Java - 对象映射器 - 要列出的数字的 JSON 数组<Long>

Question

在我的前端，我发送了这个 JSON：

"ids": [ 123421, 15643, 51243],

"user": {

   "name": "John",

   "email": "[e-mail]" 

}

下面是我的 Spring 端点：

@PostMapping(value = "/sendToOficial")

public ResponseEntity<?> sendToOficial(@RequestBody Map<String, Object> payload) {

ObjectMapper mapper = new ObjectMapper();

List<Long> pointsIds = mapper.convertValue( payload.get("pointsIds"), List.class );

UsuarioDTO autorAlteracao = mapper.convertValue(payload.get("user"), UsuarioDTO.class);

for (Long idPoint : pointsIds) { ... }

但是我收到了一个 Cast Exception，因为它不能将 Integer 转换为 Long。

我无法将“ids”数字接收为整数，我想接收为长整数。请问，我怎么能这样？

Answer 1

首先，定义用于映射请求对象的 POJO：public class RequestObj implements Serializable{&nbsp; &nbsp; private List<Long> ids;&nbsp; &nbsp; private UsuarioDTO user;&nbsp; &nbsp; /* getters and setters here */}public class UsuarioDTO implements Serializable{&nbsp; &nbsp; private String name;&nbsp; &nbsp; private String email;&nbsp; &nbsp; /* getters and setters here */}然后修改您的端点：@PostMapping(value = "/sendToOficial")public ResponseEntity<?> sendToOficial(@RequestBody RequestObj payload) {通过这种方式，您也不需要使用ObjectMapper. 就打电话payload.getIds()。还要考虑这样，如果有效负载发生变化，您只需要更改RequestObj定义，而使用ObjectMapper会强制您以一种重要的方式更新端点。将有效载荷表示与控制逻辑分开会更好也更安全。

Answer 2

在jackson-databind-2.6.x及更高版本中，您可以使用配置功能ObjectMapper将低类型int值（适合 32 位的long值）配置为序列化值DeserializationFeature#USE_LONG_FOR_INTS：@PostMapping(value = "/sendToOficial")public ResponseEntity<?> sendToOficial(@RequestBody Map<String, Object> payload) {&nbsp; &nbsp; ObjectMapper mapper = new ObjectMapper().configure(DeserializationFeature .USE_LONG_FOR_INTS, true);&nbsp; &nbsp; List<Long> pointsIds = mapper.convertValue( payload.get("pointsIds"), List.class );&nbsp; &nbsp; UsuarioDTO autorAlteracao = mapper.convertValue(payload.get("user"), UsuarioDTO.class);&nbsp; &nbsp; for (Long idPoint : pointsIds) { // ... }}

Answer 3

如果您只想让映射器读入List<Long>，请使用此技巧通过子类化获取完整的泛型类型信息。例子ObjectMapper mapper = new ObjectMapper();List<Long>listOfLong=mapper.readValue("[ 123421, 15643, 51243]" ,&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; new TypeReference<List<Long>>() {&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; });System.out.println(listOfLong);印刷[123421, 15643, 51243]