Spring Boot中使用Dubbo

高并发下Redis会出现的问题：

缓存穿透
缓存雪崩
热点缓存

一、定义commons工程11-dubboCommons

（1）创建工程

创建Maven的Java工程，并命名为11-dubboCommons

（2）定义pom文件






<groupId>com.abc</groupId>





<artifactId>11-dubboCommons</artifactId>





<version>1.0-SNAPSHOT</version>





 





<properties>





	<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>





	<maven.compiler.source>1.8</maven.compiler.source>





	<maven.compiler.target>1.8</maven.compiler.target>





</properties>





 





<dependencies>





	<dependency>





		<groupId>org.projectlombok</groupId>





		<artifactId>lombok</artifactId>





		<version>1.18.4</version>





		<scope>provided</scope>





	</dependency>





</dependencies>

（3）定义实体类

（4）定义业务接口

（5）将工程安装到本地库

运行Maven的install命令，将工程安装到本地版本库，以备其它工程使用

二、定义提供者11-provider-springboot

（1）创建工程

创建一个Spring Boot工程，并重命名为11-provider-springboot

（2）定义pom文件

A、添加dubbo与spring boot整合依赖

B、添加zkClient依赖

C、其它依赖

dubboCommons依赖
spring boot与redis整合依赖
mybatis与spring boot整合依赖
数据源Druid依赖
mysql驱动依赖
slf4j-log4j12依赖
spring-boot-starter-web依赖






<groupId>com.abc</groupId>





    <artifactId>11-provider-springboot</artifactId>





    <version>0.0.1-SNAPSHOT</version>





 





    <parent>





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





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





        <version>2.1.5.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>





        <!--dubbo与spring boot整合依赖-->





        <dependency>





            <groupId>com.alibaba.spring.boot</groupId>





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





            <version>2.0.0</version>





        </dependency>





        <!-- zk客户端依赖：zkclient -->





        <dependency>





            <groupId>com.101tec</groupId>





            <artifactId>zkclient</artifactId>





            <version>0.10</version>





        </dependency>





        <dependency>





            <groupId>com.abc</groupId>





            <artifactId>11-dubboCommons</artifactId>





            <version>1.0-SNAPSHOT</version>





        </dependency>





        <!--Spring Boot与Redis整合依赖-->





        <dependency>





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





            <artifactId>spring-boot-starter-data-redis</artifactId>





        </dependency>





        <!--mybatis与Spring Boot整合依赖-->





        <dependency>





            <groupId>org.mybatis.spring.boot</groupId>





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





            <version>1.3.2</version>





        </dependency>





        <!--数据源Druid依赖-->





        <dependency>





            <groupId>com.alibaba</groupId>





            <artifactId>druid</artifactId>





            <version>1.1.10</version>





        </dependency>





        <!--MySQL驱动依赖-->





        <dependency>





            <groupId>mysql</groupId>





            <artifactId>mysql-connector-java</artifactId>





            <version>5.1.47</version>





        </dependency>





        <dependency>





            <groupId>org.slf4j</groupId>





            <artifactId>slf4j-log4j12</artifactId>





            <version>1.7.25</version>





            <scope>test</scope>





        </dependency>





        <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>





 





    <build>





        <plugins>





            <plugin>





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





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





            </plugin>





        </plugins>





 





        <resources>





            <!--注册dao包下mybatis映射文件为资源目录-->





            <resource>





                <directory>src/main/java</directory>





                <includes>





                    <include>**/*.xml</include>





                </includes>





            </resource>





        </resources>





    </build>

（3）定义Service实现类






import com.abc.bean.Employee;





import com.abc.dao.EmployeeDao;





import com.alibaba.dubbo.config.annotation.Service;





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





import org.springframework.cache.annotation.CacheEvict;





import org.springframework.cache.annotation.Cacheable;





import org.springframework.data.redis.core.BoundValueOperations;





import org.springframework.data.redis.core.RedisTemplate;





import org.springframework.stereotype.Component;





import org.springframework.transaction.annotation.Transactional;





 





import java.util.concurrent.TimeUnit;





 





@Service   // Dubbo的注解  <dubbo:service/>





@Component





public class EmployeeServiceImpl implements EmployeeService {





    @Autowired





    private EmployeeDao dao;





    @Autowired





    private RedisTemplate<Object, Object> redisTemplate;





 





    // 当有对象插入时会清空realTimeCache缓存空间





    @CacheEvict(value="realTimeCache", allEntries = true)





    @Transactional(rollbackFor = Exception.class)





    @Override





    public void addEmployee(Employee employee) {





        dao.insertEmployee(employee);





    }





 





    // 一旦有了查询结果，则会将此结果写入到realTimeCache缓存





    // key是employee_加上方法参数





    @Cacheable(value = {"realTimeCache"}, key = "'employee_'+#id")





