英文:
Return Hashmap from Spring Rest API
问题
我想使用这段代码从Rest API获取一些数据：
public Map<Integer, String> getCategoriesList() {Map<Integer, String> list = new HashMap<>();list.put(1, "Electronics");list.put(2, "Outdoor and Sports");list.put(3, "Home and Garden");list.put(4, "Home appliances");list.put(5, "Air conditioners and heaters");list.put(6, "IT accessories");list.put(7, "Photo and Video");list.put(8, "TV Video and Gaming");return list;}@GetMapping("categories")public ResponseEntity<List<String>> getCategoriesList() {return (ResponseEntity<List<String>>) categoriesService.getCategoriesList();}
我得到错误：class java.util.HashMap cannot be cast to class org.springframework.http.ResponseEntity
以何种适当的方式将这些数据作为响应返回？
英文:
I want to use this code to get some data from Rest API:
public Map<Integer, String> getCategoriesList() {Map<Integer, String> list = new HashMap<>();list.put(1, "Electronics");list.put(2, "Outdoor and Sports");list.put(3, "Home and Garden");list.put(4, "Home appliances");list.put(5, "Air conditioners and heaters");list.put(6, "IT accessories");list.put(7, "Photo and Video");list.put(8, "TV Video and Gaming");return list;}@GetMapping("categories")public ResponseEntity<List<String>> getCategoriesList() {return (ResponseEntity<List<String>>) categoriesService.getCategoriesList();}
I get error: class java.util.HashMap cannot be cast to class org.springframework.http.ResponseEntity
What is the appropriate way to return this data as a response?
答案1
得分: 2
你不能像那样将一个类型强制转换为另一个类型... 尝试这样做：
使用ResponseEntity包装：
@GetMapping("categories")public ResponseEntity<Map<Integer, String>> getCategoriesList() {return new ResponseEntity<Map<Integer, String>>(categoriesService.getCategoriesList(), HttpStatus.OK);}
不使用ResponseEntity包装：
@GetMapping("categories")@ResponseStatus(code = HttpStatus.OK)public Map<Integer, String> getCategoriesList() {return categoriesService.getCategoriesList();}
因为这两种类型的映射都为Jackson所知（我假设您在Spring中用于序列化/反序列化的是Jackson），所以不需要做任何其他操作。
英文:
You cannot cast one type to another like that...try this
ResponseEntity type:
@GetMapping("categories")public ResponseEntity<Map<Integer, String>> getCategoriesList() {return new ResponseEntity<Map<Integer,String>>(categoriesService.getCategoriesList(), HttpStatus.OK);}
Without ResponseEntity wrapper
@GetMapping("categories")@ResponseStatus(code = HttpStatus.OK)public Map<Integer, String> getCategoriesList() {return categoriesService.getCategoriesList();}
Since both types of map are known to jackson (I presume that's what you are using in spring for serialization/deserialization), no need to do anything more.
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