声明式服务调用Feign

2022-07-10 11:12:09

什么是 Feign

Feign 是种声明式、模板化的 HTTP 客户端(仅在 consumer 中使用)。

什么是声明式，有什么作用，解决什么问题？

声明式调用就像调用本地方法一样调用远程方法;无感知远程 http 请求。

1，Spring Cloud 的声明式调用, 可以做到使用 HTTP 请求远程服务时能就像调用本地方法一样的体验，开发者完全感知不到这是远程方法，更感知不到这是个 HTTP 请求。

2，它像 Dubbo一样，consumer 直接调用接口方法调用 provider，而不需要通过常规的 Http Client 构造请求再解析返回数据。

3，它解决了让开发者调用远程接口就跟调用本地方法样，无需关注与远程的交互细节，更无需关注分布式环境开发。

项目架构

spring-boot-feign-service

pom文件

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

    <modelVersion>4.0.0</modelVersion>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.1.11.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <groupId>com.bjsxt</groupId>

    <artifactId>spring-boot-feign-service</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>spring-boot-feign-service</name>

    <description>spring-boot-feign-service</description>

    <properties>

        <java.version>1.8</java.version>

        <spring-cloud.version>Greenwich.SR4</spring-cloud.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>

        </dependency>

        <dependency>

            <groupId>org.projectlombok</groupId>

            <artifactId>lombok</artifactId>

            <optional>true</optional>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

        </dependency>

    </dependencies>

    <dependencyManagement>

        <dependencies>

            <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>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

实体类

com.bjsxt.pojo.Product

package com.bjsxt.pojo;

import lombok.Data;

@Data

public class Product {

    private int id;

    private String name;

    public Product(int id, String name) {

        this.id = id;

        this.name = name;

    }

    public Product() {

    }

}

接口（Feign的核心之一）

com.bjsxt.service.ProduceService

package com.bjsxt.service;

import com.bjsxt.pojo.Product;

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

import java.util.List;

@RequestMapping("/product")

public interface ProduceService {

    /**

     * 查询所有产品

     * @return

     */

    @RequestMapping(value = "/findall",method = RequestMethod.GET)

    public List<Product> findAll();

    /**

     * 根据商品id，查询商品

     * @param id

     * @return

     */

    @RequestMapping(value = "/findbyid",method = RequestMethod.GET)

    public Product getProductById(@RequestParam("id") Integer id);

    /**

     * 新增商品 get方式

     * @param id

     * @param name

     */

    @RequestMapping(value = "/add",method = RequestMethod.GET)

    public Product addproduct(@RequestParam("id") Integer id,@RequestParam("name") String name);

    /***

     * 新增商品 post方式

     * @param product

     * @return

     */

    @RequestMapping(value = "/add",method = RequestMethod.POST)

    public Product addPro(@RequestBody Product product);

}

生产者

pom文件（关联server）

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

    <modelVersion>4.0.0</modelVersion>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.1.11.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <groupId>com.bjsxt</groupId>

    <artifactId>spring-boot-feign-prodvider</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>spring-boot-feign-prodvider</name>

    <description>spring-boot-feign-prodvider</description>

    <properties>

        <java.version>1.8</java.version>

        <spring-cloud.version>Greenwich.SR4</spring-cloud.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

        <!--导入service-->

        <dependency>

            <groupId>com.bjsxt</groupId>

            <artifactId>spring-boot-feign-service</artifactId>

            <version>0.0.1-SNAPSHOT</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

        </dependency>

    </dependencies>

    <dependencyManagement>

        <dependencies>

            <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>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

配置文件

src/main/resources/application.properties

spring.application.name=yxfProductProvider

server.port=9001

#设置服务注册中心地址，指向另一个注册中心

eureka.client.service-url.defaultZone=http://admin:1234@192.168.41.242:5050/eureka/,http://admin:1234@192.168.41.242:5051/eureka/

控制层（Feign的核心之一）

com.bjsxt.controller.ProductController

package com.bjsxt.controller;

import com.bjsxt.pojo.Product;

import com.bjsxt.service.ProduceService;

import org.springframework.stereotype.Controller;

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

import java.util.ArrayList;

import java.util.List;

@RestController

public class ProductController implements ProduceService {

    @Override

    public List<Product> findAll() {

        List<Product> list=new ArrayList<>();

        list.add(new Product(1,"电视"));

        list.add(new Product(2,"风扇"));

        list.add(new Product(3,"冰箱"));

        list.add(new Product(4,"电脑"));

        return list;

    }

    @Override

    public Product getProductById(Integer id) {

        return new Product(id,"SpringCloud");

    }

    @Override

    public Product addproduct(Integer id, String name) {

        return new Product(id,name);

    }

    @Override

    public Product addPro(Product product) {

        return product;

