diff --git a/src/main/java/org/hostsharing/hsadminng/service/CustomerService.java b/src/main/java/org/hostsharing/hsadminng/service/CustomerService.java
index 9bff0e66..06d8d978 100644
--- a/src/main/java/org/hostsharing/hsadminng/service/CustomerService.java
+++ b/src/main/java/org/hostsharing/hsadminng/service/CustomerService.java
@@ -18,7 +18,7 @@ import java.util.Optional;
  */
 @Service
 @Transactional
-public class CustomerService implements DtoLoader<CustomerDTO> {
+public class CustomerService implements IdToDtoResolver<CustomerDTO> {
 
     private final Logger log = LoggerFactory.getLogger(CustomerService.class);
 
diff --git a/src/main/java/org/hostsharing/hsadminng/service/DtoLoader.java b/src/main/java/org/hostsharing/hsadminng/service/IdToDtoResolver.java
similarity index 75%
rename from src/main/java/org/hostsharing/hsadminng/service/DtoLoader.java
rename to src/main/java/org/hostsharing/hsadminng/service/IdToDtoResolver.java
index ae30d79b..14b15828 100644
--- a/src/main/java/org/hostsharing/hsadminng/service/DtoLoader.java
+++ b/src/main/java/org/hostsharing/hsadminng/service/IdToDtoResolver.java
@@ -2,6 +2,6 @@ package org.hostsharing.hsadminng.service;
 
 import java.util.Optional;
 
-public interface DtoLoader<T> {
+public interface IdToDtoResolver<T> {
     Optional<? extends T> findOne(Long id);
 }
diff --git a/src/main/java/org/hostsharing/hsadminng/service/MembershipService.java b/src/main/java/org/hostsharing/hsadminng/service/MembershipService.java
index d611e713..473f5d7e 100644
--- a/src/main/java/org/hostsharing/hsadminng/service/MembershipService.java
+++ b/src/main/java/org/hostsharing/hsadminng/service/MembershipService.java
@@ -19,7 +19,7 @@ import java.util.Optional;
  */
 @Service
 @Transactional
-public class MembershipService implements DtoLoader<MembershipDTO> {
+public class MembershipService implements IdToDtoResolver<MembershipDTO> {
 
     private final Logger log = LoggerFactory.getLogger(MembershipService.class);
 
diff --git a/src/main/java/org/hostsharing/hsadminng/service/accessfilter/JSonAccessFilter.java b/src/main/java/org/hostsharing/hsadminng/service/accessfilter/JSonAccessFilter.java
index 86d88bba..45d2b7ac 100644
--- a/src/main/java/org/hostsharing/hsadminng/service/accessfilter/JSonAccessFilter.java
+++ b/src/main/java/org/hostsharing/hsadminng/service/accessfilter/JSonAccessFilter.java
@@ -1,17 +1,16 @@
 package org.hostsharing.hsadminng.service.accessfilter;
 
-import org.apache.commons.lang3.NotImplementedException;
 import org.hostsharing.hsadminng.security.SecurityUtils;
-import org.hostsharing.hsadminng.service.CustomerService;
-import org.hostsharing.hsadminng.service.DtoLoader;
-import org.hostsharing.hsadminng.service.MembershipService;
-import org.hostsharing.hsadminng.service.dto.CustomerDTO;
+import org.hostsharing.hsadminng.service.IdToDtoResolver;
 import org.hostsharing.hsadminng.service.dto.MembershipDTO;
 import org.hostsharing.hsadminng.service.util.ReflectionUtil;
 import org.springframework.context.ApplicationContext;
 
+import javax.persistence.EntityNotFoundException;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Field;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
 
 abstract class JSonAccessFilter<T> {
     private final ApplicationContext ctx;
@@ -50,43 +49,51 @@ abstract class JSonAccessFilter<T> {
      */
     Role getLoginUserRole() {
         final Role roleOnSelf = getLoginUserRoleOnSelf();
-        if ( roleOnSelf.isIndependent() ) {
+        if (roleOnSelf.isIndependent()) {
             return roleOnSelf;
         }
         return getLoginUserRoleOnAncestorOfDtoClassIfHigher(roleOnSelf, dto);
     }
 
     private Role getLoginUserRoleOnSelf() {
-        return SecurityUtils.getLoginUserRoleFor(dto.getClass(), getId() );
+        return SecurityUtils.getLoginUserRoleFor(dto.getClass(), getId());
     }
 
     private Role getLoginUserRoleOnAncestorOfDtoClassIfHigher(final Role baseRole, final Object dto) {
         final Field parentIdField = determineFieldWithAnnotation(dto.getClass(), ParentId.class);
 
