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透过源码解决 Seata AT 模式整合 Mybatis-Plus 失去 MP 特性的问题

发布于 2021-05-17 05:09:41 字数 23158 浏览 1245 评论 0 收藏 0

项目地址：https://gitee.com/itCjb/springboot-dubbo-mybatisplus-seata

介绍

Mybatis-Plus：MyBatis-Plus（简称 MP）是一个 MyBatis 的增强工具，在 MyBatis 的基础上只做增强不做改变，为简化开发、提高效率而生。

MP配置：

<bean id="sqlSessionFactory" class="com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
</bean>

Seata：Seata 是一款开源的分布式事务解决方案，致力于提供高性能和简单易用的分布式事务服务。Seata 将为用户提供了 AT、TCC、SAGA 和 XA 事务模式，为用户打造一站式的分布式解决方案。

AT模式机制：

一阶段：业务数据和回滚日志记录在同一个本地事务中提交，释放本地锁和连接资源。
二阶段：
- 提交异步化，非常快速地完成。
- 回滚通过一阶段的回滚日志进行反向补偿。

分析原因

1.首先我们通过介绍，可以看到，mp是需要注册sqlSessionFactory，注入数据源，而Seata是通过代理数据源来保证事务的正常回滚跟提交。

2.我们来看基于seata的官方demo提供的SeataAutoConfig的代码

package org.test.config;
 
import javax.sql.DataSource; 
 
import org.apache.ibatis.session.SqlSessionFactory;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
 
import com.alibaba.druid.pool.DruidDataSource;
import com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean;
 
import io.seata.rm.datasource.DataSourceProxy;
import io.seata.spring.annotation.GlobalTransactionScanner;
 
@Configuration
public class SeataAutoConfig {
	@Autowired(required = true)
	private DataSourceProperties dataSourceProperties;
	private final static Logger logger = LoggerFactory.getLogger(SeataAutoConfig.class);
 
	@Bean(name = "dataSource") // 声明其为Bean实例
	@Primary // 在同样的DataSource中，首先使用被标注的DataSource
	public DataSource druidDataSource() {
		DruidDataSource druidDataSource = new DruidDataSource();
		logger.info("dataSourceProperties.getUrl():{}",dataSourceProperties.getUrl());
		druidDataSource.setUrl(dataSourceProperties.getUrl());
		druidDataSource.setUsername(dataSourceProperties.getUsername());
		druidDataSource.setPassword(dataSourceProperties.getPassword());
		druidDataSource.setDriverClassName(dataSourceProperties.getDriverClassName());
		druidDataSource.setInitialSize(0);
		druidDataSource.setMaxActive(180);
		druidDataSource.setMaxWait(60000);
		druidDataSource.setMinIdle(0);
		druidDataSource.setValidationQuery("Select 1 from DUAL");
		druidDataSource.setTestOnBorrow(false);
		druidDataSource.setTestOnReturn(false);
		druidDataSource.setTestWhileIdle(true);
		druidDataSource.setTimeBetweenEvictionRunsMillis(60000);
		druidDataSource.setMinEvictableIdleTimeMillis(25200000);
		druidDataSource.setRemoveAbandoned(true);
		druidDataSource.setRemoveAbandonedTimeout(1800);
		druidDataSource.setLogAbandoned(true);
		logger.info("装载dataSource........");
		return druidDataSource;
	}
 
	/**
	 * init datasource proxy
	 * 
	 * @Param: druidDataSource datasource bean instance
	 * @Return: DataSourceProxy datasource proxy
	 */
	@Bean
	public DataSourceProxy dataSourceProxy(DataSource dataSource) {
		logger.info("代理dataSource........");
		return new DataSourceProxy(dataSource);
	}
 
	@Bean
	public SqlSessionFactory sqlSessionFactory(DataSourceProxy dataSourceProxy) throws Exception {
		MybatisSqlSessionFactoryBean factory = new MybatisSqlSessionFactoryBean();
		factory.setDataSource(dataSourceProxy);
        factory.setMapperLocations(new PathMatchingResourcePatternResolver()
            .getResources("classpath*:/mapper/*.xml"));
		return factory.getObject();
	}
 
	/**
	 * init global transaction scanner
	 *
	 * @Return: GlobalTransactionScanner
	 */
	@Bean
	public GlobalTransactionScanner globalTransactionScanner() {
		logger.info("配置seata........");
		return new GlobalTransactionScanner("test-service", "test-group");
	}
}

首先看到我们的seata配置数据源的类里,我们配置了一个数据源,然后又配置了一个seata代理datasource的bean,这时候.

