Spring全家桶——SpringCloud之Feign(Finchley版)

Feign是一个声明式的Web服务客户端。

是什么？
例如我在一个服务的interace上注解@FeignClient(value = “eureka-client”）
就是声明服务名称告诉其他服务等这个就是eureka-client 的服务客户端
它使编写Web服务客户端变得更容易

要使用Feign，请创建接口并注解,有可插入的注解支持，包括Feign注释和JAX-RS注释。

JAX-RS注释:JAX-RS是JAVAEE6 引入的,JAX-RS即Java API for RESTful Web Services
是Java的应用程序接口,如:
@Path标注资源类或方法的相对路径
@GET，@PUT，@POST，@DELETE 请求方式

Feign还支持可插拔编码器和解码器。

Spring Cloud Netflix 为 Feign提供了下面默认的配置Bean
Decoder feignDecoder: ResponseEntityDecoder
Encoder feignEncoder: SpringEncoder
Spring Cloud增加了对Spring MVC注释的支持
并使用了Spring Web中默认使用的相同HttpMessageConverters。

Spring Cloud集成了Ribbon和Eureka，在使用Feign时提供负载均衡的http客户端。

白话文：微服务架构端口很多，我们要统一端口就要用到Feign去各个服务拿接口；需要从一个服务调用另外一个服务的数据也可以直接使用Feign，也就是通过这种方式开发调用远程服务就像是调用本地服务一样方便。

准备工作

环境

IDEA 2018.3
Gradle 4.10
springCloudVersion Finchley.RELEASE
无eureka-server的可以去github下载源码:https://github.com/cuifuan/springcloud-tools
创建的是子项目，父项目Github下载

创建eureka-client服务

gradle配置 build.gradle

dependencies {
    implementation 'org.springframework.cloud:spring-cloud-starter-netflix-eureka-client'
    implementation 'org.springframework.boot:spring-boot-starter-web'
    implementation project(":tools-common-entity")
}

创建启动类 ToolsEurekaClientApplication.java

package store.zabbix.toolseurekaclient;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@SpringBootApplication
@EnableEurekaClient
@RestController
public class ToolsEurekaClientApplication {

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

    @Value("${server.port}")
    private int port;

    @GetMapping("test")
    public String showPort(@RequestParam(value = "name",required = false) String name){
        if (name == null)
            name = "Anonymous";
        return "my port is "+port +" -> my name is"+name;
    }

}

资源文件 application.yml

eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka/
server:
  port: 8762
spring:
  application:
    name: eureka-client

业务接口 UserService.java

package store.zabbix.toolseurekaclient.service;


import store.zabbix.common.entity.User;

import java.util.List;

public interface UserService {

    Integer createUser(User user);

    List<User> getUserAll(String username,Long id);

    Integer updateUser(User user);

    Integer deleteUser(List<Integer> ids);

}

业务实现层 UserServiceImpl.java

package store.zabbix.toolseurekaclient.service.impl;

import lombok.extern.slf4j.Slf4j;
import org.springframework.stereotype.Service;
import store.zabbix.common.entity.User;
import store.zabbix.toolseurekaclient.service.UserService;

import java.util.ArrayList;
import java.util.List;


@Service
@Slf4j
public class UserServiceImpl implements UserService {
    @Override
    public Integer createUser(User user) {
        log.info("创建数据：{}",user.toString());
        return 1;
    }

    @Override
    public List<User> getUserAll(String username,Long id) {
        log.info("查询全部->参数1:{}->参数2:{}",username,id);
        User user=new User(1L,"admin","123456");
        return new ArrayList<User>(){{add(user);}};
    }

    @Override
    public Integer updateUser(User user) {
        log.info("更新数据..{}",user.toString());
        return 1;
    }

    @Override
    public Integer deleteUser(List<Integer> ids) {
        log.info("删除用户ids->{}",ids.toString());
        return 1;
    }
}

控制层 UserController.java

package store.zabbix.toolseurekaclient.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import store.zabbix.common.entity.User;
import store.zabbix.toolseurekaclient.service.UserService;

import java.util.List;

@RestController
@RequestMapping("user")
public class UserController {

    private final UserService userService;

    @Autowired
    public UserController(UserService userService) {
        this.userService = userService;
    }

