src/main/java/net/hostsharing/hsadminng/hs/office/partner/HsOfficePartnerController.java

@@ -104,6 +104,23 @@ public class HsOfficePartnerController implements HsOfficePartnersApi {
         return ResponseEntity.ok(mapper.map(result.get(), HsOfficePartnerResource.class));
     }
 
+    @Override
+    @Transactional(readOnly = true)
+    @Timed("app.office.partners.api.getSinglePartnerByPartnerNumber")
+    public ResponseEntity<HsOfficePartnerResource> getSinglePartnerByPartnerNumber(
+            final String currentSubject,
+            final String assumedRoles,
+            final Integer partnerNumber) {
+
+        context.define(currentSubject, assumedRoles);
+
+        final var result = partnerRepo.findPartnerByPartnerNumber(partnerNumber);
+        if (result.isEmpty()) {
+            return ResponseEntity.notFound().build();
+        }
+        return ResponseEntity.ok(mapper.map(result.get(), HsOfficePartnerResource.class));
+    }
+
     @Override
     @Transactional
     @Timed("app.office.partners.api.deletePartnerByUuid")

src/main/java/net/hostsharing/hsadminng/hs/office/partner/HsOfficePartnerRepository.java

@@ -32,7 +32,7 @@ public interface HsOfficePartnerRepository extends Repository<HsOfficePartnerEnt
     List<HsOfficePartnerEntity> findPartnerByOptionalNameLike(String name);
 
     @Timed("app.office.partners.repo.findPartnerByPartnerNumber")
-    HsOfficePartnerEntity findPartnerByPartnerNumber(Integer partnerNumber);
+    Optional<HsOfficePartnerEntity> findPartnerByPartnerNumber(Integer partnerNumber);
 
     @Timed("app.office.partners.repo.save")
     HsOfficePartnerEntity save(final HsOfficePartnerEntity entity);

src/main/resources/api-definition/hs-office/hs-office-partners-with-partnerNumber.yaml

@@ -0,0 +1,28 @@
+get:
+    tags:
+        - hs-office-partners
+    description: 'Fetch a single business partner by its partner-number (prefixed with "P-"), if visible for the current subject.'
+    operationId: getSinglePartnerByPartnerNumber
+    parameters:
+        - $ref: 'auth.yaml#/components/parameters/currentSubject'
+        - $ref: 'auth.yaml#/components/parameters/assumedRoles'
+        - name: partnerNumber
+          in: path
+          required: true
+          schema:
+              type: integer
+              minimum: 10000
+              maximum: 99999
+          description: partner-number (prefixed with "P-") of the partner to fetch.
+    responses:
+        "200":
+            description: OK
+            content:
+                'application/json':
+                    schema:
+                        $ref: 'hs-office-partner-schemas.yaml#/components/schemas/HsOfficePartner'
+
+        "401":
+            $ref: 'error-responses.yaml#/components/responses/Unauthorized'
+        "403":
+            $ref: 'error-responses.yaml#/components/responses/Forbidden'

src/main/resources/api-definition/hs-office/hs-office.yaml

@@ -13,6 +13,9 @@ paths:
   /api/hs/office/partners:
     $ref: "hs-office-partners.yaml"
 
+  /api/hs/office/partners/P-{partnerNumber}:
+    $ref: "hs-office-partners-with-partnerNumber.yaml"
+
   /api/hs/office/partners/{partnerUUID}:
     $ref: "hs-office-partners-with-uuid.yaml"
 

src/test/java/net/hostsharing/hsadminng/hs/office/debitor/HsOfficeDebitorRepositoryIntegrationTest.java

@@ -83,7 +83,7 @@ class HsOfficeDebitorRepositoryIntegrationTest extends ContextBasedTestWithClean
             // given
             context("superuser-alex@hostsharing.net");
             final var count = debitorRepo.count();
-            final var givenPartner = partnerRepo.findPartnerByPartnerNumber(10001);
+            final var givenPartner = partnerRepo.findPartnerByPartnerNumber(10001).orElseThrow();
             final var givenPartnerPerson = one(personRepo.findPersonByOptionalNameLike("First GmbH"));
             final var givenContact = one(contactrealRepo.findContactByOptionalCaptionLike("first contact"));
 

src/test/java/net/hostsharing/hsadminng/hs/office/membership/HsOfficeMembershipControllerAcceptanceTest.java

@@ -112,16 +112,16 @@ class HsOfficeMembershipControllerAcceptanceTest extends ContextBasedTestWithCle
         void globalAdmin_canViewMembershipsByPartnerUuid() {
 
             context.define("superuser-alex@hostsharing.net");
-            final var partner = partnerRepo.findPartnerByPartnerNumber(10001);
+            final var partner = partnerRepo.findPartnerByPartnerNumber(10001).orElseThrow();
 
             RestAssured // @formatter:off
-                    .given()
+                .given()
                     .header("current-subject", "superuser-alex@hostsharing.net")
                     .port(port)
-                    .when()
+                .when()
                     .queryParam("partnerUuid", partner.getUuid() )
                     .get("http://localhost/api/hs/office/memberships")
-                    .then().log().all().assertThat()
+                .then().log().all().assertThat()
                     .statusCode(200)
                     .contentType("application/json")
                     .body("", lenientlyEquals("""

src/test/java/net/hostsharing/hsadminng/hs/office/partner/HsOfficePartnerControllerRestTest.java

@@ -168,6 +168,45 @@ class HsOfficePartnerControllerRestTest {
         }
     }
 
+    @Nested
+    class GetSinglePartnerByPartnerNumber {
+
+        @Test
+        void respondWithPartner_ifPartnerNumberIsAvailable() throws Exception {
+            // given
+            when(partnerRepo.findPartnerByPartnerNumber(12345)).thenReturn(Optional.of(HsOfficePartnerEntity.builder()
+                    .partnerNumber(12345)
+                    .build()));
+
+            // when
+            mockMvc.perform(MockMvcRequestBuilders
+                    .get("/api/hs/office/partners/P-12345")
+                    .header("current-subject", "superuser-alex@hostsharing.net")
+                    .contentType(MediaType.APPLICATION_JSON)
+                    .accept(MediaType.APPLICATION_JSON))
+
+            // then
+            .andExpect(status().isOk())
+            .andExpect(jsonPath("partnerNumber", is("P-12345")));
+        }
+
+        @Test
+        void respondNotFound_ifPartnerNumberIsNotAvailable() throws Exception {
+            // given
+            when(partnerRepo.findPartnerByPartnerNumber(12345)).thenReturn(Optional.empty());
+
+            // when
+            mockMvc.perform(MockMvcRequestBuilders
+                    .get("/api/hs/office/partners/P-12345")
+                    .header("current-subject", "superuser-alex@hostsharing.net")
+                    .contentType(MediaType.APPLICATION_JSON)
+                    .accept(MediaType.APPLICATION_JSON))
+
+            // then
+            .andExpect(status().isNotFound());
+        }
+    }
+
     @Nested
     class DeletePartner {
 

src/test/java/net/hostsharing/hsadminng/hs/office/partner/HsOfficePartnerRepositoryIntegrationTest.java

@@ -243,7 +243,7 @@ class HsOfficePartnerRepositoryIntegrationTest extends ContextBasedTestWithClean
             context("superuser-alex@hostsharing.net");
 
             // when
-            final var result = partnerRepo.findPartnerByPartnerNumber(10001);
+            final var result = partnerRepo.findPartnerByPartnerNumber(10001).orElseThrow();
 
             // then
             assertThat(result)