src/main/java/net/hostsharing/hsadminng/hs/booking/item/HsBookingItemEntity.java

@@ -158,8 +158,8 @@ public class HsBookingItemEntity implements Stringifyable, BaseEntity<HsBookingI
     }
 
     @Override
-    public Map<String, Object> directProps() {
+    public PatchableMapWrapper<Object> directProps() {
-        return resources;
+        return getResources();
     }
 
     @Override

src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetEntity.java

@@ -128,8 +128,8 @@ public class HsHostingAssetEntity implements HsHostingAsset {
     }
 
     @Override
-    public Map<String, Object> directProps() {
+    public PatchableMapWrapper<Object> directProps() {
-        return config;
+        return getConfig();
     }
 
     @Override

src/main/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetEntityPatcher.java

@@ -14,7 +14,7 @@ public class HsHostingAssetEntityPatcher implements EntityPatcher<HsHostingAsset
     private final EntityManager em;
     private final HsHostingAssetEntity entity;
 
-    HsHostingAssetEntityPatcher(final EntityManager em, final HsHostingAssetEntity entity) {
+    public HsHostingAssetEntityPatcher(final EntityManager em, final HsHostingAssetEntity entity) {
         this.em = em;
         this.entity = entity;
     }

src/main/java/net/hostsharing/hsadminng/hs/validation/PropertiesProvider.java

@@ -1,11 +1,11 @@
 package net.hostsharing.hsadminng.hs.validation;
 
-import java.util.Map;
+import net.hostsharing.hsadminng.mapper.PatchableMapWrapper;
 
 public interface PropertiesProvider {
 
     boolean isLoaded();
-    Map<String, Object> directProps();
+    PatchableMapWrapper directProps();
     Object getContextValue(final String propName);
 
     default <T> T getDirectValue(final String propName, final Class<T> clazz) {
@@ -16,6 +16,10 @@ public interface PropertiesProvider {
         return cast(propName, directProps().get(propName), clazz, defaultValue);
     }
 
+    default boolean isPatched(String propertyName) {
+        return directProps().isPatched(propertyName);
+    }
+
     default <T>  T getContextValue(final String propName, final Class<T> clazz) {
         return cast(propName, getContextValue(propName), clazz, null);
     }

src/main/java/net/hostsharing/hsadminng/hs/validation/ValidatableProperty.java

@@ -206,6 +206,9 @@ public abstract class ValidatableProperty<P extends ValidatableProperty<?, ?>, T
             if (required == TRUE) {
                 result.add(propertyName + "' is required but missing");
             }
+            if (isWriteOnce() && propsProvider.isLoaded() && propsProvider.isPatched(propertyName) ) {
+                result.add(propertyName + "' is write-once but got removed");
+            }
             validateRequiresAtLeastOneOf(result, propsProvider);
         }
         if (propValue != null){
@@ -248,10 +251,12 @@ public abstract class ValidatableProperty<P extends ValidatableProperty<?, ?>, T
     }
 
     protected void validate(final List<String> result, final T propValue, final PropertiesProvider propProvider) {
-
         if (isReadOnly() && propValue != null) {
             result.add(propertyName + "' is readonly but given as " + display(propValue));
         }
+        if (isWriteOnce() && propProvider.isLoaded() && propValue != null && propProvider.isPatched(propertyName) ) {
+            result.add(propertyName + "' is write-once but given as " + display(propValue));
+        }
     }
 
     public void verifyConsistency(final Map.Entry<? extends Enum<?>, ?> typeDef) {

src/main/java/net/hostsharing/hsadminng/mapper/PatchableMapWrapper.java

@@ -7,7 +7,9 @@ import org.apache.commons.lang3.tuple.ImmutablePair;
 
 import jakarta.validation.constraints.NotNull;
 import java.util.Collection;
+import java.util.HashSet;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 import java.util.function.Consumer;
 
@@ -23,6 +25,7 @@ public class PatchableMapWrapper<T> implements Map<String, T> {
             .configure(SerializationFeature.INDENT_OUTPUT, true);
 
     private final Map<String, T> delegate;
+    private final Set<String> patched = new HashSet<>();
 
     private PatchableMapWrapper(final Map<String, T> map) {
         delegate = map;
@@ -36,6 +39,10 @@ public class PatchableMapWrapper<T> implements Map<String, T> {
         });
     }
 
