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Java 使用EclipseLink自定义JPA字段名映射

java jakarta-ee jpa

Java 使用EclipseLink自定义JPA字段名映射,java,jakarta-ee,jpa,eclipselink,Java,Jakarta Ee,Jpa,Eclipselink,由于历史原因，我需要在当前使用EclipseLink的项目中，将驼峰大小写名称映射为下划线分隔的名称。我知道我们可以在JPA中单独定制名称映射，但是我们有一个很长的驼峰大小写名称列表要更改，所以如果可能的话，我们希望避免这种样板代码 我想达到的目标如下。假设我们有一个实体类，如下所示： @Entity public class FooBar { @Id @GeneratedValue private Long id; @Temporal( TemporalType.TI

由于历史原因，我需要在当前使用EclipseLink的项目中，将驼峰大小写名称映射为下划线分隔的名称。我知道我们可以在JPA中单独定制名称映射，但是我们有一个很长的驼峰大小写名称列表要更改，所以如果可能的话，我们希望避免这种样板代码

我想达到的目标如下。假设我们有一个实体类，如下所示：

@Entity
public class FooBar {
    @Id @GeneratedValue
    private Long id;

    @Temporal( TemporalType.TIMESTAMP )
    private Date dateCreated;
}
我希望这个类映射到一个名为“foo_bar”的表，列为“id”和“date_created”。请注意，数据库中的所有名称都是小写的

我搜索了一下，找到了一个更改表名的解决方案。但是，我不知道如何更改实体类中的字段名

下面是我的名称映射自定义程序，其中方法
updateFieldNameMappings（）
没有将
fieldName
映射到
field\u name
，这正是我想要实现的。问题归结为如何获得类定义中的字段名。那么，在日食中我该怎么做呢

public class JpaNameMappingCustomizer implements SessionCustomizer {

    @Override
    public void customize( Session session ) throws Exception {
        Map<Class, ClassDescriptor> descs = session.getDescriptors();
        Collection<ClassDescriptor> descriptors = descs.values();

        // This code assumes single table per descriptor!
        for (ClassDescriptor desc : descriptors) {
            updateTableNameMapping( desc );
            updateFieldNameMapping( desc );
        }
    }

    private void updateTableNameMapping ( ClassDescriptor desc ) {
        Class clazz = desc.getJavaClass();
        String tableName = camelCaseToUnderscore( clazz.getSimpleName() );
        desc.setTableName( tableName );
    }

    private void updateFieldNameMapping ( ClassDescriptor desc ) {
        // build name maps
        Field[] fields = desc.getJavaClass().getDeclaredFields();
        String tableName = desc.getTableName();
        Map<String,String> nameMap = new HashMap<>();
        String prefix = tableName + ".";
        for( Field field : fields ) {
            String name = field.getName();
            String key = prefix + name.toUpperCase();
            String value = prefix + camelCaseToUnderscore( name );
            nameMap.put( key, value );
        }

        for (DatabaseMapping mapping : desc.getMappings()) {
            if (mapping.isDirectToFieldMapping()) {
                DirectToFieldMapping directMapping = (DirectToFieldMapping) mapping;
                String oldFieldName = directMapping.getFieldName(); // format: table_name.FIELD
                directMapping.setFieldName( nameMap.get( oldFieldName ) );
            }
        }
    }

    private String camelCaseToUnderscore( String camelCase ) {
        return camelCase.trim().replaceAll("(?<!^)[A-Z](?!$)", "_$0").toLowerCase();
    }
}
我认为您没有在
persistence.xml中添加以下行，即
EclipseLink
使用自己的
SessionCustomizer


<property name="eclipselink.session.customizer" value="your.company.package.name.JpaNameMappingCustomizer"/>






提及



而不是


directMapping.setFieldName(nameMap.get(oldFieldName ));


