Mybatis-plus 源码解读

简述

本篇主要针对MybatisPlus源码进行解读。

案例

上一篇已经讲了Springboot如何集成MybatisPlus：
springboot-mybatis-plus集成篇

源码解析

和Springboot集成Mybatis一样，

依赖了mybatis-plus-spring-boot3-starter，其中主要关注spring.factories和org.springframework.boot.autoconfigure.AutoConfiguration.imports

spring.factories

# Auto Configure
org.springframework.boot.env.EnvironmentPostProcessor=\com.baomidou.mybatisplus.autoconfigure.SafetyEncryptProcessor
org.springframework.boot.autoconfigure.EnableAutoConfiguration=\com.baomidou.mybatisplus.autoconfigure.MybatisPlusInnerInterceptorAutoConfiguration,\com.baomidou.mybatisplus.autoconfigure.IdentifierGeneratorAutoConfiguration,\com.baomidou.mybatisplus.autoconfigure.MybatisPlusLanguageDriverAutoConfiguration,\com.baomidou.mybatisplus.autoconfigure.MybatisPlusAutoConfiguration,\com.baomidou.mybatisplus.autoconfigure.DdlAutoConfiguration
# Depends On Database Initialization Detectors
org.springframework.boot.sql.init.dependency.DependsOnDatabaseInitializationDetector=\
com.baomidou.mybatisplus.autoconfigure.MybatisDependsOnDatabaseInitializationDetector

org.springframework.boot.autoconfigure.AutoConfiguration.imports

com.baomidou.mybatisplus.autoconfigure.MybatisPlusInnerInterceptorAutoConfiguration
com.baomidou.mybatisplus.autoconfigure.IdentifierGeneratorAutoConfiguration
com.baomidou.mybatisplus.autoconfigure.MybatisPlusLanguageDriverAutoConfiguration
com.baomidou.mybatisplus.autoconfigure.MybatisPlusAutoConfiguration
com.baomidou.mybatisplus.autoconfigure.DdlAutoConfiguration

MybatisPlusInnerInterceptorAutoConfiguration：拦截器自动配置，主要用来扩展插件功能，例如mybatis分页组件，mybatis-plus中的租户组件
MybatisPlusAutoConfiguration: 这个自动配置类和Mybatis-starter中的MybatisAutoConfiguration功能作用是一样的

MybatisPlusInnerInterceptorAutoConfiguration.java

@Configuration(proxyBeanMethods = false
)
@ConditionalOnBean({InnerInterceptor.class})
@ConditionalOnMissingBean({MybatisPlusInterceptor.class})
public class MybatisPlusInnerInterceptorAutoConfiguration {public MybatisPlusInnerInterceptorAutoConfiguration() {}@Beanpublic MybatisPlusInterceptor defaultMybatisPlusInterceptor(List<InnerInterceptor> innerInterceptorList) {MybatisPlusInterceptor plusInterceptor = new MybatisPlusInterceptor();plusInterceptor.setInterceptors(innerInterceptorList);return plusInterceptor;}
}

