前言

其實(shí)一般不寫(xiě)這樣的分析的，但是這次呢一是為了記錄下來(lái)分析過(guò)程，二是給大家分享一下@MapperScan注解掃描包的流程吧。

提出問(wèn)題

@MapperScan("com.fast")掃描的是com.fast這個(gè)包下面的bean是毋庸置疑的，但是包括子包下面的bean嗎？

疑問(wèn)案例

比如com.fast.master.dao,還有com.fast.second.dao這些包下面的bean是否會(huì)一起被掃描到？

分析

1. 查看MapperScan注解，掃描包主要是這個(gè)@Import({MapperScannerRegistrar.class})

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({MapperScannerRegistrar.class})
@Repeatable(MapperScans.class)
public @interface MapperScan {
    String[] value() default {};

    String[] basePackages() default {};
     
    Class<?>[] basePackageClasses() default {};
     
    Class<? extends BeanNameGenerator> nameGenerator() default BeanNameGenerator.class;
     
    Class<? extends Annotation> annotationClass() default Annotation.class;
     
    Class<?> markerInterface() default Class.class;
     
    String sqlSessionTemplateRef() default "";
     
    String sqlSessionFactoryRef() default "";
     
    Class<? extends MapperFactoryBean> factoryBean() default MapperFactoryBean.class;
}

2. 找到MapperScannerRegistrar.class看實(shí)現(xiàn)過(guò)程，就不全貼了，主要是這個(gè)注解這一塊

    void registerBeanDefinitions(AnnotationAttributes annoAttrs, BeanDefinitionRegistry registry) {
        ClassPathMapperScanner scanner = new ClassPathMapperScanner(registry);
        Optional var10000 = Optional.ofNullable(this.resourceLoader);
        Objects.requireNonNull(scanner);
        var10000.ifPresent(scanner::setResourceLoader);
        Class<? extends Annotation> annotationClass = annoAttrs.getClass("annotationClass");
        if (!Annotation.class.equals(annotationClass)) {
            scanner.setAnnotationClass(annotationClass);
        }
        Class<?> markerInterface = annoAttrs.getClass("markerInterface");
        if (!Class.class.equals(markerInterface)) {
            scanner.setMarkerInterface(markerInterface);
        }
        Class<? extends BeanNameGenerator> generatorClass = annoAttrs.getClass("nameGenerator");
        if (!BeanNameGenerator.class.equals(generatorClass)) {
            scanner.setBeanNameGenerator((BeanNameGenerator)BeanUtils.instantiateClass(generatorClass));
        }
        Class<? extends MapperFactoryBean> mapperFactoryBeanClass = annoAttrs.getClass("factoryBean");
        if (!MapperFactoryBean.class.equals(mapperFactoryBeanClass)) {
            scanner.setMapperFactoryBeanClass(mapperFactoryBeanClass);
        }
        scanner.setSqlSessionTemplateBeanName(annoAttrs.getString("sqlSessionTemplateRef"));
        scanner.setSqlSessionFactoryBeanName(annoAttrs.getString("sqlSessionFactoryRef"));
        List<String> basePackages = new ArrayList();
        basePackages.addAll((Collection)Arrays.stream(annoAttrs.getStringArray("value")).filter(StringUtils::hasText).collect(Collectors.toList()));
        basePackages.addAll((Collection)Arrays.stream(annoAttrs.getStringArray("basePackages")).filter(StringUtils::hasText).collect(Collectors.toList()));
        basePackages.addAll((Collection)Arrays.stream(annoAttrs.getClassArray("basePackageClasses")).map(ClassUtils::getPackageName).collect(Collectors.toList()));
        scanner.registerFilters();
        scanner.doScan(StringUtils.toStringArray(basePackages));
    }

這句周?chē)氖遣皇呛苁煜ぃ褪荕apperScan實(shí)現(xiàn)的注解，value，basePackages，basePackageClasses這幾個(gè)

basePackages.addAll((Collection)Arrays.stream(annoAttrs.getStringArray("value")).filter(StringUtils::hasText).collect(Collectors.toList()));
basePackages.addAll((Collection)Arrays.stream(annoAttrs.getStringArray("basePackages")).filter(StringUtils::hasText).collect(Collectors.toList()));
basePackages.addAll((Collection)Arrays.stream(annoAttrs.getClassArray("basePackageClasses")).map(ClassUtils::getPackageName).collect(Collectors.toList()));
scanner.registerFilters();
scanner.doScan(StringUtils.toStringArray(basePackages));

從scanner.doScan這句進(jìn)去，這里是開(kāi)始掃描包的地方

3. 打開(kāi)調(diào)用的方法

private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
        Iterator var3 = beanDefinitions.iterator();

        while(var3.hasNext()) {
            BeanDefinitionHolder holder = (BeanDefinitionHolder)var3.next();
            GenericBeanDefinition definition = (GenericBeanDefinition)holder.getBeanDefinition();
            String beanClassName = definition.getBeanClassName();
            LOGGER.debug(() -> {
                return "Creating MapperFactoryBean with name '" + holder.getBeanName() + "' and '" + beanClassName + "' mapperInterface";
            });
            definition.getConstructorArgumentValues().addGenericArgumentValue(beanClassName);
            definition.setBeanClass(this.mapperFactoryBeanClass);
            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(() -> {
                        return "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(() -> {
                        return "Cannot use both: sqlSessionTemplate and sqlSessionFactory together. sqlSessionFactory is ignored.";
                    });
                }
                definition.getPropertyValues().add("sqlSessionTemplate", this.sqlSessionTemplate);
                explicitFactoryUsed = true;
            }
     
            if (!explicitFactoryUsed) {
                LOGGER.debug(() -> {
                    return "Enabling autowire by type for MapperFactoryBean with name '" + holder.getBeanName() + "'.";
                });
                definition.setAutowireMode(2);
            }
        }
    }

4. 從這個(gè)方法第一行開(kāi)始debug，這里我使用@MapperScan("com.fast.framework.dao") 是掃描的com.fast.framework.dao包

這個(gè)是掃描到的包，說(shuō)明會(huì)掃描到子包，perfect，解決了開(kāi)始提出的問(wèn)題。

總結(jié)

其實(shí)這里的分析過(guò)程不是特別詳細(xì)，因?yàn)榈竭@里是證明掃描出來(lái)的包，從而間接證明掃描到的包都會(huì)被使用。剩下的：上一步怎么掃描的全部包，還有掃描到包怎么初始化的都沒(méi)有詳細(xì)分析。所以也是小水一篇吧，主要是要明白@MapperScan注解會(huì)掃描包的子包和學(xué)會(huì)這種分析思路。