+    public static <T> PatchableMapWrapper<T> of(final  Map<String, T> delegate) {
+        return new PatchableMapWrapper<T>(delegate);
+    }
+
     @NotNull
     public static <E> ImmutablePair<String, E> entry(final String key, final E value) {
         return new ImmutablePair<>(key, value);
@@ -45,6 +52,7 @@ public class PatchableMapWrapper<T> implements Map<String, T> {
         if (entries != null ) {
             delegate.clear();
             delegate.putAll(entries);
+            patched.clear();
         }
     }
 
@@ -58,6 +66,10 @@ public class PatchableMapWrapper<T> implements Map<String, T> {
         });
     }
 
+    public boolean isPatched(final String propertyName) {
+        return patched.contains(propertyName);
+    }
+
     @SneakyThrows
     public String toString() {
         return jsonWriter.writeValueAsString(delegate);
@@ -92,11 +104,17 @@ public class PatchableMapWrapper<T> implements Map<String, T> {
 
     @Override
     public T put(final String key, final T value) {
+        if (!Objects.equals(value, delegate.get(key))) {
+            patched.add(key);
+        }
         return delegate.put(key, value);
     }
 
     @Override
     public T remove(final Object key) {
+        if (delegate.containsKey(key.toString())) {
+            patched.add(key.toString());
+        }
         return delegate.remove(key);
     }
 
@@ -107,20 +125,24 @@ public class PatchableMapWrapper<T> implements Map<String, T> {
 
     @Override
     public void clear() {
+        patched.addAll(delegate.keySet());
         delegate.clear();
     }
 
     @Override
+    @NotNull
     public Set<String> keySet() {
         return delegate.keySet();
     }
 
     @Override
+    @NotNull
     public Collection<T> values() {
         return delegate.values();
     }
 
     @Override
+    @NotNull
     public Set<Entry<String, T>> entrySet() {
         return delegate.entrySet();
     }

src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetControllerAcceptanceTest.java

@@ -588,7 +588,7 @@ class HsHostingAssetControllerAcceptanceTest extends ContextBasedTestWithCleanup
             }).returnedValue()).isPresent().get()
                     .matches(asset -> {
                         assertThat(asset.getCaption()).isEqualTo("some patched test-unix-user");
-                        assertThat(asset.getConfig().toString()).isEqualTo("""
+                        assertThat(asset.getConfig().toString()).isEqualToIgnoringWhitespace("""
                                {
                                    "password": "$6$Jr5w/Y8zo8pCkqg7$/rePRbvey3R6Sz/02YTlTQcRt5qdBPTj2h5.hz.rB8NfIoND8pFOjeB7orYcPs9JNf3JDxPP2V.6MQlE5BwAY/",
                                    "shell": "/bin/bash",

src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/HsHostingAssetRepositoryIntegrationTest.java

@@ -444,6 +444,7 @@ class HsHostingAssetRepositoryIntegrationTest extends ContextBasedTestWithCleanu
                 .extracting(HsHostingAssetEntity::toString)
                 .extracting(input -> input.replaceAll("\\s+", " "))
                 .extracting(input -> input.replaceAll("\"", ""))
+                .extracting(input -> input.replaceAll("\" : ", "\": "))
                 .containsExactlyInAnyOrder(serverNames);
     }
 }

src/test/java/net/hostsharing/hsadminng/hs/hosting/asset/validators/HsEMailAddressHostingAssetValidatorUnitTest.java

@@ -4,13 +4,15 @@ import net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetEntity;
 import net.hostsharing.hsadminng.mapper.Array;
 import org.junit.jupiter.api.Test;
 
+import java.util.HashMap;
 import java.util.Map;
 
-import static java.util.Map.entry;
+import static java.util.Map.ofEntries;
 import static net.hostsharing.hsadminng.hs.booking.item.TestHsBookingItem.TEST_MANAGED_SERVER_BOOKING_ITEM;
 import static net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetType.DOMAIN_MBOX_SETUP;
 import static net.hostsharing.hsadminng.hs.hosting.asset.HsHostingAssetType.EMAIL_ADDRESS;
 import static net.hostsharing.hsadminng.hs.hosting.asset.TestHsHostingAssetEntities.TEST_MANAGED_SERVER_HOSTING_ASSET;
+import static net.hostsharing.hsadminng.mapper.PatchableMapWrapper.entry;
 import static org.assertj.core.api.Assertions.assertThat;
 
 class HsEMailAddressHostingAssetValidatorUnitTest {
@@ -28,11 +30,11 @@ class HsEMailAddressHostingAssetValidatorUnitTest {
             return HsHostingAssetEntity.builder()
                 .type(EMAIL_ADDRESS)
                 .parentAsset(domainMboxSetup)
-                .identifier("test@example.org")
+                .identifier("old-local-part@example.org")
-                .config(Map.ofEntries(
+                .config(new HashMap<>(ofEntries(
-                        entry("local-part", "test"),
+                        entry("local-part", "old-local-part"),
                         entry("target", Array.of("xyz00", "xyz00-abc", "office@example.com"))
-                ));
+                )));
     }
 
