Add a server-side apply example

examples/examples-release-latest/src/main/java/io/kubernetes/client/examples/ServerSideApplyExample.java

@@ -0,0 +1,89 @@
+/*
+Copyright 2026 The Kubernetes Authors.
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+http://www.apache.org/licenses/LICENSE-2.0
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+package io.kubernetes.client.examples;
+
+import io.kubernetes.client.openapi.ApiClient;
+import io.kubernetes.client.openapi.ApiException;
+import io.kubernetes.client.openapi.models.V1ConfigMap;
+import io.kubernetes.client.openapi.models.V1ConfigMapList;
+import io.kubernetes.client.openapi.models.V1ObjectMeta;
+import io.kubernetes.client.util.Config;
+import io.kubernetes.client.util.ServerSideApply;
+import java.io.IOException;
+import java.util.Map;
+
+/**
+ * Demonstrates server-side apply using the {@link ServerSideApply} helper.
+ *
+ * <p>Server-side apply lets you declare the desired state of a resource and have the API server
+ * merge it based on field ownership. Re-applying the same manifest is idempotent, and {@code
+ * forceConflicts} lets a field manager take ownership of fields owned by someone else.
+ *
+ * <p>This example applies a {@code ConfigMap}, mutates one field and re-applies it, and finally
+ * runs a dry-run apply that the server validates without persisting.
+ *
+ * <p>Run with:
+ *
+ * <pre>{@code
+ * mvn exec:java \
+ *   -Dexec.mainClass="io.kubernetes.client.examples.ServerSideApplyExample"
+ * }</pre>
+ */
+public final class ServerSideApplyExample {
+
+  private static final String FIELD_MANAGER = "server-side-apply-example";
+
+  private ServerSideApplyExample() {}
+
+  public static void main(String[] args) throws IOException, ApiException {
+    ApiClient client = Config.defaultClient();
+
+    V1ConfigMap configMap =
+        new V1ConfigMap()
+            .apiVersion("v1")
+            .kind("ConfigMap")
+            .metadata(new V1ObjectMeta().name("ssa-example").namespace("default"))
+            .data(Map.of("greeting", "hello"));
+
+    // First apply creates the ConfigMap and records the fields owned by this field manager.
+    V1ConfigMap applied =
+        ServerSideApply.apply(
+            client, V1ConfigMap.class, V1ConfigMapList.class, configMap, FIELD_MANAGER);
+    System.out.println("applied: " + applied.getData());
+
+    // Re-applying an updated manifest is idempotent; forceConflicts takes ownership of any field
+    // that another manager may have changed in the meantime.
+    configMap.data(Map.of("greeting", "hello again"));
+    V1ConfigMap updated =
+        ServerSideApply.builder(client)
+            .apiTypeClass(V1ConfigMap.class)
+            .apiListTypeClass(V1ConfigMapList.class)
+            .resource(configMap)
+            .fieldManager(FIELD_MANAGER)
+            .forceConflicts(true)
+            .apply();
+    System.out.println("updated: " + updated.getData());
+
+    // A dry-run apply is validated by the server but never persisted.
+    configMap.data(Map.of("greeting", "not persisted"));
+    V1ConfigMap dryRun =
+        ServerSideApply.builder(client)
+            .apiTypeClass(V1ConfigMap.class)
+            .apiListTypeClass(V1ConfigMapList.class)
+            .resource(configMap)
+            .fieldManager(FIELD_MANAGER)
+            .dryRun()
+            .apply();
+    System.out.println("dry-run (not persisted): " + dryRun.getData());
+  }
+}