/**
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* Copyright © 2015-2020 <a href="http://www.jeeplus.org/">JeePlus</a> All rights reserved.
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*/
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package com.jeeplus.common.persistence.dialect.db;
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import com.jeeplus.common.persistence.dialect.Dialect;
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/**
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* Oracle的方言实现
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* @author poplar.yfyang
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* @version 1.0 2010-10-10 下午12:31
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* @since JDK 1.5
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*/
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public class OracleDialect implements Dialect {
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@Override
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public boolean supportsLimit() {
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return true;
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}
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@Override
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public String getLimitString(String sql, int offset, int limit) {
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return getLimitString(sql, offset, Integer.toString(offset), Integer.toString(limit));
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}
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/**
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* 将sql变成分页sql语句,提供将offset及limit使用占位符号(placeholder)替换.
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* <pre>
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* 如mysql
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* dialect.getLimitString("select * from user", 12, ":offset",0,":limit") 将返回
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* select * from user limit :offset,:limit
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* </pre>
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*
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* @param sql 实际SQL语句
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* @param offset 分页开始纪录条数
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* @param offsetPlaceholder 分页开始纪录条数－占位符号
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* @param limitPlaceholder 分页纪录条数占位符号
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* @return 包含占位符的分页sql
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*/
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public String getLimitString(String sql, int offset, String offsetPlaceholder, String limitPlaceholder) {
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sql = sql.trim();
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boolean isForUpdate = false;
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if (sql.toLowerCase().endsWith(" for update")) {
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sql = sql.substring(0, sql.length() - 11);
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isForUpdate = true;
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}
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StringBuilder pagingSelect = new StringBuilder(sql.length() + 100);
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if (offset > 0) {
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pagingSelect.append("select * from ( select row_.*, rownum rownum_ from ( ");
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} else {
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pagingSelect.append("select * from ( ");
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}
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pagingSelect.append(sql);
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if (offset > 0) {
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String endString = offsetPlaceholder + "+" + limitPlaceholder;
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pagingSelect.append(" ) row_ where rownum <= "+endString+") where rownum_ > ").append(offsetPlaceholder);
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} else {
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pagingSelect.append(" ) where rownum <= "+limitPlaceholder);
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}
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if (isForUpdate) {
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pagingSelect.append(" for update");
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}
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return pagingSelect.toString();
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}
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}
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