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+/* |
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+ The MIT License (MIT) |
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+ |
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+ Copyright (c) 2014 abel533@gmail.com |
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+ |
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+ Permission is hereby granted, free of charge, to any person obtaining a copy |
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+ of this software and associated documentation files (the "Software"), to deal |
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+ in the Software without restriction, including without limitation the rights |
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+ to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
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+ copies of the Software, and to permit persons to whom the Software is |
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+ furnished to do so, subject to the following conditions: |
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+ |
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+ The above copyright notice and this permission notice shall be included in |
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+ all copies or substantial portions of the Software. |
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+ |
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+ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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+ IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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+ FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
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+ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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+ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
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+ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN |
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+ THE SOFTWARE. |
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+*/ |
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+ |
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+package com.github.pagehelper; |
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+ |
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+import org.apache.ibatis.executor.Executor; |
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+import org.apache.ibatis.mapping.*; |
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+import org.apache.ibatis.plugin.*; |
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+import org.apache.ibatis.reflection.MetaObject; |
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+import org.apache.ibatis.reflection.SystemMetaObject; |
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+import org.apache.ibatis.session.ResultHandler; |
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+import org.apache.ibatis.session.RowBounds; |
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+ |
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+import java.util.ArrayList; |
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+import java.util.List; |
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+import java.util.Properties; |
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+ |
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+/** |
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+ * Mybatis - |
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+ * |
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+ * @author liuzh/abel533/isea533 |
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+ * @version 3.2.1 |
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+ * @url http://git.fron.com.cn/free/Mybatis_PageHelper |
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+ */ |
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+@Intercepts(@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})) |
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+public class PageHelper implements Interceptor { |
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+ private static final ThreadLocal<Page> localPage = new ThreadLocal<Page>(); |
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+ |
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+ private static final List<ResultMapping> EMPTY_RESULTMAPPING = new ArrayList<ResultMapping>(0); |
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+ |
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+ //数据库方言 |
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+ private static String dialect = ""; |
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+ //RowBounds参数offset作为PageNum使用 - 默认不使用 |
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+ private static boolean offsetAsPageNum = false; |
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+ //RowBounds是否进行count查询 - 默认不查询 |
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+ private static boolean rowBoundsWithCount = false; |
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+ |
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+ /** |
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+ * 开始分页 |
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+ * |
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+ * @param pageNum |
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+ * @param pageSize |
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+ */ |
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+ public static void startPage(int pageNum, int pageSize) { |
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+ startPage(pageNum, pageSize, true); |
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+ } |
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+ |
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+ /** |
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+ * 开始分页 |
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+ * |
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+ * @param pageNum |
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+ * @param pageSize |
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+ */ |
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+ public static void startPage(int pageNum, int pageSize, boolean count) { |
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+ localPage.set(new Page(pageNum, pageSize, count ? Page.SQL_COUNT : Page.NO_SQL_COUNT)); |
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+ } |
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+ |
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+ @Override |
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+ public Object intercept(Invocation invocation) throws Throwable { |
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+ final Object[] args = invocation.getArgs(); |
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+ RowBounds rowBounds = (RowBounds) args[2]; |
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+ if (localPage.get() == null && rowBounds == RowBounds.DEFAULT) { |
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+ return invocation.proceed(); |
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+ } else { |
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+ //忽略RowBounds-否则会进行Mybatis自带的内存分页 |
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+ args[2] = RowBounds.DEFAULT; |
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+ MappedStatement ms = (MappedStatement) args[0]; |
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+ Object parameterObject = args[1]; |
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+ BoundSql boundSql = ms.getBoundSql(parameterObject); |
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+ |
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+ //分页信息 |
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+ Page page = localPage.get(); |
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+ //移除本地变量 |
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+ localPage.remove(); |
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+ |
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+ if (page == null) { |
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+ if (offsetAsPageNum) { |
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+ page = new Page(rowBounds.getOffset(), rowBounds.getLimit(), rowBoundsWithCount ? Page.SQL_COUNT : Page.NO_SQL_COUNT); |
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+ } else { |
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+ page = new Page(rowBounds, rowBoundsWithCount ? Page.SQL_COUNT : Page.NO_SQL_COUNT); |
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+ } |
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+ } |
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+ MappedStatement qs = newMappedStatement(ms, new BoundSqlSqlSource(boundSql)); |
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+ //将参数中的MappedStatement替换为新的qs，防止并发异常 |
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+ args[0] = qs; |
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+ MetaObject msObject = SystemMetaObject.forObject(qs); |
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+ String sql = (String) msObject.getValue("sqlSource.boundSql.sql"); |
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+ //简单的通过total的值来判断是否进行count查询 |
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+ if (page.getTotal() > Page.NO_SQL_COUNT) { |
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+ //求count - 重写sql |
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+ msObject.setValue("sqlSource.boundSql.sql", getCountSql(sql)); |
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+ //查询总数 |
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+ Object result = invocation.proceed(); |
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+ int totalCount = (Integer) ((List) result).get(0); |
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+ page.setTotal(totalCount); |
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+ int totalPage = totalCount / page.getPageSize() + ((totalCount % page.getPageSize() == 0) ? 0 : 1); |
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+ page.setPages(totalPage); |
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+ //分页sql - 重写sql |
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+ msObject.setValue("sqlSource.boundSql.sql", getPageSql(sql, page)); |
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+ //恢复类型 |
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+ msObject.setValue("resultMaps", ms.getResultMaps()); |
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+ //执行分页查询 |
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+ result = invocation.proceed(); |
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+ //得到处理结果 |
