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在Spring Boot中，MyBatis插件机制通过拦截器（Interceptor）来实现。拦截器允许开发人员在执行SQL语句的各个阶段（如SQL语句创建、参数处理、结果映射等）插入自定义逻辑。MyBatis的拦截器主要用于增强MyBatis的功能，如日志记录、性能监控、实现分页、数据权限控制、SQL日志、动态SQL生成等，在SQL执行之前后，提供了四个拦截点，在方法执行前后进行处理，支持不同场景的功能扩展。

@Signature参数说明

Executor接口中常见的方法

Mybatis拦截器的实现原理

@Intercepts({@Signature(type = Executor.class, method = "update", args = {MappedStatement.class, Object.class}),@Signature(type = Executor.class, method = "query", args = {MappedStatement.class, Object.class, RowBounds.class, ResultHandler.class})
})
public class MyInterceptor implements Interceptor {...
}

1 实现代码

import java.text.DateFormat;
import lombok.extern.slf4j.Slf4j;import cn.hutool.core.collection.CollUtil;import java.util.Date;
import java.util.List;
import java.util.Locale;
import java.util.Properties;
import java.util.regex.Matcher;import java.sql.Connection;import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
import org.springframework.stereotype.Component;import org.apache.ibatis.executor.statement.StatementHandler;
import org.apache.ibatis.mapping.BoundSql;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ParameterMapping;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.plugin.Intercepts;
import org.apache.ibatis.plugin.Invocation;
import org.apache.ibatis.plugin.Plugin;
import org.apache.ibatis.plugin.Signature;
import org.apache.ibatis.reflection.DefaultReflectorFactory;
import org.apache.ibatis.reflection.MetaObject;
import org.apache.ibatis.reflection.SystemMetaObject;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.type.TypeHandlerRegistry;@Slf4j
@Component
@ConditionalOnProperty(prefix = "mybatis-plus", name = "customer-log", havingValue = "true")
@Intercepts({@Signature(type = StatementHandler.class, method = "prepare", args = {Connection.class, Integer.class})})
public class MybatisLogger implements Interceptor {@Overridepublic Object intercept(Invocation invocation) throws Throwable {StatementHandler handler = (StatementHandler) invocation.getTarget();MetaObject object = MetaObject.forObject(handler,SystemMetaObject.DEFAULT_OBJECT_FACTORY,SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY,new DefaultReflectorFactory());MappedStatement statement = (MappedStatement) object.getValue("delegate.mappedStatement");log.info("SQL执行类: {}", statement.getId());log.info("SQL执行类型: {}", statement.getSqlCommandType().toString());BoundSql bound = handler.getBoundSql();Configuration configuration = statement.getConfiguration();String sql = getFullSql(configuration, bound);log.info("SQL语句: {}", sql);long start = System.currentTimeMillis();Object value = invocation.proceed();long end = System.currentTimeMillis();log.info("SQL耗时: {}", (end - start));return value;}@Overridepublic Object plugin(Object target) {return Plugin.wrap(target, this);}@Overridepublic void setProperties(Properties properties) {// 可以通过MyBatis配置文件或注解传递属性}public String getFullSql(Configuration conf, BoundSql bound) {Object object = bound.getParameterObject();List<ParameterMapping> list = bound.getParameterMappings();String sql = bound.getSql().replaceAll("[\\s]+", " ").toLowerCase(Locale.ROOT);if (CollUtil.isNotEmpty(list) && object != null) {TypeHandlerRegistry type = conf.getTypeHandlerRegistry();if (type.hasTypeHandler(object.getClass())) {sql = sql.replaceFirst("\\?", Matcher.quoteReplacement(getParaValue(object)));} else {MetaObject meta = conf.newMetaObject(object);for (ParameterMapping parameterMapping : list) {String name = parameterMapping.getProperty();if (meta.hasGetter(name)) {Object obj = meta.getValue(name);sql = sql.replaceFirst("\\?", Matcher.quoteReplacement(getParaValue(obj)));} else if (bound.hasAdditionalParameter(name)) {Object obj = bound.getAdditionalParameter(name);sql = sql.replaceFirst("\\?", Matcher.quoteReplacement(getParaValue(obj)));} else {sql = sql.replaceFirst("\\?", "缺失");}}}}return sql;}private String getParaValue(Object obj) {if (obj instanceof String) {return "'" + obj + "'";} else if (obj instanceof Date) {DateFormat formatter = DateFormat.getDateTimeInstance(DateFormat.DEFAULT, DateFormat.DEFAULT, Locale.CHINA);return "'" + formatter.format(new Date()) + "'";} else {if (obj != null) {return obj.toString();} else {return "";}}}}

2 测试结果

Closing non transactional SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@264df4aa]
Creating a new SqlSession
SqlSession [org.apache.ibatis.session.defaults.DefaultSqlSession@d91483c] was not registered for synchronization because synchronization is not active
JDBC Connection [com.alibaba.druid.proxy.jdbc.ConnectionProxyImpl@44d84b5a] will not be managed by Spring
2024-07-05 16:32:27.660  INFO 3264 --- [nio-8221-exec-1] com.xu.hander.MybatisLogger   : SQL执行类: com.xu.view.mapper.StudentMapper.selectOne
2024-07-05 16:32:27.660  INFO 3264 --- [nio-8221-exec-1] com.xu.hander.MybatisLogger   : SQL执行类型: SELECT
2024-07-05 16:32:27.660  INFO 3264 --- [nio-8221-exec-1] com.xu.hander.MybatisLogger   : SQL语句: select id,create_by,create_time,create_hour,create_date,update_by,update_time,tenant_id,user_id,cus_id,page,number,is_share,time,event from student where (cus_id = 3 and page = 3 and event = 5) order by create_time desc limit 1
2024-07-05 16:32:27.663  INFO 3264 --- [nio-8221-exec-1] com.xu.hander.MybatisLogger   : SQL耗时: 3