尝试：


在EclipseLink 2.5.0下，这为我提供了窍门。也许你可以使用我的会话定制器。它将表名和字段名转换为大小写。它支持继承和嵌入的实体。
我测试了2年，没有任何问题或副作用。享受吧


import java.sql.SQLException;
import java.util.Locale;
import java.util.Vector;
import org.eclipse.persistence.config.SessionCustomizer;
import org.eclipse.persistence.descriptors.ClassDescriptor;
import org.eclipse.persistence.internal.helper.DatabaseField;
import org.eclipse.persistence.mappings.DatabaseMapping;
import org.eclipse.persistence.sessions.Session;
import org.eclipse.persistence.tools.schemaframework.IndexDefinition;

public class CamelNamingStrategy implements SessionCustomizer {
    public static String unqualify(final String qualifiedName) {
        int loc = qualifiedName.lastIndexOf(".");
        return loc < 0 ? qualifiedName : qualifiedName.substring(qualifiedName.lastIndexOf(".") + 1);
    }

    @Override
    public void customize(final Session session) throws SQLException {
        for (ClassDescriptor descriptor : session.getDescriptors().values()) {
            if (!descriptor.getTables().isEmpty()) {
                // Take table name from @Table if exists
                String tableName = null;
                if (descriptor.getAlias().equalsIgnoreCase(descriptor.getTableName())) {
                    tableName = unqualify(descriptor.getJavaClassName());
                } else {
                    tableName = descriptor.getTableName();
                }
                tableName = camelCaseToUnderscore(tableName);
                descriptor.setTableName(tableName);
                for (IndexDefinition index : descriptor.getTables().get(0).getIndexes()) {
                    index.setTargetTable(tableName);
                }
                Vector<DatabaseMapping> mappings = descriptor.getMappings();
                camelCaseToUnderscore(mappings);
            } else if (descriptor.isAggregateDescriptor() || descriptor.isChildDescriptor()) {
                camelCaseToUnderscore(descriptor.getMappings());
            }
        }
    }

    private void camelCaseToUnderscore(Vector<DatabaseMapping> mappings) {
        for (DatabaseMapping mapping : mappings) {
            DatabaseField field = mapping.getField();
            if (mapping.isDirectToFieldMapping() && !mapping.isPrimaryKeyMapping()) {
                String attributeName = mapping.getAttributeName();
                String underScoredFieldName = camelCaseToUnderscore(attributeName);
                field.setName(underScoredFieldName);
            }
        }
    }

    private String camelCaseToUnderscore(final String name) {
        StringBuffer buf = new StringBuffer(name.replace('.', '_'));
        for (int i = 1; i < buf.length() - 1; i++) {
            if (Character.isLowerCase(buf.charAt(i - 1)) && Character.isUpperCase(buf.charAt(i))
                    && Character.isLowerCase(buf.charAt(i + 1))) {
                buf.insert(i++, '_');
            }
        }
        return buf.toString().toLowerCase(Locale.ENGLISH);
    }
}



