將Spring實戰第5版中Spring HATEOAS部分程式碼遷移到Spring HATEOAS 1.0
阿新 • • 發佈：2020-02-20
最近在閱讀Spring實戰第五版中文版，書中第6章關於Spring HATEOAS部分程式碼使用的是Spring HATEOAS 0.25的版本，而最新的Spring HATEOAS 1.0對舊版的API做了升級，導致在使用新版Spring Boot（截至文章釋出日最新的Spring Boot版本為2.2.4）載入的Spring HATEOAS 1.0.3無法正常執行書中程式碼，所以我決定在此對書中的程式碼進行遷移升級。
線上閱讀書中這一部分：https://potoyang.gitbook.io/spring-in-action-v5/di-6-zhang-chuang-jian-rest-fu-wu/6.2-qi-yong-chao-mei-ti
Spring HATEOAS 1.0 版本的變化
封裝結構的最大變化是通過引入超媒體型別註冊API來實現的，以支援Spring HATEOAS中的其他媒體型別。這導致客戶端API和伺服器API（分別命名的包）以及包中的媒體型別實現的明確分離 mediatype。
最大的變化就是將原來的資源表示為模型，具體變化如下。
在ResourceSupport/ Resource/ Resources/ PagedResources組類從來沒有真正感受到適當命名。畢竟，這些型別實際上並不表示資源，而是表示模型，可以通過超媒體資訊和提供的內容來豐富它們。這是新名稱對映到舊名稱的方式：
-
ResourceSupport就是現在RepresentationModel -
Resource就是現在EntityModel -
Resources就是現在CollectionModel -
PagedResources就是現在PagedModel
因此，ResourceAssembler已被重新命名為RepresentationModelAssembler和及其方法toResource(…)，並分別toResources(…)被重新命名為toModel(…)和toCollectionModel(…)
TypeReferences。
-
RepresentationModel.getLinks()現在公開了一個Links例項（通過List<Link>），該例項公開了其他API，以Links使用各種策略來連線和合並不同的例項。同樣，它已經變成了自繫結的泛型型別，以允許向例項新增連結的方法返回例項本身。 -
該
LinkDiscovererAPI已移動到client包。 -
在
LinkBuilder和EntityLinksAPI已經被移到了server包。 -
ControllerLinkBuilder已移入server.mvc，不推薦使用替換WebMvcLinkBuilder。 -
RelProvider已重新命名為LinkRelationProvider並返回LinkRelation例項，而不是String。 -
VndError已移至mediatype.vnderror套件。
另外注意 ResourceProcessor 介面被 RepresentationModelProcessor 取代
更多變化請參考Spring HATEOAS文件：https://spring.io/projects/spring-hateoas
程式碼遷移升級
書中程式清單6.4 為資源新增超連結
@GetMapping("/recent")
public CollectionModel<EntityModel<Taco>> recentTacos() {
PageRequest page = PageRequest.of(
0, 12, Sort.by("createdAt").descending());
List<Taco> tacos = tacoRepo.findAll(page).getContent();
CollectionModel<EntityModel<Taco>> recentResources = CollectionModel.wrap(tacos);
recentResources.add(
new Link("http://localhost:8080/design/recent", "recents"));
return recentResources;
}
消除URL硬編碼
@GetMapping("/recent")
public CollectionModel<EntityModel<Taco>> recentTacos() {
PageRequest page = PageRequest.of(
0, 12, Sort.by("createdAt").descending());
List<Taco> tacos = tacoRepo.findAll(page).getContent();
CollectionModel<EntityModel<Taco>> recentResources = CollectionModel.wrap(tacos);
recentResources.add(
linkTo(methodOn(DesignTacoController.class).recentTacos()).withRel("recents"));
return recentResources;
}
程式清單6.5 能夠攜帶領域資料和超連結列表taco資源
public class TacoResource extends RepresentationModel<TacoResource> {
@Getter
private String name;
@Getter
private Date createdAt;
@Getter
private List<Ingredient> ingredients;
public TacoResource(Taco taco) {
this.name = taco.getName();
this.createdAt = taco.getCreatedAt();
this.ingredients = taco.getIngredients();
}
}
程式清單6.6 裝配taco資源的資源裝配器
public class TacoResourceAssembler extends RepresentationModelAssemblerSupport<Taco, TacoResource> {
/**
* Creates a new {@link RepresentationModelAssemblerSupport} using the given controller class and resource type.
*
* @param controllerClass DesignTacoController {@literal DesignTacoController}.
* @param resourceType TacoResource {@literal TacoResource}.
