Spring之整合Mybatis 整合核心思路 由很多框架都需要和Spring进行整合，而整合的核心思想就是把其他框架所产生的对象放到Spring容器中，让其成为Bean。
比如Mybatis，Mybatis框架可以单独使用，而单独使用Mybatis框架就需要用到Mybatis所提供的一些类构造出对应的对象，然后使用该对象，就能使用到Mybatis框架给我们提供的功能，和Mybatis整合Spring就是为了将这些对象放入Spring容器中成为Bean，只要成为了Bean，在我们的Spring项目中就能很方便的使用这些对象了，也就能很方便的使用Mybatis框架所提供的功能了。
Mybatis-Spring 1.3.2版本

1. 通过@MapperScan导入了MapperScannerRegistrar类
2. MapperScannerRegistrar类实现了ImportBeanDefinitionRegistrar接口，所以Spring在启动时会调用MapperScannerRegistrar类中的registerBeanDefinitions方法
3. 在registerBeanDefinitions方法中定义了一个ClassPathMapperScanner对象，用来扫描mapper
4. 设置ClassPathMapperScanner对象可以扫描到接口，因为在Spring中是不会扫描接口的
5. 同时因为ClassPathMapperScanner中重写了isCandidateComponent方法，导致isCandidateComponent只会认为接口是备选者Component
6. 通过利用Spring的扫描后，会把接口扫描出来并且得到对应的BeanDefinition
7. 接下来把扫描得到的BeanDefinition进行修改，把BeanClass修改为MapperFactoryBean，把AutowireMode修改为byType
8. 扫描完成后，Spring就会基于BeanDefinition去创建Bean了，相当于每个Mapper对应一个FactoryBean
9. 在MapperFactoryBean中的getObject方法中，调用了getSqlSession()去得到一个sqlSession对象，然后根据对应的Mapper接口生成一个Mapper接口代理对象，这个代理对象就成为Spring容器中的Bean
10. sqlSession对象是Mybatis中的，一个sqlSession对象需要SqlSessionFactory来产生
11. MapperFactoryBean的AutowireMode为byType，所以Spring会自动调用set方法，有两个set方法，一个setSqlSessionFactory，一个setSqlSessionTemplate，而这两个方法执行的前提是根据方法参数类型能找到对应的bean，所以Spring容器中要存在SqlSessionFactory类型的bean或者SqlSessionTemplate类型的bean。
12. 如果你定义的是一个SqlSessionFactory类型的bean，那么最终也会被包装为一个SqlSessionTemplate对象，并且赋值给sqlSession属性
13. 而在SqlSessionTemplate类中就存在一个getMapper方法，这个方法中就产生一个Mapper接口代理对象
14. 到时候，当执行该代理对象的某个方法时，就会进入到Mybatis框架的底层执行流程，详细的请看下图

Spring整合Mybatis之后SQL执行流程： https://www.processon.com/view/link/6152cc385653bb6791db436c
源码流程
@MapperScan导入了MapperScannerRegistrar类

@Import(MapperScannerRegistrar.class) public @interface MapperScan {

MapperScannerRegistrar类实现了ImportBeanDefinitionRegistrar接口,在Spring启动时会调用MapperScannerRegistrar类中的registerBeanDefinitions方法