    @Override





    public Employee findEmployeeById(int id) {





        // 从DB查询





        System.out.println("从DB查询id = " + id);





        return dao.selectEmployeeById(id);





    }





 





    private volatile Object count;





    // 双重检测锁机制解决Reids的热点缓存问题





    @Override





    public Integer findEmployeeCount() {





        // 获取Redis操作对象





        BoundValueOperations<Object, Object> ops = redisTemplate.boundValueOps("count");





        // 从缓存获取数据





        count = ops.get();





        if(count == null) {





           synchronized (this) {





                count = ops.get();





                if(count == null) {





                    System.out.println("从DB中查询");





                    // 从DB中查询





                    count = dao.selectEmployeeCount();





                    // 将查询结果存放到Redis





                    ops.set(count, 10, TimeUnit.SECONDS);





                }





            }





        }





        return (Integer) count;





    }





}

（4）定义Dao接口

（5）定义映射文件

（6）修改启动类

在启动类上必须要添加@EnableDubboConfiguration注解，开启Dubbo的自动配置功能

（7）修改主配置文件






server:





  port: 8888





 





mybatis:





  # 注册mybatis中实体类的别名





  type-aliases-package: com.abc.bean





  # 注册映射文件





  mapper-locations: classpath:com/abc/dao/*.xml





 





spring:





  # 注册数据源





  datasource:





    # 指定数据源类型为Druid





    type: com.alibaba.druid.pool.DruidDataSource





    driver-class-name: com.mysql.jdbc.Driver





    url: jdbc:mysql:///test?useUnicode=true&amp;characterEncoding=utf8





    username: root





    password: root





 





  # 连接Redis服务器





  redis:





    host: 39.97.176.160





    port: 6379





 





  # 连接Redis高可有集群





  #  redis:





  #    sentinel:





  #      master: mymaster





  #      nodes:





  #        - sentinelOS1:26379





  #        - sentinelOS2:26379





  #        - sentinelOS3:26379





 





  # 配置缓存





  cache:





    type: redis # 指定缓存类型





    cache-names: realTimeCache  # 指定缓存区域名称





 





 





  # 功能等价于spring-boot配置文件中的<dubbo:application/>





  application:





    name: 11-provider-springboot





  # 指定zk注册中心





  dubbo:





    registry: zookeeper://39.97.176.160:2181





  # zk集群作注册中心





  # registry: zookeeper://zkOS1:2181?backup=zkOS2:2181,zkOS3:2181

三、定义消费者11-consumer-springboot

（1）创建工程

创建一个Spring Boot工程，并重命名为11-consumer-springboot

（2）定义pom文件

dubbo与spring boot整合依赖
zkClient依赖
dubboCommons依赖
JSP引擎jasper依赖
slf4j-log4j12依赖
spring-boot-starter-web依赖

（3）修改主配置文件






spring:





  # 功能等价于spring-dubbo配置文件中的<dubbo:application/>





  application:





    name: 11-consumer-springboot





  # 指定zk注册中心





  dubbo:





    registry: zookeeper://39.97.176.160:2181





    # zk集群作注册中心





    # registry: zookeeper://zkOS1:2181?backup=zkOS2:2181,zkOS3:2181

（4）创建index.jsp页面

在src/main/webapp目录下定义index.jsp文件

（5）定义处理器






package com.abc.controller;





 





import com.abc.bean.Employee;





import com.abc.service.EmployeeService;





import com.alibaba.dubbo.config.annotation.Reference;





import org.springframework.stereotype.Controller;





import org.springframework.ui.Model;





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





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





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





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





 





@Controller





@RequestMapping("/consumer/employee")





public class SomeController {





 





    // @Autowired





    @Reference   // Dubbo的注解   <dubbo:reference />





    private EmployeeService employeeService;





 





    @PostMapping("/register")





    public String someHandle(Employee employee, Model model) {





        employeeService.addEmployee(employee);





        model.addAttribute("employee", employee);





        return "/welcome.jsp";





    }





 





    @RequestMapping("/find/{id}")





    @ResponseBody





    public Employee findHandle(@PathVariable("id") int id) {





        return employeeService.findEmployeeById(id);





    }





 





    @RequestMapping("/count")





    @ResponseBody





    public Integer countHandle() {





        return employeeService.findEmployeeCount();





    }





 





}

（6）定义welcome.jsp页面

（7）修改入口类

四、测试

当有对象插入时会清空realTimeCache缓存空间

一旦有了查询结果，则会将此结果写入到realTimeCache缓存

http://localhost:8080/index.jsp 首页

http://localhost:8080//consumer/employee/find/2 根据Id查找

http://localhost:8080//consumer/employee/count 查找总数