SpringCloud Netflix（二）：服务提供者和服务消费者

什么是服务提供者和服务消费者

服务提供者：服务的被调用方，即为其他服务提供服务的服务。

服务消费者：服务的调用方，即依赖其他服务的服务。

服务提供者也可以是服务消费者，两者不是唯一性的

服务提供者和服务消费者实例

1.创建一个maven项目

在项目pom.xml里添加统一依赖，并把打包方式改为pom

<?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>

    <groupId>com.example</groupId>
    <artifactId>springcloud</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>pom</packaging>
    <name>springcloud</name>
    <description>Demo project for Spring Boot</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.8.RELEASE</version>
        <relativePath />
    </parent>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Finchley.SR2</spring-cloud.version>
        <mysql.version>8.0.19</mysql.version>
        <druid.version>1.1.10</druid.version>
        <mybatis.plus.version>3.1.0</mybatis.plus.version>
        <mybatis.plus.generator.version>3.2.0</mybatis.plus.generator.version>
        <velocity.engine.version>2.2</velocity.engine.version>
        <lombok.version>1.18.12</lombok.version>
    </properties>

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

            <dependency>
                <groupId>com.example</groupId>
                <artifactId>springcloud-dao</artifactId>
                <version>0.0.1-SNAPSHOT</version>
            </dependency>

            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>${mysql.version}</version>
            </dependency>
            <dependency>
                <groupId>com.alibaba</groupId>
                <artifactId>druid-spring-boot-starter</artifactId>
                <version>${druid.version}</version>
            </dependency>

            <dependency>
                <groupId>com.baomidou</groupId>
                <artifactId>mybatis-plus-boot-starter</artifactId>
                <version>${mybatis.plus.version}</version>
            </dependency>

            <dependency>
                <groupId>org.projectlombok</groupId>
                <artifactId>lombok</artifactId>
                <version>${lombok.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

2.在项目下创建数据库操作的module，即存放实体类和mapper的模块

添加依赖，在项目的统一依赖定义过版本的依赖无需再定义版本

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>springcloud</artifactId>
        <groupId>com.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>springcloud-dao</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>springcloud-dao</name>

    <dependencies>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--该服务使用了mybatis-plus来简化代码-->
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>
</project>

创建实体类

package com.example.springcloud.domain;

import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.extension.activerecord.Model;
import com.baomidou.mybatisplus.annotation.TableId;
import java.io.Serializable;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;

@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
public class User extends Model<User> {

    private static final long serialVersionUID=1L;

    /**
     * 主键
     */
    @TableId(value = "id", type = IdType.AUTO)
    private Long id;

    /**
     * 姓名
     */
    private String name;

    /**
     * 数据库名
     */
    private String dbName; 


    @Override
    protected Serializable pkVal() {
        return this.id;
    }

}

创建 UserMapper.xml 和 UserMapper接口

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.example.springcloud.mapper.UserMapper">

    <!-- 通用查询映射结果 -->
    <resultMap id="BaseResultMap" type="com.example.springcloud.domain.User">
        <id column="id" property="id" />
        <result column="name" property="name" />
        <result column="db_name" property="dbName" />
    </resultMap>

    <!-- 通用查询结果列 -->
    <sql id="Base_Column_List">
        id, name, db_name
    </sql>

</mapper>

package com.example.springcloud.mapper;

import com.example.springcloud.domain.User;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import org.apache.ibatis.annotations.Mapper;

public interface UserMapper extends BaseMapper<User> {

}

3.在项目下创建服务提供者

添加依赖

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>springcloud</artifactId>
        <groupId>com.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.example</groupId>
    <artifactId>springcloud-provider-8888</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>
    <name>springcloud-provider-8888</name>

    <dependencies>
        <!--引入springcloud-dao服务，就可以调用该服务下的类-->
        <dependency>
            <groupId>com.example</groupId>
            <artifactId>springcloud-dao</artifactId>
        </dependency>
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid-spring-boot-starter</artifactId>
        </dependency>
    </dependencies>
</project>

添加配置

server:
  port: 8888

spring:
  application:
    name: springcloud-provider #注册中心中的服务名
  datasource:
    driver-class-name: com.mysql.jdbc.Driver
    url: jdbc:mysql://localhost:3306/db01?useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true&serverTimezone=Asia/Shanghai
    username: root
    password: "123456"
    type: com.alibaba.druid.pool.DruidDataSource

创建service和controller（各个服务的包名最好统一 com.example.springcloud）

@Service
public class UserServiceImpl implements UserService {
    //省略代码。。。。。。。。。。。。。
}

@RestController
@RequestMapping("/user")
public class IndexController {
    @Autowired
    private UserService userService;

    @GetMapping("/{id}")
    public User getUserById(@PathVariable("id")Long id){
        User user = userService.getUserById(id);
        return user;
    }