MybatisAutoConfiguration.java

Configuration(proxyBeanMethods = false)
@ConditionalOnClass({SqlSessionFactory.class, SqlSessionFactoryBean.class})
@ConditionalOnSingleCandidate(DataSource.class)
@EnableConfigurationProperties(MybatisPlusProperties.class)
@AutoConfigureAfter({DataSourceAutoConfiguration.class, MybatisPlusLanguageDriverAutoConfiguration.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<SqlSessionFactoryBeanCustomizer> sqlSessionFactoryBeanCustomizers;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<SqlSessionFactoryBeanCustomizer>> sqlSessionFactoryBeanCustomizers,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.sqlSessionFactoryBeanCustomizers = sqlSessionFactoryBeanCustomizers.getIfAvailable();this.mybatisPlusPropertiesCustomizers = mybatisPlusPropertiesCustomizerProvider.getIfAvailable();this.applicationContext = applicationContext;}@Overridepublic 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)");}}/*** 和Springboot集成Mybatis很相似，需要定义SqlSessionFactory Bean* @param dataSource* @return* @throws Exception*/@Bean@ConditionalOnMissingBeanpublic SqlSessionFactory sqlSessionFactory(DataSource dataSource) throws Exception {// MybatisPlus自定义了MybatisSqlSessionFactoryBeanMybatisSqlSessionFactoryBean factory = new MybatisSqlSessionFactoryBean();factory.setDataSource(dataSource);factory.setVfs(SpringBootVFS.class);if (StringUtils.hasText(this.properties.getConfigLocation())) {factory.setConfigLocation(this.resourceLoader.getResource(this.properties.getConfigLocation()));}// 应用Mybatis相关配置，这里和Mybatis是有一些区别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());}this.getBeanThen(TransactionFactory.class, factory::setTransactionFactory);Class<? extends LanguageDriver> defaultLanguageDriver = this.properties.getDefaultScriptingLanguageDriver();if (!ObjectUtils.isEmpty(this.languageDrivers)) {factory.setScriptingLanguageDrivers(this.languageDrivers);}Optional.ofNullable(defaultLanguageDriver).ifPresent(factory::setDefaultScriptingLanguageDriver);applySqlSessionFactoryBeanCustomizers(factory);// 增加了全局配置GlobalConfig globalConfig = this.properties.getGlobalConfig();this.getBeanThen(MetaObjectHandler.class, globalConfig::setMetaObjectHandler);this.getBeanThen(AnnotationHandler.class, globalConfig::setAnnotationHandler);this.getBeanThen(PostInitTableInfoHandler.class, globalConfig::setPostInitTableInfoHandler);this.getBeansThen(IKeyGenerator.class, i -> globalConfig.getDbConfig().setKeyGenerators(i));this.getBeanThen(ISqlInjector.class, globalConfig::setSqlInjector);this.getBeanThen(IdentifierGenerator.class, globalConfig::setIdentifierGenerator);factory.setGlobalConfig(globalConfig);return factory.getObject();}/*** 检查spring容器里是否有对应的bean,有则进行消费** @param clazz    class* @param consumer 消费* @param <T>      泛型*/private <T> void getBeanThen(Class<T> clazz, Consumer<T> consumer) {if (this.applicationContext.getBeanNamesForType(clazz, false, false).length > 0) {consumer.accept(this.applicationContext.getBean(clazz));}}/*** 检查spring容器里是否有对应的bean,有则进行消费** @param clazz    class* @param consumer 消费* @param <T>      泛型*/private <T> void getBeansThen(Class<T> clazz, Consumer<List<T>> consumer) {if (this.applicationContext.getBeanNamesForType(clazz, false, false).length > 0) {final Map<String, T> beansOfType = this.applicationContext.getBeansOfType(clazz);List<T> clazzList = new ArrayList<>();beansOfType.forEach((k, v) -> clazzList.add(v));consumer.accept(clazzList);}}private void applyConfiguration(MybatisSqlSessionFactoryBean factory) {MybatisPlusProperties.CoreConfiguration coreConfiguration = this.properties.getConfiguration();MybatisConfiguration configuration = null;// 如果没有相关Mybatis配置文件，则使用MybatisPlus自定的MybatisConfiguration配置，而MybatisConfiguration是继承Configuration类if (coreConfiguration != null || !StringUtils.hasText(this.properties.getConfigLocation())) {configuration = new MybatisConfiguration();}if (configuration != null && coreConfiguration != null) {// 增加mybatisPlus核心配置coreConfiguration.applyTo(configuration);}if (configuration != null && !CollectionUtils.isEmpty(this.configurationCustomizers)) {for (ConfigurationCustomizer customizer : this.configurationCustomizers) {customizer.customize(configuration);}}factory.setConfiguration(configuration);}private void applySqlSessionFactoryBeanCustomizers(MybatisSqlSessionFactoryBean factory) {if (!CollectionUtils.isEmpty(this.sqlSessionFactoryBeanCustomizers)) {for (SqlSessionFactoryBeanCustomizer customizer : this.sqlSessionFactoryBeanCustomizers) {customizer.customize(factory);}}}@Bean@ConditionalOnMissingBeanpublic SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {ExecutorType executorType = this.properties.getExecutorType();if (executorType != null) {return new SqlSessionTemplate(sqlSessionFactory, executorType);} else {return new SqlSessionTemplate(sqlSessionFactory);}}/*** 自动扫描器和Mybatis的相似，扫描Mapper，自动注入SpringContext，不过Mapper自动扫描出来代理生成的Bean是MybatisSqlSessionFactoryBean类型的，* 而不是之前Mybatis中的SqlSessionFactoryBean，这是区别* 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 AutoConfiguredMapperScannerRegistrarimplements BeanFactoryAware, EnvironmentAware, ImportBeanDefinitionRegistrar {private BeanFactory beanFactory;private Environment environment;@Overridepublic 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);Set<String> propertyNames = Stream.of(beanWrapper.getPropertyDescriptors()).map(PropertyDescriptor::getName).collect(Collectors.toSet());if (propertyNames.contains("lazyInitialization")) {// Need to mybatis-spring 2.0.2+builder.addPropertyValue("lazyInitialization", "${mybatis-plus.lazy-initialization:${mybatis.lazy-initialization:false}}");}if (propertyNames.contains("defaultScope")) {// Need to mybatis-spring 2.0.6+builder.addPropertyValue("defaultScope", "${mybatis-plus.mapper-default-scope:}");}// for spring-nativeBoolean injectSqlSession = environment.getProperty("mybatis-plus.inject-sql-session-on-mapper-scan", Boolean.class);if (injectSqlSession == null) {injectSqlSession = environment.getProperty("mybatis.inject-sql-session-on-mapper-scan", Boolean.class, Boolean.TRUE);}if (injectSqlSession && this.beanFactory instanceof ListableBeanFactory) {ListableBeanFactory listableBeanFactory = (ListableBeanFactory) this.beanFactory;Optional<String> sqlSessionTemplateBeanName = Optional.ofNullable(getBeanNameForType(SqlSessionTemplate.class, listableBeanFactory));// 获取MybatisPlus定义的SqlSessionFactory，其中的sqlSessionFactoryBeanName=MybatisSqlSessionFactoryBeanOptional<String> sqlSessionFactoryBeanName = Optional.ofNullable(getBeanNameForType(SqlSessionFactory.class, listableBeanFactory));if (sqlSessionTemplateBeanName.isPresent() || !sqlSessionFactoryBeanName.isPresent()) {builder.addPropertyValue("sqlSessionTemplateBeanName",sqlSessionTemplateBeanName.orElse("sqlSessionTemplate"));} else {builder.addPropertyValue("sqlSessionFactoryBeanName", sqlSessionFactoryBeanName.get());}}builder.setRole(BeanDefinition.ROLE_INFRASTRUCTURE);registry.registerBeanDefinition(MapperScannerConfigurer.class.getName(), builder.getBeanDefinition());}@Overridepublic void setBeanFactory(BeanFactory beanFactory) {this.beanFactory = beanFactory;}@Overridepublic void setEnvironment(Environment environment) {this.environment = environment;}private String getBeanNameForType(Class<?> type, ListableBeanFactory factory) {String[] beanNames = factory.getBeanNamesForType(type);return beanNames.length > 0 ? beanNames[0] : null;}}/*** 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.*/@org.springframework.context.annotation.Configuration(proxyBeanMethods = false)@Import(AutoConfiguredMapperScannerRegistrar.class)@ConditionalOnMissingBean({MapperFactoryBean.class, MapperScannerConfigurer.class})public static class MapperScannerRegistrarNotFoundConfiguration implements InitializingBean {@Overridepublic void afterPropertiesSet() {logger.debug("Not found configuration for registering mapper bean using @MapperScan, MapperFactoryBean and MapperScannerConfigurer.");}}}