     @Test
@@ -64,10 +66,10 @@ class HsEMailAddressHostingAssetValidatorUnitTest {
     void rejectsInvalidProperties() {
         // given
         final var emailAddressHostingAssetEntity = validEntityBuilder()
-                .config(Map.ofEntries(
+                .config(new HashMap<>(ofEntries(
                         entry("local-part", "no@allowed"),
                         entry("sub-domain", "no@allowedeither"),
-                        entry("target", Array.of("xyz00", "xyz00-abc", "garbage", "office@example.com"))))
+                        entry("target", Array.of("xyz00", "xyz00-abc", "garbage", "office@example.com")))))
                 .build();
         final var validator = HostingAssetEntityValidatorRegistry.forType(emailAddressHostingAssetEntity.getType());
 
@@ -76,9 +78,69 @@ class HsEMailAddressHostingAssetValidatorUnitTest {
 
         // then
         assertThat(result).containsExactlyInAnyOrder(
-                "'EMAIL_ADDRESS:test@example.org.config.local-part' is expected to match any of [^[a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+$] but 'no@allowed' does not match",
+                "'EMAIL_ADDRESS:old-local-part@example.org.config.local-part' is expected to match any of [^[a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+$] but 'no@allowed' does not match",
-                "'EMAIL_ADDRESS:test@example.org.config.sub-domain' is expected to match any of [^[a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+$] but 'no@allowedeither' does not match",
+                "'EMAIL_ADDRESS:old-local-part@example.org.config.sub-domain' is expected to match any of [^[a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+$] but 'no@allowedeither' does not match",
-                "'EMAIL_ADDRESS:test@example.org.config.target' is expected to match any of [^[a-z][a-z0-9]{2}[0-9]{2}(-[a-z0-9][a-z0-9\\._-]*)?$, ^([a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+)?@[a-zA-Z0-9.-]+$, ^nobody$] but 'garbage' does not match any");
+                "'EMAIL_ADDRESS:old-local-part@example.org.config.target' is expected to match any of [^[a-z][a-z0-9]{2}[0-9]{2}(-[a-z0-9][a-z0-9\\._-]*)?$, ^([a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+)?@[a-zA-Z0-9.-]+$, ^nobody$] but 'garbage' does not match any");
+    }
+
+    @Test
+    void rejectsOverwritingWriteOnceProperties() {
+        // given
+        final var emailAddressHostingAssetEntity = validEntityBuilder()
+                .isLoaded(true)
+                .build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(emailAddressHostingAssetEntity.getType());
+
+        // when
+        emailAddressHostingAssetEntity.getConfig().put("local-part", "new-local-part");
+        emailAddressHostingAssetEntity.getConfig().put("sub-domain", "new-sub-domain");
+        final var result = validator.validateEntity(emailAddressHostingAssetEntity);
+
+        // then
+        assertThat(result).containsExactlyInAnyOrder(
+                "'EMAIL_ADDRESS:old-local-part@example.org.config.local-part' is write-once but given as 'new-local-part'",
+                "'EMAIL_ADDRESS:old-local-part@example.org.config.sub-domain' is write-once but given as 'new-sub-domain'");
+    }
+
+    @Test
+    void rejectsRemovingWriteOnceProperties() {
+        // given
+        final var emailAddressHostingAssetEntity = validEntityBuilder()
+                .config(new HashMap<>(ofEntries(
+                        entry("local-part", "old-local-part"),
+                        entry("sub-domain", "old-sub-domain"),
+                        entry("target", Array.of("xyz00", "xyz00-abc", "office@example.com"))
+                )))
+                .isLoaded(true)
+                .build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(emailAddressHostingAssetEntity.getType());
+
+        // when
+        emailAddressHostingAssetEntity.getConfig().remove("local-part");
+        emailAddressHostingAssetEntity.getConfig().remove("sub-domain");
+        final var result = validator.validateEntity(emailAddressHostingAssetEntity);
+
+        // then
+        assertThat(result).containsExactlyInAnyOrder(
+                "'EMAIL_ADDRESS:old-local-part@example.org.config.local-part' is write-once but got removed",
+                "'EMAIL_ADDRESS:old-local-part@example.org.config.sub-domain' is write-once but got removed");
+    }
+
+    @Test
+    void acceptsOverwritingWriteOncePropertiesWithSameValues() {
+        // given
+        final var emailAddressHostingAssetEntity = validEntityBuilder()
+                .isLoaded(true)
+                .build();
+        final var validator = HostingAssetEntityValidatorRegistry.forType(emailAddressHostingAssetEntity.getType());
+
+        // when
+        emailAddressHostingAssetEntity.getConfig().put("local-part", "old-local-part");
+        emailAddressHostingAssetEntity.getConfig().remove("sub-domain"); // is not there anyway
+        final var result = validator.validateEntity(emailAddressHostingAssetEntity);
+
+        // then
+        assertThat(result).isEmpty();
     }
 
