java - 使用 EclipseLink 在 JPA 2.1 中注册转换器

Question

在 JavaEE 环境中，我使用带有 EclipseLink 的 JPA 2.1 实现，

我有一些实体包含 enums .所以我为这些枚举创建了转换器。

汽车实体:

@Entity
public class Car implements Serializable {

    private static final long serialVersionUID = 6L;

    @Id
    private String      id;

    @Convert (converter = CarColorConverter.class)
    private CarColor    color;

    public enum CarColor {
        Black,
        Gray,
        White,
        Red
    };

    public Car () {
        id = GenerateUUID.id ();
    }

    ....
}

CarColor 转换器:

@Converter (converterClass = CarColorConverter.class, name = "CarColorConverter") 
public class CarColorConverter implements AttributeConverter<CarColor, String> { 

    private static final String BLACK   = "Black";
    private static final String GRAY    = "Gray";
    private static final String WHITE   = "White";
    private static final String RED     = "Red";

    @Override
    public String convertToDatabaseColumn (CarColor entityData) {

        switch (entityData) {
            case Black:
                return BLACK;

            case Gray:
                return GRAY;

            case White:
                return WHITE;

            case Red:
                return RED;

            default:
                throw new IllegalArgumentException ("Unknown : " + entityData);
        }
    }

    @Override
    public CarColor convertToEntityAttribute (String dbData) {

        switch (dbData) {
            case BLACK:
                return CarColor.Black;

            case GRAY:
                return CarColor.Gray;

            case WHITE:
                return CarColor.White;

            case RED:
                return CarColor.Red;

            default:
                throw new IllegalArgumentException ("Unknown : " + dbData);
        }
    }
}

持久性.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence 
    version="2.1"
    xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">

    <persistence-unit name="xyz-restful-api" transaction-type="RESOURCE_LOCAL">

        <!-- Converters -->
        <!--<class>com.xyz.model.converters.CarColorConverter</class>-->

        <!-- Entities / Model -->
        <class>com.xtz.model.Car</class>

        <properties>
            ...
        </properties>

    </persistence-unit>

</persistence>

当我评论 在persistence.xml 文件上声明转换器，并尝试将我的实体保留在数据库中我收到此错误:“ 请确保转换器类名称正确且存在于持久性单元定义中。” .并且没有编译时异常，只有一个非常明确的警告:

Class "com.xyz.model.converters.CarTypeConverter" is annotated, but not listed in the persistence.xml file

然而，当 我取消注释 在persistence.xml 文件上的转换器声明，并尝试将我的实体保留在数据库中我收到此错误:“请确保转换器类名称正确并且存在与持久性单元定义。”。和编译时异常:

Class "com.xyz.model.converters.CarColorConverter" is listed in the persistence.xml file, but is not annotated

我是否以错误的方式声明转换器？

谢谢你。

Answer 1

试一试并确保您包含了正确的包。

汽车实体

保持不变

import javax.persistence.Convert;

@Entity
public class Car implements Serializable {

    [...]

    @Convert(converter = CarColorConverter.class)
    private CarColor    color;

    [...]
}

汽车颜色转换器

你只需要空的 Annotation

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

@Converter
public class CarColorConverter implements AttributeConverter<CarColor, String> {
    [...]
}

持久化文件

您可以 要么

根本不声明类

或

声明涉及的每个类。

一旦您需要手动声明实体(例如，当它在库中抵抗时)，那么您还需要声明所有其他实体/转换器类。

<?xml version="1.0" encoding="UTF-8"?>
<persistence 
    version="2.1"
    xmlns="http://xmlns.jcp.org/xml/ns/persistence" 
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">

    <persistence-unit name="xyz-restful-api" transaction-type="RESOURCE_LOCAL">

        <!-- Converters -->
        <class>com.xyz.model.converters.CarColorConverter</class>

        <!-- Entities / Model -->
        <class>com.xtz.model.Car</class>

        [...]
    </persistence-unit>
</persistence>