MapperFactoryBean.java

public class MapperFactoryBean<T> extends SqlSessionDaoSupport implements FactoryBean<T> {private Class<T> mapperInterface;private boolean addToConfig = true;public MapperFactoryBean() {}public MapperFactoryBean(Class<T> mapperInterface) {this.mapperInterface = mapperInterface;}protected void checkDaoConfig() {super.checkDaoConfig();Assert.notNull(this.mapperInterface, "Property 'mapperInterface' is required");Configuration configuration = this.getSqlSession().getConfiguration();if (this.addToConfig && !configuration.hasMapper(this.mapperInterface)) {try {// 这个是MybatisConfigurationconfiguration.addMapper(this.mapperInterface);} catch (Exception var6) {this.logger.error("Error while adding the mapper '" + this.mapperInterface + "' to configuration.", var6);throw new IllegalArgumentException(var6);} finally {ErrorContext.instance().reset();}}}public T getObject() throws Exception {return this.getSqlSession().getMapper(this.mapperInterface);}public Class<T> getObjectType() {return this.mapperInterface;}public boolean isSingleton() {return true;}public void setMapperInterface(Class<T> mapperInterface) {this.mapperInterface = mapperInterface;}public Class<T> getMapperInterface() {return this.mapperInterface;}public void setAddToConfig(boolean addToConfig) {this.addToConfig = addToConfig;}public boolean isAddToConfig() {return this.addToConfig;}
}