     @Test
@@ -94,7 +156,7 @@ class HsEMailAddressHostingAssetValidatorUnitTest {
 
         // then
         assertThat(result).containsExactlyInAnyOrder(
-                "'identifier' expected to match '^\\Qtest@example.org\\E$', but is 'abc00-office'");
+                "'identifier' expected to match '^\\Qold-local-part@example.org\\E$', but is 'abc00-office'");
     }
 
     @Test
@@ -112,8 +174,8 @@ class HsEMailAddressHostingAssetValidatorUnitTest {
 
         // then
         assertThat(result).containsExactlyInAnyOrder(
-                "'EMAIL_ADDRESS:test@example.org.bookingItem' must be null but is of type MANAGED_SERVER",
+                "'EMAIL_ADDRESS:old-local-part@example.org.bookingItem' must be null but is of type MANAGED_SERVER",
-                "'EMAIL_ADDRESS:test@example.org.parentAsset' must be of type DOMAIN_MBOX_SETUP but is of type MANAGED_SERVER",
+                "'EMAIL_ADDRESS:old-local-part@example.org.parentAsset' must be of type DOMAIN_MBOX_SETUP but is of type MANAGED_SERVER",
-                "'EMAIL_ADDRESS:test@example.org.assignedToAsset' must be null but is of type MANAGED_SERVER");
+                "'EMAIL_ADDRESS:old-local-part@example.org.assignedToAsset' must be null but is of type MANAGED_SERVER");
     }
 }

src/test/java/net/hostsharing/hsadminng/hs/migration/HsHostingAssetRealEntity.java

@@ -103,8 +103,8 @@ public class HsHostingAssetRealEntity implements HsHostingAsset {
     }
 
     @Override
-    public Map<String, Object> directProps() {
+    public PatchableMapWrapper<Object> directProps() {
-        return config;
+        return getConfig();
     }
 
     @Override

src/test/java/net/hostsharing/hsadminng/hs/validation/PasswordPropertyUnitTest.java

@@ -1,6 +1,7 @@
 package net.hostsharing.hsadminng.hs.validation;
 
 import net.hostsharing.hsadminng.hash.LinuxEtcShadowHashGenerator;
+import net.hostsharing.hsadminng.mapper.PatchableMapWrapper;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
@@ -109,10 +110,10 @@ class PasswordPropertyUnitTest {
             }
 
             @Override
-            public Map<String, Object> directProps() {
+            public PatchableMapWrapper<Object> directProps() {
-                return Map.ofEntries(
+                return PatchableMapWrapper.of(Map.ofEntries(
                         entry(passwordProp.propertyName, "some password")
-                );
+                ));
             }
 
             @Override

src/test/java/net/hostsharing/hsadminng/rbac/test/PatchUnitTestBase.java

@@ -34,7 +34,7 @@ public abstract class PatchUnitTestBase<R, E> {
 
     @Test
     @SuppressWarnings("unchecked")
-    void willPatchAllProperties() {
+    protected void willPatchAllProperties() {
         // given
         final var givenEntity = newInitialEntity();
         final var patchResource = newPatchResource();
@@ -55,7 +55,7 @@ public abstract class PatchUnitTestBase<R, E> {
 
     @ParameterizedTest
     @MethodSource("propertyTestCases")
-    void willPatchOnlyGivenProperty(final Property<R, Object, E, Object> testCase) {
+    protected void willPatchOnlyGivenProperty(final Property<R, Object, E, Object> testCase) {
 
         // given
         final var givenEntity = newInitialEntity();