然后我们如果直接启动mp整合seata的项目会发现,分页之类的插件会直接失效,连扫描mapper都得从代码上写,这是为什么呢?

通过阅读以上代码,是因为我们另外的配置了一个sqlSessionFactory,导致mp的sqlSessionFactory失效了,这时候我们发现了问题的所在了，即使我们不配置sqlSessionFactoryl，也会因为mp所使用的数据源不是被seata代理过后的数据源，导致分布式事务失效.但是如何解决这个问题呢?

这时候我们需要去阅读mp的源码,找到他的启动类,一看便知

/*
 * Copyright (c) 2011-2020, baomidou (jobob@qq.com).
 * <p>
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * <p>
 * https://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.baomidou.mybatisplus.autoconfigure;
 
 
import com.baomidou.mybatisplus.core.MybatisConfiguration;
import com.baomidou.mybatisplus.core.config.GlobalConfig;
import com.baomidou.mybatisplus.core.handlers.MetaObjectHandler;
import com.baomidou.mybatisplus.core.incrementer.IKeyGenerator;
import com.baomidou.mybatisplus.core.injector.ISqlInjector;
import com.baomidou.mybatisplus.extension.spring.MybatisSqlSessionFactoryBean;
import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.mapping.DatabaseIdProvider;
import org.apache.ibatis.plugin.Interceptor;
import org.apache.ibatis.scripting.LanguageDriver;
import org.apache.ibatis.session.ExecutorType;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.type.TypeHandler;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.mapper.MapperFactoryBean;
import org.mybatis.spring.mapper.MapperScannerConfigurer;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.BeanWrapper;
import org.springframework.beans.BeanWrapperImpl;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.BeanFactoryAware;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.ObjectProvider;
import org.springframework.beans.factory.support.BeanDefinitionBuilder;
import org.springframework.beans.factory.support.BeanDefinitionRegistry;
import org.springframework.boot.autoconfigure.AutoConfigurationPackages;
import org.springframework.boot.autoconfigure.AutoConfigureAfter;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.boot.autoconfigure.condition.ConditionalOnSingleCandidate;
import org.springframework.boot.autoconfigure.jdbc.DataSourceAutoConfiguration;
import org.springframework.boot.context.properties.EnableConfigurationProperties;
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Import;
import org.springframework.context.annotation.ImportBeanDefinitionRegistrar;
import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;
import org.springframework.core.type.AnnotationMetadata;
import org.springframework.util.Assert;
import org.springframework.util.CollectionUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
 
import javax.sql.DataSource;
import java.util.List;
import java.util.Optional;
import java.util.stream.Stream;
 
/**
 * {@link EnableAutoConfiguration Auto-Configuration} for Mybatis. Contributes a
 * {@link SqlSessionFactory} and a {@link SqlSessionTemplate}.
 * <p>
 * If {@link org.mybatis.spring.annotation.MapperScan} is used, or a
 * configuration file is specified as a property, those will be considered,
 * otherwise this auto-configuration will attempt to register mappers based on
 * the interface definitions in or under the root auto-configuration package.
 * </p>
 * <p> copy from {@link org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration}</p>
 *
 * @author Eddú Meléndez
 * @author Josh Long
 * @author Kazuki Shimizu
 * @author Eduardo Macarrón
 */
@Configuration
@ConditionalOnClass({SqlSessionFactory.class, SqlSessionFactoryBean.class})
@ConditionalOnSingleCandidate(DataSource.class)
@EnableConfigurationProperties(MybatisPlusProperties.class)
@AutoConfigureAfter(DataSourceAutoConfiguration.class)
public class MybatisPlusAutoConfiguration implements InitializingBean {
 
    private static final Logger logger = LoggerFactory.getLogger(MybatisPlusAutoConfiguration.class);
 
    private final MybatisPlusProperties properties;
 
    private final Interceptor[] interceptors;
 
    private final TypeHandler[] typeHandlers;
 
    private final LanguageDriver[] languageDrivers;
 
