问题描述
我正在使用 spring 数据 (mongoDb),并且我有我的存储库:
I'm using spring data (mongoDb) and I've got my repository:
public interface StoriesRepository extends PagingAndSortingRepository<Story, String> {}
然后我有一个控制器:
@RequestMapping(method = RequestMethod.GET) public ResponseEntity<Page<StoryResponse>> getStories(Pageable pageable) { Page<StoryResponse> stories = storiesRepository.findAll(pageable).map(StoryResponseMapper::toStoryResponse); return ResponseEntity.ok(stories); }
一切正常,但我无法使用 RestTemplate getForEntity 方法使用我的端点:
Everything works fine, but I can't consume my endpoint using RestTemplate getForEntity method:
def entity = restTemplate.getForEntity(getLocalhost("/story"), new TypeReference<Page<StoryResponse>>(){}.class)
我应该提供什么类来成功反序列化我的实体页面?
What class should I provide to successfully deserialize my Page of entities?
推荐答案
new TypeReference<Page<StoryResponse>>() {}
此语句的问题在于 Jackson 无法实例化抽象类型.您应该向 Jackson 提供有关如何使用具体类型实例化 Page 的信息.但它的具体类型 PageImpl 没有默认构造函数或任何 @JsonCreator,因此您也可以不使用以下代码:
The problem with this statement is that Jackson cannot instantiate an abstract type. You should give Jackson the information on how to instantiate Page with a concrete type. But its concrete type, PageImpl, has no default constructor or any @JsonCreators for that matter, so you can not use the following code either:
new TypeReference<PageImpl<StoryResponse>>() {}
由于您无法将所需的信息添加到 Page 类中,因此最好为 Page 接口创建一个自定义实现,该接口具有默认的无参数构造函数,就像在这个 answer 中一样.然后在类型引用中使用该自定义实现,如下所示:
Since you can't add the required information to the Page class, It's better to create a custom implementation for Page interface which has a default no-arg constructor, as in this answer. Then use that custom implementation in type reference, like following:
new TypeReference<CustomPageImpl<StoryResponse>>() {}
这是从链接问题复制的自定义实现:
Here are the custom implementation, copied from linked question:
public class CustomPageImpl<T> extends PageImpl<T> { private static final long serialVersionUID = 1L; private int number; private int size; private int totalPages; private int numberOfElements; private long totalElements; private boolean previousPage; private boolean firstPage; private boolean nextPage; private boolean lastPage; private List<T> content; private Sort sort; public CustomPageImpl() { super(new ArrayList<>()); } @Override public int getNumber() { return number; } public void setNumber(int number) { this.number = number; } @Override public int getSize() { return size; } public void setSize(int size) { this.size = size; } @Override public int getTotalPages() { return totalPages; } public void setTotalPages(int totalPages) { this.totalPages = totalPages; } @Override public int getNumberOfElements() { return numberOfElements; } public void setNumberOfElements(int numberOfElements) { this.numberOfElements = numberOfElements; } @Override public long getTotalElements() { return totalElements; } public void setTotalElements(long totalElements) { this.totalElements = totalElements; } public boolean isPreviousPage() { return previousPage; } public void setPreviousPage(boolean previousPage) { this.previousPage = previousPage; } public boolean isFirstPage() { return firstPage; } public void setFirstPage(boolean firstPage) { this.firstPage = firstPage; } public boolean isNextPage() { return nextPage; } public void setNextPage(boolean nextPage) { this.nextPage = nextPage; } public boolean isLastPage() { return lastPage; } public void setLastPage(boolean lastPage) { this.lastPage = lastPage; } @Override public List<T> getContent() { return content; } public void setContent(List<T> content) { this.content = content; } @Override public Sort getSort() { return sort; } public void setSort(Sort sort) { this.sort = sort; } public Page<T> pageImpl() { return new PageImpl<>(getContent(), new PageRequest(getNumber(), getSize(), getSort()), getTotalElements()); } }