工具类 分页工具类PageParamBean

自己编写的分页工具类，根据不同的数据库类型，生成对应的分页sql信息，分享给大家，希望大家共勉，工具类有些地方，大家可能不需要，请根绝自己的需要进行修改使用，核心逻辑都在，如果大家觉得有什么不妥，欢迎大家随时指正

 package com.ideal.ieai.server.util;

 import com.ideal.ieai.core.JudgeDB;

 /**
  * @ClassName:  PageParamBean
  * @Description: 根据数据库类型不同生成不同的分页方法的工具类
  * @author: yue_sun
  * @date:   2019年1月3日 下午12:53:09
  *
  * @Copyright: 2019-2027 www.idealinfo.com Inc. All rights reserved.
  *
  */
 public class PageParamBean
 {
     private String sql;
     private int    pagePara1 = 0;
     private int    pagePara2 = 0;

     private static String        mysql     = "mysql";
     private static String        oracle    = "oracle";
     private static String        db2       = "db2";

     private static PageParamBean instance  = null;

     private PageParamBean()
     {

     }

     public static PageParamBean getInstance ()
     {
         if (null == instance)
         {
             instance = new PageParamBean();
         }
         return instance;
     }

     public String getSql ()
     {
         return sql;
     }

     public void setSql ( String sql )
     {
         this.sql = sql;
     }

     public int getPagePara1 ()
     {
         return pagePara1;
     }

     public void setPagePara1 ( int pagePara1 )
     {
         this.pagePara1 = pagePara1;
     }

     public int getPagePara2 ()
     {
         return pagePara2;
     }

     public void setPagePara2 ( int pagePara2 )
     {
         this.pagePara2 = pagePara2;
     }

     /**
      * @Title: getParamPageBean
      * @Description: 获取分页sql及分页参数方法
      * @param sql
      * @param start
      * @param limit
      * @return
      * @author: yue_sun
      * @date:   2019年1月2日 上午10:09:25
      */
     public PageParamBean getParamPageBean ( String sql, int start, int limit )
     {
         PageParamBean paramBean = new PageParamBean();
         int pageParam1 = 0;
         int pageParam2 = 0;
         switch (JudgeDB.IEAI_DB_TYPE)
         {
             case 1:
                 sql = getQueryPageSQL(oracle, sql);
                 pageParam1 = start + limit;
                 pageParam2 = start;
                 break;
             case 2:
                 sql = getQueryPageSQL(db2, sql);
                 pageParam1 = start + 1;
                 pageParam2 = start + limit;
                 break;
             case 3:
                 sql = getQueryPageSQL(mysql, sql);
                 pageParam1 = start;
                 pageParam2 = limit;
                 break;
             default:
                 break;
         }
         paramBean.setSql(sql);
         paramBean.setPagePara1(pageParam1);
         paramBean.setPagePara2(pageParam2);
         return paramBean;
     }

     public PageParamBean getParamPageBean ( String sql, String order, int start, int limit )
     {
         PageParamBean paramBean = new PageParamBean();
         int pageParam1 = 0;
         int pageParam2 = 0;
         switch (JudgeDB.IEAI_DB_TYPE)
         {
             case 1:
                 sql = getQueryPageSQLNew(oracle, order, sql);
                 pageParam1 = start + limit;
                 pageParam2 = start;
                 break;
             case 2:
                 sql = getQueryPageSQLNew(db2, order, sql);
                 pageParam1 = start;
                 pageParam2 = start + limit;
                 break;
             case 3:
                 sql = getQueryPageSQLNew(mysql, order, sql);
                 pageParam1 = start;
                 pageParam2 = limit;
                 break;
             default:
                 break;
         }
         paramBean.setSql(sql);
         paramBean.setPagePara1(pageParam1);
         paramBean.setPagePara2(pageParam2);
         return paramBean;
     }

     /**
      * @Title: getQueryPageSQL
      * @Description: 组织各种数据库的分页查询sql
      * @param dbType
      * @param sql
      * @return
       * @author: yue_sun
      * @date:   2019年1月3日 上午9:40:40
      */
     public static String getQueryPageSQL ( String dbType, String sql )
     {
         StringBuilder stringBuffer = new StringBuilder();
         if (dbType.equals("mysql"))
         {
             stringBuffer.append(sql);
             stringBuffer.append(" limit ?,?");
         }
         if (dbType.equals("oracle"))
         {
             stringBuffer.append("select * from ( select row_.*, rownum rownum_ from ( ");
             stringBuffer.append(sql);
             stringBuffer.append(" ) row_ where rownum <= ?) where rownum_ > ?");
         }
         if (dbType.equals("microsoft sql server"))
         {
             stringBuffer.append("select top ? ");
             if (sql.indexOf("order by") != -1)
             {
                 stringBuffer.append(sql.substring(sql.indexOf("select") + 7, sql.indexOf("order by")));