    @GetMapping("/")
    public List<User> getAllUser(){
        return userService.getAllUser();
    }

    //因为消费者传输的对象都是JSON类型，所以需加@RequestBody注解，否则会报错
    @PostMapping("/add")
    public int addUser(@RequestBody User user){ 
        return userService.addUser(user);
    }
}

创建启动类，需添加@MapperScan 注解，否则服务可能会找不到mapper接口

@SpringBootApplication
@MapperScan("com.example.springcloud.mapper")
public class Provider_8888 {

    public static void main(String[] args) {
        SpringApplication.run(Provider_8888.class,args);
    }
}

4.在项目下创建服务消费者

springcloud中由服务消费者调用服务提供者一共有两种方法rest和feign

通过RestTemplate调用

spring框架提供的RestTemplate类可用于在应用中调用rest服务，它简化了与http服务的通信方式，统一了RESTful的标准，封装了http链接，我们只需要传入url及返回值类型即可。

RestTemplate类是为调用REST服务而设计的，因此它的主要方法与REST的基础紧密相连，后者是HTTP协议的方法:HEAD、GET、POST、PUT、DELETE和OPTIONS。而RestTemplate类具有headForHeaders()、getForObject()、postForObject()、put()和delete()等方法。

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>springcloud</artifactId>
        <groupId>com.example</groupId>
        <version>1.0-SNAPSHOT</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>springcloud-consumer</artifactId>

    <dependencies>
        <dependency>
            <groupId>com.example</groupId>
            <artifactId>springcloud-dao</artifactId>
        </dependency>
    </dependencies>
</project>

添加配置

server:
  port: 80

创建RestTemplate的注入配置类，方便调用

@Configuration
public class BeanConfig {
    @Bean
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }
}

创建controller调用服务提供者

package com.example.springcloud.controller;

import com.example.springcloud.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;

import java.util.List;

@RestController
@RequestMapping("/consumer")
public class IndexController {
c
    @Autowired
    private RestTemplate restTemplate;c

    // http://ip地址:调用服务的端口/[服务提供者controller类上的RequestMapping/]
    //如果服务提供者controller类上不加RequestMapping，[]里的路径可去掉
    private static final String URL = "http://localhost:8888/user/";

    @RequestMapping("/user/{id}")
    public User getUserById(@PathVariable("id")Integer id) {
        return restTemplate.getForObject(URL+id, User.class);
    }

    @RequestMapping("/user/list")
    public List<User> getAllUser(){
        return restTemplate.getForObject(URL, List.class);
    }

    @RequestMapping("/user/add")
    public int addUser(User dept){
        return restTemplate.postForObject(URL+"add", dept, Integer.class);
    }

}

创建启动类

//停止SpringBootApplication数据连接池自动配置
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class Consumer {

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

}

访问http://localhost/consumer/user/1 ，服务消费者则会通过 http://localhost:8888/user/1 获取返回值User

通过Feign调用

Feign 的英文表意为“假装，伪装，变形”，是一个http请求调用的轻量级框架，可以以Java接口注解的方式调用Http请求，而不用像Java中通过封装HTTP请求报文的方式直接调用。Feign通过处理注解，将请求模板化，当实际调用的时候，传入参数，根据参数再应用到请求上，进而转化成真正的请求，这种请求相对而言比较直观。

创建feign接口，对应服务提供者者controller的方法

@Component
@FeignClient(value = "SPRINGCLOUD-PROVIDER")//对应服务名，服务提供者者的spring.application.name
@RequestMapping("/user")
public interface UserFeignClient {

    @GetMapping("/{id}")
    User getUserById(@PathVariable("id") Integer id);

    @GetMapping("/")
    List<User> getAllUser();

    @PostMapping("/add")
    int addUser(@RequestBody User user);
}

通过feign调用服务提供者

package com.example.springcloud.controller;

import com.example.consumer.service.HystrixService;
import com.example.springcloud.domain.User;
import com.example.springcloud.feign.UserFeignClient;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.List;

@RestController
@RequestMapping("/consumer")
public class IndexController {

    @Autowired
    private UserFeignClient userFeignClient;


    @RequestMapping("/user/{id}")
    public User getDeptById(@PathVariable("id")Integer id){
        return userFeignClient.getUserById(id);
    }

    @RequestMapping("/user/list")
    public List<User> getAllDept(){
        return userFeignClient.getAllUser();
    }

    @RequestMapping("/user/add")
    public int addDept(User user){
        return userFeignClient.addUser(user);
    }

}

创建启动类，添加@EnableFeignClients注解

@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
@EnableFeignClients(basePackages = {"com.example.springcloud"})//对应feign接口所在的包
public class FeignConsumer {

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

}

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