03.`feign`→服务间的通信

2020-09-09  本文已影响0人  风安峻_
1. 依赖

  1. spring-cloud-starter-openfeign依赖

    <dependencies>
    <!-- feign -->
    <dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-openfeign</artifactId>
    </dependency>
</dependencies>

  2. 说明

    1. 消费者添加spring-cloud-starter-openfeign的依赖即可，提供者不需要

    2. spring-cloud-starter-openfeign的父依赖

      <properties>
    <spring-cloud.version>Hoxton.SR7</spring-cloud.version>
</properties>

<dependencyManagement>
    <dependencies>
        <!-- spring-cloud 父依赖 -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-dependencies</artifactId>
            <version>${spring-cloud.version}</version>
            <type>pom</type>
            <scope>import</scope>
        </dependency>
    </dependencies>
</dependencyManagement>

    3. 提供者要注册到注册中心，消费者要从注册中心拉取提供者信息

      <properties>
     <spring-cloud-alibaba.version>2.2.1.RELEASE</spring-cloud-alibaba.version>
</properties>

<dependencies>
    <!-- nacos 注册中心 -->
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId>
    </dependency>
</dependencies>

<dependencyManagement>
    <!-- spring-cloud-alibaba 父依赖 -->
    <dependency>
        <groupId>com.alibaba.cloud</groupId>
        <artifactId>spring-cloud-alibaba-dependencies</artifactId>
        <version>${spring-cloud-alibaba.version}</version>
        <type>pom</type>
        <scope>import</scope>
    </dependency>
</dependencyManagement>
2. 配置

  1. feign-provider提供者

    1. application.yml主配置文件

      server:
  port: 8081
  servlet:
    # 提供者一般不设置前缀，这是为了演示
    context-path: /api/v1
spring:
  application:
    # 注册到注册中心的服务名
    name: feign-provider
  cloud:
    nacos:
      discovery:
        # nacos注册中心的地址
        server-addr: 120.25.207.44:8848
        cluster-name: ${spring.application.name}

    2. 启动类

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

// 开启 nacos 注册中心扫描，发现该服务
@EnableDiscoveryClient
@SpringBootApplication
public class FeignProviderApplication {

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

}

  2. feign-consumer消费者

    1. application.yml主配置文件

      server:
  port: 8082
spring:
  application:
    # 注册到注册中心的服务名，不注册到注册中心可以不写
    name: feign-consumer
  cloud:
    nacos:
      discovery:
        # nacos 注册中心的地址
        server-addr: 120.25.207.44:8848
        # 不将自己注册到注册中心
        register-enabled: false
feign:
  okhttp:
    # feign 启用 okhttp，性能最好
    enabled: true

    2. 启动类

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

// 启动 feign 客户端
@EnableFeignClients
// 开启 nacos 注册中心扫描，发现该服务
@EnableDiscoveryClient
@SpringBootApplication
public class FeignConsumerApplication {

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

}
      • @EnableFeignClients启动feign客户端
      • @EnableDiscoveryClient开启注册中心扫描，发现该服务
3. feign组件的使用

  1. feign-consumer消费者的远程调用类中用@FeignClient注解标记

    import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;

@Service
@FeignClient(value = "feign-provider", path = "/api/v1/provider")
public interface ProviderService {

}

    1. value = "feign-provider"的值feign-provider为提供者注册到注册中心的服务名

      提供者的服务名

    2. path = "/api/v1/provider"是提供者的ProviderController的访问路径，/api/v1/是提供者在application.yml主配置文件配置的context-path

  2. 消费者的远程调用类中，一个参数必须使用@RequestParam或@PathVariable修饰，feign底层一个参数时会自动放进请求体中默认使用post请求（不用@RequestParam或@PathVariable有可能取到的值为null），Get请求直接报错，提供者的controller可以不用@RequestParam修饰

    1. @RequestParam栗子，GetMapping或者PostMapping都可以

      1. 提供者controller

        import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/provider")
public class ProviderController {
   @GetMapping("/testParam")
    public String testParam(String userId) {
        return "ProviderController_testParam_" + userId;
    }

    @PostMapping("/testPostMappingParam")
    public String testPostMappingParam(String userId) {
        return "ProviderController_testPostMappingParam_" + userId;
    }
}

      2. 消费者

        1. 远程调用类

          import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;

@Service
@FeignClient(value = "feign-provider", path = "/api/v1/provider")
public interface ProviderService {
    /**
     * 对应 public String testParam(String userId){}
     *
     * @param userId 用户id
     * @return 字符串
     */
    @GetMapping("/testParam")
    String testParam(@RequestParam String userId);

    /**
     * 对应 public String testPostMappingParam(String userId){}
     *
     * @param userId 用户id
     * @return 字符串
     */
    @PostMapping("/testPostMappingParam")
    String testPostMappingParam(@RequestParam String userId);
}

        2. controller

          import com.sheng.cloud.feign.service.ProviderService;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;

@RestController
@RequestMapping("/consumer")
public class ConsumerController {
    @Resource
    private ProviderService providerService;
 
    @GetMapping("/testParam")
    public String testParam(String userId) {
        return providerService.testParam(userId);
    }

    @PostMapping("/testPostMappingParam")
    public String testPostMappingParam(String userId) {
        return providerService.testPostMappingParam(userId);
    }
}

