修改Mybatis-Plus源码利用反射支持Seata代理数据源

准备工作

1.拉取mybatisplus项目源码

开始

1.阅读mp的启动类源码

/*
 * Copyright (c) 2011-2020, baomidou ([email protected]).
 * 

 * 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
 * 

 * https://www.apache.org/licenses/LICENSE-2.0
 * 

 * 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}.
 * 

 * 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.
 * 
 * 
 copy from {@link org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration}
 *
 * @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 configurationCustomizers;

    private final List mybatisPlusPropertiesCustomizers;

    private final ApplicationContext applicationContext;


    public MybatisPlusAutoConfiguration(MybatisPlusProperties properties,
                                        ObjectProvider interceptorsProvider,
                                        ObjectProvider typeHandlersProvider,
                                        ObjectProvider languageDriversProvider,
                                        ResourceLoader resourceLoader,
                                        ObjectProvider databaseIdProvider,
                                        ObjectProvider> configurationCustomizersProvider,
                                        ObjectProvider> 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 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 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.");
        }
    }
}

2.找到创建sqlSessionFactory的方法

    @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 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();
    }

3.修改注入DataSource处的代码:

    @SuppressWarnings("SpringJavaInjectionPointsAutowiringInspection")
    @Bean
    @ConditionalOnMissingBean
    public SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {
        // TODO 使用 MybatisSqlSessionFactoryBean 而不是 SqlSessionFactoryBean
        MybatisSqlSessionFactoryBean factory = new MybatisSqlSessionFactoryBean();
        try {
            Constructor dataSourceProxy = Class.forName("io.seata.rm.datasource.DataSourceProxy").getConstructor(DataSource.class);
            dataSource = (DataSource)dataSourceProxy.newInstance(dataSource);
        } catch (Exception e) {
        }
        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 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
        this.getBeanThen(MetaObjectHandler.class, globalConfig::setMetaObjectHandler);
        // TODO 注入主键生成器
        this.getBeanThen(IKeyGenerator.class, i -> globalConfig.getDbConfig().setKeyGenerator(i));
        // TODO 注入sql注入器
        this.getBeanThen(ISqlInjector.class, globalConfig::setSqlInjector);
        // TODO 注入ID生成器
        this.getBeanThen(IdentifierGenerator.class, globalConfig::setIdentifierGenerator);
        // TODO 设置 GlobalConfig 到 MybatisSqlSessionFactoryBean
        factory.setGlobalConfig(globalConfig);
        return factory.getObject();
    }

5.打包发往自己的私服使用(此处不再说明)

总结

要点代码:

        try {
            Constructor dataSourceProxy = Class.forName("io.seata.rm.datasource.DataSourceProxy").getConstructor(DataSource.class);
            dataSource = (DataSource)dataSourceProxy.newInstance(dataSource);
        } catch (Exception e) {
        }

其实就是利用反射来查看seata的DataSourceProxy类是否存在,存在我们就把mp准备注入的datasource改为被seata代理过后的,这样就可保障seataAT模式在二阶段执行回滚提交等操作正常使用