Add IceGrid/query Java demo (#627)

Author: pepone

java/IceGrid/query/.gitignore

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+# Gradle generated build files
+bin
+build
+.gradle

java/IceGrid/query/README.md

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+# IceGrid Query
+
+This demo shows how to use the Query object provided by the IceGrid registry to lookup a well-known object by type.
+
+## Ice prerequisites
+
+- Install IceGrid. See [Ice service installation].
+
+## Building the demo
+
+The demo has two Gradle projects, **client** and **server**, both using the [application plugin].
+
+To build the demo, run:
+
+```shell
+./gradlew installDist
+```
+
+This creates a self-contained distribution under build/install/ for each application.
+Each distribution includes:
+
+- a bin/ directory with start scripts, and
+- a lib/ directory containing the application JAR and all its runtime dependencies.
+
+In our IceGrid deployment, we call java directly and set the class path to include everything in the distribution’s lib/
+directory. This ensures both the server JAR and its dependencies (such as Ice) are available at runtime.
+
+## Running the demo
+
+First, start the IceGrid registry in its own terminal:
+
+```shell
+icegridregistry --Ice.Config=config.registry
+```
+
+Then, start the IceGrid node in its own terminal:
+
+```shell
+icegridnode --Ice.Config=config.node
+```
+
+Next, deploy the "GreeterHall" application in this IceGrid deployment:
+
+```shell
+icegridadmin --Ice.Config=config.admin -e "application add greeter-hall.xml"
+```
+
+Finally, run the client application:
+
+```shell
+./gradlew :client:run --quiet
+```
+
+[Application plugin]: https://docs.gradle.org/current/userguide/application_plugin.html
+[Ice service installation]: https://github.com/zeroc-ice/ice/blob/main/NIGHTLY.md#ice-services

java/IceGrid/query/client/build.gradle.kts

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+// Copyright (c) ZeroC, Inc.
+
+plugins {
+    // Apply the application plugin to tell gradle this is a runnable Java application.
+    id("application")
+
+    // Apply the Slice-tools plugin to enable Slice compilation.
+    id("com.zeroc.slice-tools") version "3.8.+"
+
+    // Pull in our local 'convention plugin' to enable linting.
+    id("zeroc-linting")
+}
+
+dependencies {
+    // Add the Ice and IceGrid libraries as an implementation dependencies.
+    implementation("com.zeroc:ice:3.8.+")
+    implementation("com.zeroc:icegrid:3.8.+")
+}
+
+sourceSets {
+    main {
+        // Add the Greeter.ice file from the parent slice directory to the main source set.
+        slice {
+            srcDirs("../slice")
+        }
+    }
+}
+
+application {
+    // Specify the main entry point for the application.
+    mainClass.set("com.example.icegrid.query.client.Client")
+}

java/IceGrid/query/client/src/main/java/com/example/icegrid/query/client/Client.java

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+// Copyright (c) ZeroC, Inc.
+
+package com.example.icegrid.query.client;
+
+import com.example.visitorcenter.GreeterPrx;
+import com.zeroc.Ice.Communicator;
+import com.zeroc.Ice.LocatorPrx;
+import com.zeroc.Ice.ObjectPrx;
+import com.zeroc.Ice.Util;
+import com.zeroc.IceGrid.QueryPrx;
+
+class Client {
+    public static void main(String[] args) {
+        // Create an Ice communicator. We'll use this communicator to create proxies and manage outgoing connections.
+        try (Communicator communicator = Util.initialize(args)) {
+
+            // Set the default locator of the new communicator. It's the address of the Locator hosted by our IceGrid
+            // registry. You can also set this proxy with the Ice.Default.Locator property.
+            communicator.setDefaultLocator(
+                LocatorPrx.createProxy(communicator, "IceGrid/Locator:tcp -h localhost -p 4061"));
+
+            // Create a proxy to the Query object hosted by the IceGrid registry. "IceGrid/Query" a well-known proxy,
+            // without addressing information.
+            QueryPrx query = QueryPrx.createProxy(communicator, "IceGrid/Query");
+
+            // Look up an object with type ::VisitorCenter::Greeter.
+            String greeterTypeId = GreeterPrx.ice_staticId(); // ::VisitorCenter::Greeter
+            ObjectPrx proxy = query.findObjectByType(greeterTypeId);
+
+            if (proxy == null) {
+                System.out.println(
+                    String.format("The IceGrid registry doesn't know any object with type '%s'.", greeterTypeId));
+            } else {
+                // Cast the object proxy to a Greeter proxy.
+                GreeterPrx greeter = GreeterPrx.uncheckedCast(proxy);
+
+                // Send a request to the remote object and get the response.
+                String greeting = greeter.greet(System.getProperty("user.name"));
+                System.out.println(greeting);
+
+                // Send another request to the remote object. With the default configuration we use for this client,
+                // this request reuses the connection and reaches the same server, even when we have multiple
+                // replicated servers.
+                greeting = greeter.greet("alice");
+                System.out.println(greeting);
+            }
+        }
+    }
+}

java/IceGrid/query/config.admin

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+# Config file for icegridadmin
+
+# A proxy to the Locator object hosted by the IceGrid registry.
+Ice.Default.Locator=IceGrid/Locator:tcp -h localhost -p 4061
+
+# Dummy username and password. They work because IceGrid is configured with the NullPermissionsVerifier.
+IceGridAdmin.Username=foo
+IceGridAdmin.Password=bar

java/IceGrid/query/config.node

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+# Config file for icegridnode
+
+# A proxy to the Locator object hosted by the IceGrid registry.
+Ice.Default.Locator=IceGrid/Locator:tcp -h localhost -p 4061
+
+# The name of this IceGrid node.
+IceGrid.Node.Name=node1
+
+# The endpoints of this node's object adapter. This object adapter receives requests from the IceGrid registry.
+# We configure this object adapter to listen on an OS-assigned tcp port on the loopback interface since the IceGrid
+# registry runs on the same host in this deployment.
+IceGrid.Node.Endpoints=tcp -h 127.0.0.1
+
+# The directory where the node stores the config files for the Ice servers it starts.
+IceGrid.Node.Data=db/node
+
+# Trace activation of Ice servers (3 = very verbose).
+IceGrid.Node.Trace.Activator=3

java/IceGrid/query/config.registry

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+# Config file for icegridregistry
+
+# The endpoints of this registry's client object adapter. This object adapter receives requests from the clients.
+# We configure it to listen on tcp port 4061, on all interfaces.
+IceGrid.Registry.Client.Endpoints=tcp -p 4061
+
+# The endpoints of this registry's server object adapter. This object adapter receives requests from the servers when
+# they register/unregister themselves or their endpoints with the registry.
+# We configure this object adapter to listen on an OS-assigned tcp port, on all interfaces.
+IceGrid.Registry.Server.Endpoints=tcp
+
+# The endpoints of this registry's internal object adapter. This object adapter receives requests from the IceGrid
+# nodes.
+# We configure this object adapter to listen on an OS-assigned tcp port, on the loopback interface since the IceGrid
+# node runs on the same host in this deployment.
+IceGrid.Registry.Internal.Endpoints=tcp -h 127.0.0.1
+
+# The directory when the registry stores its LMDB database. This directory must exist and be writable by the registry.
+IceGrid.Registry.LMDB.Path=db/registry
+
+# The admin interface of the registry accepts any username/password combination.
+IceGrid.Registry.AdminPermissionsVerifier=IceGrid/NullPermissionsVerifier

java/IceGrid/query/db/node/.gitignore

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+servers/
+tmp/

java/IceGrid/query/db/registry/.gitignore

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+*.mdb
+*.lock