MybatisConfiguration.java

/** Copyright (c) 2011-2024, baomidou (jobob@qq.com).** 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**     http://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.core;import com.baomidou.mybatisplus.core.handlers.CompositeEnumTypeHandler;
import com.baomidou.mybatisplus.core.mapper.Mapper;
import com.baomidou.mybatisplus.core.metadata.TableInfoHelper;
import com.baomidou.mybatisplus.core.toolkit.GlobalConfigUtils;
import com.baomidou.mybatisplus.core.toolkit.ReflectionKit;
import com.baomidou.mybatisplus.core.toolkit.StringPool;
import lombok.Getter;
import lombok.Setter;
import org.apache.ibatis.binding.MapperRegistry;
import org.apache.ibatis.cache.Cache;
import org.apache.ibatis.executor.Executor;
import org.apache.ibatis.executor.keygen.KeyGenerator;
import org.apache.ibatis.logging.Log;
import org.apache.ibatis.logging.LogFactory;
import org.apache.ibatis.mapping.Environment;
import org.apache.ibatis.mapping.MappedStatement;
import org.apache.ibatis.mapping.ParameterMap;
import org.apache.ibatis.mapping.ResultMap;
import org.apache.ibatis.parsing.XNode;
import org.apache.ibatis.scripting.LanguageDriver;
import org.apache.ibatis.session.Configuration;
import org.apache.ibatis.session.ExecutorType;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.transaction.Transaction;
import org.apache.ibatis.type.TypeHandler;import java.util.Collection;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.BiFunction;
import java.util.stream.Collectors;/*** replace default Configuration class* <p>Caratacus 2016/9/25 replace mapperRegistry</p>** @author hubin* @since 2016-01-23*/
public class MybatisConfiguration extends Configuration {private static final Log logger = LogFactory.getLog(MybatisConfiguration.class);/*** Mapper 注册*/protected final MybatisMapperRegistry mybatisMapperRegistry = new MybatisMapperRegistry(this);protected final Map<String, Cache> caches = new StrictMap<>("Caches collection");protected final Map<String, ResultMap> resultMaps = new StrictMap<>("Result Maps collection");protected final Map<String, ParameterMap> parameterMaps = new StrictMap<>("Parameter Maps collection");protected final Map<String, KeyGenerator> keyGenerators = new StrictMap<>("Key Generators collection");protected final Map<String, XNode> sqlFragments = new StrictMap<>("XML fragments parsed from previous mappers");protected final Map<String, MappedStatement> mappedStatements = new StrictMap<MappedStatement>("Mapped Statements collection").conflictMessageProducer((savedValue, targetValue) ->". please check " + savedValue.getResource() + " and " + targetValue.getResource());/*** 是否生成短key缓存** @since 3.4.0*/@Setter@Getterprivate boolean useGeneratedShortKey = true;public MybatisConfiguration(Environment environment) {this();this.environment = environment;}/*** 初始化调用*/public MybatisConfiguration() {super();this.mapUnderscoreToCamelCase = true;typeHandlerRegistry.setDefaultEnumTypeHandler(CompositeEnumTypeHandler.class);languageRegistry.setDefaultDriverClass(MybatisXMLLanguageDriver.class);}/*** MybatisPlus 加载 SQL 顺序：* <p> 1、加载 XML中的 SQL </p>* <p> 2、加载 SqlProvider 中的 SQL </p>* <p> 3、XmlSql 与 SqlProvider不能包含相同的 SQL </p>* <p>调整后的 SQL优先级：XmlSql > sqlProvider > CurdSql </p>*/@Overridepublic void addMappedStatement(MappedStatement ms) {if (mappedStatements.containsKey(ms.getId())) {/** 说明已加载了xml中的节点； 忽略mapper中的 SqlProvider 数据*/logger.error("mapper[" + ms.getId() + "] is ignored, because it exists, maybe from xml file");return;}mappedStatements.put(ms.getId(), ms);}/*** 使用自己的 MybatisMapperRegistry*/@Overridepublic MapperRegistry getMapperRegistry() {return mybatisMapperRegistry;}/*** 使用自己的 MybatisMapperRegistry*/@Overridepublic <T> void addMapper(Class<T> type) {mybatisMapperRegistry.addMapper(type);}/*** 新增注入新的 Mapper 信息，新增前会清理之前的缓存信息** @param type Mapper Type* @deprecated 3.5.8 不建议在实际生产环境中使用.*/@Deprecatedpublic <T> void addNewMapper(Class<T> type) {this.removeMapper(type);this.addMapper(type);}/*** 移除 Mapper 相关缓存，支持 GroovyClassLoader 动态注入 Mapper** @param type Mapper Type* @deprecated 3.5.8 不建议在实际生产环境中使用.