    private final ResourceLoader resourceLoader;
 
    private final DatabaseIdProvider databaseIdProvider;
 
    private final List<ConfigurationCustomizer> configurationCustomizers;
 
    private final List<MybatisPlusPropertiesCustomizer> mybatisPlusPropertiesCustomizers;
 
    private final ApplicationContext applicationContext;
 
 
    public MybatisPlusAutoConfiguration(MybatisPlusProperties properties,
                                        ObjectProvider<Interceptor[]> interceptorsProvider,
                                        ObjectProvider<TypeHandler[]> typeHandlersProvider,
                                        ObjectProvider<LanguageDriver[]> languageDriversProvider,
                                        ResourceLoader resourceLoader,
                                        ObjectProvider<DatabaseIdProvider> databaseIdProvider,
                                        ObjectProvider<List<ConfigurationCustomizer>> configurationCustomizersProvider,
                                        ObjectProvider<List<MybatisPlusPropertiesCustomizer>> mybatisPlusPropertiesCustomizerProvider,
                                        ApplicationContext applicationContext) {
        this.properties = properties;
        this.interceptors = interceptorsProvider.getIfAvailable();
        this.typeHandlers = typeHandlersProvider.getIfAvailable();
        this.languageDrivers = languageDriversProvider.getIfAvailable();
        this.resourceLoader = resourceLoader;
        this.databaseIdProvider = databaseIdProvider.getIfAvailable();
        this.configurationCustomizers = configurationCustomizersProvider.getIfAvailable();
        this.mybatisPlusPropertiesCustomizers = mybatisPlusPropertiesCustomizerProvider.getIfAvailable();
        this.applicationContext = applicationContext;
    }
 
    @Override
    public void afterPropertiesSet() {
        if (!CollectionUtils.isEmpty(mybatisPlusPropertiesCustomizers)) {
            mybatisPlusPropertiesCustomizers.forEach(i -> i.customize(properties));
        }
        checkConfigFileExists();
    }
 
    private void checkConfigFileExists() {
        if (this.properties.isCheckConfigLocation() && StringUtils.hasText(this.properties.getConfigLocation())) {
            Resource resource = this.resourceLoader.getResource(this.properties.getConfigLocation());
            Assert.state(resource.exists(),
                "Cannot find config location: " + resource + " (please add config file or check your Mybatis configuration)");
        }
    }
 
    @SuppressWarnings("SpringJavaInjectionPointsAutowiringInspection")
    @Bean
    @ConditionalOnMissingBean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        // TODO 使用 MybatisSqlSessionFactoryBean 而不是 SqlSessionFactoryBean
        MybatisSqlSessionFactoryBean factory = new MybatisSqlSessionFactoryBean();
        factory.setDataSource(dataSource);
        factory.setVfs(SpringBootVFS.class);
        if (StringUtils.hasText(this.properties.getConfigLocation())) {
            factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));
        }
        applyConfiguration(factory);
        if (this.properties.getConfigurationProperties() != null) {
            factory.setConfigurationProperties(this.properties.getConfigurationProperties());
        }
        if (!ObjectUtils.isEmpty(this.interceptors)) {
            factory.setPlugins(this.interceptors);
        }
        if (this.databaseIdProvider != null) {
            factory.setDatabaseIdProvider(this.databaseIdProvider);
        }
        if (StringUtils.hasLength(this.properties.getTypeAliasesPackage())) {
            factory.setTypeAliasesPackage(this.properties.getTypeAliasesPackage());
        }
        if (this.properties.getTypeAliasesSuperType() != null) {
            factory.setTypeAliasesSuperType(this.properties.getTypeAliasesSuperType());
        }
        if (StringUtils.hasLength(this.properties.getTypeHandlersPackage())) {
            factory.setTypeHandlersPackage(this.properties.getTypeHandlersPackage());
        }
        if (!ObjectUtils.isEmpty(this.typeHandlers)) {
            factory.setTypeHandlers(this.typeHandlers);
        }
        if (!ObjectUtils.isEmpty(this.properties.resolveMapperLocations())) {
            factory.setMapperLocations(this.properties.resolveMapperLocations());
        }
 
