一.背景
在很多业务场景下我们需要去拦截sql，达到不入侵原有代码业务处理一些东西，比如：分页操作，数据权限过滤操作，SQL执行时间性能监控等等，这里我们就可以用到Mybatis的拦截器Interceptor

二.Mybatis核心对象介绍
从MyBatis代码实现的角度来看，MyBatis的主要的核心部件有以下几个：

Configuration 初始化基础配置，比如MyBatis的别名等，一些重要的类型对象，如，插件，映射器，ObjectFactory和typeHandler对象，MyBatis所有的配置信息都维持在Configuration对象之中
SqlSessionFactory SqlSession工厂
SqlSession 作为MyBatis工作的主要顶层API，表示和数据库交互的会话，完成必要数据库增删改查功能
Executor MyBatis执行器，是MyBatis 调度的核心，负责SQL语句的生成和查询缓存的维护
StatementHandler 封装了JDBC Statement操作，负责对JDBC statement 的操作，如设置参数、将Statement结果集转换成List集合。
ParameterHandler 负责对用户传递的参数转换成JDBC Statement 所需要的参数，
ResultSetHandler 负责将JDBC返回的ResultSet结果集对象转换成List类型的集合；
TypeHandler 负责java数据类型和jdbc数据类型之间的映射和转换
MappedStatement MappedStatement维护了一条<select|update|delete|insert>节点的封装，
SqlSource 负责根据用户传递的parameterObject，动态地生成SQL语句，将信息封装到BoundSql对象中，并返回
BoundSql 表示动态生成的SQL语句以及相应的参数信息
三. Mybatis执行概要图

