SpringBoot 动态代理实现三方接口调用
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>
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