ObjectMapper 将字符串值（json 格式）转换为对象

Question

我的 api 回复是这样的

{
  "name": "jackson",
  "age": 33,
  "hobby_list": "[{\"name\":\"soccer\", \"priority\":2}, {\"name\":\"game\", \"priority\":1}, {\"name\":\"reading\", \"priority\":3}]"
}

我想将 hobby_list 字符串值反序列化为对象。

class Person {
  @JsonProperty("name")
  private String name;

  @JsonProperty("age")
  private Integer age;

  @JsonProperty("hobby_list")
  private List<Hobby> hobbyList;
}

class Hobby(
  @JsonProperty("name")
  private String name;

  @JsonProperty("priority")
  private Integer priority;
)

如您所知，它不起作用。

Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList<com.joont.domain.Hobby>` out of VALUE_STRING token

解决问题的最佳做法是什么？
注解？配置？自定义解串器？

Answer 1

您可以通过注册自定义解串器来转换它们，如下所示：

public class PersonDeserializer extends JsonDeserializer<Person> {

    @Override
    public Person deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
        ObjectCodec oc = jp.getCodec();
        JsonNode node = oc.readTree(jp);

        final Integer age = node.get("age").asInt();
        final String name = node.get("name").asText();
        final String hobbyListAsString = node.get("hobby_list").asText();

        ObjectMapper mapper = new ObjectMapper();
        // convert JSON array to List of objects
        List<Hobby> hobbyList = Arrays.asList(mapper.readValue(hobbyListAsString, Hobby[].class));

        Person person = new Person();
        person.setName(name);
        person.setAge(age);
        person.setHobbyList(hobbyList);

        return person;
    }
}

并且在 root 的 pojo 中使用注释 @JsonDeserialize(using = PersonDeserializer.class) 以便可以注册上述反序列化器。在下面附上参考资料：

@JsonDeserialize(using = PersonDeserializer.class)
@Data
public class Person {
    @JsonProperty("name")
    private String name;

    @JsonProperty("age")
    private Integer age;

    @JsonProperty("hobby_list")
    private List<Hobby> hobbyList;
}

然后我可以将上面的 hobby_list 字符串反序列化为对象

ObjectMapper mapper = new ObjectMapper();
Person person = mapper.readValue(content, Person.class);
System.out.println(person.getHobbyList());

ObjectMapper 将字符串值（json 格式）转换为对象

ObjectMapper convert string value(json format) to object

java

json

jackson