content: /**
   * Copyright &copy; 2012-2016 <a href="https://github.com/HuangBingGui/jeespring">jeespring</a> All rights reserved.
   */
  package com.jeespring.common.persistence.dialect;
  
  /**
   * Oracle的方言实现
   * @author poplar.yfyang
   * @version 1.0 2010-10-10 下午12:31
   * @since JDK 1.5
   */
  public class OracleDialect implements Dialect {
      @Override
      public boolean supportsLimit() {
          return true;
      }
  
      @Override
      public String getLimitString(String sql, int offset, int limit) {
          return getLimitString(sql, offset, Integer.toString(offset), Integer.toString(limit));
      }
  
      /**
       * 将sql变成分页sql语句,提供将offset及limit使用占位符号(placeholder)替换.
       * <pre>
       * 如mysql
       * dialect.getLimitString("select * from user", 12, ":offset",0,":limit") 将返回
       * select * from user limit :offset,:limit
       * </pre>
       *
       * @param sql               实际SQL语句
       * @param offset            分页开始纪录条数
       * @param offsetPlaceholder 分页开始纪录条数－占位符号
       * @param limitPlaceholder  分页纪录条数占位符号
       * @return 包含占位符的分页sql
       */
      public String getLimitString(String sql, int offset, String offsetPlaceholder, String limitPlaceholder) {
          sql = sql.trim();
          boolean isForUpdate = false;
          if (sql.toLowerCase().endsWith(" for update")) {
              sql = sql.substring(0, sql.length() - 11);
              isForUpdate = true;
          }
          StringBuilder pagingSelect = new StringBuilder(sql.length() + 100);
  
          if (offset > 0) {
  			pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( ");
  		} else {
  			pagingSelect.append("select * from ( ");
  		}
  		pagingSelect.append(sql);
  		if (offset > 0) {
  			String endString = offsetPlaceholder + "+" + limitPlaceholder;
  			pagingSelect.append(" ) row_ where rownum <= "+endString+") where rownum_ > ").append(offsetPlaceholder);
  		} else {
  			pagingSelect.append(" ) where rownum <= "+limitPlaceholder);
  		}
  
          if (isForUpdate) {
              pagingSelect.append(" for update");
          }
  
          return pagingSelect.toString();
      }
  
  }
  