import java.sql.SQLException；
导入java.util.Locale；
导入java.util.Vector；
导入org.eclipse.persistence.config.SessionCustomizer；
导入org.eclipse.persistence.descriptors.ClassDescriptor；
导入org.eclipse.persistence.internal.helper.DatabaseField；
导入org.eclipse.persistence.mappings.DatabaseMapping；
导入org.eclipse.persistence.sessions.Session；
导入org.eclipse.persistence.tools.schemaframework.IndexDefinition；
公共类CamelNamingStrategy实现SessionCustomizer{
公共静态字符串不合格（最终字符串合格名称）{
int loc=qualifiedName.lastIndexOf（“.”）；
返回loc<0？qualifiedName:qualifiedName.substring（qualifiedName.lastIndexOf（“.”+1）；
}
@凌驾
public void customize（最终会话）引发SQLException{
for（类描述符描述符：session.getDescriptors（）.values（））{
如果（！descriptor.getTables（）.isEmpty（））{
//如果存在，则从@table获取表名
字符串tableName=null；
if（descriptor.getAlias（）.equalsIgnoreCase（descriptor.getTableName（）））{
tableName=不合格（descriptor.getJavaClassName（））；
}否则{
tableName=descriptor.getTableName（）；
}
tableName=camelCaseToUnderscore（tableName）；
descriptor.setTableName（tableName）；
for（IndexDefinition索引：descriptor.getTables（）.get（0.getIndexes（））{
index.setTargetTable（表名）；
}
向量映射=descriptor.getMappings（）；
camelCaseToUnderscore（映射）；
}else if（descriptor.isaggregatedDescriptor（）| | descriptor.isChildDescriptor（））{
camelCaseToUnderscore（descriptor.getMappings（））；
}
}
}
private CaseTounderScore（向量映射）{
for（数据库映射：映射）{
DatabaseField=mapping.getField（）；
if（mapping.isDirectToFieldMapping（）&&！mapping.isPrimaryKeyMapping（））{
字符串attributeName=mapping.getAttributeName（）；
字符串下划线FieldName=camelCaseToUnderscore（attributeName）；
field.setName（下划线FieldName）；
}
}
}
私有字符串camelCaseToUnderscore（最终字符串名称）{
StringBuffer buf=新的StringBuffer（名称.replace（'.'，''）；
对于（int i=1；i
如果您想使用@Column注释区分非注释元素和注释元素，那么我发现了一个非常漂亮的示例：


public class CamelCaseSessionCustomizer implements SessionCustomizer {

@Override
public void customize(Session session) throws SQLException {
    for (ClassDescriptor descriptor : session.getDescriptors().values()) {
        // Only change the table name for non-embedable entities with no
        // @Table already
        if (!descriptor.getTables().isEmpty() && descriptor.getAlias().equalsIgnoreCase(descriptor.getTableName())) {
            String tableName = addUnderscores(descriptor.getTableName());
            descriptor.setTableName(tableName);
            for (IndexDefinition index : descriptor.getTables().get(0).getIndexes()) {
                index.setTargetTable(tableName);
            }
        }
        for (DatabaseMapping mapping : descriptor.getMappings()) {
            // Only change the column name for non-embedable entities with
            // no @Column already

            if (mapping instanceof AggregateObjectMapping) {
                for (Association association : ((AggregateObjectMapping) mapping).getAggregateToSourceFieldAssociations()) {
                    DatabaseField field = (DatabaseField) association.getValue();
                    field.setName(addUnderscores(field.getName()));

                    for (DatabaseMapping attrMapping : session.getDescriptor(((AggregateObjectMapping) mapping).getReferenceClass()).getMappings()) {
                        if (attrMapping.getAttributeName().equalsIgnoreCase((String) association.getKey())) {
                            ((AggregateObjectMapping) mapping).addFieldTranslation(field, addUnderscores(attrMapping.getAttributeName()));
                            ((AggregateObjectMapping) mapping).getAggregateToSourceFields().remove(association.getKey());
                            break;
                        }
                    }
                }
            } else if (mapping instanceof ObjectReferenceMapping) {
                for (DatabaseField foreignKey : ((ObjectReferenceMapping) mapping).getForeignKeyFields()) {
                    foreignKey.setName(addUnderscores(foreignKey.getName()));
                }
            } else if (mapping instanceof DirectMapMapping) {
                for (DatabaseField referenceKey : ((DirectMapMapping) mapping).getReferenceKeyFields()) {
                    referenceKey.setName(addUnderscores(referenceKey.getName()));
                }
                for (DatabaseField sourceKey : ((DirectMapMapping) mapping).getSourceKeyFields()) {
                    sourceKey.setName(addUnderscores(sourceKey.getName()));
                }
            } else {
                DatabaseField field = mapping.getField();
                if (field != null && !mapping.getAttributeName().isEmpty() && field.getName().equalsIgnoreCase(mapping.getAttributeName())) {
                    field.setName(addUnderscores(mapping.getAttributeName()));
                }
            }
        }
    }
}