*/@Deprecatedpublic <T> void removeMapper(Class<T> type) {Set<String> mapperRegistryCache = GlobalConfigUtils.getGlobalConfig(this).getMapperRegistryCache();final String mapperType = type.toString();if (mapperRegistryCache.contains(mapperType)) {// 清空实体表信息映射信息TableInfoHelper.remove(ReflectionKit.getSuperClassGenericType(type, Mapper.class, 0));// 清空 Mapper 缓存信息this.mybatisMapperRegistry.removeMapper(type);this.loadedResources.remove(type.toString());this.loadedResources.remove(type.getName().replace(StringPool.DOT, StringPool.SLASH) + ".xml");mapperRegistryCache.remove(mapperType);// 清空 Mapper 方法 mappedStatement 缓存信息String typeKey = type.getName() + StringPool.DOT;String simpleName = type.getSimpleName();mappedStatements.keySet().stream().filter(ms -> ms.startsWith(typeKey) || ms.equals(simpleName)).collect(Collectors.toSet()).forEach(mappedStatements::remove);resultMaps.keySet().stream().filter(r -> r.startsWith(typeKey)).collect(Collectors.toSet()).forEach(resultMaps::remove);parameterMaps.keySet().stream().filter(p -> p.startsWith(typeKey)).collect(Collectors.toSet()).forEach(parameterMaps::remove);keyGenerators.keySet().stream().filter(k -> k.startsWith(typeKey)).collect(Collectors.toSet()).forEach(keyGenerators::remove);sqlFragments.keySet().stream().filter(s -> s.startsWith(typeKey)).collect(Collectors.toSet()).forEach(sqlFragments::remove);caches.keySet().stream().filter(p -> p.equals(type.getName()) || p.equals(simpleName)).collect(Collectors.toSet()).forEach(caches::remove);}}/*** 使用自己的 MybatisMapperRegistry*/@Overridepublic void addMappers(String packageName, Class<?> superType) {mybatisMapperRegistry.addMappers(packageName, superType);}/*** 使用自己的 MybatisMapperRegistry*/@Overridepublic void addMappers(String packageName) {mybatisMapperRegistry.addMappers(packageName);}/*** 使用自己的 MybatisMapperRegistry*/@Overridepublic <T> T getMapper(Class<T> type, SqlSession sqlSession) {return mybatisMapperRegistry.getMapper(type, sqlSession);}/*** 使用自己的 MybatisMapperRegistry*/@Overridepublic boolean hasMapper(Class<?> type) {return mybatisMapperRegistry.hasMapper(type);}/*** 指定动态SQL生成的默认语言** @param driver LanguageDriver*/@Overridepublic void setDefaultScriptingLanguage(Class<? extends LanguageDriver> driver) {if (driver == null) {driver = MybatisXMLLanguageDriver.class;}getLanguageRegistry().setDefaultDriverClass(driver);}@Overridepublic void setDefaultEnumTypeHandler(Class<? extends TypeHandler> typeHandler) {if (typeHandler != null) {CompositeEnumTypeHandler.setDefaultEnumTypeHandler(typeHandler);}}@Overridepublic void addKeyGenerator(String id, KeyGenerator keyGenerator) {keyGenerators.put(id, keyGenerator);}@Overridepublic Collection<String> getKeyGeneratorNames() {return keyGenerators.keySet();}@Overridepublic Collection<KeyGenerator> getKeyGenerators() {return keyGenerators.values();}@Overridepublic KeyGenerator getKeyGenerator(String id) {return keyGenerators.get(id);}@Overridepublic boolean hasKeyGenerator(String id) {return keyGenerators.containsKey(id);}@Overridepublic void addCache(Cache cache) {caches.put(cache.getId(), cache);}@Overridepublic Collection<String> getCacheNames() {return caches.keySet();}@Overridepublic Collection<Cache> getCaches() {return caches.values();}@Overridepublic Cache getCache(String id) {return caches.get(id);}@Overridepublic boolean hasCache(String id) {return caches.containsKey(id);}@Overridepublic void addResultMap(ResultMap rm) {resultMaps.put(rm.getId(), rm);checkLocallyForDiscriminatedNestedResultMaps(rm);checkGloballyForDiscriminatedNestedResultMaps(rm);}@Overridepublic Collection<String> getResultMapNames() {return resultMaps.keySet();}@Overridepublic Collection<ResultMap> getResultMaps() {return resultMaps.values();}@Overridepublic ResultMap getResultMap(String id) {return resultMaps.get(id);}@Overridepublic boolean hasResultMap(String id) {return resultMaps.containsKey(id);}@Overridepublic void addParameterMap(ParameterMap pm) {parameterMaps.put(pm.getId(), pm);}@Overridepublic Collection<String> getParameterMapNames() {return parameterMaps.keySet();}@Overridepublic Collection<ParameterMap> getParameterMaps() {return parameterMaps.values();}@Overridepublic ParameterMap getParameterMap(String id) {return parameterMaps.get(id);}@Overridepublic boolean hasParameterMap(String id) {return parameterMaps.containsKey(id);}@Overridepublic Map<String, XNode> getSqlFragments() {return sqlFragments;}@Overridepublic