Add a hook to add system properties to the Cli

Author: adwsingh

mcp/mcp-cli/src/main/java/software/amazon/smithy/java/mcp/cli/CliSystemPropertiesInitializer.java

@@ -0,0 +1,17 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.java.mcp.cli;
+
+import java.util.Map;
+
+/**
+ * This class gives a hook to add system properties as the first step in main.
+ * Implementations should ensure they don't trigger any classloading in the implementations to avoid race between adding a system property and using it.
+ */
+public interface CliSystemPropertiesInitializer {
+
+    Map<String, String> getSystemProperties();
+}

mcp/mcp-cli/src/main/java/software/amazon/smithy/java/mcp/cli/McpCli.java

@@ -8,7 +8,6 @@
 import java.util.List;
 import java.util.ServiceLoader;
 import picocli.CommandLine;
-import picocli.CommandLine.Command;
 import software.amazon.smithy.java.mcp.cli.commands.Configure;
 import software.amazon.smithy.java.mcp.cli.commands.InstallBundle;
 import software.amazon.smithy.java.mcp.cli.commands.ListBundles;
@@ -22,14 +21,17 @@
  * It discovers and registers all available configuration commands and
  * sets up the command hierarchy.
  */
-@Command(name = "mcp-registry", versionProvider = VersionProvider.class, mixinStandardHelpOptions = true,
-        scope = CommandLine.ScopeType.INHERIT)
 public class McpCli {
 
+    private McpCli() {
+        throw new UnsupportedOperationException();
+    }
+
     public static void main(String[] args) {
+        addSystemProperties();
         var configureCommand = new CommandLine(new Configure());
         discoverConfigurationCommands().forEach(configureCommand::addSubcommand);
-        var commandLine = new CommandLine(new McpCli())
+        var commandLine = new CommandLine(new McpRegistry())
                 .addSubcommand(new StartServer())
                 .addSubcommand(new ListBundles())
                 .addSubcommand(new InstallBundle())
@@ -38,6 +40,14 @@ public static void main(String[] args) {
         commandLine.execute(args);
     }
 
+    private static void addSystemProperties() {
+        System.setProperty("jdk.httpclient.allowRestrictedHeaders", "host"); //This is required for JavaHttpClientTransport.
+        var loader = ServiceLoader.load(CliSystemPropertiesInitializer.class);
+        for (var initializer : loader) {
+            initializer.getSystemProperties().forEach(System::setProperty);
+        }
+    }
+
     /**
      * Discovers and loads all ConfigurationCommand implementations using the Java ServiceLoader.
      *

mcp/mcp-cli/src/main/java/software/amazon/smithy/java/mcp/cli/McpRegistry.java

@@ -0,0 +1,12 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.java.mcp.cli;
+
+import picocli.CommandLine;
+
+@CommandLine.Command(name = "mcp-registry", versionProvider = VersionProvider.class, mixinStandardHelpOptions = true,
+        scope = CommandLine.ScopeType.INHERIT)
+class McpRegistry {}