模拟解析Mapper接口

点此返回

public class MapperPostProcessor  implements BeanDefinitionRegistryPostProcessor {
    @Override
    public void postProcessBeanDefinitionRegistry
            (BeanDefinitionRegistry beanFactory) 
            throws BeansException {
        try {
            //扫描 mapper 包下的资源（使用通配符解析器）
            PathMatchingResourcePatternResolver resolver = 
                    new PathMatchingResourcePatternResolver();
            Resource[] resources = resolver
                    .getResources("classpath:com/itheima/a05/mapper/**/*.class");

            //创建名称生成器对象
            AnnotationBeanNameGenerator generator = new AnnotationBeanNameGenerator();

            //读取类的元数据信息
            CachingMetadataReaderFactory factory = new CachingMetadataReaderFactory();
            for (Resource resource : resources) {
                MetadataReader reader = factory.getMetadataReader(resource);
                ClassMetadata classMetadata = reader.getClassMetadata();
                //判断是否是接口
                if (classMetadata.isInterface()) {
                    //生成 BeanDefinition
                    AbstractBeanDefinition bd1 = 
                            BeanDefinitionBuilder
                                    .genericBeanDefinition(MapperFactoryBean.class)
                                    //给构造方法设置参数值（接口名称）
                                    .addConstructorArgValue(classMetadata.getClassName())
                                    //设置装配模式
                                    .setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE)   
                                    .getBeanDefinition();
                    
                    //再生成一个 BeanDefinition
                    AbstractBeanDefinition bd2 = 
                                    BeanDefinitionBuilder
                                    .genericBeanDefinition(classMetadata.getClassName())
                                    .getBeanDefinition();
                    //根据bd2生成名称，以免覆盖bd1生成的名称
                    String beanName = generator.generateBeanName(bd2, beanFactory);

                    //注册到Bean工厂
                    beanFactory.registerBeanDefinition(beanName,bd1);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    @Override
    public void postProcessBeanFactory
            (ConfigurableListableBeanFactory beanFactory)
            throws BeansException {
    }
}

当其他类调用时，只需调用容器的registerBean方法，传入对实现类.class文件即可

public class BeanApp {
    private static final Logger log = LoggerFactory.getLogger(BeanApp.class);
    public static void main(String[] args) throws IOException {
        //创建一个干净容器
        GenericApplicationContext context = new GenericApplicationContext();
        context.registerBean("config", Config.class);

        //解析Mapper接口
        context.registerBean(MapperPostProcessor.class);

        //初始化容器
        context.refresh();
        for (String name : context.getBeanDefinitionNames()) {
            System.out.println(name);
        }
        //销毁容器
        context.close();
    }
}