使用EclipseLink在JPA 2.1中注册转换器 [英] Registering Converters in JPA 2.1 with EclipseLink

问题描述

在JavaEE环境中，我使用EclipseLink的JPA 2.1实现，

On JavaEE environment, I use JPA 2.1 implementation with EclipseLink,

我有一些实体包含 enums 。所以我为这些枚举创建了转换器。

I have some entities that contain enums. So I have created converters for these enumerations.

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);
        }
    }
}

persistence.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>

1. 当我发表评论时在persistence.xml文件中声明转换器，并尝试在DB中保留我的实体我收到此错误： 请确保转换器类名称正确并且存在持久性单元定义。 。并且没有编译时异常，只有一个非常明确的警告：

1. When I comment the declaration of the converter on the persistence.xml file, and try to persist my entities in the DB I get this error : "Please ensure the converter class name is correct and exists with the persistence unit definition.". and no compilation time exception, only a warning pretty explicit :

类com.xyz.model.converters.CarTypeConverter是注释的，但是未列在persistence.xml文件中

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

但是，当我取消注释时，声明转换器在persistence.xml文件上，并尝试在DB中保留我的实体我收到此错误：请确保转换器类名称正确并且存在持久性单元定义。。和编译时间异常：

However, when I uncomment the declaration of the converter on the on the persistence.xml file, and try to persist my entities in the DB I get this error : "Please ensure the converter class name is correct and exists with the persistence unit definition.". and a compilation time exception :

类com.xyz.model.converters.CarColorConverter列在persistence.xml文件中，但是没有注释

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？

Am I declaring the converters in a wrong way ?

谢谢。

推荐答案

试一试，确保你已经包含正确的套餐。

Give this a try and ensure you have included the correct packages.

保持相同

import javax.persistence.Convert;

@Entity
public class Car implements Serializable {

    [...]

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

    [...]
}

CarColor Converter

您只需要空注释

CarColor Converter

You only need the empty Annotation

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

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

persistence.xml

您可以

• 根本不申报任何课程

或

• 声明所涉及的每个类。

一旦你需要手动声明一个实体（例如当它在库中抵制时） ）那么你还需要声明所有其他实体/转换器类。

As soon as you need to declare an entity manually (e.g. when it resists in a library) then you also need do declare all other entity/converter classes.

<?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>

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