/************************************************************************
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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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http://www.apache.org/licenses/LICENSE-2.0
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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 core.plugin.mybatis;
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import common.model.BaseModel;
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import core.plugin.mybatis.dialect.Dialect;
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import core.plugin.mybatis.dialect.SqlDialetHelper;
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import org.apache.commons.lang3.StringUtils;
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import org.apache.commons.lang3.reflect.FieldUtils;
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import org.apache.ibatis.executor.parameter.ParameterHandler;
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import org.apache.ibatis.executor.statement.PreparedStatementHandler;
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import org.apache.ibatis.executor.statement.StatementHandler;
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import org.apache.ibatis.mapping.BoundSql;
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import org.apache.ibatis.plugin.*;
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import org.apache.ibatis.session.Configuration;
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import org.apache.ibatis.session.RowBounds;
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import java.sql.Connection;
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import java.util.Properties;
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/**
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* 通用分页根据不同的数据库实现
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*
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* @author CSJ
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*
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*/
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@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class }) })
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public class PageInterceptor implements Interceptor {
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private final static String SQL_SELECT_REGEX = "(?is)^\\s*SELECT.*$";
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private final static String SQL_COUNT_REGEX = "(?is)^\\s*SELECT\\s+COUNT\\s*\\(\\s*(?:\\*|\\w+)\\s*\\).*$";
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@Override
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public Object intercept(Invocation inv) throws Throwable {
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StatementHandler target = (StatementHandler) inv.getTarget();
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BoundSql boundSql = target.getBoundSql();
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String sql = boundSql.getSql();
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if (StringUtils.isBlank(sql)) {
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return inv.proceed();
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}
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// 是否为select查询语句且不是count语句
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if (sql.matches(SQL_SELECT_REGEX) && !sql.matches(SQL_COUNT_REGEX)) {
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// 拦截到的prepare方法参数是一个Connection对象
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Connection connection = (Connection) inv.getArgs()[0];
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String dbType = connection.getMetaData().getDatabaseProductName();
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Dialect dialect = SqlDialetHelper.getDialetByDbType(dbType);
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Object obj = FieldUtils.readField(target, "delegate", true);
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// 反射获取 RowBounds 对象。
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RowBounds rowBounds = (RowBounds) FieldUtils.readField(obj, "rowBounds", true);
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// 添加Mapper接口情况下,分页支持
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if(rowBounds == null || rowBounds == RowBounds.DEFAULT) {
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ParameterHandler parameterHandler = (ParameterHandler) FieldUtils.readField(obj, "parameterHandler", true);
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Object paramObj = parameterHandler.getParameterObject();
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if(paramObj != null && paramObj instanceof BaseModel) {
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BaseModel entity = (BaseModel) paramObj;
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if(entity.isPaging()) {
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int offset = entity.getStart();
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int limit = entity.getLimit();
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if(offset == 0 && limit == 0) {
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rowBounds = RowBounds.DEFAULT;
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} else {
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rowBounds = new RowBounds(offset, limit);
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}
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}
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}
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}
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// 分页参数存在且不为默认值时进行分页SQL构造
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if (rowBounds != null && rowBounds != RowBounds.DEFAULT) {
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// 保存此次查询的记录总数
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PreparedStatementHandler preparedStatHandler = (PreparedStatementHandler) obj;
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Configuration configuration = (Configuration) FieldUtils.readField(preparedStatHandler,
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"configuration", true);
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MybatisHelper.getCount(dialect.getSqlWithCount(sql), preparedStatHandler, configuration, boundSql,
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connection);
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// 构造分页语句SQL
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FieldUtils.writeField(boundSql, "sql", dialect.getSqlWithPagination(sql, rowBounds), true);
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// 一定要还原否则将无法得到下一组数据(第一次的数据被缓存了)
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FieldUtils.writeField(rowBounds, "offset", RowBounds.NO_ROW_OFFSET, true);
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FieldUtils.writeField(rowBounds, "limit", RowBounds.NO_ROW_LIMIT, true);
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}
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}
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return inv.proceed();
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}
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@Override
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public Object plugin(Object target) {
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return Plugin.wrap(target, this);
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}
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@Override
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public void setProperties(Properties properties) {
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}
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}
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