public class MapperScannerRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware {private ResourceLoader resourceLoader; /** * {@inheritDoc} */ @Override public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {AnnotationAttributes annoAttrs = AnnotationAttributes.fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName())); //定义了一个ClassPathMapperScanner对象，用来扫描mapper ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry); // this check is needed in Spring 3.1 if (resourceLoader != null) { scanner.setResourceLoader(resourceLoader); }Class annotationClass = annoAttrs.getClass("annotationClass"); if (!Annotation.class.equals(annotationClass)) { scanner.setAnnotationClass(annotationClass); } //设置ClassPathMapperScanner对象可以扫描到接口，因为在Spring中是不会扫描接口的 Class markerInterface = annoAttrs.getClass("markerInterface"); if (!Class.class.equals(markerInterface)) { scanner.setMarkerInterface(markerInterface); }Class generatorClass = annoAttrs.getClass("nameGenerator"); if (!BeanNameGenerator.class.equals(generatorClass)) { scanner.setBeanNameGenerator(BeanUtils.instantiateClass(generatorClass)); }Class mapperFactoryBeanClass = annoAttrs.getClass("factoryBean"); if (!MapperFactoryBean.class.equals(mapperFactoryBeanClass)) { scanner.setMapperFactoryBean(BeanUtils.instantiateClass(mapperFactoryBeanClass)); }scanner.setSqlSessionTemplateBeanName(annoAttrs.getString("sqlSessionTemplateRef")); scanner.setSqlSessionFactoryBeanName(annoAttrs.getString("sqlSessionFactoryRef")); List basePackages = new ArrayList(); for (String pkg : annoAttrs.getStringArray("value")) { if (StringUtils.hasText(pkg)) { basePackages.add(pkg); } } for (String pkg : annoAttrs.getStringArray("basePackages")) { if (StringUtils.hasText(pkg)) { basePackages.add(pkg); } } for (Class clazz : annoAttrs.getClassArray("basePackageClasses")) { basePackages.add(ClassUtils.getPackageName(clazz)); } //添加TypeFilter,总是返回true,用于绕过spring的doscan的scanCandidateComponents方法的isCandidateComponent判断 scanner.registerFilters(); scanner.doScan(StringUtils.toStringArray(basePackages)); }/** * {@inheritDoc} */ @Override public void setResourceLoader(ResourceLoader resourceLoader) { this.resourceLoader = resourceLoader; }}

ClassPathMapperScanner中重写了isCandidateComponent方法，导致isCandidateComponent只会认为接口是备选者Component

@Override protected boolean isCandidateComponent(AnnotatedBeanDefinition beanDefinition) { return beanDefinition.getMetadata().isInterface() && beanDefinition.getMetadata().isIndependent(); }

通过利用Spring的扫描后，会把接口扫描出来并且得到对应的BeanDefinition

@Override public Set doScan(String... basePackages) { Set beanDefinitions = super.doScan(basePackages); if (beanDefinitions.isEmpty()) { logger.warn("No MyBatis mapper was found in '" + Arrays.toString(basePackages) + "' package. Please check your configuration."); } else { //核心方法 processBeanDefinitions(beanDefinitions); }return beanDefinitions; }private void processBeanDefinitions(Set beanDefinitions) { GenericBeanDefinition definition; for (BeanDefinitionHolder holder : beanDefinitions) { definition = (GenericBeanDefinition) holder.getBeanDefinition(); if (logger.isDebugEnabled()) { logger.debug("Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + definition.getBeanClassName() + "' mapperInterface"); }// the mapper interface is the original class of the bean // but, the actual class of the bean is MapperFactoryBean //MapperFactoryBean的构造器,参数就是对应的mapper接口 definition.getConstructorArgumentValues().addGenericArgumentValue(definition.getBeanClassName()); // issue #59 //把BeanClass修改为MapperFactoryBean definition.setBeanClass(this.mapperFactoryBean.getClass()); definition.getPropertyValues().add("addToConfig", this.addToConfig); boolean explicitFactoryUsed = false; if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) { definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName)); explicitFactoryUsed = true; } else if (this.sqlSessionFactory != null) { definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory); explicitFactoryUsed = true; }if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) { if (explicitFactoryUsed) { logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored."); } definition.getPropertyValues().add("sqlSessionTemplate", new RuntimeBeanReference(this.sqlSessionTemplateBeanName)); explicitFactoryUsed = true; } else if (this.sqlSessionTemplate != null) { if (explicitFactoryUsed) { logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored."); } definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate); explicitFactoryUsed = true; }if (!explicitFactoryUsed) { if (logger.isDebugEnabled()) { logger.debug("Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'."); } //把AutowireMode修改为byType,会根据set来自动注入 definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE); } } }

