task: add endpoint to request single field definitions

module-core/src/main/java/io/goobi/vocabulary/api/FieldDefinitionController.java

@@ -0,0 +1,27 @@
+package io.goobi.vocabulary.api;
+
+import io.goobi.vocabulary.api.assemblers.FieldDefinitionAssembler;
+import io.goobi.vocabulary.exchange.FieldDefinition;
+import io.goobi.vocabulary.service.manager.FieldDefinitionDTOManager;
+import org.springframework.hateoas.EntityModel;
+import org.springframework.web.bind.annotation.GetMapping;
+import org.springframework.web.bind.annotation.PathVariable;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+@RestController
+@RequestMapping("/api/v1")
+public class FieldDefinitionController {
+    private final FieldDefinitionDTOManager manager;
+    private final FieldDefinitionAssembler assembler;
+
+    public FieldDefinitionController(FieldDefinitionDTOManager manager, FieldDefinitionAssembler assembler) {
+        this.manager = manager;
+        this.assembler = assembler;
+    }
+
+    @GetMapping("/fieldDefinitions/{id}")
+    public EntityModel<FieldDefinition> one(@PathVariable long id) {
+        return assembler.toModel(manager.get(id));
+    }
+}

module-core/src/main/java/io/goobi/vocabulary/api/assemblers/FieldDefinitionAssembler.java

@@ -0,0 +1,22 @@
+package io.goobi.vocabulary.api.assemblers;
+
+import io.goobi.vocabulary.api.FieldTypeController;
+import io.goobi.vocabulary.api.VocabularySchemaController;
+import io.goobi.vocabulary.exchange.FieldDefinition;
+import org.springframework.hateoas.EntityModel;
+import org.springframework.hateoas.server.RepresentationModelAssembler;
+import org.springframework.stereotype.Component;
+
+import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.linkTo;
+import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.methodOn;
+
+@Component
+public class FieldDefinitionAssembler implements RepresentationModelAssembler<FieldDefinition, EntityModel<FieldDefinition>> {
+    @Override
+    public EntityModel<FieldDefinition> toModel(FieldDefinition entity) {
+        return EntityModel.of(entity,
+                linkTo(methodOn(FieldTypeController.class).one(entity.getId())).withSelfRel(),
+                linkTo(methodOn(VocabularySchemaController.class).one(entity.getSchemaId())).withRel("schema")
+        );
+    }
+}

module-core/src/main/java/io/goobi/vocabulary/service/manager/FieldDefinitionDTOManager.java

@@ -0,0 +1,25 @@
+package io.goobi.vocabulary.service.manager;
+
+import io.goobi.vocabulary.exception.EntityNotFoundException;
+import io.goobi.vocabulary.exchange.FieldDefinition;
+import io.goobi.vocabulary.repositories.FieldDefinitionRepository;
+import io.goobi.vocabulary.service.exchange.DTOMapper;
+import org.springframework.stereotype.Service;
+
+@Service
+public class FieldDefinitionDTOManager {
+    private final FieldDefinitionRepository fieldDefinitionRepository;
+    private final DTOMapper modelMapper;
+
+    public FieldDefinitionDTOManager(FieldDefinitionRepository fieldDefinitionRepository, DTOMapper modelMapper) {
+        this.fieldDefinitionRepository = fieldDefinitionRepository;
+        this.modelMapper = modelMapper;
+    }
+
+    public FieldDefinition get(long id) {
+        return modelMapper.toDTO(
+                fieldDefinitionRepository.findById(id)
+                        .orElseThrow(() -> new EntityNotFoundException(FieldDefinition.class, id))
+        );
+    }
+}