(options);
        DeployEventStream events = galaxy.watchDeployEvents(/* lastSeenDeployTime */ null)) {
    while (events.hasNext()) {
        DeployEvent event = events.next();
        // event.getSequence(), event.getObservedAt(),
        // event.getTimeOfLastDeploy() / getTimeOfLastDeployPresent(),
        // event.getObjectCount(), event.getAttributeCount()
    }
}

Pass an Instant for lastSeenDeployTime to suppress the bootstrap event when the cached deploy time matches what the caller already has. DeployEventStream implements Iterator<DeployEvent> and AutoCloseable; closing it cancels the underlying gRPC call.

For callback delivery (e.g. when the consumer wants to drive a queue or reactive pipeline), use the async variant:

DeployEventSubscription subscription = galaxy.watchDeployEventsAsync(
        lastSeen,
        new StreamObserver<>() {
            @Override public void onNext(DeployEvent value) { /* ... */ }
            @Override public void onError(Throwable t) { /* ... */ }
            @Override public void onCompleted() { /* ... */ }
        });
// later:
subscription.cancel(); // or subscription.close()

The matching CLI subcommand streams events until cancelled (Ctrl+C) and prints one line per event in text mode or one JSON object per event with --json:

gradle :zb-mom-ww-mxgateway-cli:run --args="galaxy-watch --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="galaxy-watch --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --last-seen-deploy-time 2026-04-28T18:30:00Z --limit 5"

CLI Usage

Run the CLI through Gradle:

gradle :zb-mom-ww-mxgateway-cli:run --args="version --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="open-session --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --client-session-name java-cli --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="register --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --client-name java-cli --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="add-item --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --server-handle 1 --item TestObject.TestInt --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="advise --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --server-handle 1 --item-handle 1 --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="write --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --server-handle 1 --item-handle 1 --type int32 --value 123 --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="stream-events --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --session-id <id> --limit 1 --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="stream-alarms --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --filter-prefix Galaxy --limit 1 --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="acknowledge-alarm --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --reference \"\\Galaxy\Area001.Pump001.PumpFault\" --json"
gradle :zb-mom-ww-mxgateway-cli:run --args="smoke --endpoint localhost:5000 --api-key-env MXGATEWAY_API_KEY --plaintext --item TestObject.TestInt --json"

The CLI accepts --api-key, --api-key-env, --plaintext, --ca-file, --server-name-override, --timeout, and --json on gateway commands. JSON output redacts API keys.

Use TLS options for a secured gateway:

gradle :zb-mom-ww-mxgateway-cli:run --args="smoke --endpoint mxgateway.example.local:5001 --ca-file C:\certs\mxgateway-ca.pem --server-name-override mxgateway.example.local --api-key-env MXGATEWAY_API_KEY --item TestObject.TestInt --json"

Build And Test

Run the Java checks from clients/java:

gradle test

The build uses the Java 21 Gradle toolchain, compiles generated protobuf/gRPC code, and runs JUnit 5 tests for the client wrapper, shared behavior fixtures, in-process gRPC behavior, stream cancellation, and CLI parser/output behavior.

Packaging

Create local library and CLI artifacts from clients/java:

gradle :zb-mom-ww-mxgateway-client:jar :zb-mom-ww-mxgateway-cli:installDist

The library jar is under zb-mom-ww-mxgateway-client/build/libs. The installed CLI distribution is under zb-mom-ww-mxgateway-cli/build/install/zb-mom-ww-mxgateway-cli.

Integration Checks

Run live checks only when a gateway and MXAccess-backed worker are available:

$env:MXGATEWAY_INTEGRATION = '1'
$env:MXGATEWAY_ENDPOINT = 'localhost:5000'
$env:MXGATEWAY_API_KEY = '<gateway-api-key>'
$env:MXGATEWAY_TEST_ITEM = 'TestObject.TestInt'
gradle :zb-mom-ww-mxgateway-cli:run --args="smoke --endpoint $env:MXGATEWAY_ENDPOINT --plaintext --api-key-env MXGATEWAY_API_KEY --item $env:MXGATEWAY_TEST_ITEM --json"

README.md

Java Client