springboot aop来实现读写分离和事物配置

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使用Spring实现读写分离 1 背景我们一般应用对数据库而言都是“读多写少”，也就说对数据库读取数据的压力比较大，有一个思路就是说采用数据库集群的方案，其中一个是主库，负责写入数据，我们称之为：写库；其它都是从库，负责读取数据，我们称之为：读库； 2 方案解决读写分离的方案有两种：应用层解决和中间件解决。 2.1 应用层解决：优点：多数据源切换方便，由程序自动完成；不需要引入中间件... 阅读详情

AI摘要

本文介绍如何使用Spring Boot和AOP技术实现数据库读写分离，并配置事务管理，减轻主数据库的压力，提高应用性能。

springboot aop来实现读写分离，以及事物配置

什么事读写分离

读写分离，基本的原理是让主数据库处理事务性增、改、删操作（INSERT、UPDATE、DELETE），而从数据库处理SELECT查询操作。数据库复制被用来把事务性操作导致的变更同步到集群中的从数据库。

为什么要实现读写分离

增加冗余
增加了机器的处理能力
对于读操作为主的应用，使用读写分离是最好的场景，因为可以确保写的服务器压力更小，而读又可以接受点时间上的延迟。

实现

本文介绍利用spring aop来动态切换数据源来实现读写分离。

先建一个maven项目，导入springBoot依赖。

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.2.RELEASE</version>
</parent>

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

    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-aop</artifactId>
    </dependency>
    <!--mybatis-->
    <dependency>
        <groupId>org.mybatis.spring.boot</groupId>
        <artifactId>mybatis-spring-boot-starter</artifactId>
        <version>1.3.1</version>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>
    <!-- druid -->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>${druid.version}</version>
    </dependency>
    <!-- mysql connector-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>${mysql-connector.version}</version>
    </dependency>

    <!--test-->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>

</dependencies>

然后在配置文件application.yml中自定义数据源配置项

server:
  port: 8080
logging:
  level:
    org.springframework: INFO
    com.qiang: DEBUG
spring:
  output:
    ansi:
      enabled: always
  datasource:
    type: com.alibaba.druid.pool.DruidDataSource
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/db_area?characterEncoding=utf-8&serverTimezone=Asia/Shanghai
    username: root
    password: root
  db:
    readsize: 2
    read0:
      type: com.alibaba.druid.pool.DruidDataSource
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/db_area?characterEncoding=utf-8&serverTimezone=Asia/Shanghai
      username: root
      password: root

    read1:
      type: com.alibaba.druid.pool.DruidDataSource
      driver-class-name: com.mysql.cj.jdbc.Driver
      url: jdbc:mysql://localhost:3306/db_area?characterEncoding=utf-8&serverTimezone=Asia/Shanghai
      username: root
      password: root
  aop:
    auto: true
    proxy-target-class: true

配置Druid

package com.qiang.config;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.autoconfigure.jdbc.DataSourceBuilder;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;

import javax.sql.DataSource;

/**
 * @author gengqiang
 * @date 2018/5/3
 */
@Configuration
public class DruidConfig {

    private Logger logger = LoggerFactory.getLogger(DruidConfig.class

    /**
     * 主据源
     * @return
     */
    @Primary
    @Bean(name = "dataSource")
    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSource dataSource() {
        return DataSourceBuilder.create().type(com.alibaba.druid.pool.DruidDataSource.class).build();

    }

    /**
     * 从数据源1
     * @return
     */
    @Bean(name = "readDataSource0")
    @ConfigurationProperties(prefix = "spring.db.read0")
    public DataSource readDataSource0() {
        return DataSourceBuilder.create().type(com.alibaba.druid.pool.DruidDataSource.class).build();

    }
    /**
     * 从数据源2
     * @return
     */
    @Bean(name = "readDataSource1")
    @ConfigurationProperties(prefix = "spring.db.read1")
    public DataSource readDataSource1() {
        return DataSourceBuilder.create().type(com.alibaba.druid.pool.DruidDataSource.class).build();

