MyBatis 教程 - MyBatis插件（Plugins）开发

2019-11-08 03:07:35

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MyBatis 允许你在已映射语句执行过程中的某一点进行拦截调用。默认情况下，MyBatis 允许使用插件来拦截的方法调用包括：

Executor (update, query, flushStatements, commit, rollback, getTransaction, close, isClosed)ParameterHandler (getParameterObject, setParameters)ResultSetHandler (handleResultSets, handleOutputParameters)StatementHandler (PRepare, parameterize, batch, update, query)

这些类中方法的细节可以通过查看每个方法的签名来发现，或者直接查看 MyBatis 的发行包中的源代码。假设你想做的不仅仅是监控方法的调用，那么你应该很好的了解正在重写的方法的行为。因为如果在试图修改或重写已有方法的行为的时候，你很可能在破坏 MyBatis 的核心模块。这些都是更低层的类和方法，所以使用插件的时候要特别当心。

通过 MyBatis 提供的强大机制，使用插件是非常简单的，只需实现 Interceptor 接口，并指定了想要拦截的方法签名即可。

自定义插件

需求：

把Mybatis所有执行的sql都记录下来。

代码实现

通过对 MyBatis org.apache.ibatis.executor.statementStatementHandler 中的prepare 方法进行拦截即可。

prepare 方法签名如下：

Statement prepare(Connection connection, Integer transactionTimeout) throws SQLException;

自定义一个类，实现 org.apache.ibatis.pluginInterceptor 接口，代码如下：

package com.bytebeats.mybatis3.interceptor;import org.apache.ibatis.executor.statement.StatementHandler;import org.apache.ibatis.mapping.BoundSql;import org.apache.ibatis.plugin.*;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import java.sql.Connection;import java.util.Properties;/** * ${DESCRipTION} * * @author Ricky Fung * @date 2017-02-17 11:52 */@Intercepts({ @Signature(type = StatementHandler.class, method = "prepare", args = { Connection.class, Integer.class}) })public class SQLStatsInterceptor implements Interceptor { private final Logger logger = LoggerFactory.getLogger(this.getClass()); @Override public Object intercept(Invocation invocation) throws Throwable { StatementHandler statementHandler = (StatementHandler) invocation.getTarget(); BoundSql boundSql = statementHandler.getBoundSql(); String sql = boundSql.getSql(); logger.info("mybatis intercept sql:{}", sql); return invocation.proceed(); } @Override public Object plugin(Object target) { return Plugin.wrap(target, this); } @Override public void setProperties(Properties properties) { String dialect = properties.getProperty("dialect"); logger.info("mybatis intercept dialect:{}", dialect); }}

这样一个插件就开发完成了，接下来需要在 mybatis-config.xml 文件中增加 plugins节点，完整配置如下：

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration> <plugins> <plugin interceptor="com.bytebeats.mybatis3.interceptor.SQLStatsInterceptor"> <property name="dialect" value="MySQL" /> </plugin> </plugins></configuration>

spring-mybatis.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:context="http://www.springframework.org/schema/context" xmlns:util="http://www.springframework.org/schema/util" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd"> <util:properties id="db" location="classpath:db.properties"/>  <bean name="parentDatasource" abstract="true" class="com.alibaba.druid.pool.DruidDataSource">  <property name="initialSize" value="1" />  <property name="maxActive" value="100" />  <property name="minIdle" value="20" />  <property name="maxWait" value="30000" /> <property name="validationQuery" value="SELECT 1" /> <property name="testOnBorrow" value="true" /> <property name="testOnReturn" value="true" /> <property name="testWhileIdle" value="true" />  <property name="timeBetweenEvictionRunsMillis" value="60000" />  <property name="minEvictableIdleTimeMillis" value="25200000" />  <property name="removeAbandoned" value="true" />  <property name="removeAbandonedTimeout" value="1800" />  <property name="logAbandoned" value="true" />  <property name="filters" value="mergeStat" /> </bean>  <bean name="trade" init-method="init" destroy-method="close" parent="parentDatasource"> <property name="driverClassName" value="#{db['trade.jdbc.driverClassName']}" /> <property name="url" value="#{db['trade.jdbc.url']}" /> <property name="username" value="#{db['trade.jdbc.username']}" /> <property name="passWord" value="#{db['trade.jdbc.password']}" /> </bean>  <bean name="admin" init-method="init" destroy-method="close" parent="parentDatasource"> <property name="driverClassName" value="#{db['admin.jdbc.driverClassName']}" /> <property name="url" value="#{db['admin.jdbc.url']}" /> <property name="username" value="#{db['admin.jdbc.username']}" /> <property name="password" value="#{db['admin.jdbc.password']}" /> </bean>  <bean id="tradeSqlsessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="dataSource" ref="trade" /> <property name="mapperLocations" value="classpath*:mapper/trade/*Mapper.xml" /> <property name="configLocation" value="classpath:mybatis-config.xml" /> <property name="typeAliasesPackage" value="com.bytebeats.mybatis3.domain.trade" /> </bean> <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"> <property name="basePackage" value="com.bytebeats.mybatis3.mapper.trade" /> <property name="sqlSessionFactoryBeanName" value="tradeSqlSessionFactory" /> </bean>  <bean id="adminSqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"> <property name="dataSource" ref="admin" /> <property name="mapperLocations" value="classpath*:mapper/admin/*Mapper.xml" /> <property name="typeAliasesPackage" value="com.bytebeats.mybatis3.domain.admin" /> </bean> <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"> <property name="basePackage" value="com.bytebeats.mybatis3.mapper.admin" /> <property name="sqlSessionFactoryBeanName" value="adminSqlSessionFactory" /> </bean>  <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"> <property name="dataSource" ref="trade" /> </bean> <tx:annotation-driven transaction-manager="transactionManager" /></beans>

maven依赖

<properties> <java.version>1.7</java.version> <spring.version>4.2.7.RELEASE</spring.version> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> </properties> <dependencies>  <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> <exclusions> <exclusion> <artifactId>commons-logging</artifactId> <groupId>commons-logging</groupId> </exclusion> </exclusions> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context-support</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-webmvc</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-tx</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-jdbc</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>javax.servlet</groupId> <artifactId>javax.servlet-api</artifactId> <version>3.1.0</version> </dependency>  <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.26</version> </dependency> <dependency> <groupId>com.alibaba</groupId> <artifactId>druid</artifactId> <version>1.0.25</version> </dependency>  <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.4.1</version> </dependency> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis-spring</artifactId> <version>1.3.0</version> </dependency>  <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>1.7.21</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>log4j-over-slf4j</artifactId> <version>1.7.21</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>jcl-over-slf4j</artifactId> <version>1.7.21</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-core</artifactId> <version>1.1.7</version> </dependency> <dependency> <groupId>ch.qos.logback</groupId> <artifactId>logback-classic</artifactId> <version>1.1.7</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>${junit.version}</version> <scope>test</scope> </dependency> </dependencies>