beforeQuery - 查询操作前置拦截
- 方法签名
void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds,ResultHandler resultHandler, BoundSql boundSql)
- 用途
- 在执行查询SQL之前拦截
- 可以修改查询参数、SQL语句或执行环境
- 典型应用场景
- 动态表名替换
- 多租户数据过滤
- SQL性能监控开始
- 查询条件自动增强
beforeQuery 方法参数详解
beforeQuery 是 MyBatis-Plus 中非常重要的查询拦截方法，参数解析。
- Executor executor
- 作用
MyBatis 执行器，用于执行SQL操作
- 典型使用场景
获取当前事务状态
执行额外的查询操作
访问缓存
- 示例
Transaction transaction = executor.getTransaction();
boolean isCommited = transaction.isCommited();
- MappedStatement ms
- 作用
包含了一条SQL语句的所有配置信息
- 重要属性
id：Mapper方法的全限定名 (如 "com.example.UserMapper.selectById")
sqlCommandType：SQL类型 (SELECT/INSERT/UPDATE/DELETE)
configuration：MyBatis配置对象
- 示例
String mapperMethod = ms.getId(); // 获取当前执行的Mapper方法
SqlCommandType sqlType = ms.getSqlCommandType(); // 判断SQL类型
- Object parameter
- 作用
Mapper方法传入的参数
- 处理技巧
可能是单个参数、Map或@Param注解标注的多参数，需要根据实际业务判断参数类型
- 示例
if (parameter instanceof Map) {Map<?,?> paramMap = (Map<?,?>) parameter;Object idValue = paramMap.get("id");
} else if (parameter instanceof Long) {Long id = (Long) parameter;
}
- RowBounds rowBounds
- 作用
内存分页参数（不推荐使用）
- 注意
MyBatis-Plus推荐使用IPage进行物理分页
这个参数通常用于兼容旧代码
- 示例
int offset = rowBounds.getOffset(); // 获取偏移量
int limit = rowBounds.getLimit(); // 获取每页数量
- ResultHandler resultHandler
- 作用
自定义结果集处理器
- 典型使用
很少在拦截器中直接使用
可用于自定义结果集处理逻辑
- BoundSql boundSql
- 作用
包含最终要执行的SQL和参数映射信息
- 核心功能
获取和修改SQL语句
访问参数映射
获取参数值
- 示例
String sql = boundSql.getSql(); // 获取SQL
List<ParameterMapping> mappings = boundSql.getParameterMappings(); // 获取参数映射
Object parameterObject = boundSql.getParameterObject(); // 获取参数对象
测试使用
# 实现额外的业务数据权限，将task.task_id IN (）自动拼写在sql中
import cn.hutool.core.collection.CollectionUtil;
import cn.hutool.core.util.ReflectUtil;
import com.baomidou.mybatisplus.extension.plugins.inner.InnerInterceptor;
import com.zq.common.core.domain.TaskIdQuery;
import net.sf.jsqlparser.expression.LongValue;
import net.sf.jsqlparser.expression.operators.relational.ExpressionList;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.session.ResultHandler;
import org.apache.ibatis.session.RowBounds;import java.sql.SQLException;
import java.util.Map;
import java.util.Set;public class StationPermissionInterceptor implements InnerInterceptor {@Overridepublic void beforeQuery(Executor executor, MappedStatement ms, Object parameter, RowBounds rowBounds, ResultHandler resultHandler, BoundSql boundSql) throws SQLException {if (ms.getId().equals("com.zq.mes.craft.mapper.ExecTaskMapper.testPage")) {if (parameter instanceof Map) {Map<?, ?> paramMap = (Map<?, ?>) parameter;Object idValue = paramMap.get("query");TaskIdQuery query = (TaskIdQuery) idValue;Set<Long> taskIds = query.getTaskIds();if (CollectionUtil.isEmpty(taskIds)) {return;}String taskIdsSQL = convertSetToSqlString(taskIds);String originalSql = boundSql.getSql();String whereClause = " WHERE task.task_id IN ( " + taskIdsSQL + " )";String newSql;if (originalSql.contains("WHERE")) {newSql = originalSql.replace("WHERE", whereClause + " AND ");} else if (originalSql.contains("where")) {newSql = originalSql.replace("where", whereClause + " and ");} else {newSql = originalSql + whereClause;}// 使用反射修改SQLReflectUtil.setFieldValue(boundSql, "sql", newSql);}}}public String convertSetToSqlString(Set<Long> ids) {ExpressionList expressionList = new ExpressionList();ids.forEach(id -> expressionList.addExpressions(new LongValue(id)));return expressionList.toString();}
}# MybatisPlus的配置文件，需将StationPermissionInterceptor加入import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.BlockAttackInnerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.OptimisticLockerInnerInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import com.zq.framework.interceptor.StationPermissionInterceptor;
import lombok.RequiredArgsConstructor;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.transaction.annotation.EnableTransactionManagement;/*** MybatisPlus配置** @author zq*/
@EnableTransactionManagement(proxyTargetClass = true)
@Configuration
@RequiredArgsConstructor
public class MybatisPlusConfig {@Beanpublic MybatisPlusInterceptor mybatisPlusInterceptor() {MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();// 分页插件interceptor.addInnerInterceptor(paginationInnerInterceptor());// 乐观锁插件interceptor.addInnerInterceptor(optimisticLockerInnerInterceptor());// 阻断插件interceptor.addInnerInterceptor(blockAttackInnerInterceptor());// 测试自定义interceptor.addInnerInterceptor(new StationPermissionInterceptor());return interceptor;}/*** 分页插件，自动识别数据库类型 https://baomidou.com/guide/interceptor-pagination.html*/public PaginationInnerInterceptor paginationInnerInterceptor() {PaginationInnerInterceptor paginationInnerInterceptor = new PaginationInnerInterceptor();// 设置数据库类型为mysqlpaginationInnerInterceptor.setDbType(DbType.MYSQL);// 设置最大单页限制数量，默认 500 条，-1 不受限制paginationInnerInterceptor.setMaxLimit(-1L);return paginationInnerInterceptor;}/*** 乐观锁插件 https://baomidou.com/guide/interceptor-optimistic-locker.html*/public OptimisticLockerInnerInterceptor optimisticLockerInnerInterceptor() {return new OptimisticLockerInnerInterceptor();}/*** 如果是对全表的删除或更新操作，就会终止该操作 https://baomidou.com/guide/interceptor-block-attack.html*/public BlockAttackInnerInterceptor blockAttackInnerInterceptor() {return new BlockAttackInnerInterceptor();}
}
