<bean id="userMapper" class="org.mybatis.spring.mapper.MapperFactoryBean"><property name="mapperInterface" value="org.mybatis.spring.sample.mapper.UserMapper" /><property name="sqlSessionFactory" ref="sqlSessionFactory" />
</bean>

<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"><property name="basePackage" value="org.mybatis.spring.sample.mapper" />
</bean>

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {2     if (this.processPropertyPlaceHolders) {3       processPropertyPlaceHolders();4     }5 6     ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);7     scanner.setAddToConfig(this.addToConfig);8     scanner.setAnnotationClass(this.annotationClass);9     scanner.setMarkerInterface(this.markerInterface);
10     scanner.setSqlSessionFactory(this.sqlSessionFactory);
11     scanner.setSqlSessionTemplate(this.sqlSessionTemplate);
12     scanner.setSqlSessionFactoryBeanName(this.sqlSessionFactoryBeanName);
13     scanner.setSqlSessionTemplateBeanName(this.sqlSessionTemplateBeanName);
14     scanner.setResourceLoader(this.applicationContext);
15     scanner.setBeanNameGenerator(this.nameGenerator);
16     scanner.registerFilters();
17     scanner.scan(StringUtils.tokenizeToStringArray(this.basePackage, ConfigurableApplicationContext.CONFIG_LOCATION_DELIMITERS));
18   }把Mapper接口转换成MapperFactoryBean的代码在地17行这个方法里，让我们跟踪进去看一下。  1   @Override2   public Set<BeanDefinitionHolder> doScan(String... basePackages) {3     Set<BeanDefinitionHolder> beanDefinitions = super.doScan(basePackages);4 5     if (beanDefinitions.isEmpty()) {6       logger.warn("No MyBatis mapper was found in '" + Arrays.toString(basePackages) + "' package. Please check your configuration.");7     } else {8       for (BeanDefinitionHolder holder : beanDefinitions) {9         GenericBeanDefinition definition = (GenericBeanDefinition) holder.getBeanDefinition();
10
11         if (logger.isDebugEnabled()) {
12           logger.debug("Creating MapperFactoryBean with name '" + holder.getBeanName()
13               + "' and '" + definition.getBeanClassName() + "' mapperInterface");
14         }
15
16         // the mapper interface is the original class of the bean
17         // but, the actual class of the bean is MapperFactoryBean
18         //把接口的类型设置进去
19         definition.getPropertyValues().add("mapperInterface", definition.getBeanClassName());
20         //设置Bean的真实类型MapperFactoryBean
21         definition.setBeanClass(MapperFactoryBean.class);
22         //是否把Mapper接口加入到Mybatis的Config当中去
23         definition.getPropertyValues().add("addToConfig", this.addToConfig);
24
25         boolean explicitFactoryUsed = false;
26         //如果sqlSessionFactoryBeanName的名字不为空 则在Spring容器中查询
27         //适合多数据源
28         if (StringUtils.hasText(this.sqlSessionFactoryBeanName)) {
29           definition.getPropertyValues().add("sqlSessionFactory", new RuntimeBeanReference(this.sqlSessionFactoryBeanName));
30           explicitFactoryUsed = true;
31         } else if (this.sqlSessionFactory != null) {
32           definition.getPropertyValues().add("sqlSessionFactory", this.sqlSessionFactory);
33           explicitFactoryUsed = true;
34         }
35
36         //如果sqlSessionTemplateBeanName的名字不为空 则在Spring容器中查询
37         //适合多数据源
38         if (StringUtils.ha
39         if (StringUtils.hasText(this.sqlSessionTemplateBeanName)) {
40           if (explicitFactoryUsed) {
41             logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
42           }
43           definition.getPropertyValues().add("sqlSessionTemplate", new RuntimeBeanReference(this.sqlSessionTemplateBeanName));
44           explicitFactoryUsed = true;
45         } else if (this.sqlSessionTemplate != null) {
46           if (explicitFactoryUsed) {
47             logger.warn("Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.");
48           }
49           definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);
50           explicitFactoryUsed = true;
51         }
52
53         if (!explicitFactoryUsed) {
54           if (logger.isDebugEnabled()) {
55             logger.debug("Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.");
56           }
57           definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
58         }
59       }
60     }
61     //这个集合返回以后 Spring容器会将里面的所有内容注册到容器中
62     return beanDefinitions;
63   }