Hibernate 映射字段问题[ImprovedNamingStrategy]

Hibernate 映射字段问题[ImprovedNamingStrategy]

时间 2014-05-31 17:38:06 CSDN博客
原文 http://blog.csdn.net/dracotianlong/article/details/27834143
主题 Java

Hibernate 使用JPA 对于映射有3种规则可以配置：DefaultNamingStrategy，ImprovedNamingStrategy，EJB3NamingStrategy

这里只说ImprovedNamingStrategy，其他自行看Hibernate代码，ImprovedNamingStrategy的代码如下，是一个singleton instance：

/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2010, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors.  All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA  02110-1301  USA
*/
package org.hibernate.cfg;

import java.io.Serializable;

import org.hibernate.util.StringHelper;
import org.hibernate.AssertionFailure;

/**
* An improved naming strategy that prefers embedded
* underscores to mixed case names
* @see DefaultNamingStrategy the default strategy
* @author Gavin King
*/
public class ImprovedNamingStrategy implements NamingStrategy, Serializable {

/**
* A convenient singleton instance
*/
public static final NamingStrategy INSTANCE = new ImprovedNamingStrategy();

/**
* Return the unqualified class name, mixed case converted to
* underscores
*/
public String classToTableName(String className) {
return addUnderscores( StringHelper.unqualify(className) );
}
/**
* Return the full property path with underscore seperators, mixed
* case converted to underscores
*/
public String propertyToColumnName(String propertyName) {
return addUnderscores( StringHelper.unqualify(propertyName) );
}
/**
* Convert mixed case to underscores
*/
public String tableName(String tableName) {
return addUnderscores(tableName);
}
/**
* Convert mixed case to underscores
*/
public String columnName(String columnName) {
return addUnderscores(columnName);
}

protected static String addUnderscores(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();
}

public String collectionTableName(
String ownerEntity, String ownerEntityTable, String associatedEntity, String associatedEntityTable,
String propertyName
) {
return tableName( ownerEntityTable + '_' + propertyToColumnName(propertyName) );
}

/**
* Return the argument
*/
public String joinKeyColumnName(String joinedColumn, String joinedTable) {
return columnName( joinedColumn );
}

/**
* Return the property name or propertyTableName
*/
public String foreignKeyColumnName(
String propertyName, String propertyEntityName, String propertyTableName, String referencedColumnName
) {
String header = propertyName != null ? StringHelper.unqualify( propertyName ) : propertyTableName;
if (header == null) throw new AssertionFailure("NamingStrategy not properly filled");
return columnName( header ); //+ "_" + referencedColumnName not used for backward compatibility
}

/**
* Return the column name or the unqualified property name
*/
public String logicalColumnName(String columnName, String propertyName) {
return StringHelper.isNotEmpty( columnName ) ? columnName : StringHelper.unqualify( propertyName );
}

/**
* Returns either the table name if explicit or
* if there is an associated table, the concatenation of owner entity table and associated table
* otherwise the concatenation of owner entity table and the unqualified property name
*/
public String logicalCollectionTableName(String tableName,
String ownerEntityTable, String associatedEntityTable, String propertyName
) {
if ( tableName != null ) {
return tableName;
}
else {
//use of a stringbuffer to workaround a JDK bug
return new StringBuffer(ownerEntityTable).append("_")
.append(
associatedEntityTable != null ?
associatedEntityTable :
StringHelper.unqualify( propertyName )
).toString();
}
}
/**
* Return the column name if explicit or the concatenation of the property name and the referenced column
*/
public String logicalCollectionColumnName(String columnName, String propertyName, String referencedColumn) {
return StringHelper.isNotEmpty( columnName ) ?
columnName :
StringHelper.unqualify( propertyName ) + "_" + referencedColumn;
}
}

addUnderscores 用于处理 当表名和列名在Java的种规则符合 UserNameTable（表）和 userNameColumn（列），就会被解析为user_name_table 和 user_name_column ,具体return的处理的是propertyToColumnName。 but呢，如果一旦配置了这个规则，spring ＋jpa配置如下：

-

<prop key="hibernate.ejb.naming_strategy">org.hibernate.cfg.ImprovedNamingStrategy</prop>

就会忽略了注释中的@Column中的name，其实这个name地方就是为了映射数据库字段，结果配置了这个就不care了。我去。看下hibernate解释

https://hibernate.atlassian.net/browse/HHH-8616

觉得是这是一个bug，不知道为啥就这样fix bug 了。

/*
* Copyright 2012-2014 sencloud.com.cn. All rights reserved.
* Support: http://www.sencloud.com.cn * License: http://www.sencloud.com.cn/license */
package com.sencloud.hibernate.cfg;

import java.io.Serializable;

import org.hibernate.cfg.ImprovedNamingStrategy;
import org.hibernate.cfg.NamingStrategy;
import org.hibernate.util.StringHelper;

/**
* ImprovedNamingStrategy－ hibernate映射规则
*
* @author xutianlong
* @version 3.0
*/
public class MoShopImprovedNamingStrategy extends ImprovedNamingStrategy
implements NamingStrategy, Serializable {
/**
*
*/
private static final long serialVersionUID = 3088474161734101900L;

public String propertyToColumnName(String propertyName) {
if (propertyName.endsWith("__")) {
return propertyName.replace("__", "").toLowerCase();
}
return addUnderscores(StringHelper.unqualify(propertyName));
}
}

改下配置：

<prop key="hibernate.ejb.naming_strategy">com.sencloud.hibernate.cfg.MoShopImprovedNamingStrategy</prop>

那么怎么使用这个呢？ propertyName必须以 "__"结尾了，然后在规则中统一toLowerCase。 有点那个啥了。

@Column(nullable = false, length=100)
private String userName__;