private static String addUnderscores(String name) {
    if (name.equalsIgnoreCase("begintime")) {
        System.err.println();
    }
    StringBuffer buf = new StringBuffer(name.replace('.', '_'));
    for (int i = 1; i < buf.length() - 1; i++) {
        if (Character.isLowerCase(buf.charAt(i - 1)) && Character.isUpperCase(buf.charAt(i)) && Character.isLowerCase(buf.charAt(i + 1))) {
            buf.insert(i++, '_');
        }
    }
    return buf.toString().toLowerCase();
}

}



公共类CamelCaseSessionCustomizer实现SessionCustomizer{
@凌驾
public void customize（会话）引发SQLException{
for（类描述符描述符：session.getDescriptors（）.values（））{
//仅更改不带
//@已经有桌子了
if（！descriptor.getTables（）.isEmpty（）&&descriptor.getAlias（）.equalsIgnoreCase（descriptor.getTableName（）））{
String tableName=add下划线（descriptor.getTableName（））；
descriptor.setTableName（tableName）；
for（IndexDefinition索引：descriptor.getTables（）.get（0.getIndexes（））{
index.setTargetTable（表名）；
}
}
for（数据库映射：descriptor.getMappings（））{
//仅更改具有的不可嵌入实体的列名
//已经没有@列了
if（聚合对象映射的映射实例）{
对于（关联：（（AggregateObjectMapping）映射）。GetAggregateSourceFieldAssociations（）{
DatabaseField=（DatabaseField）association.getValue（）；
field.setName（add下划线（field.getName（））；
对于（DatabaseMapping attrMapping:session.getDescriptor（（（AggregateObjectMapping）映射）。getReferenceClass（）

import java.sql.SQLException;
import java.util.Locale;
import java.util.Vector;
import org.eclipse.persistence.config.SessionCustomizer;
import org.eclipse.persistence.descriptors.ClassDescriptor;
import org.eclipse.persistence.internal.helper.DatabaseField;
import org.eclipse.persistence.mappings.DatabaseMapping;
import org.eclipse.persistence.sessions.Session;
import org.eclipse.persistence.tools.schemaframework.IndexDefinition;

public class CamelNamingStrategy implements SessionCustomizer {
    public static String unqualify(final String qualifiedName) {
        int loc = qualifiedName.lastIndexOf(".");
        return loc < 0 ? qualifiedName : qualifiedName.substring(qualifiedName.lastIndexOf(".") + 1);
    }

    @Override
    public void customize(final Session session) throws SQLException {
        for (ClassDescriptor descriptor : session.getDescriptors().values()) {
            if (!descriptor.getTables().isEmpty()) {
                // Take table name from @Table if exists
                String tableName = null;
                if (descriptor.getAlias().equalsIgnoreCase(descriptor.getTableName())) {
                    tableName = unqualify(descriptor.getJavaClassName());
                } else {
                    tableName = descriptor.getTableName();
                }
                tableName = camelCaseToUnderscore(tableName);
                descriptor.setTableName(tableName);
                for (IndexDefinition index : descriptor.getTables().get(0).getIndexes()) {
                    index.setTargetTable(tableName);
                }
                Vector<DatabaseMapping> mappings = descriptor.getMappings();
                camelCaseToUnderscore(mappings);
            } else if (descriptor.isAggregateDescriptor() || descriptor.isChildDescriptor()) {
                camelCaseToUnderscore(descriptor.getMappings());
            }
        }
    }

