JsonMappingException:无法从START_OBJECT标记中反序列化java.lang.Integer的实例

Question

我想用Spring Boot编写一个小而简单的REST服务.这是REST服务代码:

@Async
@RequestMapping(value = "/getuser", method = POST, consumes = "application/json", produces = "application/json")
public @ResponseBody Record getRecord(@RequestBody Integer userId) {
    Record result = null;
    // Omitted logic

    return result;
}

我发送的JSON对象如下:

{
    "userId": 3
}

这是我得到的例外:

WARN 964 --- [XNIO-2 task-7] .wsmsDefaultHandlerExceptionResolver:无法读取HTTP消息:org.springframework.http.converter.HttpMessageNotReadableException:无法读取文档:无法从START_OBJECT反序列化java.lang.Integer的实例令牌在[来源:java.io.PushbackInputStream@12e7333c; line:1,column:1]; 嵌套异常是com.fasterxml.jackson.databind.JsonMappingException:无法在[来源:java.io.PushbackInputStream@12e7333c;中的START_OBJECT标记中反序列化java.lang.Integer的实例.line:1,column:1]

Answer 1

显然杰克逊不能将传递的JSON反序列化为Integer.如果您坚持通过请求体发送用户的JSON表示,则应该将其封装userId在另一个bean中,如下所示:

public class User {
    private Integer userId;
    // getters and setters
}

然后使用该bean作为处理程序方法参数:

@RequestMapping(...)
public @ResponseBody Record getRecord(@RequestBody User user) { ... }

如果你不喜欢创建另一个bean的开销,你可以传递路径变量的userId一部分,例如.为了做到这一点:/getuser/15

@RequestMapping(value = "/getuser/{userId}", method = POST, produces = "application/json")
public @ResponseBody Record getRecord(@PathVariable Integer userId) { ... }

由于您不再在请求正文中发送JSON,因此应删除该consumes属性.

Answer 2

Perhaps you are trying to send a request with JSON text in its body from a Postman client or something similar like this:

{
 "userId": 3
}

This cannot be deserialized by Jackson since this is not an Integer (it seems to be, but it isn't). An Integer object from java.lang Integer is a little more complex.

For your Postman request to work, simply put (without curly braces { }):

3