java - 使用 ObjectMapper 反序列化对象时将驼峰命名法转换为下划线

Question

我有一个固定文件person.json，

{
   "fistName": "John"
   "lastName": "Smith"
}

我有一个名为 Person 的类

public class Person {
  private String firstName;
  private String lastName;
  //.. getters and setters
}

我使用 ObjectMapper 反序列化 Person，如下所示

ObjectMapper mapper = new ObjectMapper(); 
Person person = mapper.readValue(new FileInputStream(new File("person.json")),Person.class);

我收到此错误，

    java.lang.RuntimeException: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: 
Unrecognized field "firstName" (class com.foo.Person), not marked as ignorable (2 known properties: , "first_name", "last_name"])

我使用时遇到同样的错误
mapper.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);。

我的问题是为什么会出现此错误以及如何解决它？

Answer 1

因为你要求 jackson 使用naming strategy将驼峰式大小写(即 firstName)转换为带下划线的小写字母，即 first_name。

<小时/>

public class App {
    public static void main(String[] args) throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        Person person = mapper.readValue(new FileInputStream(new File("/path/to/person.json")),Person.class);
        System.out.println(person);
    }
}

@Data // lombok @Data
public class Person {
    private String firstName;
    private String lastName;
}

和person.json(已修复):

{
    "firstName": "John",
    "lastName": "Smith"
}

输出:

Person(firstName=John, lastName=Smith)