扫描完成后，Spring就会基于BeanDefinition去创建Bean了，相当于每个Mapper对应一个MapperFactoryBean

public class MapperFactoryBean extends SqlSessionDaoSupport implements FactoryBean {//被代理对象的类型 private Class mapperInterface; private boolean addToConfig = true; public MapperFactoryBean() { //intentionally empty }public MapperFactoryBean(Class mapperInterface) { this.mapperInterface = mapperInterface; }/** * {@inheritDoc} */ @Override protected void checkDaoConfig() { super.checkDaoConfig(); notNull(this.mapperInterface, "Property 'mapperInterface' is required"); Configuration configuration = getSqlSession().getConfiguration(); if (this.addToConfig && !configuration.hasMapper(this.mapperInterface)) { try { configuration.addMapper(this.mapperInterface); } catch (Exception e) { logger.error("Error while adding the mapper '" + this.mapperInterface + "' to configuration.", e); throw new IllegalArgumentException(e); } finally { ErrorContext.instance().reset(); } } }/** * {@inheritDoc} */ @Override public T getObject() throws Exception { //这里就会生成jdk动态代理对象 //调用了getSqlSession()去得到一个sqlSession对象，然后根据对应的Mapper接口生成一个Mapper接口代理对象，这个代理对象就成为Spring容器中的Bean return getSqlSession().getMapper(this.mapperInterface); }/** * {@inheritDoc} */ @Override public Class getObjectType() { //类型就是接口的类型 return this.mapperInterface; }/** * {@inheritDoc} */ @Override public boolean isSingleton() { return true; }}

sqlSession对象是Mybatis中的，一个sqlSession对象需要SqlSessionFactory来产生,使用sqlSessionFactory添加了一个SqlSessionTemplate再转换成sqlSession

public abstract class SqlSessionDaoSupport extends DaoSupport {private SqlSession sqlSession; private boolean externalSqlSession; public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) { if (!this.externalSqlSession) { //使用sqlSessionFactory添加了一个SqlSessionTemplate再转换成sqlSession this.sqlSession = new SqlSessionTemplate(sqlSessionFactory); } }public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) { this.sqlSession = sqlSessionTemplate; this.externalSqlSession = true; }/** * Users should use this method to get a SqlSession to call its statement methods * This is SqlSession is managed by spring. Users should not commit/rollback/close it * because it will be automatically done. * * @return Spring managed thread safe SqlSession */ public SqlSession getSqlSession() { //这里就是返回的SqlSession对象 return this.sqlSession; }/** * {@inheritDoc} */ @Override protected void checkDaoConfig() { notNull(this.sqlSession, "Property 'sqlSessionFactory' or 'sqlSessionTemplate' are required"); }}

而在SqlSessionTemplate类中就存在一个getMapper方法，这个方法中就产生一个Mapper接口代理对象

public class SqlSessionTemplate implements SqlSession, DisposableBean {private final SqlSessionFactory sqlSessionFactory; private final ExecutorType executorType; //注意,这里的SqlSession其实是sqlSessionProxy private final SqlSession sqlSessionProxy; private final PersistenceExceptionTranslator exceptionTranslator; /** * Constructs a Spring managed SqlSession with the {@code SqlSessionFactory} * provided as an argument. * * @param sqlSessionFactory */ public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory) { this(sqlSessionFactory, sqlSessionFactory.getConfiguration().getDefaultExecutorType()); }/** * Constructs a Spring managed SqlSession with the {@code SqlSessionFactory} * provided as an argument and the given {@code ExecutorType} * {@code ExecutorType} cannot be changed once the {@code SqlSessionTemplate} * is constructed. * * @param sqlSessionFactory * @param executorType */ public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType) { this(sqlSessionFactory, executorType, new MyBatisExceptionTranslator( sqlSessionFactory.getConfiguration().getEnvironment().getDataSource(), true)); }/** * Constructs a Spring managed {@code SqlSession} with the given * {@code SqlSessionFactory} and {@code ExecutorType}. * A custom {@code SQLExceptionTranslator} can be provided as an * argument so any {@code PersistenceException} thrown by MyBatis * can be custom translated to a {@code RuntimeException} * The {@code SQLExceptionTranslator} can also be null and thus no * exception translation will be done and MyBatis exceptions will be * thrown * * @param sqlSessionFactory * @param executorType * @param exceptionTranslator */ public SqlSessionTemplate(SqlSessionFactory sqlSessionFactory, ExecutorType executorType, PersistenceExceptionTranslator exceptionTranslator) {notNull(sqlSessionFactory, "Property 'sqlSessionFactory' is required"); notNull(executorType, "Property 'executorType' is required"); this.sqlSessionFactory = sqlSessionFactory; this.executorType = executorType; this.exceptionTranslator = exceptionTranslator; //注意,这里的SqlSession其实是sqlSessionProxy代理对象 this.sqlSessionProxy = (SqlSession) newProxyInstance( SqlSessionFactory.class.getClassLoader(), new Class[] { SqlSession.class }, new SqlSessionInterceptor()); }@Override public T getMapper(Class type) { return getConfiguration().getMapper(type, this); }}

