Java 不更改 POJO 的不区分大小写的 JSON 到 POJO 映射
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Case insensitive JSON to POJO mapping without changing the POJO
提问by Mark Fellner
Does anyone know how com.fasterxml.Hymanson.databind.ObjectMapper is able to map JSON properties to POJO properties case insensitive?
有谁知道 com.fasterxml.Hymanson.databind.ObjectMapper 如何能够将 JSON 属性映射到不区分大小写的 POJO 属性？
JSON-String:
JSON 字符串：
[{"FIRSTNAME":"John","LASTNAME":"Doe","DATEOFBIRTH":"1980-07-16T18:25:00.000Z"}]
[{"FIRSTNAME":"John","LASTNAME":"Doe","DATEOFBIRTH":"1980-07-16T18:25:00.000Z"}]
POJO-Class:
POJO级：
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:
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"));
}
This ends up in following error:
com.fasterxml.Hymanson.databind.JsonMappingException: Can not deserialize instance of ...
这最终会出现以下错误：
com.fasterxml.Hymanson.databind.JsonMappingException: Can not deserialize instance of ...
It's not possible to change neither JSON-String nor POJO-Class.
无法更改 JSON-String 和 POJO-Class。
回答by Dhananjay
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:
我遇到了同样的问题，找不到解决此问题的全局方法。但是，您可以为每个属性设置 2 个 setter 来实现此目的：
@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 herebut this might have a performance overhead
回答by Harry Glasgow
I was in the same kind of situation and had to convert to a map and then copy the values over manually.
我处于同样的情况，不得不转换为地图，然后手动复制值。
import com.fasterxml.Hymanson.core.type.TypeReference;
Map<String, String> map =
mapper.readValue(jsonAsString, new TypeReference<Map<String, String>>(){});
回答by Nicolas Riousset
This behaviour was introduced in Hymanson 2.5.0. You can configure the mapper to be case insensitive using MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES.
此行为是在 Hymanson 2.5.0 中引入的。您可以使用 MapperFeature 将映射器配置为不区分大小写。ACCEPT_CASE_INSENSITIVE_PROPERTIES。
For example :
例如 ：
ObjectMapper mapper = new ObjectMapper();
mapper.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);
回答by Dmitry Kokora
You can solve this problem by configuring the mapper, as described by the @Nicolas Riousset.
您可以通过配置映射器来解决此问题，如@Nicolas Riousset 所述。
In addition, since version Hymanson 2.9 you can do the same using annotation @JsonFormat(with = JsonFormat.Feature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)over a field or class, which is a more flexible option.
此外，从 Hymanson 2.9 版本开始，您可以@JsonFormat(with = JsonFormat.Feature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)在字段或类上使用注释来执行相同的操作，这是一个更灵活的选项。
@JsonFormat(with = JsonFormat.Feature.ACCEPT_CASE_INSENSITIVE_PROPERTIES)
private String firstName;
回答by jmojico
An alternative solution is to specify JSON field names case-sensitive:
另一种解决方案是指定 JSON 字段名称区分大小写：
public Movie(){
//Hymanson deserialize
}
@JsonProperty("Title")
public String getTitle() {
return title;
}
@JsonProperty("Year")
public String getYear() {
return year;
}
@JsonProperty("imdbID")
public String getImdbID() {
return imdbID;
}
回答by Marcus Vinícius Voltolim
package br.com.marcusvoltolim.util;
import com.fasterxml.Hymanson.databind.DeserializationFeature;
import com.fasterxml.Hymanson.databind.MapperFeature;
import com.fasterxml.Hymanson.databind.ObjectMapper;
import lombok.extern.log4j.Log4j;
@Log4j
public class JsonUtils {
private static final ObjectMapper OBJECT_MAPPER;
static {
OBJECT_MAPPER = new ObjectMapper();
OBJECT_MAPPER.configure(MapperFeature.ACCEPT_CASE_INSENSITIVE_PROPERTIES, true);
OBJECT_MAPPER.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
}
public static <T> T fromJson(final String json, final Class<T> classe) {
try {
return OBJECT_MAPPER.readValue(json, classe);
} catch (Exception e) {
log.error(e);
try {
return classe.newInstance();
} catch (InstantiationException | IllegalAccessException ex) {
return null;
}
}
}
}
