FeignClient 在不同场景中的应用

FeignClient 使用

为了测试方便，这里提供四个项目

1. user-server
2. user-server-api
3. spring-boot-feign
4. spring-mvc-feign

Spring Cloud 使用

user-server项目

提供服务，暂时提供三个简单的查询操作

Controller

package com.zyndev.server.user.controller;import com.zyndev.commontool.web.BaseResponse;import com.zyndev.server.user.entity.UserEntity;import com.zyndev.server.user.service.IUserService;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.*;/** * @author: 张瑀楠 [e-mail] */@RestController@RequestMapping("user")public class UserController {    @Autowired    private IUserService userService;    @DeleteMapping("deleteById")    public BaseResponse deleteByID(@RequestParam("id")Integer id) {        try {            Integer retVal = userService.deleteByID(id);            if (retVal == null || retVal == 0) {                return BaseResponse.fail("删除失败");            }            return BaseResponse.success(null);        } catch (Exception e) {            return BaseResponse.fail(e.getMessage());        }    }    @GetMapping("getUserByUID")    public BaseResponse getUserByID(@RequestParam("id")Integer id) {        try {            UserEntity userEntity = userService.getUserByID(id);            if (userEntity == null) {                return BaseResponse.fail("未找到用户信息");            }            return BaseResponse.success(userEntity);        } catch (Exception e) {            return BaseResponse.fail(e.getMessage());        }    }}

user-server-api

提供一个消费方使用服务的API

package com.zyndev.server.user.api;import com.zyndev.commontool.web.BaseResponse;import com.zyndev.server.user.hystrix.UserServiceHystrix;import org.springframework.cloud.netflix.feign.FeignClient;import org.springframework.web.bind.annotation.DeleteMapping;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;/** * Desc:  * @author: 张瑀楠 [e-mail]  * TODO: */@FeignClient(name = "user-server",url = "${user-server-api.url}", path = "user", fallback = UserServiceHystrix.class)public interface UserServiceAPI {    @DeleteMapping("deleteById")    public BaseResponse deleteByID(@RequestParam("id")Integer id);    @GetMapping("getUserByUID")    public BaseResponse getUserByID(@RequestParam("id")Integer id);}

其中通过动态配置 url 来实现在 spring cloud 外部环境调用接口

FeignClient注解源码

package org.springframework.cloud.netflix.feign;import java.lang.annotation.Documented;import java.lang.annotation.ElementType;import java.lang.annotation.Retention;import java.lang.annotation.RetentionPolicy;import java.lang.annotation.Target;import org.springframework.core.annotation.AliasFor;/** * Annotation for interfaces declaring that a REST client with that interface should be * created (e.g. for autowiring into another component). If ribbon is available it will be * used to load balance the backend requests, and the load balancer can be configured * using a <code>@RibbonClient</code> with the same name (i.e. value) as the feign client. * * @author Spencer Gibb * @author Venil Noronha */@Target(ElementType.TYPE)@Retention(RetentionPolicy.RUNTIME)@Documentedpublic @interface FeignClient {    /**     * The name of the service with optional protocol prefix. Synonym for {@link #name()     * name}. A name must be specified for all clients, whether or not a url is provided.     * Can be specified as property key, eg: ${propertyKey}.     */    @AliasFor("name")    String value() default "";    /**     * The service id with optional protocol prefix. Synonym for {@link #value() value}.     *     * @deprecated use {@link #name() name} instead     */    @Deprecated    String serviceId() default "";    /**     * The service id with optional protocol prefix. Synonym for {@link #value() value}.     */    @AliasFor("value")    String name() default "";    /**     * Sets the <code>@Qualifier</code> value for the feign client.     */    String qualifier() default "";    /**     * An absolute URL or resolvable hostname (the protocol is optional).     */    String url() default "";    /**     * Whether 404s should be decoded instead of throwing FeignExceptions     */    boolean decode404() default false;    /**     * A custom <code>@Configuration</code> for the feign client. Can contain override     * <code>@Bean</code> definition for the pieces that make up the client, for instance     * {@link feign.codec.Decoder}, {@link feign.codec.Encoder}, {@link feign.Contract}.     *     * @see FeignClientsConfiguration for the defaults     */    Class<?>[] configuration() default {};    /**     * Fallback class for the specified Feign client interface. The fallback class must     * implement the interface annotated by this annotation and be a valid spring bean.     */    Class<?> fallback() default void.class;    /**     * Define a fallback factory for the specified Feign client interface. The fallback     * factory must produce instances of fallback classes that implement the interface     * annotated by {@link FeignClient}. The fallback factory must be a valid spring     * bean.     *     * @see feign.hystrix.FallbackFactory for details.     */    Class<?> fallbackFactory() default void.class;    /**     * Path prefix to be used by all method-level mappings. Can be used with or without     * <code>@RibbonClient</code>.     */    String path() default "";    /**     * Whether to mark the feign proxy as a primary bean. Defaults to true.     */    boolean primary() default true;}

