spring boot 动态生成接口实现类的场景分析
目录
- 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<T> implements FactoryBean<T>, InvocationHandler { private Class<T> interfaceClass; public Class<T> getInterfaceClass() { return interfaceClass; } public void setInterfaceClass(Class<T> 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; @Component public class ScanHttpClients implements BeanDefinitionRegistryPostProcessor, ApplicationContextAware { private final Logger logger = LoggerFactory.getLogger(ScanHttpClients.class); private ApplicationContext ctx; public void run(BeanDefinitionRegistry registry) { Set<Class<?>> 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 @Aspect public 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; @MyHttpClient public interface MyHttpClientTest { @PostMapping(value = "test/t1") Object test(String param); }
项目结构:
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