             } else if (sql.indexOf("group by") != -1)
             {

             } else
             {
                 stringBuffer.append(sql.substring(sql.indexOf("select") + 7, sql.length()));
             }
             stringBuffer.append("  where 1 not in (select top ? 1 ");
             stringBuffer.append(sql.substring(sql.indexOf("from"), sql.length()));
             stringBuffer.append(" )");
         }
         if (dbType.equals("postgresql"))
         {
             stringBuffer.append(sql);
             stringBuffer.append(" limit ? offset ?");
         }
         if (dbType.indexOf("db2") != -1)
         {
             stringBuffer.append("select * from( select rownumber() over() as rownum_ ,a1.* from ( ");

             stringBuffer.append(sql);

             stringBuffer.append(" ) a1) a2 where a2.rownum_ between ? and ? ");
         }

         if (dbType.indexOf("hsql") != -1)
         {
             stringBuffer.append("select limit ? ? * from (");
             stringBuffer.append(sql);
             stringBuffer.append(" )");
         }

         return stringBuffer.toString();
     }

     /**
      * @Title: getQueryPageSQLNew
      * @Description:   重载该方法，oracle 和 DB2 都用 > 和 <= 来做分页（加入order排序条件）
      * @param dbType
      * @param order
      * @param sql
      * @return
      * @author: yue_sun
      * @date:   2019年1月3日 上午9:40:40
      */
     public static String getQueryPageSQLNew ( String dbType, String order, String sql )
     {
         StringBuilder stringBuffer = new StringBuilder();
         if (dbType.equals("mysql"))
         {
             stringBuffer.append(sql);
             stringBuffer.append(" " + order + " ");
             stringBuffer.append(" limit ?,?");
         }
         if (dbType.equals("oracle"))
         {
             stringBuffer.append("SELECT * FROM  ( SELECT  row_number() over(" + order + ") AS RN ,  A.* FROM ( ");
             stringBuffer.append(sql);
             stringBuffer.append(" )  A  ) B WHERE  B.RN <= ? and B.RN > ?");
         }
         if (dbType.equals("microsoft sql server"))
         {
             stringBuffer.append("select top ? ");
             if (sql.indexOf("order by") != -1)
             {
                 stringBuffer.append(sql.substring(sql.indexOf("select") + 7, sql.indexOf("order by")));

             } else
             {
                 stringBuffer.append(sql.substring(sql.indexOf("select") + 7, sql.length()));
             }
             stringBuffer.append("  where 1 not in (select top ? 1 ");
             stringBuffer.append(sql.substring(sql.indexOf("from"), sql.length()));
             stringBuffer.append(" )");
         }
         if (dbType.equals("postgresql"))
         {
             stringBuffer.append(sql);
             stringBuffer.append(" limit ? offset ?");
         }
         if (dbType.indexOf("db2") != -1)
         {
             stringBuffer.append("SELECT * FROM  ( SELECT  ROW_NUMBER() OVER(" + order + ") AS RN ,  A.* FROM (");

             stringBuffer.append(sql);

             stringBuffer.append(" )  A  ) B WHERE  B.RN > ? and B.RN <= ?");
         }

         if (dbType.indexOf("hsql") != -1)
         {
             stringBuffer.append("select limit ? ? * from (");
             stringBuffer.append(sql);
             stringBuffer.append(" )");
         }

         return stringBuffer.toString();
     }

     /**
      * @Title: toCount
      * @Description: 生成查询总数的sql的方法
      * @param sql
      * @return
      * @author: yue_sun
      * @date:   2019年1月2日 上午10:12:25
      */
     public String toCount ( String sql )
     {
         StringBuilder stringBuilder = new StringBuilder();
         stringBuilder.append("SELECT COUNT(1) AS COUNT FROM ( ");
         stringBuilder.append(sql);
         stringBuilder.append(" ) TOTAL");
         return stringBuilder.toString();
     }

 }