<bean id="configurer" class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
    <property name="basePackage" value="com.jame.dao"/>
</bean>

@Override
public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) {
    if (this.processPropertyPlaceHolders) {
        processPropertyPlaceHolders();
    }

    ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
    ..........
    scanner.registerFilters();
    scanner.scan(
        StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
}

public int scan(String... basePackages) {
    int beanCountAtScanStart = this.registry.getBeanDefinitionCount();

    doScan(basePackages);

    // Register annotation config processors, if necessary.
    if (this.includeAnnotationConfig) {
        AnnotationConfigUtils.registerAnnotationConfigProcessors(this.registry);
    }

    return (this.registry.getBeanDefinitionCount() - beanCountAtScanStart);
}

@Override
public Set<BeanDefinitionHolder> doScan(String... basePackages) {
    Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);

    if (beanDefinitions.isEmpty()) {
        LOGGER.warn(() -> "No MyBatis mapper was found in '" + Arrays.toString(basePackages)
                    + "' package. Please check your configuration.");
    } else {
        processBeanDefinitions(beanDefinitions);
    }

    return beanDefinitions;
}

private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
    AbstractBeanDefinition definition;
    BeanDefinitionRegistry registry = getRegistry();
    for (BeanDefinitionHolder holder : beanDefinitions) {
        definition = (AbstractBeanDefinition) holder.getBeanDefinition();
       	.........
        //主要看這行
        definition.setBeanClass(this.mapperFactoryBeanClass);
	  .........
        if (!definition.isSingleton()) {
            BeanDefinitionHolder proxyHolder = ScopedProxyUtils.createScopedProxy(holder, registry, true);
            if (registry.containsBeanDefinition(proxyHolder.getBeanName())) {
                registry.removeBeanDefinition(proxyHolder.getBeanName());
            }
            registry.registerBeanDefinition(proxyHolder.getBeanName(), proxyHolder.getBeanDefinition());
        }
    }
}

protected <T> T doGetBean(
    String name, @Nullable Class<T> requiredType, @Nullable Object[] args, boolean typeCheckOnly)
    throws BeansException {
    //獲取對(duì)應(yīng)的beanName
    String beanName = transformedBeanName(name);
    Object bean;
    Object sharedInstance = getSingleton(beanName);

    if (sharedInstance != null && args == null) {
        bean = getObjectForBeanInstance(sharedInstance, name, beanName, null);
    }
	.......
    // Create bean instance.
    if (mbd.isSingleton()) {
        sharedInstance = getSingleton(beanName, () -> {
            try {
                //真正創(chuàng)建對(duì)象的地方
                return createBean(beanName, mbd, args);
            }
            catch (BeansException ex) {
                // Explicitly remove instance from singleton cache: It might have been put there
                // eagerly by the creation process, to allow for circular reference resolution.
                // Also remove any beans that received a temporary reference to the bean.
                destroySingleton(beanName);
                throw ex;
            }
        });
        bean = getObjectForBeanInstance(sharedInstance, name, beanName, mbd);
    }     
}

protected Object getObjectForBeanInstance(
    Object beanInstance, String name, String beanName, @Nullable RootBeanDefinition mbd) {

    if (BeanFactoryUtils.isFactoryDereference(name)) {
        if (beanInstance instanceof NullBean) {
            return beanInstance;
        }
        if (!(beanInstance instanceof FactoryBean)) {
            throw new BeanIsNotAFactoryException(beanName, beanInstance.getClass());
        }
    }
	.....
}

if (!(beanInstance instanceof FactoryBean) || BeanFactoryUtils.isFactoryDereference(name)) {
    return beanInstance;
}

Object object = null;
// 如果beanDefinition為null,則嘗試從緩存中獲取給定的FactoryBean公開的對(duì)象
if (mbd == null) {
    //嘗試從緩存中加載bean
    object = getCachedObjectForFactoryBean(beanName);
}
// 未能從緩存中獲得FactoryBean公開的對(duì)象,則說明該bean是一個(gè)新創(chuàng)建的bean
if (object == null) {
    FactoryBean<?> factory = (FactoryBean<?>) beanInstance;
    if (mbd == null && containsBeanDefinition(beanName)) {
        mbd = getMergedLocalBeanDefinition(beanName);
    }
    boolean synthetic = (mbd != null && mbd.isSynthetic());
    // 從給定的FactoryBean中獲取指定的beanName對(duì)象
    object = getObjectFromFactoryBean(factory, beanName, !synthetic);
}
return object;

protected Object getObjectFromFactoryBean(FactoryBean<?> factory, String beanName, boolean shouldPostProcess) {
    if (factory.isSingleton() && containsSingleton(beanName)) {
        synchronized (getSingletonMutex()) {
            Object object = this.factoryBeanObjectCache.get(beanName);
            if (object == null) {
                //調(diào)用factoryBean的getObject方法
                object = doGetObjectFromFactoryBean(factory, beanName);
                Object alreadyThere = this.factoryBeanObjectCache.get(beanName);
                if (alreadyThere != null) {
                    object = alreadyThere;
                }
            }
            ..........
        }
    }
}

private Object doGetObjectFromFactoryBean(FactoryBean<?> factory, String beanName) throws BeanCreationException {
    Object object;
    try {
        if (System.getSecurityManager() != null) {
            AccessControlContext acc = getAccessControlContext();
            try {
                object = AccessController.doPrivileged((PrivilegedExceptionAction<Object>) factory::getObject, acc);
            }
            catch (PrivilegedActionException pae) {
                throw pae.getException();
            }
        }
        else {
            //調(diào)用重寫的getObject方法
            object = factory.getObject();
        }
    }
   	.......
    return object;
}

@Override
public T getObject() throws Exception {
    return getSqlSession().getMapper(this.mapperInterface);
}

@Override
public <T> T getMapper(Class<T> type) {
    return configuration.getMapper(type, this);
}

public <T> T getMapper(Class<T> type, SqlSession sqlSession) {
    final MapperProxyFactory<T> mapperProxyFactory = (MapperProxyFactory<T>) knownMappers.get(type);
    if (mapperProxyFactory == null) {
        throw new BindingException("Type " + type + " is not known to the MapperRegistry.");
    }
    try {
        return mapperProxyFactory.newInstance(sqlSession);
    } catch (Exception e) {
        throw new BindingException("Error getting mapper instance. Cause: " + e, e);
    }
}

public T newInstance(SqlSession sqlSession) {
    final MapperProxy<T> mapperProxy = new MapperProxy<>(sqlSession, mapperInterface, methodCache);
    return newInstance(mapperProxy);
}

protected T newInstance(MapperProxy<T> mapperProxy) {
    return (T) Proxy.newProxyInstance(mapperInterface.getClassLoader(), new Class[] { mapperInterface }, mapperProxy);
}