Issue #47: scaffold Java Gradle build

clients/java/mxgateway-cli/src/main/java/com/dohertylan/mxgateway/cli/MxGatewayCli.java

@@ -0,0 +1,53 @@
+package com.dohertylan.mxgateway.cli;
+
+import com.dohertylan.mxgateway.client.MxGatewayClientVersion;
+import java.io.PrintWriter;
+import java.util.concurrent.Callable;
+import picocli.CommandLine;
+import picocli.CommandLine.Command;
+import picocli.CommandLine.Model.CommandSpec;
+import picocli.CommandLine.Spec;
+
+@Command(
+        name = "mxgw-java",
+        mixinStandardHelpOptions = true,
+        description = "MXAccess Gateway Java test CLI.",
+        subcommands = MxGatewayCli.VersionCommand.class)
+public final class MxGatewayCli implements Callable<Integer> {
+    @Spec
+    private CommandSpec spec;
+
+    public static void main(String[] args) {
+        int exitCode = new CommandLine(new MxGatewayCli()).execute(args);
+        System.exit(exitCode);
+    }
+
+    public static int execute(PrintWriter out, PrintWriter err, String... args) {
+        CommandLine commandLine = new CommandLine(new MxGatewayCli());
+        commandLine.setOut(out);
+        commandLine.setErr(err);
+        return commandLine.execute(args);
+    }
+
+    @Override
+    public Integer call() {
+        spec.commandLine().usage(spec.commandLine().getOut());
+        return 0;
+    }
+
+    @Command(name = "version", description = "Prints the Java client scaffold version.")
+    public static final class VersionCommand implements Callable<Integer> {
+        @Spec
+        private CommandSpec spec;
+
+        @Override
+        public Integer call() {
+            spec.commandLine().getOut().printf(
+                    "mxgateway-java %s gatewayProtocolVersion=%d workerProtocolVersion=%d%n",
+                    MxGatewayClientVersion.clientVersion(),
+                    MxGatewayClientVersion.gatewayProtocolVersion(),
+                    MxGatewayClientVersion.workerProtocolVersion());
+            return 0;
+        }
+    }
+}

clients/java/mxgateway-cli/src/test/java/com/dohertylan/mxgateway/cli/MxGatewayCliTests.java

@@ -0,0 +1,27 @@
+package com.dohertylan.mxgateway.cli;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import org.junit.jupiter.api.Test;
+
+final class MxGatewayCliTests {
+    @Test
+    void versionCommandPrintsProtocolVersions() {
+        StringWriter output = new StringWriter();
+        StringWriter errors = new StringWriter();
+
+        int exitCode = MxGatewayCli.execute(
+                new PrintWriter(output, true),
+                new PrintWriter(errors, true),
+                "version");
+
+        assertEquals(0, exitCode);
+        assertEquals("", errors.toString());
+        assertTrue(output.toString().contains("mxgateway-java 0.1.0"));
+        assertTrue(output.toString().contains("gatewayProtocolVersion=1"));
+        assertTrue(output.toString().contains("workerProtocolVersion=1"));
+    }
+}