java@DiscriminatorValue类型不匹配：无法从整数转换为字符串

Question

虽然我将父类定义为使用Integer类型的鉴别器列，但编译器始终为使用Integer鉴别器值的子类提供错误：Type mismatch: cannot convert from Integer to String

@Table(name="ITEMS")
@Inheritance(strategy=InheritanceType.SINGLE_TABLE)
@DiscriminatorColumn(name="ITEM_CATEGORY",discriminatorType=DiscriminatorType.INTEGER)
public class Item { ....}


@Entity
@DiscriminatorValue(value=ItemCategory.Values.LEARNING_DUTY)
public class LearningDuty extends Item {...}


public static class Values {
        
        public static final Integer LEARNING_DUTY = 3;

    }

pom文件：

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.0.0.RELEASE</version>
    <relativePath/> <!-- lookup parent from repository -->
</parent>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
    <spring.version>5.0.2.RELEASE</spring.version>
</properties>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-jpa</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-data-rest</artifactId>
    </dependency>

我尝试清理项目并重建，重新启动IDE，但问题仍然存在 我用的是STS4

Answer 1

Java是一种静态类型语言。因此discriminatorType=DiscriminatorType.INTEGER无法更改DiscriminatorValue的value的类型

It's explained e.g. here：

The DiscriminatorValue annotation specifies the discriminator value for each class. Though this annotation's value is always a string, the implementation will parse it according to the DiscriminatorColumn's discriminatorType property above.

因此，必须按如下方式指定鉴别器值：

@DiscriminatorValue(value=""+ItemCategory.Values.LEARNING_DUTY)