    private void camelCaseToUnderscore(Vector<DatabaseMapping> mappings) {
        for (DatabaseMapping mapping : mappings) {
            DatabaseField field = mapping.getField();
            if (mapping.isDirectToFieldMapping() && !mapping.isPrimaryKeyMapping()) {
                String attributeName = mapping.getAttributeName();
                String underScoredFieldName = camelCaseToUnderscore(attributeName);
                field.setName(underScoredFieldName);
            }
        }
    }

    private String camelCaseToUnderscore(final String name) {
        StringBuffer buf = new StringBuffer(name.replace('.', '_'));
        for (int i = 1; i < buf.length() - 1; i++) {
            if (Character.isLowerCase(buf.charAt(i - 1)) && Character.isUpperCase(buf.charAt(i))
                    && Character.isLowerCase(buf.charAt(i + 1))) {
                buf.insert(i++, '_');
            }
        }
        return buf.toString().toLowerCase(Locale.ENGLISH);
    }
}



public class CamelCaseSessionCustomizer implements SessionCustomizer {

@Override
public void customize(Session session) throws SQLException {
    for (ClassDescriptor descriptor : session.getDescriptors().values()) {
        // Only change the table name for non-embedable entities with no
        // @Table already
        if (!descriptor.getTables().isEmpty() && descriptor.getAlias().equalsIgnoreCase(descriptor.getTableName())) {
            String tableName = addUnderscores(descriptor.getTableName());
            descriptor.setTableName(tableName);
            for (IndexDefinition index : descriptor.getTables().get(0).getIndexes()) {
                index.setTargetTable(tableName);
            }
        }
        for (DatabaseMapping mapping : descriptor.getMappings()) {
            // Only change the column name for non-embedable entities with
            // no @Column already

            if (mapping instanceof AggregateObjectMapping) {
                for (Association association : ((AggregateObjectMapping) mapping).getAggregateToSourceFieldAssociations()) {
                    DatabaseField field = (DatabaseField) association.getValue();
                    field.setName(addUnderscores(field.getName()));

                    for (DatabaseMapping attrMapping : session.getDescriptor(((AggregateObjectMapping) mapping).getReferenceClass()).getMappings()) {
                        if (attrMapping.getAttributeName().equalsIgnoreCase((String) association.getKey())) {
                            ((AggregateObjectMapping) mapping).addFieldTranslation(field, addUnderscores(attrMapping.getAttributeName()));
                            ((AggregateObjectMapping) mapping).getAggregateToSourceFields().remove(association.getKey());
                            break;
                        }
                    }
                }
            } else if (mapping instanceof ObjectReferenceMapping) {
                for (DatabaseField foreignKey : ((ObjectReferenceMapping) mapping).getForeignKeyFields()) {
                    foreignKey.setName(addUnderscores(foreignKey.getName()));
                }
            } else if (mapping instanceof DirectMapMapping) {
                for (DatabaseField referenceKey : ((DirectMapMapping) mapping).getReferenceKeyFields()) {
                    referenceKey.setName(addUnderscores(referenceKey.getName()));
                }
                for (DatabaseField sourceKey : ((DirectMapMapping) mapping).getSourceKeyFields()) {
                    sourceKey.setName(addUnderscores(sourceKey.getName()));
                }
            } else {
                DatabaseField field = mapping.getField();
                if (field != null && !mapping.getAttributeName().isEmpty() && field.getName().equalsIgnoreCase(mapping.getAttributeName())) {
                    field.setName(addUnderscores(mapping.getAttributeName()));
                }
            }
        }
    }
}

private static String addUnderscores(String name) {
    if (name.equalsIgnoreCase("begintime")) {
        System.err.println();
    }
    StringBuffer buf = new StringBuffer(name.replace('.', '_'));
    for (int i = 1; i < buf.length() - 1; i++) {
        if (Character.isLowerCase(buf.charAt(i - 1)) && Character.isUpperCase(buf.charAt(i)) && Character.isLowerCase(buf.charAt(i + 1))) {
            buf.insert(i++, '_');
        }
    }
    return buf.toString().toLowerCase();
}

}