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删除文件 mybatis-flex-core/src/main/java/com/mybatisflex/core/paginate/PaginateInterceptor.java
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王帅
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/*
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* Copyright (c) 2022-2023, Mybatis-Flex (fuhai999@gmail.com).
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* <p>
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* <p>
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* http://www.apache.org/licenses/LICENSE-2.0
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* <p>
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.mybatisflex.core.paginate;
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import com.mybatisflex.core.dialect.LimitOffsetProcessor;
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import com.mybatisflex.core.query.QueryWrapper;
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import org.apache.ibatis.cache.CacheKey;
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import org.apache.ibatis.executor.Executor;
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import org.apache.ibatis.mapping.BoundSql;
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import org.apache.ibatis.mapping.MappedStatement;
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import org.apache.ibatis.mapping.ResultMap;
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import org.apache.ibatis.plugin.Interceptor;
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import org.apache.ibatis.plugin.Intercepts;
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import org.apache.ibatis.plugin.Invocation;
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import org.apache.ibatis.plugin.Signature;
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import org.apache.ibatis.session.ResultHandler;
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import org.apache.ibatis.session.RowBounds;
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import java.sql.SQLException;
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import java.util.Collections;
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import java.util.List;
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import java.util.Map;
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import java.util.Map.Entry;
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/**
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* 分页拦截器。
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*
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* @author 王帅
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* @since 2023-05-18
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*/
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@Intercepts({
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@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class}),
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@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class, CacheKey.class, BoundSql.class})
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})
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@SuppressWarnings({"rawtypes", "unchecked"})
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public class PaginateInterceptor implements Interceptor {
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/**
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* 拦截 Executor 的两个 query 方法，实现分页操作。<br>
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* {@link Executor#query(MappedStatement, Object, RowBounds, ResultHandler)} <br>
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* {@link Executor#query(MappedStatement, Object, RowBounds, ResultHandler, CacheKey, BoundSql)}
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*/
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@Override
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public Object intercept(Invocation invocation) throws Throwable {
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// 获取 Executor 对象 query 方法的参数列表
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Object[] args = invocation.getArgs();
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// 获取两个 query 方法都有的参数
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MappedStatement ms = (MappedStatement) args[0];
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Object parameters = args[1];
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RowBounds rowBounds = (RowBounds) args[2];
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ResultHandler resultHandler = (ResultHandler) args[3];
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// 获取 Executor 对象
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Executor executor = (Executor) invocation.getTarget();
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BoundSql boundSql;
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// 两个 query 方法参数不相同，获取 BoundSql 的方式不同
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if (args.length == 4) {
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// 4 个参数时
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boundSql = ms.getBoundSql(parameters);
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} else {
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// 6 个参数时
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boundSql = (BoundSql) args[5];
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}
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// 获取拦截查询方法是否有 Page 参数
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Page page = getPage(parameters);
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// 没有 Page 参数就认为不是分页操作
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if (page == null) {
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return invocation.proceed();
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}
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// 设置分页数据
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page.setRecords(executeQuery(executor, ms, parameters, rowBounds, resultHandler, boundSql, page));
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// 设置数据总数量
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page.setTotalRow(executeCount(executor, ms, parameters, rowBounds, resultHandler, boundSql));
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return Collections.singletonList(page);
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}
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/**
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* 查询被拦截方法的参数有没有 {@link Page} 对象。
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*/
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private Page getPage(Object parameters) {
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if (parameters != null) {
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if (parameters instanceof Map) {
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Map<?, ?> parameterMap = (Map<?, ?>) parameters;
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for (Entry entry : parameterMap.entrySet()) {
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if (entry.getValue() instanceof Page) {
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return (Page) entry.getValue();
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}
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}
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} else if (parameters instanceof Page) {
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return (Page) parameters;
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}
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}
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return null;
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}
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/**
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* 根据 {@link Page} 对象中页码（{@link Page#getPageNumber()}）
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* 和每页显示的数量（{@link Page#getPageSize()}），构建 SQL 语句，
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* 查询指定页的内容。
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*/