    }

}

配置Mybaits

package com.qiang.config;

import com.qiang.config.db.DataSourceType;
import com.qiang.config.db.RoutingDataSource;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.annotation.MapperScan;
import org.mybatis.spring.boot.autoconfigure.SpringBootVFS;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.jdbc.datasource.DataSourceTransactionManager;
import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;
import org.springframework.transaction.PlatformTransactionManager;
import org.springframework.transaction.annotation.EnableTransactionManagement;
import org.springframework.transaction.annotation.TransactionManagementConfigurer;

import javax.sql.DataSource;
import java.io.IOException;
import java.util.HashMap;
import java.util.Map;

/**
 * @author gengqiang
 * @date 2018/5/3
 */
@Configuration
@EnableTransactionManagement(order = 2)
@MapperScan(basePackages = {"com.qiang.demo.mapper"})
public class MybatisConfig  implements TransactionManagementConfigurer, ApplicationContextAware {


    private static ApplicationContext context;


    /**
     * 写库数据源
     */
    @Autowired
    private DataSource dataSource;

    /**
     * 读数据源数量
     */
    @Value("${spring.db.readsize}")
    private Integer readsize;
    /**
     * 数据源路由代理
     *
     * @return
     */

    @Bean
    public AbstractRoutingDataSource routingDataSouceProxy() {
        RoutingDataSource proxy = new RoutingDataSource(readsize);
        Map<Object, Object> targetDataSources = new HashMap<>(readsize + 1);
        targetDataSources.put(DataSourceType.WRITE.getType(), dataSource);
        for (int i = 0; i < readsize; i++) {
            DataSource d = context.getBean("readDataSource" + i, DataSource.class);
            targetDataSources.put(i, d);
        }
        proxy.setDefaultTargetDataSource(dataSource);
        proxy.setTargetDataSources(targetDataSources);
        return proxy;
    }

    @Bean
    @ConditionalOnMissingBean
    public SqlSessionFactoryBean sqlSessionFactory() throws IOException {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(routingDataSouceProxy());
        bean.setVfs(SpringBootVFS.class);
        bean.setTypeAliasesPackage("com.qiang");
        Resource configResource = new ClassPathResource("/mybatis-config.xml");
        bean.setConfigLocation(configResource);
        ResourcePatternResolver mapperResource = new PathMatchingResourcePatternResolver();
        bean.setMapperLocations(mapperResource.getResources("classpath*:mapper/**/*.xml"));
        return bean;
    }

    @Override
    public PlatformTransactionManager annotationDrivenTransactionManager() {
        return new DataSourceTransactionManager(routingDataSouceProxy());
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        if (context == null) {
            context = applicationContext;
        }
    }
}

其中实现数据源切换的功能就是自定义一个类扩展AbstractRoutingDataSource抽象类，就是代码中的定义的RoutingDataSource，其实该相当于数据源DataSourcer的路由中介，可以实现在项目运行时根据相应key值切换到对应的数据源DataSource上。

RoutingDataSource.class

package com.qiang.config.db;

import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;

import java.util.concurrent.atomic.AtomicInteger;

/**
 * 数据源路由
 *
 * @author gengqiang
 */
public class RoutingDataSource extends AbstractRoutingDataSource {

    private AtomicInteger count = new AtomicInteger(0);

    private int readsize;

    public RoutingDataSource(int readsize) {
        this.readsize = readsize;
    }

    @Override
    protected Object determineCurrentLookupKey() {
        String typeKey = DataSourceContextHolder.getJdbcType();
        if (typeKey == null) {
            logger.error("无法确定数据源");
        }
        if (typeKey.equals(DataSourceType.WRITE.getType())) {
            return DataSourceType.WRITE.getType();
        }
        //读库进行负载均衡
        int a = count.getAndAdd(1);
        int lookupkey = a % readsize;
        return lookupkey;
    }

