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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：
多数据源注入到sqlSessionFactory
POM增加如下依赖：
<!--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>
</div>
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)
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
</div>
创建数据源
@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();
}
}
</div>
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
@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;
}
}
</div>
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
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();
}
}
</div>
注解实现
/**
* 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 {
}
</div>
Spring AOP对注解的拦截
@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 readOnlyCo