SpringBoot 动态代理实现三方接口调用

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、创建客户端调用类
• 六、main方法测试
• 七、启动项目

---

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

定义好注解，方便后面扫描使用了该注解的类和方法

package com.mysgk.blogdemo.annotation;

import java.lang.annotation.Documented;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;

import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.TYPE;
import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * @author mysgk
 * @link https://www.cnblogs.com/mysgk/p/15619895.html
 * <p>
 * 这里应该还有一个注解来标识方法，demo为了方便都使用该注解
 */
@Retention(RUNTIME)
@Target({TYPE, METHOD})
@Documented
public @interface MyHttpClient {
}

二、建立动态代理类

用于产生代理类并执行对应方法

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;

/**
 * @author mysgk
 * @link https://www.cnblogs.com/mysgk/p/15619895.html
 */
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 {
		final Class[] interfaces = {interfaceClass};
		return (T) Proxy.newProxyInstance(this.getClass().getClassLoader(), interfaces, this);
	}

	@Override
	public Class<?> getObjectType() {
		return interfaceClass;
	}

	@Override
	public boolean isSingleton() {
		return true;
	}

	/**
	 * 真正执行的方法,会被aop拦截
	 */
	@Override
	public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
		return "invoke " + interfaceClass.getName() + "." + method.getName() + " , do anything ..";
	}
}

三、注入spring容器

在项目启动时，扫描第一步定义的注解，生成该类的实现类，并将其注入到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.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.stereotype.Component;
import java.util.Set;

/**
 * @author mysgk
 * @link https://www.cnblogs.com/mysgk/p/15619895.html
 */
@Component
public class ScanHttpClients implements BeanDefinitionRegistryPostProcessor {

	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 {

	}
}

四、编写拦截器

拦截动态代理生成的方法，实现我们真正的业务逻辑

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;

/**
 * @author mysgk
 * @link https://www.cnblogs.com/mysgk/p/15619895.html
 */
@Component
@Aspect
public class InterceptAnnotation {

	@Autowired
	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("http://www.baidu.com", HttpMethod.GET, HttpEntity.EMPTY, Object.class);
		return exchange.getBody();
	}

}

五、创建客户端调用类

此类实现将远程接口当做本地方法调用

package com.mysgk.blogdemo.client;

import com.mysgk.blogdemo.annotation.MyHttpClient;
import org.springframework.web.bind.annotation.PostMapping;

/**
 * @author mysgk
 * @link https://www.cnblogs.com/mysgk/p/15619895.html
 */
@MyHttpClient
public interface MyHttpClientTest {

	@MyHttpClient
	@PostMapping(value = "test/t1")
	Object test(String param);

}

六、main方法测试

注入客户端进行调用

package com.mysgk.blogdemo;

import com.mysgk.blogdemo.client.MyHttpClientTest;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

/**
 * @author mysgk
 * @link https://www.cnblogs.com/mysgk/p/15619895.html
 */
@SpringBootApplication
@RestController
public class Main {

	@Bean
	RestTemplate restTemplate() {
		return new RestTemplate();
	}

	@Autowired
	MyHttpClientTest myHttpClientTest;

	public static void main(String[] args) {
		SpringApplication.run(Main.class, args);
	}

	@GetMapping("/t1")
	public Object t1() {
		return myHttpClientTest.test("1");
	}
}

七、启动项目

访问 127.0.0.1:8080/t1,得到如下结果

此时我们调用的是

myHttpClientTest.test

但是真正运行的是

RibbonAopProxyFactory.invoke 

此时返回的应该是

invoke com.mysgk.blogdemo.client.MyHttpClientTest.test  , do anything ..

由于我们使用aop拦截了该方法，所以最终的结果是访问到了baidu
调用流程图

最后附上pom

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>org.example</groupId>
    <artifactId>bolgdemo</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
            <version>2.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-aop</artifactId>
            <version>2.1.6.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>cn.hutool</groupId>
            <artifactId>hutool-all</artifactId>
            <version>5.3.10</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
            <version>2.1.5.RELEASE</version>
            <exclusions>
                <exclusion>
                    <artifactId>httpclient</artifactId>
                    <groupId>org.apache.httpcomponents</groupId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <artifactId>httpclient</artifactId>
            <groupId>org.apache.httpcomponents</groupId>
            <version>4.5.13</version>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.5.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>

    </build>
</project>