    }

}

启动类

com.bjsxt.SpringBootFeignProdviderApplication

package com.bjsxt;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.netflix.eureka.EnableEurekaClient;

@SpringBootApplication

@EnableEurekaClient

public class SpringBootFeignProdviderApplication {

    public static void main(String[] args) {

        SpringApplication.run(SpringBootFeignProdviderApplication.class, args);

    }

}

消费者

pom文件（同样关联server）

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

    <modelVersion>4.0.0</modelVersion>

    <parent>

        <groupId>org.springframework.boot</groupId>

        <artifactId>spring-boot-starter-parent</artifactId>

        <version>2.1.11.RELEASE</version>

        <relativePath/> <!-- lookup parent from repository -->

    </parent>

    <groupId>com.bjsxt</groupId>

    <artifactId>spring-boot-feign-consumer</artifactId>

    <version>0.0.1-SNAPSHOT</version>

    <name>spring-boot-feign-consumer</name>

    <description>spring-boot-feign-consumer</description>

    <properties>

        <java.version>1.8</java.version>

        <spring-cloud.version>Greenwich.SR4</spring-cloud.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-web</artifactId>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>

        </dependency>

        <!--导入service-->

        <dependency>

            <groupId>com.bjsxt</groupId>

            <artifactId>spring-boot-feign-service</artifactId>

            <version>0.0.1-SNAPSHOT</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.cloud</groupId>

            <artifactId>spring-cloud-starter-feign</artifactId>

            <version>1.4.4.RELEASE</version>

        </dependency>

        <dependency>

            <groupId>org.springframework.boot</groupId>

            <artifactId>spring-boot-starter-test</artifactId>

            <scope>test</scope>

        </dependency>

    </dependencies>

    <dependencyManagement>

        <dependencies>

            <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>

    <build>

        <plugins>

            <plugin>

                <groupId>org.springframework.boot</groupId>

                <artifactId>spring-boot-maven-plugin</artifactId>

            </plugin>

        </plugins>

    </build>

</project>

配置文件

src/main/resources/application.properties

spring.application.name=yxfProductConsumer

server.port=9002

#设置服务注册中心地址，指向另一个注册中心

eureka.client.service-url.defaultZone=http://admin:1234@192.168.41.242:5050/eureka/,http://admin:1234@192.168.41.242:5051/eureka/

接口（继承服务的接口）

com.bjsxt.service.ProduceConsumerService

package com.bjsxt.service;

import com.bjsxt.service.ProduceService;

import org.springframework.cloud.openfeign.FeignClient;

@FeignClient(name = "yxfProductProvider")

public interface ProduceConsumerService extends ProduceService {

}

控制层

com.bjsxt.controller.ProductConsumerController

package com.bjsxt.controller;

import com.bjsxt.service.ProduceConsumerService;

import com.bjsxt.pojo.Product;

import org.springframework.beans.factory.annotation.Autowired;

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

import java.util.List;

@RestController

public class ProductConsumerController {

    @Autowired

    private ProduceConsumerService produceConsumerService;

    /**

     * 查询所有

     * @return

     */

    @RequestMapping(value = "/pro",method = RequestMethod.GET)

    public List<Product> getProduce(){

        List<Product> all = produceConsumerService.findAll();

        return all;

    }

    /**

     * 根据id,获取商品，传递单个参数

     * @param id

     * @return

     */

    @RequestMapping(value = "/get",method = RequestMethod.GET)

    public Product getProducebyid(@RequestParam("id") Integer id){

        Product product = produceConsumerService.getProductById(id);

        return product;

    }

    /**

     * 添加商品，传递多个参数 get方式

     * @param id

     * @param name

     * @return

     */

    @RequestMapping(value = "/add",method = RequestMethod.GET)

    public Product addProduct(@RequestParam("id") Integer id,@RequestParam("name") String name){

        Product product = produceConsumerService.addproduct(id,name);

        return product;

    }

    /**

     * 添加商品，传递多个参数，内部是post

     * @param product

     * @return

     */

    @RequestMapping(value = "/addpro",method = RequestMethod.GET)

    public Product addPro(Product product){

        Product pro = produceConsumerService.addPro(product);

        return pro;

    }

}

启动类

com.bjsxt.SpringBootFeignConsumerApplication

package com.bjsxt;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.SpringBootApplication;

import org.springframework.cloud.client.discovery.EnableDiscoveryClient;

import org.springframework.cloud.openfeign.EnableFeignClients;

@EnableFeignClients

@EnableDiscoveryClient

@SpringBootApplication

public class SpringBootFeignConsumerApplication {

    public static void main(String[] args) {

        SpringApplication.run(SpringBootFeignConsumerApplication.class, args);

    }

}

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