hibernate自定义主键生成器详解

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生成主键的类

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 1 package action; 2  3 import java.io.Serializable; 4 import java.util.List; 5 import java.util.Properties; 6  7 import org.hibernate.HibernateException; 8 import org.hibernate.MappingException; 9 import org.hibernate.dialect.Dialect;10 import org.hibernate.engine.QueryParameters;11 import org.hibernate.engine.SessionImplementor;12 import org.hibernate.id.Configurable;13 import org.hibernate.id.IdentifierGenerator;14 import org.hibernate.type.Type;15 /**16  * 17 * 类名称：      GeneratePK   18 * 类描述：     在hibernate的基础上自动生成自定义的主键19 * 创建人：     andy_lj  20 * 创建时间：2012-08-10 上午11:40:50     21 * 修改备注：   22 * @version23  */24 public class GeneratePK implements Configurable, IdentifierGenerator {25     public String sign;// user000000001中的user26     public String classname; //实体类的类名27     public String pk;//主键名字28     public String idLength;//user000000001的长度29     30     /**31      * 取得User.hbm.xml中的自定义的值32      */33     @Override34     public void configure(Type arg0, Properties arg1, Dialect arg2)35             throws MappingException {36         this.classname = arg1.getProperty("classname");37         this.pk = arg1.getProperty("pk");38         this.sign = arg1.getProperty("sign");39         this.idLength = arg1.getProperty("idLength");40     }41     /**42      * 生成主键43      */44     @Override45     public Serializable generate(SessionImplementor arg0, Object arg1)46             throws HibernateException {47          //获得主键的长度48         int leng = Integer.valueOf(idLength);49         //需要查询数据库中最大的ID号50         StringBuffer sql = new StringBuffer("select max(a.").append(pk)51                                                             .append(") from ")52                                                             .append(classname)53                                                             .append(" as a where a.")54                                                             .append(pk)55                                                             .append(" like '")56                                                             .append(sign)57                                                             .append("%'");58         QueryParameters qp = new QueryParameters();59         List ls = arg0.list(sql.toString(), qp);60         String max = (String) ls.get(0);61         int i = 0;62         //如果是第一次添加记录那么就是类似user00000000163         if (max == null || max.trim().equals("")) {64             max = "1";65             for(; i < leng-sign.length()-1; i++) {66                 max = "0" + max;67             }68             i = 0;69             return sign + max;70         }//不是第一次的操作,并且记录的长度没有超过从配置文件中读取的长度71         else if(max != null && max.length() <= leng) {72             max = max.replaceAll(sign, "");73             Integer imax = Integer.parseInt(max) + 1;74             String returnnum = String.valueOf(imax);75             int zero = leng-sign.length()-returnnum.length();76             for(; i < zero; i++) {77                 returnnum = "0" + returnnum;78             }79             i = 0;80             return sign + returnnum;81         }//不是第一次的操作,记录的长度超过了从配置文件中读取的长度82         else {83             leng = max.length();84             max = max.replaceAll(sign, "");85             Integer imax = Integer.parseInt(max) + 1;86             String returnnum = String.valueOf(imax);87             int zero = leng-sign.length()-returnnum.length();88             for(; i < zero; i++) {89                 returnnum = "0" + returnnum;90             }91             return sign + returnnum;92         }93     }94 95 }

配置文件：User.hbm.xml

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 1 <?xml version="1.0" encoding="UTF-8"?> 2 <!DOCTYPE hibernate-mapping PUBLIC  3     "-//Hibernate/Hibernate Mapping DTD 3.0//EN" 4     "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd"> 5 <hibernate-mapping package="entity"> 6     <class name="User" table="TEMP" lazy="false"> 7         <id name="userId" column="userId"> 8             <generator class="action.GeneratePK" > 9               <param name="classname">User</param>10               <param name="pk">userId</param>11               <param name="sign">poli</param>12               <param name="idLength">13</param>13             </generator>14         </id>15         <property name="name" column="name" />16         <property name="age" column="age" type="integer"/>17         <property name="address" column="address" />18     </class>19 </hibernate-mapping>

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