详解Spring中实现接口动态的解决方法

public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {
 if (this.processPropertyPlaceHolders) {
  processPropertyPlaceHolders();
 }

 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.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);
}

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 {
 for (BeanDefinitionHolder holder : beanDefinitions) {
  GenericBeanDefinition 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
  definition.getPropertyValues().add("mapperInterface", definition.getBeanClassName());
  definition.setBeanClass(MapperFactoryBean.class);

  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() + "'.");
  }
  definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);
  }
 }
 }

 return beanDefinitions;
}

public class MapperFactoryBean<T> extends SqlSessionDaoSupport implements FactoryBean<T> {

 private Class<T> mapperInterface;

 private boolean addToConfig = true;

 /**
 * Sets the mapper interface of the MyBatis mapper
 *
 * @param mapperInterface class of the interface
 */
 public void setMapperInterface(Class<T> mapperInterface) {
 this.mapperInterface = mapperInterface;
 }

 /**
 * If addToConfig is false the mapper will not be added to MyBatis. This means
 * it must have been included in mybatis-config.xml.
 * <p>
 * If it is true, the mapper will be added to MyBatis in the case it is not already
 * registered.
 * <p>
 * By default addToCofig is true.
 *
 * @param addToConfig
 */
 public void setAddToConfig(boolean addToConfig) {
 this.addToConfig = addToConfig;
 }

 /**
 * {@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 (Throwable t) {
  logger.error("Error while adding the mapper '" + this.mapperInterface + "' to configuration.", t);
  throw new IllegalArgumentException(t);
  } finally {
  ErrorContext.instance().reset();
  }
 }
 }

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

 /**
 * {@inheritDoc}
 */
 public Class<T> getObjectType() {
 return this.mapperInterface;
 }

 /**
 * {@inheritDoc}
 */
 public boolean isSingleton() {
 return true;
 }