    @GetMapping
    public List<User> getUserList(String username,Long id){
        return userService.getUserAll(username,id);
    }

    @PostMapping
    public Integer createUser(@RequestBody User user){
        return userService.createUser(user);
    }

    @PutMapping
    public Integer updateUser(@RequestBody User user){
        return userService.updateUser(user);
    }

    @DeleteMapping
    public Integer deleteUSer(@RequestBody List<Integer> idList){
        return userService.deleteUser(idList);
    }
}

由上面的server.port 可知端口为8762
可是如果我们有多个eureka-client怎么办
会造成后端接口访问端口太多
所以在这里可以采用feign进行统一调度

新建tools-routing服务

build.gradle

dependencies {
    implementation "org.springframework.cloud:spring-cloud-starter-openfeign"
    implementation 'org.springframework.cloud:spring-cloud-starter-netflix-eureka-client'
    implementation 'org.springframework.cloud:spring-cloud-starter-netflix-hystrix'
}

新建的是子项目，依赖管理统一在父项目，子项目只声明自己单独使用的依赖，父项目在github可以进行拉取，地址在上面

启动类 ToolsRoutingApplication.java

package store.zabbix.toolsrouting;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
public class ToolsRoutingApplication {

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

}

核心就是开启@EnableFeignClients注解

application.yml

server:
  port: 8765
eureka:
  client:
    service-url:
      defaultZone: http://127.0.0.1:8761/eureka/
spring:
  application:
    name: service-feign

创建UserServiceClients调用eureka-client接口

package store.zabbix.toolsrouting.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import store.zabbix.common.entity.User;

import java.util.List;

@FeignClient("eureka-client")
public interface UserServiceClients {
    @GetMapping
    List<User> getUserList(String name,Long id);
}

@FeignClient是核心,@FeignClient里value的值是eureka-client的application.yml声明的，如下：

spring:
  application:
    name: eureka-client

启动ToolsRoutingApplication.java
发现启动报错

说明:
@GetMapping在这个版本可以使用，其传值要使用@RequestParam
在一些版本无法使用@GetMapping，需使用@RequestMapping(value = “user”,method = RequestMethod.GET)

UserServiceClients接口

package store.zabbix.toolsrouting.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.*;
import store.zabbix.common.entity.User;

import java.util.List;

@FeignClient("eureka-client")
public interface UserServiceClients {
    @GetMapping("user")
//@RequestMapping(value = "user",method = RequestMethod.GET)
    List<User> getUserList(@RequestParam("username") String name,@RequestParam("id") Long id);
//这里不加@RequestParam会报异常IllegalStateException: Method has too many Body parameters，造成无法启动
    @PostMapping("user")
    Integer createUser(@RequestBody User user);

    @PutMapping(value = "user",produces = "application/json")
    Integer updateUser(@RequestBody User user);

    @DeleteMapping(value = "user",produces = "application/json")
    Integer deleteUser(@RequestBody List<Integer> ids);
}

说明：PUT和DELETE请求，使用json传输List时或许会报错，请在注解内加上参数produces = “application/json”，如@DeleteMapping(value = “user”,produces = “application/json”)

创建 `UserController.java` 控制访问层

package store.zabbix.toolsrouting.controller;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import store.zabbix.common.entity.User;
import store.zabbix.common.entity.bean.ResultBean;
import store.zabbix.toolsrouting.service.UserServiceClients;

import java.util.List;

@RequestMapping("user")
@RestController
public class UserController {
    private final UserServiceClients userServiceClients;

    @Autowired
    public UserController(UserServiceClients userServiceClients) {
        this.userServiceClients = userServiceClients;
    }

    @GetMapping
    public ResultBean<List<User>> getUserList(String name, Long id) {
        return new ResultBean<>(userServiceClients.getUserList(name, id));
    }

    @PostMapping
    public ResultBean<Integer> createUser(@RequestBody User user) {
        return new ResultBean<>(userServiceClients.createUser(user));
    }

    @PutMapping
    public ResultBean<Integer> updateUser(@RequestBody User user){
        return new ResultBean<>(userServiceClients.updateUser(user));
    }

    @DeleteMapping
    public ResultBean<Integer> deleteUser(@RequestBody List<Integer> integerList){
        return new ResultBean<>(userServiceClients.deleteUser(integerList));
    }
}