        // TODO 对源码做了一定的修改(因为源码适配了老旧的mybatis版本,但我们不需要适配)
        Class<? extends LanguageDriver> defaultLanguageDriver = this.properties.getDefaultScriptingLanguageDriver();
        if (!ObjectUtils.isEmpty(this.languageDrivers)) {
            factory.setScriptingLanguageDrivers(this.languageDrivers);
        }
        Optional.ofNullable(defaultLanguageDriver).ifPresent(factory::setDefaultScriptingLanguageDriver);
 
        // TODO 自定义枚举包
        if (StringUtils.hasLength(this.properties.getTypeEnumsPackage())) {
            factory.setTypeEnumsPackage(this.properties.getTypeEnumsPackage());
        }
        // TODO 此处必为非 NULL
        GlobalConfig globalConfig = this.properties.getGlobalConfig();
        // TODO 注入填充器
        if (this.applicationContext.getBeanNamesForType(MetaObjectHandler.class,
            false, false).length > 0) {
            MetaObjectHandler metaObjectHandler = this.applicationContext.getBean(MetaObjectHandler.class);
            globalConfig.setMetaObjectHandler(metaObjectHandler);
        }
        // TODO 注入主键生成器
        if (this.applicationContext.getBeanNamesForType(IKeyGenerator.class, false,
            false).length > 0) {
            IKeyGenerator keyGenerator = this.applicationContext.getBean(IKeyGenerator.class);
            globalConfig.getDbConfig().setKeyGenerator(keyGenerator);
        }
        // TODO 注入sql注入器
        if (this.applicationContext.getBeanNamesForType(ISqlInjector.class, false,
            false).length > 0) {
            ISqlInjector iSqlInjector = this.applicationContext.getBean(ISqlInjector.class);
            globalConfig.setSqlInjector(iSqlInjector);
        }
        // TODO 设置 GlobalConfig 到 MybatisSqlSessionFactoryBean
        factory.setGlobalConfig(globalConfig);
        return factory.getObject();
    }
 
    // TODO 入参使用 MybatisSqlSessionFactoryBean
    private void applyConfiguration(MybatisSqlSessionFactoryBean factory) {
        // TODO 使用 MybatisConfiguration
        MybatisConfiguration configuration = this.properties.getConfiguration();
        if (configuration == null && !StringUtils.hasText(this.properties.getConfigLocation())) {
            configuration = new MybatisConfiguration();
        }
        if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {
            for (ConfigurationCustomizer customizer : this.configurationCustomizers) {
                customizer.customize(configuration);
            }
        }
        factory.setConfiguration(configuration);
    }
 
    @Bean
    @ConditionalOnMissingBean
    public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
        ExecutorType executorType = this.properties.getExecutorType();
        if (executorType != null) {
            return new SqlSessionTemplate(sqlSessionFactory, executorType);
        } else {
            return new SqlSessionTemplate(sqlSessionFactory);
        }
    }
 
    /**
     * This will just scan the same base package as Spring Boot does. If you want more power, you can explicitly use
     * {@link org.mybatis.spring.annotation.MapperScan} but this will get typed mappers working correctly, out-of-the-box,
     * similar to using Spring Data JPA repositories.
     */
    public static class AutoConfiguredMapperScannerRegistrar implements BeanFactoryAware, ImportBeanDefinitionRegistrar {
 
        private BeanFactory beanFactory;
 
        @Override
        public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {
 
            if (!AutoConfigurationPackages.has(this.beanFactory)) {
                logger.debug("Could not determine auto-configuration package, automatic mapper scanning disabled.");
                return;
            }
 
            logger.debug("Searching for mappers annotated with @Mapper");
 
            List<String> packages = AutoConfigurationPackages.get(this.beanFactory);
            if (logger.isDebugEnabled()) {
                packages.forEach(pkg -> logger.debug("Using auto-configuration base package '{}'", pkg));
            }
 
            BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class);
            builder.addPropertyValue("processPropertyPlaceHolders", true);
            builder.addPropertyValue("annotationClass", Mapper.class);
            builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(packages));
            BeanWrapper beanWrapper = new BeanWrapperImpl(MapperScannerConfigurer.class);
            Stream.of(beanWrapper.getPropertyDescriptors())
                // Need to mybatis-spring 2.0.2+
                .filter(x -> x.getName().equals("lazyInitialization")).findAny()
                .ifPresent(x -> builder.addPropertyValue("lazyInitialization", "${mybatis.lazy-initialization:false}"));
            registry.registerBeanDefinition(MapperScannerConfigurer.class.getName(), builder.getBeanDefinition());
        }
 
