spring|spring boot 动态生成接口实现类的场景分析 springboot动态生成接口实现类的

一: 定义注解
二: 建立动态代理类
三: 注入spring容器
四: 编写拦截器
五: 新建测试类

在某些业务场景中，我们只需要业务代码中定义相应的接口或者相应的注解，并不需要实现对应的逻辑。
比如 mybatis和feign：在 mybatis 中，我们只需要定义对应的mapper接口；在 feign 中，我们只需要定义对应业务系统中的接口即可。
那么在这种场景下，具体的业务逻辑时怎么执行的呢，其实原理都是动态代理。
我们这里不具体介绍动态代理，主要看一下它在springboot项目中的实际应用，下面我们模仿feign来实现一个调用三方接口的 httpclient。

一: 定义注解

package com.mysgk.blogdemo.annotation; public @interface MyHttpClient {}

二: 建立动态代理类

package com.mysgk.blogdemo.proxy; import org.springframework.beans.factory.FactoryBean; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.lang.reflect.Proxy; public class RibbonAopProxyFactory implements FactoryBean, InvocationHandler { private Class interfaceClass; public Class getInterfaceClass() {return interfaceClass; } public void setInterfaceClass(Class interfaceClass) {this.interfaceClass = interfaceClass; } @Override public T getObject() throws Exception {return (T) Proxy.newProxyInstance(this.getClass().getClassLoader(), new Class[]{interfaceClass}, this); } @Override public Class getObjectType() {return interfaceClass; } @Override public boolean isSingleton() {return true; } /**真正执行的方法*/ @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {return "invoke " + proxy.getClass().getName() + "." + method.getName() + " , do anything .."; }}

三: 注入spring容器

package com.mysgk.blogdemo.start; import cn.hutool.core.util.ClassUtil; import cn.hutool.core.util.StrUtil; import com.mysgk.blogdemo.annotation.MyHttpClient; import com.mysgk.blogdemo.proxy.RibbonAopProxyFactory; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.BeansException; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.beans.factory.support.BeanDefinitionBuilder; import org.springframework.beans.factory.support.BeanDefinitionRegistry; import org.springframework.beans.factory.support.BeanDefinitionRegistryPostProcessor; import org.springframework.beans.factory.support.GenericBeanDefinition; import org.springframework.context.ApplicationContext; import org.springframework.context.ApplicationContextAware; import org.springframework.stereotype.Component; import java.util.Set; @Componentpublic class ScanHttpClients implements BeanDefinitionRegistryPostProcessor, ApplicationContextAware { private final Logger logger = LoggerFactory.getLogger(ScanHttpClients.class); private ApplicationContext ctx; public void run(BeanDefinitionRegistry registry) {Set> scanPackage = ClassUtil.scanPackageByAnnotation("com.mysgk", MyHttpClient.class); for (Class cls : scanPackage) {BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(cls); GenericBeanDefinition definition = (GenericBeanDefinition) builder.getRawBeanDefinition(); definition.getPropertyValues().add("interfaceClass", definition.getBeanClassName()); definition.setBeanClass(RibbonAopProxyFactory.class); definition.setAutowireMode(GenericBeanDefinition.AUTOWIRE_BY_TYPE); String beanName = StrUtil.removePreAndLowerFirst(cls.getSimpleName(), 0) + "RibbonClient"; registry.registerBeanDefinition(beanName, definition); } } @Override public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry registry) throws BeansException {run(registry); } @Override public void postProcessBeanFactory(ConfigurableListableBeanFactory beanFactory) throws BeansException { } @Override public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {this.ctx = ctx; }}

四: 编写拦截器

package com.mysgk.blogdemo.aop; import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.annotation.Pointcut; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.http.HttpEntity; import org.springframework.http.HttpMethod; import org.springframework.http.ResponseEntity; import org.springframework.stereotype.Component; import org.springframework.web.client.RestTemplate; @Component@Aspectpublic class InterceptAnnotation { @Autowired private RestTemplate ribbonLoadBalanced; @Pointcut("@annotation(com.mysgk.blogdemo.annotation.MyHttpClient)") public void execute() { } @Around("execute()") public Object interceptAnnotation(ProceedingJoinPoint joinPoint) throws Throwable {/*** 此处省略获取 url, httpMethod, requestEntity, responseType 等参数的处理过程*/ResponseEntity exchange = ribbonLoadBalanced.exchange("url", HttpMethod.GET, HttpEntity.EMPTY, Object.class); return exchange.getBody(); }}

五: 新建测试类

package com.mysgk.blogdemo.client; import com.mysgk.blogdemo.annotation.MyHttpClient; import org.springframework.web.bind.annotation.PostMapping; import org.springframework.web.bind.annotation.RequestBody; @MyHttpClientpublic interface MyHttpClientTest { @PostMapping(value = "https://www.it610.com/article/test/t1") Object test(String param); }

项目结构：