在大数据高并发的应用场景下，为了更快的响应用户请求，读写分离是比较常见的应对方案。读写分离会使用多数据源的使用。下面记录如何搭建SpringBoot2 + Druid + Mybatis 多数据源配置以及在使用过程遇到的问题。
一、先从pom.xml入手（使用springboot 2的版本）
org.springframework.boot
spring-boot-starter-parent
2.1.5.RELEASE
org.springframework.boot
spring-boot-starter
org.springframework.boot
spring-boot-starter-web
org.mybatis.spring.boot
mybatis-spring-boot-starter
2.0.1
mysql
mysql-connector-java
8.0.16
com.alibaba
druid-spring-boot-starter
1.1.17
javax.inject
javax.inject
1
inject是java依赖注入标准。spring默认支持识别。spring自带的@Autowired的缺省情况等价于JSR-330的@Inject注解；@Qualifier的缺省的根据Bean名字注入情况等价于JSR-330的@Named注解。
二、添加读取DB的Mapper
@Mapper
public interface AssetMapper {
@Select("select * from Asset where account = #{account}")
Asset queryName(String account);
}
此处使用mybatis的注解功能，因此可以少省去*.xml等配置文件。
三、添加多数据源的配置参数
spring.datasource.druid.write.url=jdbc:mysql://192.168.0.110:3306/master?characterEncoding=utf-8&serverTimezone=Asia/Shanghai
spring.datasource.druid.write.username=root
spring.datasource.druid.write.password=123456
spring.datasource.druid.write.driver-class-name=com.mysql.cj.jdbc.Driver
#
spring.datasource.druid.read.url=jdbc:mysql://192.168.0.110:3306/slave1?characterEncoding=utf-8&serverTimezone=Asia/Shanghai
spring.datasource.druid.read.username=root
spring.datasource.druid.read.password=123456
spring.datasource.druid.read.driver-class-name=com.mysql.cj.jdbc.Driver
新版本mysql的url后面必需要添加serverTimezone=。 不然会报以下异常：
2019-06-05 18:47:24.058 ERROR 17804 --- [-Create-6910184] com.alibaba.druid.pool.DruidDataSource : create connection SQLException, url: jdbc:mysql://localhost:3306/master, errorCode 0, state 01S00
java.sql.SQLException: The server time zone value '�й���ʱ��' is unrecognized or represents more than one time zone. You must configure either the server or JDBC driver (via the serverTimezone configuration property) to use a more specifc time zone value if you want to utilize time zone support.
四、配置数据源
@Configuration
public class DataSourceConfig {
@Bean(name = "masterDataSource")
@ConfigurationProperties(prefix = "spring.datasource.druid.write")
@Primary
public DataSource masterDataSource() {
return DruidDataSourceBuilder.create().build();
}
@Bean(name = "slaveDataSource")
@ConfigurationProperties(prefix = "spring.datasource.druid.read")
public DataSource slaveDataSource() {
return DruidDataSourceBuilder.create().build();
}
@Inject
@Named("masterDataSource")
private DataSource masterDataSource;
@Inject
@Named("slaveDataSource")
private DataSource slaveDataSource;
/**
* 根据数据源创建SqlSessionFactory
*/
@Bean
public SqlSessionFactory sqlSessionFactory(DynamicDataSource dataSource) throws Exception {
SqlSessionFactoryBean sessionFactory = new SqlSessionFactoryBean();
sessionFactory.setDataSource(dataSource);
return sessionFactory.getObject();
}
}
SqlSessionFactory必需要重新创建，若不创建会报循环调用异常
Caused by: org.springframework.beans.factory.BeanCurrentlyInCreationException: Error creating bean with name 'masterDataSource': Requested bean is currently in creation: Is there an unresolvable circular reference?
因为SqlSessionFactory还是走默认创建的方式 。
上下文中如何得知使用那个数据源，可使用ThreadLocal来处理。
五、数据源路由
public class DataSourceContextRouting implements AutoCloseable {
static final ThreadLocal dataSourceKeyThreadLocal = new ThreadLocal<>();
public String getDataSourceName(){
String key = dataSourceKeyThreadLocal.get();
return StringUtils.isBlank(key) ?"masterDataSource":key;
}
public DataSourceContextRouting(String key){
dataSourceKeyThreadLocal.set(key);
}
@Override
public void close() throws Exception {
dataSourceKeyThreadLocal.remove();
}
} spring的提供动态源实现功能。只需要继承AbstractRoutingDataSource，并重写protected Object determineCurrentLookupKey()
public class DynamicDataSource extends AbstractRoutingDataSource {
@Override
protected Object determineCurrentLookupKey() {
return DataSourceContextRouting.getDataSourceName();
}
}
//此为核心代码
@Bean
public DynamicDataSource dataSource() {
Map, Object> targetDataSources = new HashMap<>();
targetDataSources.put("masterDataSource", masterDataSource);
targetDataSources.put("slaveDataSource", slaveDataSource);
DynamicDataSource dataSource = new DynamicDataSource();
//设置数据源映射
dataSource.setTargetDataSources(targetDataSources);
//设置默认数据源，当无法映射到数据源时会使用默认数据源
dataSource.setDefaultTargetDataSource(slaveDataSource);
dataSource.afterPropertiesSet();
return dataSource;
}
六、controller路由切换
@RequestMapping("master")
public String master(String account){
String key = "masterDataSource";
new DataSourceContextRouting(key);
//TODO .....
}
@RequestMapping("slave")
public String slave(String account){
String key = "slaveDataSource";
new DataSourceContextRouting(key);
//TODO......
}
到此为止，整个多数据源配置完成了。
但这种对代码侵入比较多，可以使用注解的方式来处理。先定义注解标识
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface TargetDataSource {
String value();
}
使用注解那需要对此进行解析切入，因此就需要用上spring AOP的功能。
首先添加maven依赖
org.springframework.boot
spring-boot-starter-aop
然后添加对其解析Aspect
@Aspect
@Named
public class DataSourceRoutingAspect {
@Around("@annotation(targetDataSource)")
public Object routingWithDataSource(ProceedingJoinPoint joinPoint, TargetDataSource targetDataSource) throws Throwable {
String key = targetDataSource.value();
try (DataSourceContextRouting ctx = new DataSourceContextRouting(key)) {
return joinPoint.proceed();
}
}
}
@RequestMapping("master")
@TargetDataSource("masterDataSource")
public String master(String account){
TODO:.....
}
@RequestMapping("slave")
@TargetDataSource("slaveDataSource")
public String slave(String account){
TODO:.....
}