在源码中可以看到比较有用的四个注解 name ,url, fallback ,path

• name 指定微服务的实例名称，唯一，必填，通过实例名称可以得到实例对应的访问地址
• fallback 配置熔断
• url 配置一个绝对的地址访问，默认为空字符串，当其不空时，则使用该地址访问
• path 配置一个所有方法级别的mappings 相当于在类上加 requestMapping, 例如上面的UserServiceAPI 所有访问地址为 /user/xxx

注意：FeignClient 请求路径和 包名 无关,

/user/xxx1/user/xxx2/user/xxx3

如果想放着以上地址，api 有三种实现方式

1. 在所有的方法中 写明全路径 例如 @RequestMapping(“/user/xxx1”)
2. 在类上写 @RequestMapping(“user”) 在对应方法写 @RequestMapping(“xxx1”)
3. 使用 FeignClient 的 path 标注

如果在spring cloud项目内部使用，可以直接引入 user-server-api

<dependency>    <groupId>com.zyndev</groupId>    <artifactId>user-server-api</artifactId>    <version>0.0.1-SNAPSHOT</version></dependency>

需要注意的是，因为在 feignclient 中使用占位符,所以你需要在配置文件中添加

user-server-api.url=

否则会报出如下异常信息

org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'com.zyndev.server.user.api.UserServiceAPI' defined in null: Could not resolve placeholder 'user-server-api.url' in value "http://${user-server-api.url}"; nested exception is java.lang.IllegalArgumentException: Could not resolve placeholder 'user-server-api.url' in value "http://${user-server-api.url}"    at org.springframework.beans.factory.config.PlaceholderConfigurerSupport.doProcessProperties(PlaceholderConfigurerSupport.java:223) ~[spring-beans-4.3.11.RELEASE.jar:4.3.11.RELEASE]    at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.processProperties(PropertySourcesPlaceholderConfigurer.java:180) ~[spring-context-4.3.11.RELEASE.jar:4.3.11.RELEASE]    at org.springframework.context.support.PropertySourcesPlaceholderConfigurer.postProcessBeanFactory(PropertySourcesPlaceholderConfigurer.java:152) ~[spring-context-4.3.11.RELEASE.jar:4.3.11.RELEASE]    at org.springframework.context.support.PostProcessorRegistrationDelegate.invokeBeanFactoryPostProcessors(PostProcessorRegistrationDelegate.java:281) ~[spring-context-4.3.11.RELEASE.jar:4.3.11.RELEASE]    at org.springf

Spring boot 使用

这里的spring boot项目值的是不需要注册到微服务中，单独的项目

1. 首先引入依赖

<dependency>    <groupId>org.springframework.boot</groupId>    <artifactId>spring-boot-starter-web</artifactId></dependency><dependency>    <groupId>com.zyndev</groupId>    <artifactId>user-server-api</artifactId>    <version>0.0.1-SNAPSHOT</version></dependency>

1. 在配置文件添加如下配置
   其中后面的地址为网关访问地址

user-server-api.url=192.168.0.101:8089/api/user-server/

1. 在启动类中添加注解

@EnableFeignClients(basePackages={"com.zyndev.server.user.api"})@SpringBootApplicationpublic class SpringBootFeignApplication {    public static void main(String[] args) {        SpringApplication.run(SpringBootFeignApplication.class, args);    }}

传统Spring项目使用

这里的传统Spring项目指的是没有使用spring boot的spring项目，例如ssm

精力有限只测试了 spring mvc 项目

1. 配置
   如果使用非 spring cloud，则应该在 api 的 FeignClient 注解上设置 url,例如例子程序

在项目配置 properties 文件，这里我使用 server.properties

下面是我测试的时候自己起的 网关地址

server.properties

user-server-api.url=192.168.0.101:8089/api/user-server/

这里配置的 spring mvc 项目，配置servlet 主要为了加载 application.xml
web.xml

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xmlns="http://java.sun.com/xml/ns/javaee"         xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"         version="3.0">    <display-name>Archetype Created Web Application</display-name>    <servlet>        <servlet-name>dispatcherServlet</servlet-name>        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>        <init-param>            <param-name>contextConfigLocation</param-name>            <param-value>classpath:spring/application.xml</param-value>        </init-param>        <load-on-startup>1</load-on-startup>    </servlet>    <servlet-mapping>        <servlet-name>dispatcherServlet</servlet-name>        <url-pattern>/</url-pattern>    </servlet-mapping></web-app>

application.xml

这里主要为了加载属性文件

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"       xmlns:context="http://www.springframework.org/schema/context"       xmlns:mvc="http://www.springframework.org/schema/mvc"       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"       xsi:schemaLocation="http://www.springframework.org/schema/beans       http://www.springframework.org/schema/beans/spring-beans.xsd       http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.3.xsd       http://www.springframework.org/schema/context       http://www.springframework.org/schema/context/spring-context.xsd">    <!-- 包扫描，暂时扫描全部包 -->    <context:component-scan base-package="com.renren" />    <context:property-placeholder location="classpath:microserver/server.properties"></context:property-placeholder>    <bean class="org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter"/>    <mvc:default-servlet-handler/>    <mvc:annotation-driven/></beans>

