SpringCloud系列二：硬编码实现简单的服务提供者与服务消费者

从本文开始，以一个电影售票系统为例讲解Spring Cloud

1. 版本

　　jdk：1.8

　　SpringBoot：2.0.0.RELEASE

　　SpringCloud：Finchley.M8

2. 系统信息

　　使用Spring Data JPA做为持久层框架，使用H2做为数据库

3. 编写服务提供者

　　开发：

　　> 建立一个Spring Boot项目。pom.xml内容以下：

<?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>com.itmuch.cloud</groupId>
    <artifactId>microservice-simple-provider-user</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

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


</project>

　　其中，spring-boot-starter-web提供了SpringMVC支持；spring-boot-starter-data-jpa提供了Spring Data JPA的支持。

　　> 准备好建表语句，在项目的resources目录下建立sql文件夹，在sql文件夹下创建schema.sql，并添加以下内容：

DROP TABLE user if EXISTS; CREATE TABLE user ( id bigint generated BY DEFAULT AS IDENTITY, username VARCHAR(40), name VARCHAR(20), age INT(3), balance DECIMAL(10, 2), PRIMARY KEY (id) );

　　> 准备几条数据，在sql文件夹下建立data.sql，并添加以下内容：

INSERT INTO user (id, username, name, age, balance) VALUES (1, 'account1', '张三', 20, 100.00); INSERT INTO user (id, username, name, age, balance) VALUES (2, 'account2', '李四', 28, 180.00); INSERT INTO user (id, username, name, age, balance) VALUES (3, 'account3', '王五', 32, 280.00);

　　> 建立用户实体类

package com.itmuch.cloud.microservicesimpleprovideruser.pojo; import javax.persistence.*; import java.math.BigDecimal; @Entity public class User { @Id @GeneratedValue(strategy = GenerationType.AUTO) private Long id; @Column private String username; @Column private String name; @Column private Integer age; @Column private BigDecimal balance; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public BigDecimal getBalance() { return balance; } public void setBalance(BigDecimal balance) { this.balance = balance; } }

　　> 建立DAO

package com.itmuch.cloud.microservicesimpleprovideruser.dao; import com.itmuch.cloud.microservicesimpleprovideruser.pojo.User; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.stereotype.Repository; @Repository public interface UserRepository extends JpaRepository<User, Long> { }

　　> 建立Controller

package com.itmuch.cloud.microservicesimpleprovideruser.controller; import com.itmuch.cloud.microservicesimpleprovideruser.dao.UserRepository; import com.itmuch.cloud.microservicesimpleprovideruser.pojo.User; 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.RestController; @RestController public class UserController { @Autowired private UserRepository userRepository; @GetMapping("/{id}") public User findById(@PathVariable Long id) { User findOne = userRepository.findById(id).get(); return findOne; } }

　　> 编写配置文件。将application.properties重命名为application.yml。

server: port: 8000 spring: jpa: generate-ddl: false show-sql: true hibernate: ddl-auto: none datasource: # 指定数据源 platform: h2 # 指定数据源类型 url: jdbc:h2:mem:cloud # 指定h2数据库的链接地址 driver-class-name: org.h2.Driver # 指定h2数据库的驱动 username: root # 指定h2数据库的登陆用户 password: 20121221 # 指定h2数据库的登陆密码 schema: classpath:/sql/schema.sql # 指定h2数据库的建表脚本 data: classpath:/sql/data.sql # 指定h2数据库的数据脚本 h2: console: path: /h2-console enabled: true logging: level: org.hibernate: info org.hibernate.type.descriptor.sql.BasicBinder: TRACE org.hibernate.type.descriptor.sql.BasicExtractor: TRACE info: app: name: microservice-simple-provider-user encoding: UTF-8 java: source: 1.8 target: 1.8

　　测试：

　　在开发中整合了actuator模块，Spring Boot Actuator提供了不少监控端点。

　　具体可查看：http://www.cnblogs.com/jinjiyese153/p/8607895.html

　　> Spring Boot Actuator测试

　　启动Spring Boot项目，访问：http://localhost:8000/actuator/health，若以下图，则正常

　　（默认只展现状态，详细信息不展现。若想查看详细信息，可点击上方URL查看）

　　> 项目测试

　　启动Spring Boot项目，访问：http://localhost:8000/1，若以下图，则正常

 4. 编写服务消费者

　　开发：

　　> 建立一个Spring Boot项目。pom.xml内容以下：

<?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>com.itmuch.cloud</groupId>
    <artifactId>microservice-simple-consumer-movie</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.0.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.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-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

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


</project>

　　> 建立一个用户实体类

package com.itmuch.cloud.microservicesimpleconsumermovie.pojo; import java.math.BigDecimal; public class User { private Long id; private String username; private String name; private Integer age; private BigDecimal balance; public Long getId() { return id; } public void setId(Long id) { this.id = id; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Integer getAge() { return age; } public void setAge(Integer age) { this.age = age; } public BigDecimal getBalance() { return balance; } public void setBalance(BigDecimal balance) { this.balance = balance; } }

　　> 修改启动类

package com.itmuch.cloud.microservicesimpleconsumermovie; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; import org.springframework.context.annotation.Bean; import org.springframework.web.client.RestTemplate; @SpringBootApplication public class MicroserviceSimpleConsumerMovieApplication { public static void main(String[] args) { SpringApplication.run(MicroserviceSimpleConsumerMovieApplication.class, args); } @Bean public RestTemplate restTemplate() { return new RestTemplate(); } }

　　> 建立Controller，在其中使用RestTemplate请求用户微服务的API。

package com.itmuch.cloud.microservicesimpleconsumermovie.controller; import com.itmuch.cloud.microservicesimpleconsumermovie.pojo.User; 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.RestController; import org.springframework.web.client.RestTemplate; @RestController public class MovieController { @Autowired private RestTemplate restTemplate; @GetMapping("/user/{id}") public User findById(@PathVariable Long id) { return this.restTemplate.getForObject("http://localhost:8000/" + id, User.class); } }

　　> 编写配置文件。将application.properties重命名为application.yml。

server: port: 8010 info: app: name: microservice-simple-consumer-movie encoding: UTF-8 java: source: 1.8 target: 1.8

　　测试：

　　在开发中一样整合了actuator模块

　　具体可查看：http://www.cnblogs.com/jinjiyese153/p/8607895.html

　　> Spring Boot Actuator测试

　　启动Spring Boot项目，访问：http://localhost:8010/actuator/health，若以下图，则正常

　　> 项目测试

　　启动Spring Boot项目，访问：http://localhost:8010/user/1，若以下图，则正常

5. 总结

　　在传统的应用程序中，通常都是这样作的。然而，这种方式存在问题。

　　1. 适用场景有限：若是服务提供者的网络地址（IP和端口）发生了变化，将会影响服务消费者。

　　2. 没法动弹伸缩：在生成环境中，每一个微服务通常都会部署多个实例，从而实现容灾和负载均衡。在微服务架构的系统中，还须要系统具有自动伸缩的能力，例如动态增长节点等。硬编码没法适应这种需求。

　　将会在下一篇博客中，解决这些问题。敬请期待~~~

6. 参考
　　周立 --- 《Spring Cloud与Docker微服务架构与实战》