Collection<String> getMappedStatementNames() {buildAllStatements();return mappedStatements.keySet();}@Overridepublic Collection<MappedStatement> getMappedStatements() {buildAllStatements();return mappedStatements.values();}@Overridepublic MappedStatement getMappedStatement(String id) {return this.getMappedStatement(id, true);}@Overridepublic MappedStatement getMappedStatement(String id, boolean validateIncompleteStatements) {if (validateIncompleteStatements) {buildAllStatements();}return mappedStatements.get(id);}@Overridepublic boolean hasStatement(String statementName, boolean validateIncompleteStatements) {if (validateIncompleteStatements) {buildAllStatements();}return mappedStatements.containsKey(statementName);}@Overridepublic Executor newExecutor(Transaction transaction, ExecutorType executorType) {return super.newExecutor(transaction, executorType);}// Slow but a one time cost. A better solution is welcome.@Overridepublic void checkGloballyForDiscriminatedNestedResultMaps(ResultMap rm) {if (rm.hasNestedResultMaps()) {final String resultMapId = rm.getId();for (Object resultMapObject : resultMaps.values()) {if (resultMapObject instanceof ResultMap) {ResultMap entryResultMap = (ResultMap) resultMapObject;if (!entryResultMap.hasNestedResultMaps() && entryResultMap.getDiscriminator() != null) {Collection<String> discriminatedResultMapNames = entryResultMap.getDiscriminator().getDiscriminatorMap().values();if (discriminatedResultMapNames.contains(resultMapId)) {entryResultMap.forceNestedResultMaps();}}}}}}// Slow but a one time cost. A better solution is welcome.@Overrideprotected void checkLocallyForDiscriminatedNestedResultMaps(ResultMap rm) {if (!rm.hasNestedResultMaps() && rm.getDiscriminator() != null) {for (String discriminatedResultMapName : rm.getDiscriminator().getDiscriminatorMap().values()) {if (hasResultMap(discriminatedResultMapName)) {ResultMap discriminatedResultMap = resultMaps.get(discriminatedResultMapName);if (discriminatedResultMap.hasNestedResultMaps()) {rm.forceNestedResultMaps();break;}}}}}protected class StrictMap<V> extends ConcurrentHashMap<String, V> {private static final long serialVersionUID = -4950446264854982944L;private final String name;private BiFunction<V, V, String> conflictMessageProducer;private final Object AMBIGUITY_INSTANCE = new Object();public StrictMap(String name, int initialCapacity, float loadFactor) {super(initialCapacity, loadFactor);this.name = name;}public StrictMap(String name, int initialCapacity) {super(initialCapacity);this.name = name;}public StrictMap(String name) {super();this.name = name;}public StrictMap(String name, Map<String, ? extends V> m) {super(m);this.name = name;}/*** Assign a function for producing a conflict error message when contains value with the same key.* <p>* function arguments are 1st is saved value and 2nd is target value.** @param conflictMessageProducer A function for producing a conflict error message* @return a conflict error message* @since 3.5.0*/public StrictMap<V> conflictMessageProducer(BiFunction<V, V, String> conflictMessageProducer) {this.conflictMessageProducer = conflictMessageProducer;return this;}@Override@SuppressWarnings("unchecked")public V put(String key, V value) {if (containsKey(key)) {throw new IllegalArgumentException(name + " already contains value for " + key+ (conflictMessageProducer == null ? StringPool.EMPTY : conflictMessageProducer.apply(super.get(key), value)));}if (useGeneratedShortKey) {if (key.contains(StringPool.DOT)) {final String shortKey = getShortName(key);if (super.get(shortKey) == null) {super.put(shortKey, value);} else {super.put(shortKey, (V) AMBIGUITY_INSTANCE);}}}return super.put(key, value);}@Overridepublic boolean containsKey(Object key) {if (key == null) {return false;}return super.get(key) != null;}@Overridepublic V get(Object key) {V value = super.get(key);if (value == null) {throw new IllegalArgumentException(name + " does not contain value for " + key);}if (useGeneratedShortKey && AMBIGUITY_INSTANCE == value) {throw new IllegalArgumentException(key + " is ambiguous in " + name+ " (try using the full name including the namespace, or rename one of the entries)");}return value;}private String getShortName(String key) {final String[] keyParts = key.split("\\.");return keyParts[keyParts.length - 1];}}
}

