SpringCloud microservice [Practical] | Service splitting and remote calling

Table of contents

1: Service splitting and remote calling

1. Service splitting

2. Call between services

3. Providers and consumers 

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1: Service splitting and remote calling

1. Service splitting

Things to note when splitting services

1. Single responsibility: Do not develop the same business repeatedly for different microservices;

2. Data independence: Do not access the databases of other microservices;

3. Service-oriented: Expose your business as an interface for other microservices to call;

Case: Parent projectcloud-demo, the sub-project order-service queries the order based on the id, and the user-service queries the user table based on the id

Step 1: Prepare database tables---database separation

tb_user table of cloud_user database

tb_order table of cloud_order database

Step 2: Parent project cloud-demo---project separation

Mainly use pom.xml to specify some version numbers

<?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">
    <modelVersion>4.0.0</modelVersion>

    <groupId>cn.itcast.demo</groupId>
    <artifactId>cloud-demo</artifactId>
    <version>1.0</version>
    <modules>
        <module>user-service</module>
        <module>order-service</module>
    </modules>

    <packaging>pom</packaging>
    <!--SpringBoot项目-->
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.9.RELEASE</version>
        <relativePath/>
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <!--版本号-->
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR10</spring-cloud.version>
        <mysql.version>5.1.47</mysql.version>
        <mybatis.version>2.1.1</mybatis.version>
    </properties>

    <dependencyManagement>
        <dependencies>
            <!-- springCloud -->
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
            <!-- mysql驱动 -->
            <dependency>
                <groupId>mysql</groupId>
                <artifactId>mysql-connector-java</artifactId>
                <version>${mysql.version}</version>
            </dependency>
            <!--mybatis-->
            <dependency>
                <groupId>org.mybatis.spring.boot</groupId>
                <artifactId>mybatis-spring-boot-starter</artifactId>
                <version>${mybatis.version}</version>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
        </dependency>
    </dependencies>
</project>

Step 3: Subproject order-service

Project structure directory:

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/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>cloud-demo</artifactId>
        <groupId>cn.itcast.demo</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>order-service</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

PoJo classOrder

package cn.itcast.order.pojo;

import lombok.Data;

@Data
public class Order {
    private Long id;
    private Long price;
    private String name;
    private Integer num;
    private Long userId;
    private User user;
}

Pojo class User

package cn.itcast.order.pojo;

import lombok.Data;

@Data
public class User {
    private Long id;
    private String username;
    private String address;
}

 mapper interface

package cn.itcast.order.mapper;

import cn.itcast.order.pojo.Order;
import org.apache.ibatis.annotations.Select;

public interface OrderMapper {

    @Select("select * from tb_order where id = #{id}")
    Order findById(Long id);
}

Service calls mapper interface

package cn.itcast.order.service;

import cn.itcast.order.mapper.OrderMapper;
import cn.itcast.order.pojo.Order;
import cn.itcast.order.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

@Service
public class OrderService {

    @Autowired
    private OrderMapper orderMapper;

    public Order queryOrderById(Long orderId) {
        // 1.查询订单
        Order order = orderMapper.findById(orderId);
        // 4.返回
        return order;
    }
}

Controller calls Service

package cn.itcast.order.web;

import cn.itcast.order.pojo.Order;
import cn.itcast.order.service.OrderService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/order")
public class OrderController {

   @Autowired
   private OrderService orderService;

    @GetMapping("/{orderId}")
    // @RequestMapping("/order")  和@GetMapping("/{orderId}")等价于@GetMapping("/user/{orderId})
    public Order queryOrderByUserId(@PathVariable("orderId") Long orderId) {
        // 根据id查询订单并返回
        return orderService.queryOrderById(orderId);
    }
}

application.yml configuration

server:
  port: 8080
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/cloud_order?useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver
mybatis:
  type-aliases-package: cn.itcast.user.pojo
  configuration:
    map-underscore-to-camel-case: true
logging:
  level:
    cn.itcast: debug
  pattern:
    dateformat: MM-dd HH:mm:ss:SSS

Step 4: Subproject user-service

Project structure directory:

 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/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <parent>
        <artifactId>cloud-demo</artifactId>
        <groupId>cn.itcast.demo</groupId>
        <version>1.0</version>
    </parent>
    <modelVersion>4.0.0</modelVersion>

    <artifactId>user-service</artifactId>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>
        <!--mybatis-->
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
        </dependency>
    </dependencies>
    <build>
        <finalName>app</finalName>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

Pojo class User

package cn.itcast.order.pojo;

import lombok.Data;

@Data
public class User {
    private Long id;
    private String username;
    private String address;
}

 mapper interface

package cn.itcast.user.mapper;

import cn.itcast.user.pojo.User;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;

public interface UserMapper {
    
    @Select("select * from tb_user where id = #{id}")
    User findById(@Param("id") Long id);
}