添加配置类

package com.renren.config;import com.google.gson.Gson;import org.springframework.boot.autoconfigure.ImportAutoConfiguration;import org.springframework.boot.autoconfigure.web.HttpMessageConverters;import org.springframework.cloud.netflix.feign.EnableFeignClients;import org.springframework.cloud.netflix.feign.FeignAutoConfiguration;import org.springframework.cloud.netflix.feign.ribbon.FeignRibbonClientAutoConfiguration;import org.springframework.cloud.netflix.ribbon.RibbonAutoConfiguration;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import org.springframework.http.converter.HttpMessageConverter;import org.springframework.http.converter.json.GsonHttpMessageConverter;import java.util.ArrayList;import java.util.Collection;/** * @author 张瑀楠 [e-mail] * @version 1.0 * time: 2017/12/13 11:40 * TODO: */@ImportAutoConfiguration({RibbonAutoConfiguration.class, FeignRibbonClientAutoConfiguration.class, FeignAutoConfiguration.class})@EnableFeignClients(basePackages={"com.zyndev.server.user.api"})@Configurationpublic class Config {    @Bean    public HttpMessageConverters customConverters() {        Collection<HttpMessageConverter<?>> messageConverters = new ArrayList<>();        GsonHttpMessageConverter gsonHttpMessageConverter = new GsonHttpMessageConverter();        messageConverters.add(gsonHttpMessageConverter);        return new HttpMessageConverters(true, messageConverters);    }}

EnableFeignClients 设置对应的 api 路径，可设置多个，其中要配置一个 HttpMessageConverters 用来解码，可设置其他

package com.renren.controller;import com.zyndev.commontool.web.BaseResponse;import com.zyndev.server.user.api.UserServiceAPI;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.RestController;import java.util.HashMap;import java.util.Map;/** * @author 张瑀楠 [e-mail] * @version 1.0 * time: 2017/12/13 16:23 * TODO: */@RestControllerpublic class IndexController {    @Autowired    private UserServiceAPI userServiceAPI;    @RequestMapping("testGetUserById")    public Map testApi(@RequestParam("id") Integer id) {        Map<String, Object> result = new HashMap<>();        result.put("name", "testApi");        if (userServiceAPI == null) {            System.out.println("userServiceAPI is null");        }        else {            BaseResponse baseResponse = userServiceAPI.getUserByID(id);            result.put("response", baseResponse);        }        return result;    }}

userServiceAPI直接注入即可

对应pom文件

<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/maven-v4_0_0.xsd">    <modelVersion>4.0.0</modelVersion>    <groupId>com.renren</groupId>    <artifactId>spring-feign</artifactId>    <packaging>war</packaging>    <version>1.0-SNAPSHOT</version>    <name>spring-feign Maven Webapp</name>    <url>http://maven.apache.org</url>    <properties>        <spring.version>4.3.8.RELEASE</spring.version>        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>    </properties>    <dependencies>        <dependency>            <groupId>junit</groupId>            <artifactId>junit</artifactId>            <version>4.12</version>            <scope>test</scope>        </dependency>        <dependency>            <groupId>org.springframework</groupId>            <artifactId>spring-webmvc</artifactId>            <version>${spring.version}</version>        </dependency>        <dependency>            <groupId>com.alibaba</groupId>            <artifactId>fastjson</artifactId>            <version>1.2.32</version>        </dependency>        <dependency>            <groupId>com.google.code.gson</groupId>            <artifactId>gson</artifactId>            <version>2.3.1</version>        </dependency>        <dependency>            <groupId>com.zyndev</groupId>            <artifactId>user-server-api</artifactId>            <version>0.0.1-SNAPSHOT</version>            <exclusions>                <exclusion>                    <groupId>org.springframework.cloud</groupId>                    <artifactId>spring-cloud-starter-eureka</artifactId>                </exclusion>                <exclusion>                    <groupId>org.springframework.boot</groupId>                    <artifactId>spring-boot-starter-web</artifactId>                </exclusion>            </exclusions>        </dependency>    </dependencies>    <build>        <finalName>spring-feign</finalName>        <plugins>            <plugin>                <groupId>org.apache.maven.plugins</groupId>                <artifactId>maven-compiler-plugin</artifactId>                <configuration>                    <source>1.8</source>                    <target>1.8</target>                </configuration>            </plugin>        </plugins>    </build></project>

具体代码见：https://github.com/zyndev/zyndev-spring-cloud