MybatisMapperRegistry.java

public class MybatisMapperRegistry extends MapperRegistry {private final Configuration config;private final Map<Class<?>, MybatisMapperProxyFactory<?>> knownMappers = new ConcurrentHashMap<>();public MybatisMapperRegistry(Configuration config) {super(config);this.config = config;}@SuppressWarnings("unchecked")@Overridepublic <T> T getMapper(Class<T> type, SqlSession sqlSession) {// fix https://github.com/baomidou/mybatis-plus/issues/4247MybatisMapperProxyFactory<T> mapperProxyFactory = (MybatisMapperProxyFactory<T>) knownMappers.get(type);if (mapperProxyFactory == null) {mapperProxyFactory = (MybatisMapperProxyFactory<T>) knownMappers.entrySet().stream().filter(t -> t.getKey().getName().equals(type.getName())).findFirst().map(Map.Entry::getValue).orElseThrow(() -> new BindingException("Type " + type + " is not known to the MybatisPlusMapperRegistry."));}try {return mapperProxyFactory.newInstance(sqlSession);} catch (Exception e) {throw new BindingException("Error getting mapper instance. Cause: " + e, e);}}@Overridepublic <T> boolean hasMapper(Class<T> type) {return knownMappers.containsKey(type);}/*** 清空 Mapper 缓存信息*/protected <T> void removeMapper(Class<T> type) {knownMappers.entrySet().stream().filter(t -> t.getKey().getName().equals(type.getName())).findFirst().ifPresent(t -> knownMappers.remove(t.getKey()));}@Overridepublic <T> void addMapper(Class<T> type) {if (type.isInterface()) {if (hasMapper(type)) {return;
//                throw new BindingException("Type " + type + " is already known to the MapperRegistry.");}boolean loadCompleted = false;try {knownMappers.put(type, new MybatisMapperProxyFactory<>(type));// It's important that the type is added before the parser is run// otherwise the binding may automatically be attempted by the// mapper parser. If the type is already known, it won't try.// MybatisPlus注解解析器MybatisMapperAnnotationBuilder parser = new MybatisMapperAnnotationBuilder(config, type);parser.parse();loadCompleted = true;} finally {if (!loadCompleted) {knownMappers.remove(type);}}}}/*** 使用自己的 knownMappers*/@Overridepublic Collection<Class<?>> getMappers() {return Collections.unmodifiableCollection(knownMappers.keySet());}}

MybatisMapperAnnotationBuilder.java MybatisPlus核心构造器，主要解析相关实体类的信息，例如TableName、Id、TableFiled；MybatisPlus自己相关的注解；