    2. @PathVariable栗子，GetMapping或者PostMapping都可以

      1. 提供者controller

        import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/provider")
public class ProviderController {
    @GetMapping("/testPathVariable/{userId}")
    public String testPathVariable(@PathVariable String userId) {
        return "ProviderController_testPathVariable_" + userId;
    }
}

      2. 消费者

        1. 远程调用类

          import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;

@Service
@FeignClient(value = "feign-provider", path = "/api/v1/provider")
public interface ProviderService {
    /**
     * 对应 public String testPathVariable(@PathVariable String userId){}
     *
     * @param userId 用户id
     * @return 字符串
     */
    @GetMapping("/testPathVariable/{userId}")
    String testPathVariable(@PathVariable String userId);
}

        2. controller

          import com.sheng.cloud.feign.service.ProviderService;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;

@RestController
@RequestMapping("/consumer")
public class ConsumerController {
    @Resource
    private ProviderService providerService;
 
        @GetMapping("/testPathVariable/{userId}")
        public String testPathVariable(@PathVariable String userId) {
            return providerService.testPathVariable(userId);
        }
}

  3. 消费者的远程调用类中，两个参数或以上必须使用@RequestParam或@PathVariable修饰，不修饰不能启动，会直接报错。提供者的controller可以不用@RequestParam修饰

    1. @RequestParam栗子，GetMapping或者PostMapping都可以

      1. 提供者controller

        import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/provider")
public class ProviderController {
    @PostMapping("/login")
    public String login(String username, String password) {
        return "ProviderController_login_username: " + username + "_password: " + password;
    }
}

      2. 消费者

        1. 远程调用类

          import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;

@Service
@FeignClient(value = "feign-provider", path = "/api/v1/provider")
public interface ProviderService {
    /**
     * 对应 public String login(String username, String password){}
     *
     * @param username 用户名
     * @param password 密码
     * @return 字符串
     */
    @PostMapping("/login")
    String login(@RequestParam String username, @RequestParam String password);
}

        2. controller

          import com.sheng.cloud.feign.service.ProviderService;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;

@RestController
@RequestMapping("/consumer")
public class ConsumerController {
    @Resource
    private ProviderService providerService;
 
    @PostMapping("/login")
    public String login(String username, String password) {
        return providerService.login(username, password);
    }   
}
    2. @PathVariable栗子，GetMapping或者PostMapping都可以

      1. 提供者controller

        import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/provider")
public class ProviderController {
    @GetMapping("/loginByPathVariable/{username}/{password}")
    public String loginByPathVariable(@PathVariable String username, @PathVariable String password) {
        return "ProviderController_login_username: " + username + "password: " + password;
    }
}

      2. 消费者

        1. 远程调用类

          import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;

@Service
@FeignClient(value = "feign-provider", path = "/api/v1/provider")
public interface ProviderService {
    /**
     * 对应 public String loginByPathVariable(@PathVariable String username, @PathVariable String password){}
     *
     * @param username 用户名
     * @param password 密码
     * @return 字符串
     */
    @GetMapping("/loginByPathVariable/{username}/{password}")
    String loginByPathVariable(@PathVariable String username, @PathVariable String password);
}

        2. controller

          import com.sheng.cloud.feign.service.ProviderService;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;

@RestController
@RequestMapping("/consumer")
public class ConsumerController {
    @Resource
    private ProviderService providerService;
 
    @GetMapping("/loginByPathVariable/{username}/{password}")
    public String loginByPathVariable(@PathVariable String username, @PathVariable String password) {
        return providerService.loginByPathVariable(username, password);
    }   
}

  4. 如果消费者的远程调用类的形参是JavaBean对象，那么提供者的controller对应的方法的形参必须用@RequestBody标记，否则取到的值为null，因为feign底层默认将对象序列化成json数据进行传递。

    1. 结果

      1. 不用@RequestBody修饰

        不用@RequestBody修饰

      2. @RequestBody修饰

        @RequestBody修饰

    2. 栗子

      1. 提供者controller

        import com.sheng.cloud.feign.dto.UserDto;
import org.springframework.web.bind.annotation.*;

@RestController
@RequestMapping("/provider")
public class ProviderController {
    @PostMapping("/getUser")
    public UserDto getUser(@RequestBody UserDto userDto) {
        return userDto;
    }
}

      2. 消费者

        1. 远程调用类

          import com.sheng.cloud.feign.dto.UserDto;
import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.stereotype.Service;
import org.springframework.web.bind.annotation.*;

@Service
@FeignClient(value = "feign-provider", path = "/api/v1/provider")
public interface ProviderService {
    /**
     * 对应 public UserDto getUser(@RequestBody UserDto userDto){}
     *
     * @param userDto 对象
     * @return UserDto
     */
    @PostMapping("/getUser")
    UserDto getUser(UserDto userDto);
}

        2. controller

          import com.sheng.cloud.feign.dto.UserDto;
import com.sheng.cloud.feign.service.ProviderService;
import org.springframework.web.bind.annotation.*;

import javax.annotation.Resource;

@RestController
@RequestMapping("/consumer")
public class ConsumerController {
    @Resource
    private ProviderService providerService;
 
    @PostMapping("/getUser")
    public UserDto getUser(@RequestBody UserDto userDto) {
        return providerService.getUser(userDto);
    }   
}

  5. feign-demo 源码

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