SqlSessionInterceptor源码

private class SqlSessionInterceptor implements InvocationHandler { @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { SqlSession sqlSession = getSqlSession( SqlSessionTemplate.this.sqlSessionFactory, SqlSessionTemplate.this.executorType, SqlSessionTemplate.this.exceptionTranslator); try { //真正执行sql的方法 Object result = method.invoke(sqlSession, args); //这里使用ThreadLocal if (!isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)) { // force commit even on non-dirty sessions because some databases require // a commit/rollback before calling close() sqlSession.commit(true); } return result; } catch (Throwable t) { Throwable unwrapped = unwrapThrowable(t); if (SqlSessionTemplate.this.exceptionTranslator != null && unwrapped instanceof PersistenceException) { // release the connection to avoid a deadlock if the translator is no loaded. See issue #22 closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory); sqlSession = null; Throwable translated = SqlSessionTemplate.this.exceptionTranslator.translateExceptionIfPossible((PersistenceException) unwrapped); if (translated != null) { unwrapped = translated; } } throw unwrapped; } finally { if (sqlSession != null) { closeSqlSession(sqlSession, SqlSessionTemplate.this.sqlSessionFactory); } } } }

在getSqlSession中看一下

public static SqlSession getSqlSession(SqlSessionFactory sessionFactory, ExecutorType executorType, PersistenceExceptionTranslator exceptionTranslator) {notNull(sessionFactory, NO_SQL_SESSION_FACTORY_SPECIFIED); notNull(executorType, NO_EXECUTOR_TYPE_SPECIFIED); SqlSessionHolder holder = (SqlSessionHolder) TransactionSynchronizationManager.getResource(sessionFactory); SqlSession session = sessionHolder(executorType, holder); if (session != null) { return session; }if (LOGGER.isDebugEnabled()) { LOGGER.debug("Creating a new SqlSession"); } //这里sessionFactory就是DefaultSqlSessionFactory,并返回 session = sessionFactory.openSession(executorType); registerSessionHolder(sessionFactory, executorType, exceptionTranslator, session); return session; }

继续openSession

@Override public SqlSession openSession(ExecutorType execType, Connection connection) { return openSessionFromConnection(execType, connection); }@Override public Configuration getConfiguration() { return configuration; }private SqlSession openSessionFromDataSource(ExecutorType execType, TransactionIsolationLevel level, boolean autoCommit) { Transaction tx = null; try { final Environment environment = configuration.getEnvironment(); final TransactionFactory transactionFactory = getTransactionFactoryFromEnvironment(environment); tx = transactionFactory.newTransaction(environment.getDataSource(), level, autoCommit); final Executor executor = configuration.newExecutor(tx, execType); //返回了DefaultSqlSession return new DefaultSqlSession(configuration, executor, autoCommit); } catch (Exception e) { closeTransaction(tx); // may have fetched a connection so lets call close() throw ExceptionFactory.wrapException("Error opening session.Cause: " + e, e); } finally { ErrorContext.instance().reset(); } }

因为SqlSession就是是SqlSessionTemplate,因此会调用SqlSessionTemplate的selectOne方法来查询

/** * {@inheritDoc} */ @Override public T selectOne(String statement) { return this.sqlSessionProxy. selectOne(statement); }

DefaultSqlSession是线程不安全的,SqlSessionTemplate使用ThreadLocal保证线程安全
SqlSessionInterceptor.invoke方法的isSqlSessionTransactional(sqlSession, SqlSessionTemplate.this.sqlSessionFactory)

public static boolean isSqlSessionTransactional(SqlSession session, SqlSessionFactory sessionFactory) { notNull(session, NO_SQL_SESSION_SPECIFIED); notNull(sessionFactory, NO_SQL_SESSION_FACTORY_SPECIFIED); SqlSessionHolder holder = (SqlSessionHolder) TransactionSynchronizationManager.getResource(sessionFactory); return (holder != null) && (holder.getSqlSession() == session); }

