Question

我有我的实体类：

@Entity
@Table(name = "TABLE")
public class User {

    @Id
    @Column
    private UUID id;

我正在使用EclipseLink。当我尝试执行以下代码时：

em.createQuery("select t from Table").getResultList();

我有例外：

引起：org.eclipse.persistence.exceptions.ConversionException：异常描述：对象 [9ABCC78A-4C58-41D2-A672-324F6B095260]，班级[类 java.lang.String]，无法转换为[class [B]。在 org.eclipse.persistence.exceptions.ConversionException.couldNotBeConverted（ConversionException.java:78）〜[？：？] at org.eclipse.persistence.internal.helper.Helper.buildBytesFromHexString（Helper.java:266）〜[？：？] at org.eclipse.persistence.internal.helper.ConversionManager.convertObjectToByteArray（ConversionManager.java:326）〜[？：？] at org.eclipse.persistence.internal.helper.ConversionManager.convertObject（ConversionManager.java:138）〜[？：？] at org.eclipse.persistence.internal.databaseaccess.DatasourcePlatform.convertObject（DatasourcePlatform.java:179）〜[？：？] at org.eclipse.persistence.internal.descriptors.ObjectBuilder.extractPrimaryKeyFromRow（ObjectBuilder.java:3104）〜[？：？] at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject（ObjectBuilder.java:705）〜[？：？] at org.eclipse.persistence.internal.descriptors.ObjectBuilder.buildObject（ObjectBuilder.java:689）〜[？：？] at org.eclipse.persistence.queries.ObjectLevelReadQuery.buildObject（ObjectLevelReadQuery.java:805）〜[？：？] at org.eclipse.persistence.queries.ReadAllQuery.registerResultInUnitOfWork（ReadAllQuery.java:962）〜[？：？] at org.eclipse.persistence.queries.ReadAllQuery.executeObjectLevelReadQuery（ReadAllQuery.java:573）〜[？：？] at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeDatabaseQuery（ObjectLevelReadQuery.java:1175）〜[？：？] at org.eclipse.persistence.queries.DatabaseQuery.execute（DatabaseQuery.java:904）〜[？：？] at org.eclipse.persistence.queries.ObjectLevelReadQuery.execute（ObjectLevelReadQuery.java:1134）〜[？：？] at org.eclipse.persistence.queries.ReadAllQuery.execute（ReadAllQuery.java:460）〜[？：？] at org.eclipse.persistence.queries.ObjectLevelReadQuery.executeInUnitOfWork（ObjectLevelReadQuery.java:1222）〜[？：？] at org.eclipse.persistence.internal.sessions.UnitOfWorkImpl.internalExecuteQuery（UnitOfWorkImpl.java:2896）〜[？：？] at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery（AbstractSession.java:1857）〜[？：？] at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery（AbstractSession.java:1839）〜[？：？] at org.eclipse.persistence.internal.sessions.AbstractSession.executeQuery（AbstractSession.java:1804）〜[？：？] at org.eclipse.persistence.internal.jpa.QueryImpl.executeReadQuery（QueryImpl.java:258）〜[？：？] at org.eclipse.persistence.internal.jpa.QueryImpl.getResultList（QueryImpl.java:473）〜[？：？] ... 61更多

我尝试在orm.xml中添加AttributeConverter<UUID, String>，但我得到了相同的异常

<converter class="com.example.UuidConverter" auto-appy="true"/>

转换器中的'技巧'适用于PostgreSQL（我需要AttributeConverter<UUID, UUID>，因为JDBC驱动程序返回UUID），但在MSSQL上，我找不到工作解决方案。

如何处理这种情况，以便我的实体也支持MSSQL？

Answer 1

有一个窍门，希望对其他有相同问题的人有帮助

步骤1创建一个类转换器

import org.eclipse.persistence.internal.helper.DatabaseField;
import org.eclipse.persistence.mappings.DatabaseMapping;
import org.eclipse.persistence.mappings.DirectCollectionMapping;
import org.eclipse.persistence.mappings.converters.Converter;
import org.eclipse.persistence.sessions.Session;

import java.util.UUID;

public class MyUUIDConverter implements Converter {

    @Override
    public Object convertObjectValueToDataValue(Object o, Session session) {
        return o;
    }

    @Override
    public UUID convertDataValueToObjectValue(Object o, Session session) {
        return (UUID) o;
    }

    @Override
    public boolean isMutable() {
        return true;
    }

    @Override
    public void initialize(DatabaseMapping databaseMapping, Session session) {

        final DatabaseField field;

        if (databaseMapping instanceof DirectCollectionMapping) {

            // handle @ElementCollection...

            field = ((DirectCollectionMapping) databaseMapping).getDirectField();

        } else {

            field = databaseMapping.getField();

        }

        field.setSqlType(java.sql.Types.OTHER);

        field.setTypeName("java.util.UUID");

        field.setColumnDefinition("your column name in database");

    }
}

第2步，使用注释转换器实现您最近创建的类</ p>

@Entity
@Table(name = "TABLE")
@Converter(name = "myUuidConverter", converterClass = MyUUIDConverter.class)
public class User {

第3步在您的媒体资源中使用注释转换

@Convert("myUuidConverter")
  private UUID id;

Eclipselink尝试将UUID转换为MSSQL

1 个答案: