在不改变POJO的情况下，将不区分大小写的JSON转换为POJO映射 [英] Case insensitive JSON to POJO mapping without changing the POJO

问题描述

有没有人知道com.fasterxml.jackson.databind.ObjectMapper如何将JSON属性映射到POJO属性，不区分大小写？

JSON-String：

[{FIRSTNAME：John，LASTNAME：Doe，DATEOFBIRTH：1980-07-16T18：25： 00.000Z}]

POJO类：

  public class Person {
 
 private String firstName; 
 private String lastName; 
 private Date dateOfBirth; 
 
 public String getFirstName（）{
 return firstName; 
} 
 public void setFirstName（String firstName）{
 this.firstName = firstName; 
} 
 public String getLastName（）{
 return lastName; 
} 
 public void setLastName（String lastName）{
 this.lastName = lastName; 
} 
 public Date getDateOfBirth（）{
 return dateOfBirth; 
} 
 public void setDateOfBirth（Date dateOfBirth）{
 this.dateOfBirth = dateOfBirth; 
} 
} 
  

测试类：

  @Test 
 public final void testDeserializingPersonJsonToPersonClass（）
 throws JsonParseException，JsonMappingException，IOException {
 final String jsonAsString =[ {\FIRSTNAME\：\John\，\LASTNAME\：\Doe\，\DATEOFBIRTH\：\1980-07-16T18： 25：00.000Z\}] 
 final ObjectMapper mapper = new ObjectMapper（）; 
 
 final Person person = mapper.readValue（jsonAsString，Person.class）; 
 
 assertNotNull（person）; 
 assertThat（person.getFirstName（），equalTo（John））; 
} 
  

最终会出现以下错误：

com。 quickxml.jackson.databind.JsonMappingException：无法反序列化...

不可以更改JSON-String和POJO-Class。

解决方案

我也有同样的问题，找不到全局解决方法。但是，您可以为每个属性设置2个setter：

  @JsonSetter（FIRSTNAME）
 public void setFirstNameCaps （String firstName）{
 this.firstName = firstName; 
} 
 
 @JsonSetter（firstName）
 public void setFirstName（String firstName）{
 this.firstName = firstName; 
} 
  

不优雅，但适用于大小写的json字段。您也可以尝试此处所提及的解决方案，但这可能会导致性能开销

Does anyone know how com.fasterxml.jackson.databind.ObjectMapper is able to map JSON properties to POJO properties case insensitive?

JSON-String:

[{"FIRSTNAME":"John","LASTNAME":"Doe","DATEOFBIRTH":"1980-07-16T18:25:00.000Z"}]

POJO-Class:

public class Person {

    private String firstName;
    private String lastName;
    private Date dateOfBirth;

    public String getFirstName() {
        return firstName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }
    public String getLastName() {
        return lastName;
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
    }
    public Date getDateOfBirth() {
        return dateOfBirth;
    }
    public void setDateOfBirth(Date dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }
}

Test-Class:

@Test
public final void testDeserializingPersonJsonToPersonClass()
        throws JsonParseException, JsonMappingException, IOException {
    final String jsonAsString = "[{\"FIRSTNAME\":\"John\",\"LASTNAME\":\"Doe\",\"DATEOFBIRTH\":\"1980-07-16T18:25:00.000Z\"}]";
    final ObjectMapper mapper = new ObjectMapper();

    final Person person = mapper.readValue(jsonAsString, Person.class);

    assertNotNull(person);
    assertThat(person.getFirstName(), equalTo("John"));
}

This ends up in following error:
com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of ...

It's not possible to change neither JSON-String nor POJO-Class.

解决方案

I had the same problem and couldn't find a global way of solving this. However you can have 2 setters per property to achieve this:

@JsonSetter("FIRSTNAME")
public void setFirstNameCaps(String firstName) {
    this.firstName = firstName;
}

@JsonSetter("firstName")
public void setFirstName(String firstName) {
    this.firstName = firstName;
}

Not elegant but will work for both upper and lower case json fields. You can also try the solution mentioned here but this might have a performance overhead

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