跟一下getResource

@Nullable public static Object getResource(Object key) { Object actualKey = TransactionSynchronizationUtils.unwrapResourceIfNecessary(key); Object value = https://www.it610.com/article/doGetResource(actualKey); if (value != null && logger.isTraceEnabled()) { logger.trace("Retrieved value [" + value + "] for key [" + actualKey + "] bound to thread [" + Thread.currentThread().getName() + "]"); } return value; }

跟一下doGetResource

@Nullable private static Object doGetResource(Object actualKey) { Map map = resources.get(); if (map == null) { return null; } Object value = https://www.it610.com/article/map.get(actualKey); // Transparently remove ResourceHolder that was marked as void... if (value instanceof ResourceHolder && ((ResourceHolder) value).isVoid()) { map.remove(actualKey); // Remove entire ThreadLocal if empty... if (map.isEmpty()) { resources.remove(); } value = null; } return value; }

看一下resources

public abstract class TransactionSynchronizationManager {private static final Log logger = LogFactory.getLog(TransactionSynchronizationManager.class); private static final ThreadLocal> resources = new NamedThreadLocal<>("Transactional resources"); }

Mybatis-Spring 2.0.6版本

1. 通过@MapperScan导入了MapperScannerRegistrar类
2. MapperScannerRegistrar类实现了ImportBeanDefinitionRegistrar接口，所以Spring在启动时会调用MapperScannerRegistrar类中的registerBeanDefinitions方法
3. 在registerBeanDefinitions方法中注册一个MapperScannerConfigurer类型的BeanDefinition
4. 而MapperScannerConfigurer实现了BeanDefinitionRegistryPostProcessor接口，所以Spring在启动过程中时会调用它的postProcessBeanDefinitionRegistry()方法
5. 在postProcessBeanDefinitionRegistry方法中会生成一个ClassPathMapperScanner对象，然后进行扫描
6. 后续的逻辑和1.3.2版本一样。

带来的好处是，可以不使用@MapperScan注解，而可以直接定义一个Bean，比如：

@Bean public MapperScannerConfigurer mapperScannerConfigurer() { MapperScannerConfigurer mapperScannerConfigurer = new MapperScannerConfigurer(); mapperScannerConfigurer.setBasePackage("com.luban"); return mapperScannerConfigurer; }

源码流程
MapperScannerRegistrar类实现了ImportBeanDefinitionRegistrar接口，所以Spring在启动时会调用MapperScannerRegistrar类中的registerBeanDefinitions方法

@Override public void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) { AnnotationAttributes mapperScanAttrs = AnnotationAttributes .fromMap(importingClassMetadata.getAnnotationAttributes(MapperScan.class.getName())); if (mapperScanAttrs != null) { registerBeanDefinitions(importingClassMetadata, mapperScanAttrs, registry, generateBaseBeanName(importingClassMetadata, 0)); } }void registerBeanDefinitions(AnnotationMetadata annoMeta, AnnotationAttributes annoAttrs, BeanDefinitionRegistry registry, String beanName) {//注册一个MapperScannerConfigurer类型的BeanDefinition BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(MapperScannerConfigurer.class); builder.addPropertyValue("processPropertyPlaceHolders", true); Class annotationClass = annoAttrs.getClass("annotationClass"); if (!Annotation.class.equals(annotationClass)) { builder.addPropertyValue("annotationClass", annotationClass); }Class markerInterface = annoAttrs.getClass("markerInterface"); if (!Class.class.equals(markerInterface)) { builder.addPropertyValue("markerInterface", markerInterface); }Class generatorClass = annoAttrs.getClass("nameGenerator"); if (!BeanNameGenerator.class.equals(generatorClass)) { builder.addPropertyValue("nameGenerator", BeanUtils.instantiateClass(generatorClass)); }Class mapperFactoryBeanClass = annoAttrs.getClass("factoryBean"); if (!MapperFactoryBean.class.equals(mapperFactoryBeanClass)) { builder.addPropertyValue("mapperFactoryBeanClass", mapperFactoryBeanClass); }String sqlSessionTemplateRef = annoAttrs.getString("sqlSessionTemplateRef"); if (StringUtils.hasText(sqlSessionTemplateRef)) { builder.addPropertyValue("sqlSessionTemplateBeanName", annoAttrs.getString("sqlSessionTemplateRef")); }String sqlSessionFactoryRef = annoAttrs.getString("sqlSessionFactoryRef"); if (StringUtils.hasText(sqlSessionFactoryRef)) { builder.addPropertyValue("sqlSessionFactoryBeanName", annoAttrs.getString("sqlSessionFactoryRef")); }List basePackages = new ArrayList<>(); basePackages.addAll( Arrays.stream(annoAttrs.getStringArray("value")).filter(StringUtils::hasText).collect(Collectors.toList())); basePackages.addAll(Arrays.stream(annoAttrs.getStringArray("basePackages")).filter(StringUtils::hasText) .collect(Collectors.toList())); basePackages.addAll(Arrays.stream(annoAttrs.getClassArray("basePackageClasses")).map(ClassUtils::getPackageName) .collect(Collectors.toList())); if (basePackages.isEmpty()) { basePackages.add(getDefaultBasePackage(annoMeta)); }String lazyInitialization = annoAttrs.getString("lazyInitialization"); if (StringUtils.hasText(lazyInitialization)) { builder.addPropertyValue("lazyInitialization", lazyInitialization); }String defaultScope = annoAttrs.getString("defaultScope"); if (!AbstractBeanDefinition.SCOPE_DEFAULT.equals(defaultScope)) { builder.addPropertyValue("defaultScope", defaultScope); }builder.addPropertyValue("basePackage", StringUtils.collectionToCommaDelimitedString(basePackages)); registry.registerBeanDefinition(beanName, builder.getBeanDefinition()); }

