JsonMappingException：无法从START_OBJECT标记中反序列化java.lang.Integer的实例 [英] JsonMappingException: Can not deserialize instance of java.lang.Integer out of START_OBJECT token

问题描述

我想使用Spring Boot编写一个小而简单的REST服务。
这是REST服务代码：

I wanted to write a small and simple REST service using Spring Boot. Here is the REST service code:

@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：

The JSON object I sent is the following:

{
    "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：无法反序列化实例
java.lang.Integer中的START_OBJECT标记位于[来源：
java.io.PushbackInputStream@12e7333c; line：1，column：1];嵌套的
异常是com.fasterxml.jackson.databind.JsonMappingException：
不能在[来源：java.io.PushbackInputStream@12e7333c中的START_OBJECT
令牌中反序列化java.lang.Integer的实例; line：1，
column：1]

WARN 964 --- [ XNIO-2 task-7] .w.s.m.s.DefaultHandlerExceptionResolver : Failed to read HTTP message: org.springframework.http.converter.HttpMessageNotReadableException: Could not read document: Can not deserialize instance of java.lang.Integer out of START_OBJECT token at [Source: java.io.PushbackInputStream@12e7333c; line: 1, column: 1]; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.lang.Integer out of START_OBJECT token at [Source: java.io.PushbackInputStream@12e7333c; line: 1, column: 1]

推荐答案

显然杰克逊无法反序列化将JSON传递给 Integer 。如果您坚持通过请求正文发送用户的JSON表示，则应将 userId 封装在另一个bean中，如下所示：

Obviously Jackson can not deserialize the passed JSON into an Integer. If you insist to send a JSON representation of a User through the request body, you should encapsulate the userId in another bean like the following:

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：

Then use that bean as your handler method argument:

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

如果你不喜欢创建另一个bean的开销，你可以通过 userId 作为路径变量的一部分，例如 /的getUser / 15 。为了做到这一点：

If you don't like the overhead of creating another bean, you could pass the userId as part of Path Variable, e.g. /getuser/15. In order to do that:

@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，因此应删除消耗属性。

Since you no longer send a JSON in the request body, you should remove that consumes attribute.

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