Springboot整合Forest的快速入门及源码解析

项目介绍

Forest 是一个开源的 Java HTTP 客户端框架，它能够将 HTTP 的所有请求信息（包括 URL、Header 以及 Body 等信息）绑定到您自定义的 Interface 方法上，能够通过调用本地接口方法的方式发送 HTTP 请求。

源码地址

https://gitee.com/dromara/forest

快速入门

1. 引入依赖

        <dependency>
            <groupId>com.dtflys.forest</groupId>
            <artifactId>forest-spring-boot-starter</artifactId>
            <version>1.5.28</version>
        </dependency>

2. 暴露接口

@RestController
public class IndexController {
    @Value(value = "${spring.application.name}")
    private String applicationName;     //demo

    @GetMapping("/index")
    public String index() {
        return "您好，欢迎访问【" + applicationName + "】";
    }

    @GetMapping("/hello")
    public String hello(@RequestParam(required = false) String msg) throws InterruptedException {
        // 模拟业务耗时处理流程
//        Thread.sleep(2 * 1000L);
        return "hello: " + msg;
    }
}

3. 写Http接口

@Address(host = "127.0.0.1", port = "9098")
public interface MyForestClient {
    /**
     * 本地测试接口
     */
    @Get(url = "/index")
    String index();

    @Get(url = "/hello?msg=${msg}")
    String hello(@DataVariable("msg") String msg);
}

4. 测试运行

@SpringBootTest
public class ForestTest {

    @Autowired
    private MyForestClient myClient;

    @Test
    public void testForest() throws Exception {
        // 调用接口
        String index = myClient.index();
        System.out.println(index);
        String hello = myClient.hello("测试...");
        System.out.println(hello);
    }
}

源码解析

1. 导入starter后，会扫描所有依赖的 resources/META-INF/spring.factories 将加载对应的文件中写的bean，ForestAutoConfiguration。该类会引入ForestBeanRegister 。

@Configuration
@EnableConfigurationProperties({ForestConfigurationProperties.class})
@Import({ForestScannerRegister.class})
public class ForestAutoConfiguration {
    
	//...
    @Bean
    @DependsOn("forestBeanProcessor")
    @ConditionalOnMissingBean
    public ForestBeanRegister forestBeanRegister(SpringForestProperties properties,
                                                    SpringForestObjectFactory forestObjectFactory,
                                                    SpringInterceptorFactory forestInterceptorFactory,
                                                    ForestConfigurationProperties forestConfigurationProperties) {
        ForestBeanRegister register = new ForestBeanRegister(
                applicationContext,
                forestConfigurationProperties,
                properties,
                forestObjectFactory,
                forestInterceptorFactory);
        register.registerForestConfiguration();
        register.registerScanner();
        return register;
    }

2. 首先@Import({ForestScannerRegister.class}) ，会找到所有匹配的包，若 @ForestScan 注解未定义扫描包名，则扫描整个项目。
3. ForestBeanRegister#registerScanner会进行扫描注册，使用了自定义的扫描器ClassPathClientScanner，扫描匹配的方法是ClassPathClientScanner#interfaceFilter，将扫描好的匹配类生成对应的实体Bean，注册到容器中。ClassPathClientScanner#processBeanDefinitions。往容器中注入Class为ClientFactoryBean的Bean。

    private void processBeanDefinitions(Set<BeanDefinitionHolder> beanDefinitions) {
        GenericBeanDefinition definition;
        for (BeanDefinitionHolder holder : beanDefinitions) {
            definition = (GenericBeanDefinition) holder.getBeanDefinition();
            String beanClassName = definition.getBeanClassName();
            ClientFactoryBeanUtils.setupClientFactoryBean(definition, configurationId, beanClassName);
            logger.info("[Forest] Created Forest Client Bean with name '" + holder.getBeanName()
                    + "' and Proxy of '" + beanClassName + "' client interface");

        }
    }

4. ClientFactoryBean#getObject的实体类。返回的是ForestConfiguration#createInstance。生成代理类，使用的拦截拦截类是InterfaceProxyHandler。

    public <T> T createInstance(Class<T> clazz) {
        ProxyFactory<T> proxyFactory = this.getProxyFactory(clazz);
        return proxyFactory.createInstance();
    }

    //ProxyFactory#createInstance
	public T createInstance() {
        T instance = this.configuration.getInstanceCache().get(this.interfaceClass);
        boolean cacheEnabled = this.configuration.isCacheEnabled();
        if (cacheEnabled && instance != null) {
            return instance;
        } else {
            synchronized(this.configuration.getInstanceCache()) {
                instance = this.configuration.getInstanceCache().get(this.interfaceClass);
                if (cacheEnabled && instance != null) {
                    return instance;
                } else {
                    InterfaceProxyHandler<T> interfaceProxyHandler = new InterfaceProxyHandler(this.configuration, this, this.interfaceClass);
                    instance = Proxy.newProxyInstance(this.interfaceClass.getClassLoader(), new Class[]{this.interfaceClass, ForestClientProxy.class}, interfaceProxyHandler);
                    if (cacheEnabled) {
                        this.configuration.getInstanceCache().put(this.interfaceClass, instance);
                    }

                    return instance;
                }
            }
        }
    }

5. InterfaceProxyHandler该拦截类主要根据拦截方法，解析对应的注解信息，进行http请求，最核心的就是调用okhttp3的请求。

    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
        String methodName = method.getName();
        if (method.isDefault()) {
            return this.invokeDefaultMethod(proxy, method, args);
        } else {
            ForestMethod forestMethod = (ForestMethod)this.forestMethodMap.get(method);
            if (forestMethod != null) {
                return forestMethod.invoke(args);
            } else {
                if (args == null || args.length == 0) {
                    InterfaceProxyHandler.NonParamsInvocation invocation = getNonParamsInvocation(methodName);
                    if (invocation != null) {
                        return invocation.invoke(this, proxy);
                    }
                }

                if (args != null && args.length == 1) {
                    if ("equals".equals(methodName)) {
                        Object obj = args[0];
                        if (Proxy.isProxyClass(obj.getClass())) {
                            InvocationHandler h1 = Proxy.getInvocationHandler(proxy);
                            InvocationHandler h2 = Proxy.getInvocationHandler(obj);
                            return h1.equals(h2);
                        }

                        return false;
                    }

                    if ("wait".equals(methodName) && args[0] instanceof Long) {
                        proxy.wait((Long)args[0]);
                    }
                }

                if (args != null && args.length == 2 && args[0] instanceof Long && args[1] instanceof Integer && "wait".equals(methodName)) {
                    proxy.wait((Long)args[0], (Integer)args[1]);
                }

                throw new NoSuchMethodError(method.getName());
            }
        }
    }