-        if ( parentIdField == null ) {
+        if (parentIdField == null) {
             return baseRole;
         }
 
         final ParentId parentIdAnnot = parentIdField.getAnnotation(ParentId.class);
-        final Class<?> parentDtoClass = parentIdAnnot.value();
+        final Class<? extends IdToDtoResolver> parentDtoLoader = parentIdAnnot.resolver();
+        final Class<?> parentDtoClass = getGenericClassParameter(parentDtoLoader);
         final Long parentId = (Long) ReflectionUtil.getValue(dto, parentIdField);
         final Role roleOnParent = SecurityUtils.getLoginUserRoleFor(parentDtoClass, parentId);
 
-        final Object parentEntity = findParentDto(parentDtoClass, parentId);
+        final Object parentEntity = findParentDto(parentDtoLoader, parentId);
         return Role.broadest(baseRole, getLoginUserRoleOnAncestorOfDtoClassIfHigher(roleOnParent, parentEntity));
     }
 
-    private Object findParentDto(Class<?> parentDtoClass, Long parentId) {
-        // TODO: generalize, e.g. via "all beans that implement DtoLoader<CustomerDTO>
-        if ( parentDtoClass == MembershipDTO.class ) {
-            final DtoLoader<MembershipDTO> dtoLoader = ctx.getAutowireCapableBeanFactory().createBean(MembershipService.class);
-            return dtoLoader.findOne(parentId).get();
+    @SuppressWarnings("unchecked")
+    private Class<T> getGenericClassParameter(Class<? extends IdToDtoResolver> parentDtoLoader) {
+        for (Type genericInterface : parentDtoLoader.getGenericInterfaces()) {
+            if (genericInterface instanceof ParameterizedType) {
+                final ParameterizedType parameterizedType = (ParameterizedType) genericInterface;
+                if (parameterizedType.getRawType()== IdToDtoResolver.class) {
+                    return (Class<T>) parameterizedType.getActualTypeArguments()[0];
+                }
+            }
+
         }
-        if ( parentDtoClass == CustomerDTO.class ) {
-            final DtoLoader<CustomerDTO> dtoLoader = ctx.getAutowireCapableBeanFactory().createBean(CustomerService.class);
-            return dtoLoader.findOne(parentId).get();
-        }
-        throw new NotImplementedException("no DtoLoader implemented for " + parentDtoClass);
+        throw new AssertionError(parentDtoLoader.getSimpleName() + " expected to implement " + IdToDtoResolver.class.getSimpleName() + "<...DTO>");
+    }
+
+    @SuppressWarnings("unchecked")
+    private Object findParentDto(final Class<? extends IdToDtoResolver> parentDtoLoader, final Long parentId) {
+        final IdToDtoResolver<MembershipDTO> idToDtoResolver = ctx.getAutowireCapableBeanFactory().createBean(parentDtoLoader);
+        return idToDtoResolver.findOne(parentId).orElseThrow(() -> new EntityNotFoundException("Can't resolve parent entity ID " + parentId + " via " + parentDtoLoader));
     }
 
     private static Field determineFieldWithAnnotation(final Class<?> dtoClass, final Class<? extends Annotation> idAnnotationClass) {
diff --git a/src/main/java/org/hostsharing/hsadminng/service/accessfilter/ParentId.java b/src/main/java/org/hostsharing/hsadminng/service/accessfilter/ParentId.java
index 51ddc0a2..e392374e 100644
--- a/src/main/java/org/hostsharing/hsadminng/service/accessfilter/ParentId.java
+++ b/src/main/java/org/hostsharing/hsadminng/service/accessfilter/ParentId.java
@@ -1,5 +1,7 @@
 package org.hostsharing.hsadminng.service.accessfilter;
 
+import org.hostsharing.hsadminng.service.IdToDtoResolver;
+
 import java.lang.annotation.*;
 
 /**
@@ -12,6 +14,6 @@ import java.lang.annotation.*;
 @Target({ElementType.FIELD})
 @Retention(RetentionPolicy.RUNTIME)
 public @interface ParentId {
-    /// The DTO class of the referenced entity.
-    Class<?> value();
+    /// The service which can load the referenced DTO.
+    Class<? extends IdToDtoResolver<?>> resolver();
 }
diff --git a/src/main/java/org/hostsharing/hsadminng/service/dto/MembershipDTO.java b/src/main/java/org/hostsharing/hsadminng/service/dto/MembershipDTO.java
index c255c3a2..141614d9 100644
--- a/src/main/java/org/hostsharing/hsadminng/service/dto/MembershipDTO.java
+++ b/src/main/java/org/hostsharing/hsadminng/service/dto/MembershipDTO.java
@@ -1,5 +1,6 @@
 package org.hostsharing.hsadminng.service.dto;
 
