什么事讀寫分離

讀寫分離，基本的原理是讓主數(shù)據(jù)庫處理事務(wù)性增、改、刪操作（INSERT、UPDATE、DELETE），而從數(shù)據(jù)庫處理SELECT查詢操作。數(shù)據(jù)庫復(fù)制被用來把事務(wù)性操作導(dǎo)致的變更同步到集群中的從數(shù)據(jù)庫。

為什么要實現(xiàn)讀寫分離

增加冗余

增加了機(jī)器的處理能力

對于讀操作為主的應(yīng)用，使用讀寫分離是最好的場景，因為可以確保寫的服務(wù)器壓力更小，而讀又可以接受點時間上的延遲。

實現(xiàn)

本文介紹利用spring aop來動態(tài)切換數(shù)據(jù)源來實現(xiàn)讀寫分離。

先建一個maven項目，導(dǎo)入springBoot依賴。

<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中自定義數(shù)據(jù)源配置項

server: port: 8080logging: level: org.springframework: INFO com.qiang: DEBUGspring: 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 */@Configurationpublic class DruidConfig { private Logger logger = LoggerFactory.getLogger(DruidConfig.class /** * 主據(jù)源 * @return */ @Primary @Bean(name = 'dataSource') @ConfigurationProperties(prefix = 'spring.datasource') public DataSource dataSource() { return DataSourceBuilder.create().type(com.alibaba.druid.pool.DruidDataSource.class).build(); } /** * 從數(shù)據(jù)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(); } /** * 從數(shù)據(jù)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; /** * 寫庫數(shù)據(jù)源 */ @Autowired private DataSource dataSource; /** * 讀數(shù)據(jù)源數(shù)量 */ @Value('${spring.db.readsize}') private Integer readsize; /** * 數(shù)據(jù)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; } }}

其中實現(xiàn)數(shù)據(jù)源切換的功能就是自定義一個類擴(kuò)展AbstractRoutingDataSource抽象類，就是代碼中的定義的RoutingDataSource，其實該相當(dāng)于數(shù)據(jù)源DataSourcer的路由中介，可以實現(xiàn)在項目運行時根據(jù)相應(yīng)key值切換到對應(yīng)的數(shù)據(jù)源DataSource上。

RoutingDataSource.class

package com.qiang.config.db;import org.springframework.jdbc.datasource.lookup.AbstractRoutingDataSource;import java.util.concurrent.atomic.AtomicInteger;/** * 數(shù)據(jù)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('無法確定數(shù)據(jù)源'); } if (typeKey.equals(DataSourceType.WRITE.getType())) { return DataSourceType.WRITE.getType(); } //讀庫進(jìn)行負(fù)載均衡 int a = count.getAndAdd(1); int lookupkey = a % readsize; return lookupkey; }}

其中用到了2個輔助類

package com.qiang.config.db;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * 全局?jǐn)?shù)據(jù)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('切換至[讀]數(shù)據(jù)源'); local.set(DataSourceType.READ.getType()); } public static void write() { logger.debug('切換至[寫]數(shù)據(jù)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', '讀庫'), WRITE('write', '寫庫'); 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; }}

最后通過aop設(shè)置切面，攔截讀寫來動態(tài)的設(shè)置數(shù)據(jù)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;/** * 攔截數(shù)據(jù)庫讀寫 * * @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('攔截[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('攔截[write]操作'); DataSourceContextHolder.write(); }}

主要的代碼就寫好了，下面來測試一下是否讀寫分離。

寫一個測試類：

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)@SpringBootTestpublic 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); }}

其中第一個測試插入數(shù)據(jù)，第二個測試查詢。

第一測試結(jié)果：

第二個測結(jié)果：

從結(jié)果看出來第一個走的寫數(shù)據(jù)源，就是主數(shù)據(jù)源，第二個的走讀數(shù)據(jù)源，就是從數(shù)據(jù)源。

然后我們在測試一下事物，看遇到異常是否會滾。

測試：

@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();}

方法上加@Transactional，聲明一個事物。

看一下運行結(jié)果，雖然運行插入的時候，sql是運行了，但最后查詢的時候數(shù)量為0，說明會滾了。

配置事物

第一步需要加一個注解@EnableTransactionManagement，后面的參數(shù)是為了區(qū)分aop和事物執(zhí)行的順序。

然后在需要會滾的方法上加一個注解@Transactional。

源代碼地址

以上這篇使用springboot aop來實現(xiàn)讀寫分離和事物配置就是小編分享給大家的全部內(nèi)容了，希望能給大家一個參考，也希望大家多多支持好吧啦網(wǎng)。