Spring Boot 集成Mybatis实现主从(多数据源)分离方案示例

时间:2021-10-12 09:13:58

本文将介绍使用Spring Boot集成Mybatis并实现主从库分离的实现(同样适用于多数据源)。延续之前的Spring Boot 集成MyBatis。项目还将集成分页插件PageHelper、通用Mapper以及Druid。

新建一个Maven项目,最终项目结构如下:

Spring Boot 集成Mybatis实现主从(多数据源)分离方案示例

多数据源注入到sqlSessionFactory

POM增加如下依赖:

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<!--JSON-->
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-core</artifactId>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.core</groupId>
      <artifactId>jackson-databind</artifactId>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.datatype</groupId>
      <artifactId>jackson-datatype-joda</artifactId>
    </dependency>
    <dependency>
      <groupId>com.fasterxml.jackson.module</groupId>
      <artifactId>jackson-module-parameter-names</artifactId>
    </dependency>
 
    <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-jdbc</artifactId>
    </dependency>
    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.0.11</version>
    </dependency>
    <!--mybatis-->
    <dependency>
      <groupId>org.mybatis.spring.boot</groupId>
      <artifactId>mybatis-spring-boot-starter</artifactId>
      <version>1.1.1</version>
    </dependency>
    <!--mapper-->
    <dependency>
      <groupId>tk.mybatis</groupId>
      <artifactId>mapper-spring-boot-starter</artifactId>
      <version>1.1.0</version>
    </dependency>
    <!--pagehelper-->
    <dependency>
      <groupId>com.github.pagehelper</groupId>
      <artifactId>pagehelper-spring-boot-starter</artifactId>
      <version>1.1.0</version>
      <exclusions>
        <exclusion>
          <artifactId>mybatis-spring-boot-starter</artifactId>
          <groupId>org.mybatis.spring.boot</groupId>
        </exclusion>
      </exclusions>
    </dependency>

这里需要注意的是:项目是通过扩展mybatis-spring-boot-starter的org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration来实现多数据源注入的。在mybatis-spring-boot-starter:1.2.0中,该类取消了默认构造函数,因此本项目依旧使用1.1.0版本。需要关注后续版本是否会重新把扩展开放处理。

之所以依旧使用旧方案,是我个人认为开放扩展是合理的,相信在未来的版本中会回归。

如果你需要其他方案可参考传送门

增加主从库配置(application.yml)

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druid:
  type: com.alibaba.druid.pool.DruidDataSource
  master:
    url: jdbc:mysql://192.168.249.128:3307/db-test?characterEncoding=UTF-8&autoReconnect=true&zeroDateTimeBehavior=convertToNull&useUnicode=true
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: root
    initial-size: 5
    min-idle: 1
    max-active: 100
    test-on-borrow: true
  slave:
    url: jdbc:mysql://192.168.249.128:3317/db-test?characterEncoding=UTF-8&autoReconnect=true&zeroDateTimeBehavior=convertToNull&useUnicode=true&characterEncoding=utf-8
    driver-class-name: com.mysql.jdbc.Driver
    username: root
    password: root
    initial-size: 5
    min-idle: 1
    max-active: 100
    test-on-borrow: true

创建数据源

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@Configuration
@EnableTransactionManagement
public class DataSourceConfiguration {
 
  @Value("${druid.type}")
  private Class<? extends DataSource> dataSourceType;
 
  @Bean(name = "masterDataSource")
  @Primary
  @ConfigurationProperties(prefix = "druid.master")
  public DataSource masterDataSource(){
    return DataSourceBuilder.create().type(dataSourceType).build();
  }
 
  @Bean(name = "slaveDataSource")
  @ConfigurationProperties(prefix = "druid.slave")
  public DataSource slaveDataSource1(){
    return DataSourceBuilder.create().type(dataSourceType).build();
  }
}

将多数据源注入到sqlSessionFactory中

前面提到了这里通过扩展mybatis-spring-boot-starter的org.mybatis.spring.boot.autoconfigure.MybatisAutoConfiguration来实现多数据源注入的

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@Configuration
@AutoConfigureAfter({DataSourceConfiguration.class})
public class MybatisConfiguration extends MybatisAutoConfiguration {
 
  private static Log logger = LogFactory.getLog(MybatisConfiguration.class);
 
  @Resource(name = "masterDataSource")
  private DataSource masterDataSource;
  @Resource(name = "slaveDataSource")
  private DataSource slaveDataSource;
 
