springboot BeanDefinitionRegistryPostProcessor说明

向右看齐 2022-09-03 13:13 104阅读 0赞

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## springboot BeanDefinitionRegistryPostProcessor说明 ##

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**相关类与接口**

**BeanDefinitionRegistryPostProcessor**

public interface BeanDefinitionRegistryPostProcessor extends BeanFactoryPostProcessor {
        void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry var1) throws BeansException;
    }

**BeanDefinitionRegistry**

public interface BeanDefinitionRegistry extends AliasRegistry {
    
        void registerBeanDefinition(String var1, BeanDefinition var2) throws BeanDefinitionStoreException;
        void removeBeanDefinition(String var1) throws NoSuchBeanDefinitionException;
        BeanDefinition getBeanDefinition(String var1) throws NoSuchBeanDefinitionException;
    
        boolean containsBeanDefinition(String var1);
        boolean isBeanNameInUse(String var1);
    
        int getBeanDefinitionCount();
        String[] getBeanDefinitionNames();
    }

**AliasRegistry**

public interface AliasRegistry {
    
        void registerAlias(String var1, String var2);
        void removeAlias(String var1);
    
        boolean isAlias(String var1);
    
        String[] getAliases(String var1);
    }

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**示例：模拟dao层接口实现**

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**dao 层**

**QueryDao**

public interface QueryDao {
    
        @Select("select id,name,age from user where id=#{id}")
        String select(Integer id);
    }

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**myannotation 层**

**Select**

@Documented
    @Target(ElementType.METHOD)
    @Retention(RetentionPolicy.RUNTIME)
    public @interface Select {
    
        String value();
    }

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**config 层**

**CustomFactoryBean**

public class CustomFactoryBean<T> implements FactoryBean<T> {
    
        private final Class<T> mapper;
    
        @Resource
        private CustomJDBCTemplate jdbcTemplate;
    
        public CustomFactoryBean(Class<T> mapper){
           this.mapper=mapper;
        }
    
        @Override
        public Class<?> getObjectType() {
            return mapper;
        }
    
        @Override
        @SuppressWarnings("unchecked")
        public T getObject() throws Exception {
            return (T) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[]{mapper}, new InvocationHandler() {
                @Override
                public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                    Select select=method.getAnnotation(Select.class);
                    String value=select.value();
                    value=value.replace("#{id}",args[0].toString());
    
                    return jdbcTemplate.execute(value);
                }
            });
        }
    }

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**CustomBeanDefinitionRegistryPostProcessor**

@Component
    public class CustomBeanDefinitionRegistryPostProcessor implements BeanDefinitionRegistryPostProcessor {
    
        @Override
        public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
            GenericBeanDefinition beanDefinition=new GenericBeanDefinition();
            beanDefinition.setBeanClass(CustomFactoryBean.class);
            beanDefinition.setScope("singleton");
            beanDefinition.getConstructorArgumentValues().addGenericArgumentValue(QueryDao.class);
    
            beanDefinitionRegistry.registerBeanDefinition("queryDao",beanDefinition);
        }
    
        @Override
        public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
    
        }
    }

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**CustomJDBCTemplate**

@Component
    public class CustomJDBCTemplate {
    
        public String execute(String value){
            System.out.println("CustomJDBCTemplate："+value);
    
            return value;
        }
    }

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**controller 层**

**HelloController**

@RestController
    public class HelloController {
    
        @Resource
        private QueryDao queryDao;
    
        @RequestMapping("/hello")
        public String hello(){
            return queryDao.select(1);
        }
    }

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**使用测试**

**localhost:8080/hello，控制台输出：**

2021-08-08 10:27:38.098  INFO 11608 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Initializing Servlet 'dispatcherServlet'
    2021-08-08 10:27:38.110  INFO 11608 --- [nio-8080-exec-1] o.s.web.servlet.DispatcherServlet        : Completed initialization in 12 ms
    CustomJDBCTemplate：select id,name,age from user where id=1