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+ page.addAll((List) result); |
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+ //返回结果 |
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+ return page; |
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+ } else { |
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+ //分页sql - 重写sql |
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+ msObject.setValue("sqlSource.boundSql.sql", getPageSql(sql, page)); |
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+ //恢复类型 |
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+ msObject.setValue("resultMaps", ms.getResultMaps()); |
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+ //执行分页查询 |
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+ Object result = invocation.proceed(); |
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+ //得到处理结果 |
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+ page.addAll((List) result); |
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+ //返回结果 |
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+ return page; |
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+ } |
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+ } |
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+ } |
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+ |
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+ /** |
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+ * 获取总数sql - 如果要支持其他数据库，修改这里就可以 |
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+ * |
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+ * @param sql |
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+ * @return |
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+ */ |
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+ private String getCountSql(String sql) { |
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+ return "select count(0) from (" + sql + ") tmp_count"; |
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+ } |
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+ |
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+ /** |
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+ * 获取分页sql - 如果要支持其他数据库，修改这里就可以 |
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+ * |
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+ * @param sql |
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+ * @param page |
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+ * @return |
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+ */ |
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+ private String getPageSql(String sql, Page page) { |
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+ StringBuilder pageSql = new StringBuilder(200); |
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+ if ("mysql".equals(dialect)) { |
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+ pageSql.append(sql); |
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+ pageSql.append(" limit " + page.getStartRow() + "," + page.getPageSize()); |
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+ } else if ("hsqldb".equals(dialect)) { |
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+ pageSql.append(sql); |
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+ pageSql.append(" LIMIT " + page.getPageSize() + " OFFSET " + page.getStartRow()); |
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+ } else if ("oracle".equals(dialect)) { |
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+ pageSql.append("select * from ( select temp.*, rownum row_id from ( "); |
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+ pageSql.append(sql); |
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+ pageSql.append(" ) temp where rownum <= ").append(page.getEndRow()); |
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+ pageSql.append(") where row_id > ").append(page.getStartRow()); |
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+ } |
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+ return pageSql.toString(); |
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+ } |
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+ |
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+ private class BoundSqlSqlSource implements SqlSource { |
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+ BoundSql boundSql; |
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+ |
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+ public BoundSqlSqlSource(BoundSql boundSql) { |
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+ this.boundSql = boundSql; |
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+ } |
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+ |
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+ public BoundSql getBoundSql(Object parameterObject) { |
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+ return boundSql; |
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+ } |
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+ } |
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+ |
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+ /** |
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+ * 由于MappedStatement是一个全局共享的对象，因而需要复制一个对象来进行操作，防止并发访问导致错误 |
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+ * |
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+ * @param ms |
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+ * @param newSqlSource |
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+ * @return |
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+ */ |
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+ private MappedStatement newMappedStatement(MappedStatement ms, SqlSource newSqlSource) { |
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+ MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), ms.getId() + "_分页", newSqlSource, ms.getSqlCommandType()); |
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+ builder.resource(ms.getResource()); |
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+ builder.fetchSize(ms.getFetchSize()); |
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+ builder.statementType(ms.getStatementType()); |
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+ builder.keyGenerator(ms.getKeyGenerator()); |
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+ if (ms.getKeyProperties() != null && ms.getKeyProperties().length != 0) { |
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+ StringBuffer keyProperties = new StringBuffer(); |
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+ for (String keyProperty : ms.getKeyProperties()) { |
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+ keyProperties.append(keyProperty).append(","); |
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+ } |
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+ keyProperties.delete(keyProperties.length() - 1, keyProperties.length()); |
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+ builder.keyProperty(keyProperties.toString()); |
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+ } |
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+ builder.timeout(ms.getTimeout()); |
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+ builder.parameterMap(ms.getParameterMap()); |
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+ //由于resultMaps第一次需要返回int类型的结果，所以这里需要生成一个resultMap - 防止并发错误 |
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+ List<ResultMap> resultMaps = new ArrayList<ResultMap>(); |
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+ ResultMap resultMap = new ResultMap.Builder(ms.getConfiguration(), ms.getId(), int.class, EMPTY_RESULTMAPPING).build(); |
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+ resultMaps.add(resultMap); |
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+ builder.resultMaps(resultMaps); |
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+ builder.resultSetType(ms.getResultSetType()); |
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+ builder.cache(ms.getCache()); |
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+ builder.flushCacheRequired(ms.isFlushCacheRequired()); |
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+ builder.useCache(ms.isUseCache()); |
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+ |
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+ return builder.build(); |
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+ } |
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+ |
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+ /** |
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+ * 只拦截Executor |
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+ * |
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+ * @param target |
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+ * @return |
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+ */ |
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+ @Override |
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+ public Object plugin(Object target) { |
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+ if (target instanceof Executor) { |
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+ return Plugin.wrap(target, this); |
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+ } else { |
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+ return target; |
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+ } |
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+ } |
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+ |
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+ public void setProperties(Properties p) { |
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+ dialect = p.getProperty("dialect"); |
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+ if (dialect == null || dialect.equals("")) { |
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+ throw new RuntimeException("Mybatis分页插件PageHelper无法获取dialect参数!"); |
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+ } |
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+ //offset作为PageNum使用 |
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+ String offset = p.getProperty("offsetAsPageNum"); |
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+ if (offset != null && offset.toUpperCase().equals("TRUE")) { |
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+ offsetAsPageNum = true; |
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+ } |
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+ //RowBounds方式是否做count查询 |
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+ String withcount = p.getProperty("rowBoundsWithCount"); |
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+ if (withcount != null && withcount.toUpperCase().equals("TRUE")) { |
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+ rowBoundsWithCount = true; |
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+ } |
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+ } |
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+} |