Service calls mapper interface

package cn.itcast.user.service;

import cn.itcast.user.mapper.UserMapper;
import cn.itcast.user.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class UserService {

    @Autowired
    private UserMapper userMapper;

    public User queryById(Long id) {
        return userMapper.findById(id);
    }
}

Controller calls Service

package cn.itcast.user.web;

import cn.itcast.user.pojo.User;
import cn.itcast.user.service.UserService;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;

@Slf4j
@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    private UserService userService;

    /**
     * 路径： /user/110
     *
     * @param id 用户id
     * @return 用户
     */
    @GetMapping("/{id}")
    public User queryById(@PathVariable("id") Long id) {
        return userService.queryById(id);
    }
}

application.yml configuration

server:
  port: 8081
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/cloud_user?useSSL=false
    username: root
    password: 123456
    driver-class-name: com.mysql.jdbc.Driver
mybatis:
  type-aliases-package: cn.itcast.user.pojo
  configuration:
    map-underscore-to-camel-case: true
logging:
  level:
    cn.itcast: debug
  pattern:
    dateformat: MM-dd HH:mm:ss:SSS

Start these two servers (the startup classes of both projects need to be annotated with @MapperScan)

Order is accessed separately, and User information is null.

User access alone

2. Call between services

The previous project has been deployed. You can check the order information Order based on the ID alone, and you can check the user information User! But now customers are asking to check the order requirements and also find out the user information!

Requirement: While querying the order based on the order ID, return the user information to which the order belongs. 

Analysis: The order module can only find out order information, and the user module can only find out user information; but now what users require is to find out user information while querying order information.

Therefore, we have to modify the function of the order module, requiring that while querying the order information, we can also query mutual user information through the userId in the order information.

Thinking:Is it possible to directly use the order module to check the data of the user module? Obviously not, we have already analyzed the development business that should not be repeated; we can only initiate remote calls to users from orders!

solve:

①In fact, the user information is exposed to the outside through a link address @GetMapping("/user/{id}). Through this link address, you can access the database and get the user information to the browser.

② If the order module at this time can issue a link request of the http protocol, it can also return user information data and then combine it with the original order information data to complete the requirement.

So now the core question: How to send HTTP requests in the Java code of the order information module!

Spring provides aRestTemplate class tool to complete it! The specific implementation steps are as follows:

Step 1: Register RestTemplate

Inject the RestTemplate class into the startup class OrderApplication!

package cn.itcast.order;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;

@MapperScan("cn.itcast.order.mapper")
@SpringBootApplication
public class OrderApplication {

    public static void main(String[] args) {
        SpringApplication.run(OrderApplication.class, args);
    }
    
    // 注册RestTemplate
    @Bean
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }

}

Step 2: Service calls RestTemplate remotely

Call the getForObject() method through this RestTemplate class: the first parameter is the URL address, and the second parameter is the type to be returned.

package cn.itcast.order.service;

import cn.itcast.order.mapper.OrderMapper;
import cn.itcast.order.pojo.Order;
import cn.itcast.order.pojo.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.web.client.RestTemplate;

@Service
public class OrderService {

    @Autowired
    private OrderMapper orderMapper;

    // 注入RestTemplate
    @Autowired
    private RestTemplate restTemplate;

    public Order queryOrderById(Long orderId) {
        // 1.查询订单
        Order order = orderMapper.findById(orderId);
        // 2.发出请求查询用户信息
        String url = "http://localhost:8081/user/"+order.getUserId();
        User user = restTemplate.getForObject(url, User.class);
        // 3. 把用户信息封装到order
        order.setUser(user);
        // 4.返回
        return order;
    }
}

At this time, Order is accessed alone, and User information can be displayed.

Summary of microservice calling methods

①Remote calling based on the http request initiated by RestTemplate;

② HTTP request for remote call is a language-independent call, as long as you know the other party’s IP, port, interface path, and request parameters;

3. Providers and consumers 

ServiceProvider: A service called by other microservices in a business. (Provide interfaces to other microservices);

ServiceConsumer: A service that calls other microservices in a business. (Call interfaces provided by other microservices);

So which one is the provider of the order-service and user-service above? Which one is the consumer?

Thinking: Service A calls service B, and service B calls service C. So what role does service B play?

Service B is a provider relative to service A, and service B is a consumer relative to service C. This is relative, so the role of a service cannot be divided into businesses.

Summarize the service call relationship

①Service provider: Exposes the interface to be called by other microservices.

②Service consumer: Call the interface provided by other microservices.

③The roles of provider and consumer are actuallyrelative;A service can be a service at the same time Providers and service consumers.