JAVA - JSON 将枚举列表序列化为类

Question

我有这个枚举：

public enum Days implements Serializable {
    MONDAY,
    TUESDAY,
    WEDNESDAY,
    ...
}

我想在 Store 类中使用它：

 public class Store{
      private integer id_store;
      private String name;
      private Days days_visit;
}

问题是，days_visit 需要是一个数组，因为它可以超过一天；在数据库端，Days类型是days类型：

CREATE TYPE schema.days AS ENUM
   (MONDAY,
    TUESDAY,
    WEDNESDAY,
    ...);

并且表 Stores 有一个“days”数组

days_visit schema.days[],

如何在 JSON 中序列化？我试过的 JSON 是：

{"id_store":"1", "name":"The Store", "days_visit":["MONDAY", "FRIDAY"]}

但我收到此错误：

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of org.domain.Days
    out of START_ARRAY token
    at [Source: io.undertow.servlet.spec.ServletInputStreamImpl@5c2a7de1; line: 1, column: 168] (through reference chain:
    org.Stores["days_visit"])

如果我在课堂上这样声明 days_visit：

 public class Store{
      private integer id_store;
      private String name;
      private Days[] days_visit;
}

在 Wildfly 中部署时出现此错误：

[2020-01-28 11:42:09,970] Artifact app:war: Error during artifact deployment. See server log for details.
    [2020-01-28 11:42:09,970] Artifact app:war: java.lang.Exception: {"WFLYCTL0080: Failed services" => {"jboss.persistenceunit.\"app.war#org\"" => "javax.persistence.PersistenceException: [PersistenceUnit: org_app] Unable to build Hibernate SessionFactory
        Caused by: javax.persistence.PersistenceException: [PersistenceUnit: org.app] Unable to build Hibernate SessionFactory
        Caused by: org.hibernate.MappingException: Unable to instantiate custom type: org.hibernate.type.EnumType
        Caused by: java.lang.ClassCastException: class [Lpy.org.app.domain.Days;"}}

我有什么遗漏吗？

Answer 1

问题似乎在于反序列化 JSON。

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of org.domain.Days

Jackson 无法反序列化枚举。你可以编写一个自定义的反序列化方法并用@JsonCreator注解它。

根据您的要求/约束​​调整以下逻辑。

public enum Days {
    MONDAY, TUESDAY, WEDNESDAY;
    static Map<String, Days> daysLookup = new HashMap<>();

    static {
        daysLookup.put("MONDAY", MONDAY);
        daysLookup.put("TUESDAY", TUESDAY);
        daysLookup.put("WEDNESDAY", WEDNESDAY);
    }


    @JsonCreator
    public static Days[] create(@JsonProperty("days_visit") String[] days) {
        Days[] daysVisit = new Days[days.length];
        for (int i = 0; i < days.length; i++) {
            daysVisit[i] = daysLookup.get(days[i]);
        }
        return daysVisit;
    }
}