fix #5214: explicitly omitting nulls by default

CHANGELOG.md

@@ -3,6 +3,7 @@
 ### 6.8-SNAPSHOT
 
 #### Bugs
+* Fix #5214: null values are omitted by default, which means custom resources by in large won't need JsonIncludes annotations.  The only time that is required is when null is to be preserved via @JsonInclude(value = Include.ALWAYS) on the relevant field.
 
 #### Improvements
 

doc/CHEATSHEET.md

@@ -1859,6 +1859,10 @@ import io.fabric8.kubernetes.model.annotation.Version;
 public class CronTab extends CustomResource<CronTabSpec, CronTabStatus> implements Namespaced {
 }
 ```
+
+**Note:** Null values in your custom resource will be omitted by default by the client or when directly using KubernetesSerialization, or the static Serialization methods.  If you have a situation where a null value
+must be present in the serialized form, then mark the field with @JsonInclude(value = Include.ALWAYS).
+
 You can find other helper classes related to `CronTab` in our [tests](https://github.com/fabric8io/kubernetes-client/tree/master/kubernetes-tests/src/test/java/io/fabric8/kubernetes/client/mock/crd). For now, we can proceed with it's common usage examples:
 
 - Get Instance of client for our `CustomResource`:

kubernetes-client-api/src/main/java/io/fabric8/kubernetes/client/utils/KubernetesSerialization.java

@@ -16,6 +16,8 @@
 
 package io.fabric8.kubernetes.client.utils;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonInclude.Include;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.core.type.TypeReference;
 import com.fasterxml.jackson.databind.DeserializationConfig;
@@ -89,6 +91,8 @@ public KubernetesSerialization(ObjectMapper mapper, boolean searchClassloaders)
   protected void configureMapper(ObjectMapper mapper) {
     mapper.registerModules(new JavaTimeModule(), unmatchedFieldTypeModule);
     mapper.disable(DeserializationFeature.FAIL_ON_INVALID_SUBTYPE);
+    // omit null fields, but keep null map values
+    mapper.setDefaultPropertyInclusion(JsonInclude.Value.construct(Include.NON_NULL, Include.ALWAYS));
     HandlerInstantiator instanciator = mapper.getDeserializationConfig().getHandlerInstantiator();
     mapper.setConfig(mapper.getDeserializationConfig().with(new HandlerInstantiator() {
 

kubernetes-client-api/src/test/java/io/fabric8/kubernetes/client/utils/SerializationTest.java

@@ -16,6 +16,7 @@
 package io.fabric8.kubernetes.client.utils;
 
 import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonInclude.Include;
 import com.fasterxml.jackson.annotation.JsonSubTypes;
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
 import com.fasterxml.jackson.annotation.JsonUnwrapped;
@@ -77,6 +78,27 @@
 
 class SerializationTest {
 
+  static class WithNull {
+    @JsonInclude(value = Include.ALWAYS)
+    public Integer field;
+  }
+
+  static class WithoutNull {
+    public Integer field;
+  }
+
+  @Test
+  void testNullSerialization() throws Exception {
+    assertEquals("---\nfield: null\n", Serialization.asYaml(new WithNull()));
+    assertEquals("{\"field\":null}", Serialization.asJson(new WithNull()));
+    assertEquals("--- {}\n", Serialization.asYaml(new WithoutNull()));
+    assertEquals("{}", Serialization.asJson(new WithoutNull()));
+    // map null values should be preserved
+    Map<String, String> map = new HashMap<>();
+    map.put("key", null);
+    assertEquals("{\"key\":null}", Serialization.asJson(map));
+  }
+
   @Test
   void unmarshalCRDWithSchema() throws Exception {
     // Given

kubernetes-client/src/test/java/io/fabric8/kubernetes/client/internal/PatchUtilsTest.java

@@ -57,4 +57,16 @@ void testDiff() {
         PatchUtils.jsonDiff(rc1, rc2, false, new KubernetesSerialization()));
   }
 
+  @Test
+  void testDiffRemove() {
+    ReplicationController rc1 = new ReplicationControllerBuilder().withNewStatus().withFullyLabeledReplicas(1).endStatus()
+        .withNewMetadata().withName("x").endMetadata().build();
+
+    ReplicationController rc2 = new ReplicationControllerBuilder(rc1).withStatus(null).build();
+
+    assertEquals(
+        "[{\"op\":\"remove\",\"path\":\"/status\"}]",
+        PatchUtils.jsonDiff(rc1, rc2, false, new KubernetesSerialization()));
+  }
+
 }