kapok

http://forum.javaeye.com/viewtopic.php?t=8486

在Java對象里面, 偶們知道一個良好的命名規(guī)范會采用大寫單詞的首字母, 比如訂單項這個對象, 偶們會起名為OrderItem, 這樣很容易就看出來這個對象是由Order和Item 2個單詞組成的, 斷詞就很容易了, 而屬性也是如此, 比如maxPrice, totalPrice等等.

但是如果按照同樣的命名規(guī)范運到數(shù)據(jù)庫的時候, 由于很多數(shù)據(jù)庫對于表名, 字段名是大小寫不敏感的, 所以最常見的策略是加下劃線作為斷詞的依據(jù):
OrderItem -> order_item
maxPrice -> max_price

這樣運用Hibernate的時候, 偶們就得手工在mapping文件里面指明:
<class name="OrderItem" table="order_item">
<property name="maxPrice" column="max_price"/>

每個mapping關(guān)系都得手工這樣寫, 是不是很不爽? 現(xiàn)在來介紹一下net.sf.hibernate.cfg.NamingStrategy的用處, 看看它是怎么修理這個問題的, 代碼如下:

java代碼: 

import net.sf.hibernate.cfg.NamingStrategy;
import net.sf.hibernate.util.StringHelper;

/**
* An improved naming strategy that prefers embedded underscores to mixed case
* names, base on DefaultNamingStrategy and ImprovedNamingStrategy
*
*/

public class UnderscoreNamingStrategy implements NamingStrategy {

    public static final NamingStrategy INSTANCE = new UnderscoreNamingStrategy();

    protected UnderscoreNamingStrategy() {
    }

    public String classToTableName(String className) {
        return addUnderscores(StringHelper.unqualify(className));
    }

    public String propertyToColumnName(String propertyName) {
        return addUnderscores(StringHelper.unqualify(propertyName));
    }

    public String tableName(String tableName) {
        return tableName;
    }

    public String columnName(String columnName) {
        return columnName;
    }

    public String propertyToTableName(String className, String propertyName) {
        return classToTableName(className) + '_' + propertyToColumnName(propertyName);
    }

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

}

在初始化配置的時候, 把這個NamingStrategy加上:
java代碼: 

            Configuration config = new Configuration();
            config.setNamingStrategy(UnderscoreNamingStrategy.INSTANCE);

這樣mapping文件就變得簡單多了:

<class name="OrderItem">
<property name="maxPrice"/>

NamingStrategy還可以用在其他方面, 比如有些數(shù)據(jù)庫設(shè)計規(guī)范統(tǒng)一要求Table前面加上模塊名稱 (如, 屬于Order模塊的統(tǒng)一加上ORDER_ ), 比如還有些惡心規(guī)范統(tǒng)一要求表名和字段名采用4碼縮寫 (如, OrderItem -> orde_item, maxPrice -> max_pric), 這些都是NamingStrategy可以解決的臟活累活.