转载：hibernate生成自定义主键(类似user000000001——可自己通过配置文件配置)

生成主键的类：

package action;
 
 import java.io.Serializable;
 import java.util.List;
 import java.util.Properties;
 
 import org.hibernate.HibernateException;
 import org.hibernate.MappingException;
 import org.hibernate.dialect.Dialect;
 import org.hibernate.engine.QueryParameters;
 import org.hibernate.engine.SessionImplementor;
 import org.hibernate.id.Configurable;
 import org.hibernate.id.IdentifierGenerator;
 import org.hibernate.type.Type;
 /**
  * 
 * 类名称：      GeneratePK   
 * 类描述：     在hibernate的基础上自动生成自定义的主键
 * 创建人：     andy_lj  
 * 创建时间：2012-08-10 上午11:40:50     
 * 修改备注：   
 * @version
  */
 public class GeneratePK implements Configurable, IdentifierGenerator {
     public String sign;// user000000001中的user
     public String classname; //实体类的类名
     public String pk;//主键名字
     public String idLength;//user000000001的长度
     
     /**
      * 取得User.hbm.xml中的自定义的值
      */
     @Override
     public void configure(Type arg0, Properties arg1, Dialect arg2)
             throws MappingException {
         this.classname = arg1.getProperty("classname");
         this.pk = arg1.getProperty("pk");
         this.sign = arg1.getProperty("sign");
         this.idLength = arg1.getProperty("idLength");
     }
     /**
      * 生成主键
      */
     @Override
     public Serializable generate(SessionImplementor arg0, Object arg1)
             throws HibernateException {
          //获得主键的长度
         int leng = Integer.valueOf(idLength);
         //需要查询数据库中最大的ID号
         StringBuffer sql = new StringBuffer("select max(a.").append(pk)
                                                             .append(") from ")
                                                             .append(classname)
                                                             .append(" as a where a.")
                                                             .append(pk)
                                                             .append(" like '")
                                                             .append(sign)
                                                             .append("%'");
         QueryParameters qp = new QueryParameters();
         List ls = arg0.list(sql.toString(), qp);
         String max = (String) ls.get(0);
         int i = 0;
         //如果是第一次添加记录那么就是类似user000000001
         if (max == null || max.trim().equals("")) {
             max = "1";
             for(; i < leng-sign.length()-1; i++) {
                 max = "0" + max;
             }
             i = 0;
             return sign + max;
         }//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
         else if(max != null && max.length() <= leng) {
             max = max.replaceAll(sign, "");
             Integer imax = Integer.parseInt(max) + 1;
             String returnnum = String.valueOf(imax);
             int zero = leng-sign.length()-returnnum.length();
             for(; i < zero; i++) {
                 returnnum = "0" + returnnum;
             }
             i = 0;
             return sign + returnnum;
         }//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
         else {
             leng = max.length();
             max = max.replaceAll(sign, "");
             Integer imax = Integer.parseInt(max) + 1;
             String returnnum = String.valueOf(imax);
             int zero = leng-sign.length()-returnnum.length();
             for(; i < zero; i++) {
                 returnnum = "0" + returnnum;
             }
             return sign + returnnum;
         }
     }
 
 }

配置文件：User.hbm.xml

<?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE hibernate-mapping PUBLIC 
     "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
     "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
 <hibernate-mapping package="entity">
     <class name="User" table="TEMP" lazy="false">
         <id name="userId" column="userId">
             <generator class="action.GeneratePK" >
               <param name="classname">User</param>
               <param name="pk">userId</param>
               <param name="sign">poli</param>
               <param name="idLength">13</param>
             </generator>
         </id>
         <property name="name" column="name" />
         <property name="age" column="age" type="integer"/>
         <property name="address" column="address" />
     </class>
 </hibernate-mapping>