*/
public TacoResourceAssembler(Class<?> controllerClass, Class<TacoResource> resourceType) {
super(controllerClass, resourceType);
}
@Override
protected TacoResource instantiateModel(Taco taco) {
return new TacoResource(taco);
}
@Override
public TacoResource toModel(Taco entity) {
return createModelWithId(entity.getId(), entity);
}
}
之後對recentTacos()的調整
@GetMapping("/recentNew")
public CollectionModel<TacoResource> recentTacos() {
PageRequest page = PageRequest.of(
0, 12, Sort.by("createdAt").descending());
List<Taco> tacos = tacoRepo.findAll(page).getContent();
CollectionModel<TacoResource> tacoResources =
new TacoResourceAssembler(DesignTacoController.class, TacoResource.class).toCollectionModel(tacos);
tacoResources.add(linkTo(methodOn(DesignTacoController.class)
.recentTacos())
.withRel("recents"));
return tacoResources;
}
建立 IngredientResource 物件
@Data
public class IngredientResource extends RepresentationModel<IngredientResource> {
public IngredientResource(Ingredient ingredient) {
this.name = ingredient.getName();
this.type = ingredient.getType();
}
private final String name;
private final Ingredient.Type type;
}
IngredientResourceAssembler 物件
public class IngredientResourceAssembler extends RepresentationModelAssemblerSupport<Ingredient, IngredientResource> {
/**
* Creates a new {@link RepresentationModelAssemblerSupport} using the given controller class and resource type.
*
* @param controllerClass IngredientController {@literal IngredientController}.
* @param resourceType IngredientResource {@literal IngredientResource}.
*/
public IngredientResourceAssembler(Class<?> controllerClass, Class<IngredientResource> resourceType) {
super(controllerClass, resourceType);
}
@Override
protected IngredientResource instantiateModel(Ingredient entity) {
return new IngredientResource(entity);
}
@Override
public IngredientResource toModel(Ingredient entity) {
return createModelWithId(entity.getId(), entity);
}
}
對 TacoResource 物件的修改
public class TacoResource extends RepresentationModel<TacoResource> {
private static final IngredientResourceAssembler
ingredientAssembler = new IngredientResourceAssembler(IngredientController.class, IngredientResource.class);
@Getter
private String name;
@Getter
private Date createdAt;
@Getter
private CollectionModel<IngredientResource> ingredients;
public TacoResource(Taco taco) {
this.name = taco.getName();
this.createdAt = taco.getCreatedAt();
this.ingredients = ingredientAssembler.toCollectionModel(taco.getIngredients());
}
}
程式清單6.7
@RepositoryRestController
public class RecentTacosController {
private TacoRepository tacoRepo;
public RecentTacosController(TacoRepository tacoRepo) {
this.tacoRepo = tacoRepo;
}
/**
* 雖然@GetMapping對映到了“/tacos/recent”路徑，但是類級別的@Repository RestController註解會確保這個路徑新增
* Spring Data REST的基礎路徑作為字首。按照我們的配置，recentTacos()方法將會處理針對“/api/tacos/recent”的GET請求。
* */
@GetMapping(path="/tacos/recent", produces="application/hal+json")
public ResponseEntity<CollectionModel<TacoResource>> recentTacos() {
PageRequest page = PageRequest.of(
0, 12, Sort.by("createdAt").descending());
List<Taco> tacos = tacoRepo.findAll(page).getContent();
CollectionModel<TacoResource> tacoResources =
new TacoResourceAssembler(DesignTacoController.class, TacoResource.class).toCollectionModel(tacos);
tacoResources.add(
linkTo(methodOn(RecentTacosController.class).recentTacos())
.withRel("recents"));
return new ResponseEntity<>(tacoResources, HttpStatus.OK);
}
}
程式清單6.8 為Spring Data REST端點新增自定義的連結
@Bean
public RepresentationModelProcessor<PagedModel<EntityModel<Taco>>> tacoProcessor(EntityLinks links) {
return new RepresentationModelProcessor<PagedModel<EntityModel<Taco>>>() {
@Override
public PagedModel<EntityModel<Taco>> process(PagedModel<EntityModel<Taco>> resource) {
resource.add(
links.linkFor(Taco.class)
.slash("recent")
.withRel("recents"));
return resource;
}
};
}
另一種寫法
如果你覺得寫使用資源裝配器有點麻煩，那麼你還可以採用這種方法。
@GetMapping("/employees")
public ResponseEntity<CollectionModel<EntityModel<Taco>>> findAll() {
PageRequest page = PageRequest.of(
0, 12, Sort.by("createdAt").descending());
List<EntityModel<Taco>> employees = StreamSupport.stream(tacoRepo.findAll(page).spliterator(), false)
.map(employee -> new EntityModel<>(employee,
linkTo(methodOn(DesignTacoController.class).findOne(employee.getId())).withSelfRel(),
linkTo(methodOn(DesignTacoController.class).findAll()).withRel("employees")))
.collect(Collectors.toList());
return ResponseEntity.ok(
new CollectionModel<>(employees,
linkTo(methodOn(DesignTacoController.class).findAll()).withSelfRel()));
}
@GetMapping("/employees/{id}")
public ResponseEntity<EntityModel<Taco>> findOne(@PathVariable long id) {
return tacoRepo.findById(id)
.map(employee -> new EntityModel<>(employee,
linkTo(methodOn(DesignTacoController.class).findOne(employee.getId())).withSelfRel(), //
linkTo(methodOn(DesignTacoController.class).findAll()).withRel("employees"))) //
.map(ResponseEntity::ok)
.orElse(ResponseEntity.notFound().build());
}
參考來源：https://github.com/spring-projects/spring-hateoas-examples/tree/master/simplified
END