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private List executeQuery(Executor executor, MappedStatement ms,
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Object parameters, RowBounds rowBounds,
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ResultHandler resultHandler, BoundSql boundSql,
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Page page) throws SQLException {
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// 获取分页 SQL 语句
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String pageSqlStr = getPageSqlStr(boundSql.getSql(), page);
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// 构建分页查询 BoundSql 对象
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BoundSql pageSql = new BoundSql(ms.getConfiguration(), pageSqlStr, boundSql.getParameterMappings(), parameters);
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// 将原 SQL 中的占位符对应的参数，添加到新分页 SQL 中
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boundSql.getAdditionalParameters().forEach(pageSql::setAdditionalParameter);
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// 获取 CacheKey 对象
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CacheKey cacheKey = executor.createCacheKey(ms, parameters, rowBounds, pageSql);
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// 执行分页 SQL 查询数据
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return executor.query(ms, parameters, rowBounds, resultHandler, cacheKey, pageSql);
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}
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/**
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* 构建分页 SQL 语句。
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*/
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private String getPageSqlStr(String originalSql, Page page) {
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int size = page.getPageSize();
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int number = page.getPageNumber();
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int limitRows = (number - 1) * size;
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return LimitOffsetProcessor.MYSQL.process(new StringBuilder(originalSql), QueryWrapper.create(), size, limitRows).toString();
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}
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/**
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* 查询符合原 SQL 条件的数据数量。
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*/
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private Long executeCount(Executor executor, MappedStatement ms,
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Object parameters, RowBounds rowBounds,
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ResultHandler resultHandler, BoundSql boundSql) throws SQLException {
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// 获取 count 查询的 MappedStatement 对象
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MappedStatement countMs = getCountMappedStatement(ms);
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BoundSql countSql;
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if (countMs != null) {
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countSql = countMs.getBoundSql(parameters);
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} else {
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// 获取不到则构建新的 MappedStatement 对象
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countMs = buildCountMappedStatement(ms);
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// 获取 count 查询 SQL
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String countSqlStr = getCountSqlStr(boundSql.getSql());
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// 构建 count 查询 BoundSql 对象
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countSql = new BoundSql(ms.getConfiguration(), countSqlStr, boundSql.getParameterMappings(), parameters);
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// 将原 SQL 中的占位符对应的参数，添加到新 count 查询 SQL 中
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boundSql.getAdditionalParameters().forEach(countSql::setAdditionalParameter);
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}
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// 获取 CacheKey 对象
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CacheKey countKey = executor.createCacheKey(countMs, parameters, rowBounds, countSql);
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// 执行 count 查询 SQL 查询数量
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Object result = executor.query(countMs, parameters, rowBounds, resultHandler, countKey, countSql);
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// 处理结果，返回总数量
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return ((Number) ((List) result).get(0)).longValue();
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}
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/**
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* 尝试获取已经存在的 {@link MappedStatement} 对象。
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*/
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private MappedStatement getCountMappedStatement(MappedStatement ms) {
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String msId = ms.getId().concat("_COUNT");
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MappedStatement mappedStatement = null;
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try {
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mappedStatement = ms.getConfiguration().getMappedStatement(msId, false);
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} catch (Exception ignored) {
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// do nothing.
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}
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return mappedStatement;
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}
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/**
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* 构建 count 查询的 {@link MappedStatement} 对象。
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*/
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private MappedStatement buildCountMappedStatement(MappedStatement ms) {
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String countId = ms.getId() + "_Count";
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MappedStatement.Builder builder = new MappedStatement.Builder(ms.getConfiguration(), countId, ms.getSqlSource(), ms.getSqlCommandType());
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return builder.resource(ms.getResource())
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.fetchSize(ms.getFetchSize())
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.statementType(ms.getStatementType())
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.keyGenerator(ms.getKeyGenerator())
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.timeout(ms.getTimeout())
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.parameterMap(ms.getParameterMap())
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.resultMaps(Collections.singletonList(new ResultMap.Builder(ms.getConfiguration(), ms.getId(), Long.class, Collections.emptyList()).build()))
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.resultSetType(ms.getResultSetType())
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.cache(ms.getCache())
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.flushCacheRequired(ms.isFlushCacheRequired())
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.useCache(ms.isUseCache())
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.build();
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}
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/**
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* 构建 count 查询 SQL 语句。
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*/
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private String getCountSqlStr(String originalSql) {
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return String.format("SELECT COUNT(*) FROM (%s) TOTAL", originalSql);
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}
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}
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