        @Override
        public void setBeanFactory(BeanFactory beanFactory) {
            this.beanFactory = beanFactory;
        }
    }
 
    /**
     * If mapper registering configuration or mapper scanning configuration not present, this configuration allow to scan
     * mappers based on the same component-scanning path as Spring Boot itself.
     */
    @Configuration
    @Import(AutoConfiguredMapperScannerRegistrar.class)
    @ConditionalOnMissingBean({MapperFactoryBean.class, MapperScannerConfigurer.class})
    public static class MapperScannerRegistrarNotFoundConfiguration implements InitializingBean {
 
        @Override
        public void afterPropertiesSet() {
            logger.debug(
                "Not found configuration for registering mapper bean using @MapperScan, MapperFactoryBean and MapperScannerConfigurer.");
        }
    }
}

看到mp启动类里的sqlSessionFactory方法了吗,他也是一样的注入一个数据源,这时候大家应该都知道解决方法了吧?

没错,就是把被代理过的数据源给放到mp的sqlSessionFactory中.

很简单,我们需要稍微改动一下我们的seata配置类就行了

package org.test.config;

import javax.sql.DataSource;

import org.mybatis.spring.annotation.MapperScan;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import com.alibaba.druid.pool.DruidDataSource;

import io.seata.rm.datasource.DataSourceProxy;
import io.seata.spring.annotation.GlobalTransactionScanner;

@Configuration
@MapperScan("com.baomidou.springboot.mapper*")
public class SeataAutoConfig {
    @Autowired(required = true)
    private DataSourceProperties dataSourceProperties;
    private final static Logger logger = LoggerFactory.getLogger(SeataAutoConfig.class);
    private DataSourceProxy dataSourceProxy;

    @Bean(name = "dataSource") // 声明其为Bean实例
    @Primary // 在同样的DataSource中，首先使用被标注的DataSource
    public DataSource druidDataSource() {
        DruidDataSource druidDataSource = new DruidDataSource();
        logger.info("dataSourceProperties.getUrl():{}", dataSourceProperties.getUrl());
        druidDataSource.setUrl(dataSourceProperties.getUrl());
        druidDataSource.setUsername(dataSourceProperties.getUsername());
        druidDataSource.setPassword(dataSourceProperties.getPassword());
        druidDataSource.setDriverClassName(dataSourceProperties.getDriverClassName());
        druidDataSource.setInitialSize(0);
        druidDataSource.setMaxActive(180);
        druidDataSource.setMaxWait(60000);
        druidDataSource.setMinIdle(0);
        druidDataSource.setValidationQuery("Select 1 from DUAL");
        druidDataSource.setTestOnBorrow(false);
        druidDataSource.setTestOnReturn(false);
        druidDataSource.setTestWhileIdle(true);
        druidDataSource.setTimeBetweenEvictionRunsMillis(60000);
        druidDataSource.setMinEvictableIdleTimeMillis(25200000);
        druidDataSource.setRemoveAbandoned(true);
        druidDataSource.setRemoveAbandonedTimeout(1800);
        druidDataSource.setLogAbandoned(true);
        logger.info("装载dataSource........");
        dataSourceProxy = new DataSourceProxy(druidDataSource);
        return dataSourceProxy;
    }

    /**
     * init datasource proxy
     * 
     * @Param: druidDataSource datasource bean instance
     * @Return: DataSourceProxy datasource proxy
     */
    @Bean
    public DataSourceProxy dataSourceProxy() {
        logger.info("代理dataSource........");
        return dataSourceProxy;
    }

    /**
     * init global transaction scanner
     *
     * @Return: GlobalTransactionScanner
     */
    @Bean
    public GlobalTransactionScanner globalTransactionScanner() {
        logger.info("配置seata........");
        return new GlobalTransactionScanner("test-service", "test-group");
    }
}

看代码,我们去掉了自己配置的sqlSessionFactory,直接让DataSource bean返回的是一个被代理过的bean,并且我们加入了@Primary,导致mp优先使用我们配置的数据源,这样就解决了mp因为seata代理了数据源跟创建了新的sqlSessionFactory,导致mp的插件,组件失效的bug了!