# Java Client

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

## Layout

```text
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:

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

## Client Usage

Create a client with explicit transport and auth options:

```java
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:

```java
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.

```powershell
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](../../docs/GalaxyRepository.md#browsechildren) for full
request and filter semantics. This snippet documents the API as it appears once
the Java client is regenerated on the Windows host.

```java
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));
}
```

### 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`.

```java
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:

```java
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`:

```powershell
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:

```powershell
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:

```powershell
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`:

```powershell
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`:

```powershell
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:

```powershell
$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"
```

## Related Documentation

- [Client Packaging](../../docs/ClientPackaging.md)
- [Client Proto Generation](../../docs/ClientProtoGeneration.md)
- [Java Client Detailed Design](./JavaClientDesign.md)
- [Java Style Guide](../../docs/style-guides/JavaStyleGuide.md)