MapperScannerConfigurer功能就很丰富了,看下源码

public class MapperScannerConfigurer implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {private String basePackage; private boolean addToConfig = true; private String lazyInitialization; private SqlSessionFactory sqlSessionFactory; private SqlSessionTemplate sqlSessionTemplate; private String sqlSessionFactoryBeanName; private String sqlSessionTemplateBeanName; private Class annotationClass; private Class markerInterface; private Class mapperFactoryBeanClass; private ApplicationContext applicationContext; private String beanName; private boolean processPropertyPlaceHolders; private BeanNameGenerator nameGenerator; private String defaultScope; public void setMarkerInterface(Class superClass) { this.markerInterface = superClass; }@Deprecated public void setSqlSessionTemplate(SqlSessionTemplate sqlSessionTemplate) { this.sqlSessionTemplate = sqlSessionTemplate; }public void setSqlSessionTemplateBeanName(String sqlSessionTemplateName) { this.sqlSessionTemplateBeanName = sqlSessionTemplateName; }@Deprecated public void setSqlSessionFactory(SqlSessionFactory sqlSessionFactory) { this.sqlSessionFactory = sqlSessionFactory; }public void setSqlSessionFactoryBeanName(String sqlSessionFactoryName) { this.sqlSessionFactoryBeanName = sqlSessionFactoryName; }public void setProcessPropertyPlaceHolders(boolean processPropertyPlaceHolders) { this.processPropertyPlaceHolders = processPropertyPlaceHolders; }public void setMapperFactoryBeanClass(Class mapperFactoryBeanClass) { this.mapperFactoryBeanClass = mapperFactoryBeanClass; }@Override public void setApplicationContext(ApplicationContext applicationContext) { this.applicationContext = applicationContext; }@Override public void setBeanName(String name) { this.beanName = name; }public BeanNameGenerator getNameGenerator() { return nameGenerator; }public void setNameGenerator(BeanNameGenerator nameGenerator) { this.nameGenerator = nameGenerator; }public void setDefaultScope(String defaultScope) { this.defaultScope = defaultScope; }@Override public void afterPropertiesSet() throws Exception { notNull(this.basePackage, "Property 'basePackage' is required"); }@Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) { // left intentionally blank } //关键代码 @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) { if (this.processPropertyPlaceHolders) { processPropertyPlaceHolders(); } //添加ClassPathMapperScanner,进行扫描 ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry); scanner.setAddToConfig(this.addToConfig); scanner.setAnnotationClass(this.annotationClass); scanner.setMarkerInterface(this.markerInterface); scanner.setSqlSessionFactory(this.sqlSessionFactory); scanner.setSqlSessionTemplate(this.sqlSessionTemplate); scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName); scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName); scanner.setResourceLoader(this.applicationContext); scanner.setBeanNameGenerator(this.nameGenerator); scanner.setMapperFactoryBeanClass(this.mapperFactoryBeanClass); if (StringUtils.hasText(lazyInitialization)) { scanner.setLazyInitialization(Boolean.valueOf(lazyInitialization)); } if (StringUtils.hasText(defaultScope)) { scanner.setDefaultScope(defaultScope); } scanner.registerFilters(); scanner.scan( StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS)); } private void processPropertyPlaceHolders() { Map prcs = applicationContext.getBeansOfType(PropertyResourceConfigurer.class, false, false); if (!prcs.isEmpty() && applicationContext instanceof ConfigurableApplicationContext) { BeanDefinition mapperScannerBean = ((ConfigurableApplicationContext) applicationContext).getBeanFactory() .getBeanDefinition(beanName); // PropertyResourceConfigurer does not expose any methods to explicitly perform // property placeholder substitution. Instead, create a BeanFactory that just // contains this mapper scanner and post process the factory. DefaultListableBeanFactory factory = new DefaultListableBeanFactory(); factory.registerBeanDefinition(beanName, mapperScannerBean); for (PropertyResourceConfigurer prc : prcs.values()) { prc.postProcessBeanFactory(factory); }PropertyValues values = mapperScannerBean.getPropertyValues(); this.basePackage = getPropertyValue("basePackage", values); this.sqlSessionFactoryBeanName = getPropertyValue("sqlSessionFactoryBeanName", values); this.sqlSessionTemplateBeanName = getPropertyValue("sqlSessionTemplateBeanName", values); this.lazyInitialization = getPropertyValue("lazyInitialization", values); this.defaultScope = getPropertyValue("defaultScope", values); } this.basePackage = Optional.ofNullable(this.basePackage).map(getEnvironment()::resolvePlaceholders).orElse(null); this.sqlSessionFactoryBeanName = Optional.ofNullable(this.sqlSessionFactoryBeanName) .map(getEnvironment()::resolvePlaceholders).orElse(null); this.sqlSessionTemplateBeanName = Optional.ofNullable(this.sqlSessionTemplateBeanName) .map(getEnvironment()::resolvePlaceholders).orElse(null); this.lazyInitialization = Optional.ofNullable(this.lazyInitialization).map(getEnvironment()::resolvePlaceholders) .orElse(null); this.defaultScope = Optional.ofNullable(this.defaultScope).map(getEnvironment()::resolvePlaceholders).orElse(null); }private Environment getEnvironment() { return this.applicationContext.getEnvironment(); }private String getPropertyValue(String propertyName, PropertyValues values) { PropertyValue property = values.getPropertyValue(propertyName); if (property == null) { return null; }Object value = https://www.it610.com/article/property.getValue(); if (value == null) { return null; } else if (value instanceof String) { return value.toString(); } else if (value instanceof TypedStringValue) { return ((TypedStringValue) value).getValue(); } else { return null; } }}

