Spring Cloud Feign的继承特性

一 点睛

Spring Cloud Feign提供了继承特性，可以进一步减少编码量。

二 编写hello-service-api

1 创建一个基础的Maven工程，命名为hello-service-api

2 编写pom.xml

<?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/4.0.0http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.didispace</groupId>
    <artifactId>hello-service-api</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>hello-service-api</name>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.3.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
    </dependencies>

</project>

3 编写实体类User

package com.didispace.dto;

/**
* Created by Administrator on 2016/9/16.
*/
public class User {

    private String name;
    private Integer age;

    public User() {
    }

    public User(String name, Integer age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "name=" + name + ", age=" +age;
    }

}

4 编写HelloService接口

package com.didispace.service;

import com.didispace.dto.User;
import org.springframework.web.bind.annotation.*;

@RequestMapping("/refactor")
public interface HelloService {

    @RequestMapping(value = "/hello4", method = RequestMethod.GET)
    String hello(@RequestParam("name") String name) ;

    @RequestMapping(value = "/hello5", method = RequestMethod.GET)
    User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age);

    @RequestMapping(value = "/hello6", method = RequestMethod.POST)
    String hello(@RequestBody User user);

}

三 编写hello-service

1 给pom.xml增加依赖

<dependency>
    <groupId>com.didispace</groupId>
    <artifactId>hello-service-api</artifactId>
    <version>0.0.1-SNAPSHOT</version>
</dependency>

2 创建RefactorHelloController接口，实现hello-service-api中定义的接口HelloService

HelloServicepackage com.didispace.web;

import com.didispace.dto.User;
import com.didispace.service.HelloService;
import org.springframework.web.bind.annotation.*;

@RestController
public class RefactorHelloController implements HelloService {

    @Override
    public String hello(@RequestParam("name") String name) {
        return "Hello " + name;
    }

    @Override
    public User hello(@RequestHeader("name") String name, @RequestHeader("age") Integer age) {
        return new User(name, age);
    }

    @Override
    public String hello(@RequestBody User user) {
        return "Hello "+ user.getName() + ", " + user.getAge();
    }

}

通过实现的方式，在Contrlooer中不再包含以往会定义的请求映射注解@RequestMapping，在重写的时候会自动将注解带过来。在这个类中，除了实现接口的逻辑之外，只需要增加@RestController注解使该来成为一个REST接口类就可以了。

四 编写feign-consumer

1 编写RefactorHelloService接口，并继承hello-service-api包中的HelloService接口，然后添加@FeignClient注解来绑定服务。

package com.didispace.web;

import org.springframework.cloud.netflix.feign.FeignClient;

@FeignClient(value = "HELLO-SERVICE")
public interface RefactorHelloService extends com.didispace.service.HelloService {
}

2 编写控制类

package com.didispace.web;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class ConsumerController {
    @Autowired
    RefactorHelloService refactorHelloService;

    @RequestMapping(value = "/feign-consumer3", method = RequestMethod.GET)
    public String helloConsumer3() {
        StringBuilder sb = new StringBuilder();
        sb.append(refactorHelloService.hello("MIMI")).append("\n");
        sb.append(refactorHelloService.hello("MIMI", 20)).append("\n");
        sb.append(refactorHelloService.hello(new com.didispace.dto.User("MIMI", 20))).append("\n");
        return sb.toString();
    }

}

五 测试

1 先启动hello-service-api

2 再启动hello-service、feign-consumer和Eureka

3 浏览器输出http://localhost:9001/feign-consumer3