spring注册bean

手动注册bean的两种方式：

实现ImportBeanDefinitionRegistrar
实现BeanDefinitionRegistryPostProcessor

1.实现ImportBeanDefinitionRegistrar

ImportBeanDefinitionRegistrar其本质也是通过BeanDefinitionRegistryPostProcessor来实现的。实现ImportBeanDefinitionRegistrar比较简单，也有多种方式，下面这个是最简单的手动注册bean的方式。

1.1 手动创建BeanDefinition

public class Foo {public void foo() {System.out.println("Foo.foo() invoked!");}
}public class FooImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {@Overridepublic void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {BeanDefinitionBuilder bdb = BeanDefinitionBuilder.genericBeanDefinition(Foo.class);BeanDefinition bd = bdb.getBeanDefinition();registry.registerBeanDefinition("foo", bd);}
}@SpringBootApplication
@Import(FooImportBeanDefinitionRegistrar.class)
public class Main implements CommandLineRunner {@Autowiredprivate Foo foo;public static void main(String[] args) {SpringApplication.run(Main.class, args);}@Overridepublic void run(String... args) throws Exception {foo.foo();}}

Foo.foo() invoked!

1.2ClassPathBeanDefinitionScanner

public class FooImportBeanDefinitionRegistrar implements ImportBeanDefinitionRegistrar {@Overridepublic void registerBeanDefinitions(AnnotationMetadata importingClassMetadata, BeanDefinitionRegistry registry) {ClassPathBeanDefinitionScanner scanner = new ClassPathBeanDefinitionScanner(registry);scanner.addIncludeFilter(new AssignableTypeFilter(Foo.class));scanner.scan("com.study.bootwebsimple.register");//类和包必须都注入}
}

1.3扫描自定义注解

一般都是扫描自定义的注解，才会继承ClassPathBeanDefinitionScanner)。这里你可以扫描自定义的注解，生成BeanDefinition（或其代理）的定义，然后注册到spring容器中。实现代码可以参考Mybatis的
org.mybatis.spring.annotation.MapperScannerRegistrar类，Mybatis扫描Mapper注解，通过MapperFactoryBean来代理了Mapper，并将其注册到spring中

2.实现BeanDefinitionRegistryPostProcessor

@Data
public class Person {private String name;public void foo() {System.out.println("Person.foo() invoked!");}
}public class MyBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {@Overridepublic void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {BeanDefinitionBuilder bdb = BeanDefinitionBuilder.rootBeanDefinition(Person.class);bdb.addPropertyValue("name", "lipo");registry.registerBeanDefinition("person", bdb.getBeanDefinition());}@Overridepublic void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException {}
}@SpringBootApplication
@Import({FooImportBeanDefinitionRegistrar.class, MyBeanDefinitionRegistryPostProcessor.class})
public class Main implements CommandLineRunner {@Autowiredprivate Foo foo;@Autowiredprivate Person person;public static void main(String[] args) {SpringApplication.run(Main.class, args);}@Overridepublic void run(String... args) throws Exception {foo.foo();person.foo();}}

Foo.foo() invoked!
Person.foo() invoked!