整合后一级缓存失效问题 先看下图： Spring整合Mybatis之后SQL执行流程： https://www.processon.com/view/link/6152cc385653bb6791db436c
Mybatis中的一级缓存是基于SqlSession来实现的，所以在执行同一个sql时，如果使用的是同一个SqlSession对象，那么就能利用到一级缓存，提高sql的执行效率。
但是在Spring整合Mybatis后，如果没有执行某个方法时，该方法上没有加@Transactional注解，也就是没有开启Spring事务，那么后面在执行具体sql时，每执行一个sql时都会新生成一个SqlSession对象来执行该sql，这就是我们说的一级缓存失效（也就是没有使用同一个SqlSession对象），而如果开启了Spring事务，那么该Spring事务中的多个sql，在执行时会使用同一个SqlSession对象，从而一级缓存生效，具体的底层执行流程在上图。
【07-Spring整合Mybatis】个人理解：实际上Spring整合Mybatis后一级缓存失效并不是问题，是正常的实现，因为，一个方法如果没有开启Spring事务，那么在执行sql时候，那就是每个sql单独一个事务来执行，也就是单独一个SqlSession对象来执行该sql，如果开启了Spring事务，那就是多个sql属于同一个事务，那自然就应该用一个SqlSession来执行这多个sql。所以，在没有开启Spring事务的时候，SqlSession的一级缓存并不是失效了，而是存在的生命周期太短了（执行完一个sql后就被销毁了，下一个sql执行时又是一个新的SqlSession了）。

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