  @Bean
  public SqlSessionFactory sqlSessionFactory() throws Exception {
    return super.sqlSessionFactory(roundRobinDataSouceProxy());
  }
 
  public AbstractRoutingDataSource roundRobinDataSouceProxy(){
    ReadWriteSplitRoutingDataSource proxy = new ReadWriteSplitRoutingDataSource();
    Map<Object,Object> targetDataResources = new ClassLoaderRepository.SoftHashMap();
    targetDataResources.put(DbContextHolder.DbType.MASTER,masterDataSource);
    targetDataResources.put(DbContextHolder.DbType.SLAVE,slaveDataSource);
    proxy.setDefaultTargetDataSource(masterDataSource);//默认源
    proxy.setTargetDataSources(targetDataResources);
    return proxy;
  }
}

实现读写分离(多数据源分离)

这里主要思路如下:

1-将不同的数据源标识记录在ThreadLocal中

2-通过注解标识出当前的service方法使用哪个库

3-通过Spring AOP实现拦截注解并注入不同的标识到threadlocal中

4-获取源的时候通过threadlocal中不同的标识给出不同的sqlSession

标识存放ThreadLocal的实现

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public class DbContextHolder {
 
  public enum DbType{
    MASTER,SLAVE
  }
 
  private static final ThreadLocal<DbType> contextHolder = new ThreadLocal<>();
 
  public static void setDbType(DbType dbType){
    if(dbType==null)throw new NullPointerException();
    contextHolder.set(dbType);
  }
 
  public static DbType getDbType(){
    return contextHolder.get()==null?DbType.MASTER:contextHolder.get();
  }
 
  public static void clearDbType(){
    contextHolder.remove();
  }
 
}

注解实现

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/**
 * 该注解注释在service方法上,标注为链接slaves库
 * Created by Jason on 2017/3/6.
 */
@Target({ElementType.METHOD,ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
public @interface ReadOnlyConnection {
}

Spring AOP对注解的拦截

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@Aspect
@Component
public class ReadOnlyConnectionInterceptor implements Ordered {
 
  public static final Logger logger = LoggerFactory.getLogger(ReadOnlyConnectionInterceptor.class);
 
  @Around("@annotation(readOnlyConnection)")
  public Object proceed(ProceedingJoinPoint proceedingJoinPoint,ReadOnlyConnection readOnlyConnection) throws Throwable {
    try {
      logger.info("set database connection to read only");
      DbContextHolder.setDbType(DbContextHolder.DbType.SLAVE);
      Object result = proceedingJoinPoint.proceed();
      return result;
    }finally {
      DbContextHolder.clearDbType();
      logger.info("restore database connection");
    }
  }
 
 
  @Override
  public int getOrder() {
    return 0;
  }
}

根据标识获取不同源

这里我们通过扩展AbstractRoutingDataSource来获取不同的源。它是Spring提供的一个可以根据用户发起的不同请求去转换不同的数据源,比如根据用户的不同地区语言选择不同的数据库。通过查看源码可以发现,它是通过determineCurrentLookupKey()返回的不同key到sqlSessionFactory中获取不同源(前面已经展示了如何在sqlSessionFactory中注入多个源)

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public class ReadWriteSplitRoutingDataSource extends AbstractRoutingDataSource {
 
  @Override
  protected Object determineCurrentLookupKey() {
    return DbContextHolder.getDbType();
  }
}

以上就完成了读写分离(多数据源)的配置方案。下面是一个具体的实例

使用方式

Entity

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@Table(name = "t_sys_dic_type")
public class DicType extends BaseEntity{
 
  String code;
 
  String name;
 
  Integer status;
 
  ...
}

Mapper

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public interface DicTypeMapper extends BaseMapper<DicType> {
}

Service

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@Service
public class DicTypeService {
  @Autowired
  private DicTypeMapper dicTypeMapper;
 
  @ReadOnlyConnection
  public List<DicType> getAll(DicType dicType){
    if (dicType.getPage() != null && dicType.getRows() != null) {
      PageHelper.startPage(dicType.getPage(), dicType.getRows());
    }
    return dicTypeMapper.selectAll();
  }
 
}

注意这里的@ReadOnlyConnection注解

Controller

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@RestController
@RequestMapping("/dictype")
public class DicTypeController {
  @Autowired
  private DicTypeService dicTypeService;
 
  @RequestMapping(value = "/all")
  public PageInfo<DicType> getALL(DicType dicType){
    List<DicType> dicTypeList = dicTypeService.getAll(dicType);
    return new PageInfo<>(dicTypeList);
  }
}

通过mvn spring-boot:run启动后,即可通过http://localhost:9090/dictype/all 获取到数据

后台打印出

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c.a.d.m.ReadOnlyConnectionInterceptor  : set database connection to read only

说明使用了从库的链接获取数据

备注:如何保证多源事务呢?

1-在读写分离场景中不会考虑主从库事务,在纯读的上下文上使用@ReadOnlyConnection标签。其他则默认使用主库。

2-在多源场景中,Spring的@Transaction是可以保证多源的事务性的。

本文使用代码

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

原文链接:http://www.jianshu.com/p/8813ec02926a