+import org.hostsharing.hsadminng.service.CustomerService;
 import org.hostsharing.hsadminng.service.accessfilter.AccessFor;
 import org.hostsharing.hsadminng.service.accessfilter.ParentId;
 import org.hostsharing.hsadminng.service.accessfilter.Role;
@@ -36,7 +37,7 @@ public class MembershipDTO implements Serializable {
     @AccessFor(init = Role.ADMIN, read = Role.SUPPORTER)
     private String remark;
 
-    @ParentId(CustomerDTO.class)
+    @ParentId(resolver = CustomerService.class)
     @AccessFor(init = Role.ADMIN, read = {Role.CONTRACTUAL_CONTACT, Role.FINANCIAL_CONTACT})
     private Long customerId;
 
diff --git a/src/main/java/org/hostsharing/hsadminng/service/dto/ShareDTO.java b/src/main/java/org/hostsharing/hsadminng/service/dto/ShareDTO.java
index eff5bad4..b9e79209 100644
--- a/src/main/java/org/hostsharing/hsadminng/service/dto/ShareDTO.java
+++ b/src/main/java/org/hostsharing/hsadminng/service/dto/ShareDTO.java
@@ -1,6 +1,7 @@
 package org.hostsharing.hsadminng.service.dto;
 
 import org.hostsharing.hsadminng.domain.enumeration.ShareAction;
+import org.hostsharing.hsadminng.service.MembershipService;
 import org.hostsharing.hsadminng.service.accessfilter.AccessFor;
 import org.hostsharing.hsadminng.service.accessfilter.ParentId;
 import org.hostsharing.hsadminng.service.accessfilter.Role;
@@ -41,7 +42,7 @@ public class ShareDTO implements Serializable {
     @AccessFor(init = Role.ADMIN, read = Role.SUPPORTER)
     private String remark;
 
-    @ParentId(MembershipDTO.class)
+    @ParentId(resolver = MembershipService.class)
     @AccessFor(init = Role.ADMIN, read = {Role.CONTRACTUAL_CONTACT, Role.FINANCIAL_CONTACT})
     private Long membershipId;
 
diff --git a/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonDeserializerWithAccessFilterUnitTest.java b/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonDeserializerWithAccessFilterUnitTest.java
index 9c0340b8..da59b241 100644
--- a/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonDeserializerWithAccessFilterUnitTest.java
+++ b/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonDeserializerWithAccessFilterUnitTest.java
@@ -5,6 +5,7 @@ import com.fasterxml.jackson.core.ObjectCodec;
 import com.fasterxml.jackson.core.TreeNode;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.apache.commons.lang3.tuple.ImmutablePair;
+import org.hostsharing.hsadminng.service.IdToDtoResolver;
 import org.hostsharing.hsadminng.web.rest.errors.BadRequestAlertException;
 import org.junit.Before;
 import org.junit.Rule;
@@ -211,6 +212,9 @@ public class JSonDeserializerWithAccessFilterUnitTest {
         Long openLongField;
     }
 
+    abstract class GivenService implements IdToDtoResolver<GivenDto> {
+    }
+
     public static class GivenChildDto {
 
         @SelfId
@@ -218,7 +222,7 @@ public class JSonDeserializerWithAccessFilterUnitTest {
         Long id;
 
         @AccessFor(init = Role.CONTRACTUAL_CONTACT, update = Role.CONTRACTUAL_CONTACT, read = Role.ACTUAL_CUSTOMER_USER)
-        @ParentId(GivenDto.class)
+        @ParentId(resolver = GivenService.class)
         Long parentId;
 
         @AccessFor(init = {Role.TECHNICAL_CONTACT, Role.FINANCIAL_CONTACT}, update = {Role.TECHNICAL_CONTACT, Role.FINANCIAL_CONTACT})
diff --git a/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonSerializerWithAccessFilterUnitTest.java b/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonSerializerWithAccessFilterUnitTest.java
index 8cd09db8..f953bcf1 100644
--- a/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonSerializerWithAccessFilterUnitTest.java
+++ b/src/test/java/org/hostsharing/hsadminng/service/accessfilter/JSonSerializerWithAccessFilterUnitTest.java
@@ -4,6 +4,7 @@ import com.fasterxml.jackson.core.JsonGenerator;
 import org.apache.commons.lang3.NotImplementedException;
 import org.apache.commons.lang3.RandomStringUtils;
 import org.apache.commons.lang3.RandomUtils;
+import org.hostsharing.hsadminng.service.IdToDtoResolver;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -110,9 +111,12 @@ public class JSonSerializerWithAccessFilterUnitTest {
 
     }
 
+    private abstract class GivenCustomerService implements IdToDtoResolver<GivenCustomerDto> {
+    }
+
     private static class GivenDto {
 
-        @ParentId(GivenCustomerDto.class)
+        @ParentId(resolver = GivenCustomerService.class)
         Long customerId;
 
         @AccessFor(read = {Role.TECHNICAL_CONTACT, Role.FINANCIAL_CONTACT})