spring注册bean

一时失言乱红尘 2022-02-27 12:34 210阅读 0赞

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 {
        @Override
        public 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 {
    
        @Autowired
        private Foo foo;
    
        public static void main(String[] args) {
            SpringApplication.run(Main.class, args);
        }
    
        @Override
        public void run(String... args) throws Exception {
            foo.foo();
        }
    
    }

Foo.foo() invoked!

## 1.2ClassPathBeanDefinitionScanner ##

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

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