/*** 核心方法*/@Overridepublic void parse() {String resource = type.toString();if (!configuration.isResourceLoaded(resource)) {loadXmlResource();configuration.addLoadedResource(resource);String mapperName = type.getName();assistant.setCurrentNamespace(mapperName);parseCache();parseCacheRef();IgnoreStrategy ignoreStrategy = InterceptorIgnoreHelper.initSqlParserInfoCache(type);for (Method method : type.getMethods()) {if (!canHaveStatement(method)) {continue;}if (getAnnotationWrapper(method, false, Select.class, SelectProvider.class).isPresent()&& method.getAnnotation(ResultMap.class) == null) {parseResultMap(method);}try {InterceptorIgnoreHelper.initSqlParserInfoCache(ignoreStrategy, mapperName, method);parseStatement(method);} catch (IncompleteElementException e) {configuration.addIncompleteMethod(new MybatisMethodResolver(this, method));}}try {// https://github.com/baomidou/mybatis-plus/issues/3038if (GlobalConfigUtils.isSupperMapperChildren(configuration, type)) {//  是否继承了MybatisPlus Mapper类，如果继承了，才会解析MybatisPlus自带的相关方法；例如：selectById、deleteByIdparserInjector();}} catch (IncompleteElementException e) {configuration.addIncompleteMethod(new InjectorResolver(this));}}configuration.parsePendingMethods(false);}// 解析MybatisPlus 默认的注入器void parserInjector() {GlobalConfigUtils.getSqlInjector(configuration).inspectInject(assistant, type);}

AbstractSqlInjector.java

 /*** 核心方法* @param builderAssistant mapper 信息* @param mapperClass      mapper 接口的 class 对象*/@Overridepublic void inspectInject(MapperBuilderAssistant builderAssistant, Class<?> mapperClass) {Class<?> modelClass = ReflectionKit.getSuperClassGenericType(mapperClass, Mapper.class, 0);if (modelClass != null) {String className = mapperClass.toString();Set<String> mapperRegistryCache = GlobalConfigUtils.getMapperRegistryCache(builderAssistant.getConfiguration());if (!mapperRegistryCache.contains(className)) {// 实体类对应的表信息TableInfo tableInfo = TableInfoHelper.initTableInfo(builderAssistant, modelClass);// 相关默认方法。这里是MybatisPlus提供的默认方法；例如selectById,selectCount方法List<AbstractMethod> methodList = this.getMethodList(mapperClass, tableInfo);// 兼容旧代码if (CollectionUtils.isEmpty(methodList)) {methodList = this.getMethodList(builderAssistant.getConfiguration(), mapperClass, tableInfo);}if (CollectionUtils.isNotEmpty(methodList)) {// 循环注入自定义方法methodList.forEach(m -> m.inject(builderAssistant, mapperClass, modelClass, tableInfo));} else {logger.debug(className + ", No effective injection method was found.");}mapperRegistryCache.add(className);}}}

AbstractMethod
可以看一下类的继承关系：

简单介绍其中一个类：
SelectList.java

public class SelectList extends AbstractMethod {public SelectList() {this(SqlMethod.SELECT_LIST.getMethod());}/*** @param name 方法名* @since 3.5.0*/public SelectList(String name) {super(name);}@Overridepublic MappedStatement injectMappedStatement(Class<?> mapperClass, Class<?> modelClass, TableInfo tableInfo) {SqlMethod sqlMethod = SqlMethod.SELECT_LIST;//<script>%s SELECT %s FROM %s %s %s %s</script>String sql = String.format(sqlMethod.getSql(), sqlFirst(), sqlSelectColumns(tableInfo, true), tableInfo.getTableName(),// 这里自动解析QueryWrapper相关信息sqlWhereEntityWrapper(true, tableInfo), sqlOrderBy(tableInfo), sqlComment());SqlSource sqlSource = super.createSqlSource(configuration, sql, modelClass);return this.addSelectMappedStatementForTable(mapperClass, methodName, sqlSource, tableInfo);}
}

可以看到sql相关信息

总结

MybatisPlus是延用Mybatis相关特性，可以说是Mybatis的一种加强版。因为它增加了自定义类来减少相关代码。主要类有：MybatisPlusAutoConfiguration、MybatisConfiguration、MybatisMapperAnnotationBuilder、AbstractSqlInjector、DefaultSqlInjector、Wrapper

MybatisPlusAutoConfiguration: MybatisPlus自动装配器
MybatisConfiguration: MybatisPlus配置类继承Mybatis配置类，主要是对Mybatis配置的增强
MybatisMapperAnnotationBuilder: 核心类之一，主要用来解析MybatisPlus自己的注解。
AbstractSqlInjector: Sql注入器，MybatisPlus提供了相关默认的方法。
Wrapper: 条件包裹器