}

其中用到了2个辅助类

package com.qiang.config.db;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * 全局数据源
 *
 * @author gengqiang
 */
public class DataSourceContextHolder {

    private static Logger logger = LoggerFactory.getLogger(DataSourceContextHolder.class);

    private final static ThreadLocal<String> local = new ThreadLocal<>();

    public static ThreadLocal<String> getLocal() {
        return local;
    }

    public static void read() {
        logger.debug("切换至[读]数据源");
        local.set(DataSourceType.READ.getType());
    }

    public static void write() {
        logger.debug("切换至[写]数据源");
        local.set(DataSourceType.WRITE.getType());
    }

    public static String getJdbcType() {
        return local.get();
    }

}

package com.qiang.config.db;

/**
 * @author gengqiang
 */
public enum DataSourceType {
    READ("read", "读库"), WRITE("write", "写库");
    private String type;
    private String name;

    DataSourceType(String type, String name) {
        this.type = type;
        this.name = name;
    }

    public String getType() {
        return type;
    }

    public void setType(String type) {
        this.type = type;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

最后通过aop设置切面，拦截读写来动态的设置数据源

package com.qiang.config.aop;

import com.qiang.config.db.DataSourceContextHolder;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Before;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

/**
 * 拦截数据库读写
 *
 * @author gengqiang
 */

@Aspect
@Component
@Order(1)
public class DataSourceAspect {

    Logger logger = LoggerFactory.getLogger(getClass());

    @Before("execution(* com.qiang..*.*ServiceImpl.find*(..)) " +
            "|| execution(* com.qiang..*.*ServiceImpl.count*(..))" +
            "|| execution(* com.qiang..*.*ServiceImpl.sel*(..))" +
            "|| execution(* com.qiang..*.*ServiceImpl.get*(..))"
    )
    public void setReadDataSourceType() {
        logger.debug("拦截[read]方法");
        DataSourceContextHolder.read();
    }

    @Before("execution(* com.qiang..*.*ServiceImpl.insert*(..)) " +
            "|| execution(* com.qiang..*.*ServiceImpl.save*(..))" +
            "|| execution(* com.qiang..*.*ServiceImpl.update*(..))" +
            "|| execution(* com.qiang..*.*ServiceImpl.set*(..))" +
            "|| execution(* com.qiang..*.*ServiceImpl.del*(..))")
    public void setWriteDataSourceType() {
        logger.debug("拦截[write]操作");
        DataSourceContextHolder.write();
    }

}

主要的代码就写好了，下面来测试一下是否读写分离。

写一个测试类：

package com.qiang;

import com.qiang.demo.entity.Area;
import com.qiang.demo.service.AreaService;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

/**
 * @author gengqiang
 * @date 2018/5/4
 */

@RunWith(SpringRunner.class)
@SpringBootTest
public class TestApplication {

    @Autowired
    private AreaService areaService;


    @Test
    public void test() {
        Area area = new Area();
        area.setDistrictId("0000");
        area.setName("test");
        area.setParentId(0);
        area.setLevel(1);
        areaService.insert(area);
    }

    @Test
    public void test2() {
        areaService.selectByPrimaryKey(1);
    }
}

其中第一个测试插入数据，第二个测试查询。

第一测试结果：

这里写图片描述

第二个测结果：

这里写图片描述

从结果看出来第一个走的写数据源，就是主数据源，第二个的走读数据源，就是从数据源。

然后我们在测试一下事物，看遇到异常是否会滚。

测试：

   @Test
    public void contextLoads() throws Exception {
        try {
            areaService.insertBack();

        } catch (Exception e) {
//            e.printStackTrace();
        }
        System.out.println(areaService.count(new Area()));

    }

其中service：

@Override
@Transactional(rollbackFor = Exception.class)
public void insertBack() {
    Area area = new Area();
    area.setDistrictId("0000");
    area.setName("test");
    area.setParentId(0);
    area.setLevel(1);
    mapper.insert(area);
    throw new RuntimeException();
}