四.实现如下：

package com.aimin.dal.interceptor;import com.alibaba.druid.sql.SQLUtils;
import com.alibaba.druid.sql.parser.ParserException;
import com.alibaba.druid.util.JdbcConstants;
import com.enn.common.util.OperatorInfoUtil;
import com.enn.common.vo.UserInfo;
import com.enn.dal.config.MapperConfig;
import com.enn.dal.constants.MybatisConstants;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections.CollectionUtils;
import org.apache.commons.lang3.StringUtils;
import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.SqlCommandType;
import org.apache.ibatis.plugin.*;
import org.apache.ibatis.reflection.DefaultReflectorFactory;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
import com.google.common.cache.Cache;import java.sql.Connection;
import java.util.Properties;
import java.util.Set;
import java.util.regex.Matcher;
import java.util.regex.Pattern;/*** @author zlq* @date 2021/11/11* @description: Mybatis拦截器插件，拦截查询语句**/
@Slf4j
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})
})
@Component
public class MybatisInterceptor implements Interceptor {private static final String COLUMN_ENT_ID = "ent_id";private static final Pattern PATTERN_CONDITION_TENANT_ID = Pattern.compile(COLUMN_ENT_ID + " *=", Pattern.DOTALL);private static final Pattern PATTERN_MAIN_TABLE_ALIAS = Pattern.compile("(?i).*from\\s+[a-z_]+\\s+(?:as\\s+)?((?!(left|right|full|inner|join|where|group|order|limit))[a-z]+).*", Pattern.DOTALL);private static final Pattern PATTERN_CT_TABLE_SQL = Pattern.compile("(?i).*from *car_", Pattern.DOTALL);private static final Pattern PATTERN_COUNT_SQL = Pattern.compile("(?i) *select *count\\(.*\\) *from *\\((.*)\\) table_count$", Pattern.DOTALL);@Autowiredprivate Cache<String, MapperConfig> mybatisInterceptorCache;@Value(MybatisConstants.INCLUDED_MAPPER_IDS)private Set<String> includedMapperIds;@Overridepublic Object intercept(Invocation invocation) throws Throwable {StatementHandler statementHandler = (StatementHandler) invocation.getTarget();MetaObject metaObject = MetaObject.forObject(statementHandler, SystemMetaObject.DEFAULT_OBJECT_FACTORY, SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY, new DefaultReflectorFactory());/*从RoutingStatementHandler中获得处理对象PreparedStatementHandler,从这个对象中获取Mapper中的xml信息* */MappedStatement mappedStatement = (MappedStatement) metaObject.getValue("delegate.mappedStatement");if (!SqlCommandType.SELECT.equals(mappedStatement.getSqlCommandType())) {return invocation.proceed();}//配置文件中sql语句的idString sqlId = mappedStatement.getId();log.info("sqlId:{}", sqlId);// 跳过无需拦截的sqlif (CollectionUtils.isNotEmpty(includedMapperIds) && !includedMapperIds.contains(sqlId.substring(0, sqlId.lastIndexOf('.')))) {return invocation.proceed();}BoundSql boundSql = statementHandler.getBoundSql();String originalSql = boundSql.getSql().trim();if (StringUtils.isBlank(originalSql)) {return invocation.proceed();}MapperConfig mapperConfig = getMapperConfig(sqlId, originalSql);// 判断是否为业务表if (!mapperConfig.isCtTable()) {return invocation.proceed();}// 判断sql中是否已经添加了租户查询条件if (mapperConfig.isTenantIdCondition()) {return invocation.proceed();}//拼接租户相关信息final UserInfo userInfo = OperatorInfoUtil.getUserInfo();if (userInfo == null) {return invocation.proceed();}if (!StringUtils.isAlphanumeric(userInfo.getEntId())) {log.warn("非法的租户id或者租户id为空,entId:{}，未能拼接租户查询条件", userInfo.getEntId());return invocation.proceed();}log.info("entId:{}", userInfo.getEntId());StringBuilder scopeCondition = new StringBuilder();if (StringUtils.isNotBlank(mapperConfig.getMainTableAlias())) {scopeCondition.append(mapperConfig.getMainTableAlias()).append(".");}scopeCondition.append(COLUMN_ENT_ID);scopeCondition.append(MybatisConstants.EQUAL);scopeCondition.append(MybatisConstants.SINGLE_QUOTATION_MARK);scopeCondition.append(userInfo.getEntId());scopeCondition.append(MybatisConstants.SINGLE_QUOTATION_MARK);String sql = addCondition(originalSql, scopeCondition.toString());try {SQLUtils.formatMySql(sql);originalSql = sql;} catch (ParserException e) {log.warn("动态添加SQL数据过滤条件失败：{}", sql);}log.info("sql:{}", originalSql);metaObject.setValue("delegate.boundSql.sql", originalSql);return invocation.proceed();}private MapperConfig getMapperConfig(String sqlId, String originalSql) {MapperConfig mapperConfig = mybatisInterceptorCache.getIfPresent(sqlId);if (mapperConfig == null) {mapperConfig = new MapperConfig();mapperConfig.setMainTableAlias(getMainTableAlias(originalSql));mapperConfig.setCtTable(isCtTable(originalSql));mapperConfig.setTenantIdCondition(hasTenantIdCondition(originalSql));mybatisInterceptorCache.put(sqlId, mapperConfig);}return mapperConfig;}private static String addCondition(String originalSql, String scopeCondition) {String notCountSql;if ((notCountSql = getNotCountSql(originalSql)) != null) {notCountSql = SQLUtils.addCondition(notCountSql, scopeCondition, JdbcConstants.MYSQL);return "select count(0) from(" + notCountSql + ") table_count";}return SQLUtils.addCondition(originalSql, scopeCondition, JdbcConstants.MYSQL);}private static boolean hasTenantIdCondition(String sql) {sql = removeLinefeed(sql);Matcher matcher = PATTERN_CONDITION_TENANT_ID.matcher(sql);return matcher.find();}/*** 获取主表别名** @param sql sql语句* @return 主表别名*/private static String getMainTableAlias(String sql) {sql = removeLinefeed(sql);String notCountSql = getNotCountSql(sql);if (notCountSql != null) {sql = notCountSql;}sql = removeStrInBrackets(sql);Matcher matcher = PATTERN_MAIN_TABLE_ALIAS.matcher(sql);if (matcher.find()) {return matcher.group(1);}return null;}private static boolean isCtTable(String sql) {sql = removeLinefeed(sql);Matcher matcher = PATTERN_CT_TABLE_SQL.matcher(sql);return matcher.find();}private static String getNotCountSql(String sql) {sql = removeLinefeed(sql);Matcher matcher = PATTERN_COUNT_SQL.matcher(sql);return matcher.find() ? matcher.group(1) : null;}private static String removeLinefeed(String str) {return str == null ? null : str.replaceAll(MybatisConstants.SEP_LINEFEED, StringUtils.EMPTY);}@Overridepublic Object plugin(Object target) {return Plugin.wrap(target, this);}@Overridepublic void setProperties(Properties properties) {}private static String removeStrInBrackets(String str) {if (str == null) {return null;}char[] arr = str.toCharArray();boolean left = false;int leftIndex = 0;int rightIndex = 0;int num = 0;for (int i = 0; i < arr.length; i++) {switch (arr[i]) {case '(':if (!left) {left = true;leftIndex = i;}num++;break;case ')':num--;break;default:}if (left && num == 0) {rightIndex = i;break;}}if (leftIndex < rightIndex) {str = str.substring(0, leftIndex) + str.substring(rightIndex + 1, arr.length);if (str.contains(MybatisConstants.LEFT_PARENTHESIS_EN)) {return removeStrInBrackets(str);} else {return str;}}return str;}
}