1、原理图
2、创建枚举类
/**
* 存数据源key值
*/
public enum DataSourceKey {
master,salve,migration
}
3、创建自定义注解类
/**
* 自定义注解
*/
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface DBSource
{ String value() default "master"; }
4、切换数据源类
/**
* @author yehui
* 根据线程动态切换数据源
*/
@Configuration
public class DynamicDataSourceContextHolder {
private static final Logger log = LoggerFactory.getLogger(DynamicDataSourceContextHolder.class);
/**
* 设置默认数据源
*/
public static String DEFAULT_DS = "master";
/**
*用于轮训计数
*/
private static int counter = 0;
/*
* 当使用ThreadLocal维护变量时，ThreadLocal为每个使用该变量的线程提供独立的变量副本，
* 所以每一个线程都可以独立地改变自己的副本，而不会影响其它线程所对应的副本。
*/
private static final ThreadLocal<String> contextHolder = ThreadLocal.withInitial(() -> DataSourceKey.master.name());
/**
*用于在切换数据源时保证不会被其他线程修改
*/
public static Lock lock = new ReentrantLock();
/**
* 设置数据源
*/
public static void setDB(String dbType){
log.info("切换到{" + dbType + "}数据源");
contextHolder.set(dbType);
}
/**
* 得到数据源
*
*/
public static String getDB(){
return contextHolder.get();
}
/**
* 使用主数据源
*/
public static void useMasterDataSource() {
contextHolder.set(DataSourceKey.master.name());
}
/**
* 移除数据源
*/
public static void removeDB(){
contextHolder.remove();
}
/**
* The constant slaveDataSourceKeys.
*/
public static List<Object> slaveDataSourceKeys = new ArrayList<>();
/**
* 当使用只读数据源时通过轮循方式选择要使用的数据源
*/
public static String getSlaveDB(){
lock.lock();
try {
int datasourceKeyIndex = counter % slaveDataSourceKeys.size();
counter++;
return String.valueOf(slaveDataSourceKeys.get(datasourceKeyIndex));
} catch (Exception e) {
log.error(e.getMessage(), e);
e.printStackTrace();
return "master";
} finally {
lock.unlock();
}
}
}
5、获取数据源类
/**
* @author yehui
* 多数据源的选择
*/
public class DynamicDataSource extends AbstractRoutingDataSource {
private static final Logger log = LoggerFactory.getLogger(DynamicDataSource.class);
@Override
protected Object determineCurrentLookupKey() {
log.info("Current DataSource is " + DynamicDataSourceContextHolder.getDB());
return DynamicDataSourceContextHolder.getDB();
}
}
6、Aop类
/**
* @author yehui
* 自定义注解 + AOP的方式实现数据源动态切换。
*/
@Aspect
@Component
public class DynamicDataSourceAspect {
private static final Logger log = LoggerFactory.getLogger(DynamicDataSourceAspect.class);
@Before("@annotation(DBSource)")
public void beforeSwitchDB(JoinPoint joinPoint,DBSource DBSource){
//获取目标类的方法
Class<?> aClass = joinPoint.getTarget().getClass();
//获得访问的方法名
String methodName = joinPoint.getSignature().getName();
//得到方法的参数类型
Class[] parameterTypes = ((MethodSignature) joinPoint.getSignature()).getParameterTypes();
String dataSource = DynamicDataSourceContextHolder.DEFAULT_DS;
try {
Method method = aClass.getMethod(methodName, parameterTypes);
if(method.isAnnotationPresent(DBSource.class)){
DBSource db = method.getAnnotation(DBSource.class);
//指定数据源
dataSource = db.value();
}else{
//轮训设置数据源
dataSource = DynamicDataSourceContextHolder.getSlaveDB();
}
} catch (NoSuchMethodException e) {
log.error(e.getMessage(), e);
}
//设置数据源
DynamicDataSourceContextHolder.setDB(dataSource);
}
@After("@annotation(DBSource)")
public void afterSwitchDB(DBSource DBSource){
DynamicDataSourceContextHolder.removeDB();
}
}
6、application.properties文件
spring.druid.datasource.slave.password=root
spring.druid.datasource.slave.username=root
spring.druid.datasource.slave.jdbc-url=jdbc:mysql://localhost:3306/study
spring.druid.datasource.slave.driver-class-name=com.mysql.jdbc.Driver
spring.druid.datasource.master.password=root
spring.druid.datasource.master.username=root
spring.druid.datasource.master.jdbc-url=jdbc:mysql://localhost:3306/study01
spring.druid.datasource.master.driver-class-name=com.mysql.jdbc.Driver
spring.druid.datasource.migration.password=root
spring.druid.datasource.migration.username=root
#2.0版本多数据源必须是使用jdbc-url 不能使用url，否则报错 jdbcUrl is required with driverClassName
spring.druid.datasource.migration.jdbc-url=jdbc:mysql://localhost:3306/study02
spring.druid.datasource.migration.driver-class-name=com.mysql.jdbc.Driver
7、数据源配置类
/**
* @author yehui
* 数据源配置类
*/
@Configuration
public class DataSourceConfig {
/**
* 主数据
*
* @return data source
*/
@Bean("master")
@Primary
@ConfigurationProperties(prefix = "spring.druid.datasource.master")
public DataSource master() {
return DataSourceBuilder.create().build();
}
/**
* 从数据库
*
* @return data source
*/
@Bean("slave")
@ConfigurationProperties(prefix ="spring.druid.datasource.slave")
public DataSource slave() {
return DataSourceBuilder.create().build();
}
/**
* 从数据库
*
* @return data source
*/
@Bean("migration")
@ConfigurationProperties(prefix ="spring.druid.datasource.migration")
public DataSource migration() {
return DataSourceBuilder.create().build();
}
/**
* 配置动态数据源
*
* @return
*/
@Bean("dynamicDataSource")
public DataSource dynamicDataSource() {
DynamicDataSource dynamicRoutingDataSource = new DynamicDataSource();
Map<Object, Object> dataSourceMap = new HashMap<>(4);
dataSourceMap.put(DataSourceKey.master.name(), master());
dataSourceMap.put(DataSourceKey.salve.name(), slave());
dataSourceMap.put(DataSourceKey.master.name(), slave());
//设置默认的数据源
dynamicRoutingDataSource.setDefaultTargetDataSource(master());
// 多个slave数据源在此添加，自定义key，用于轮询
dataSourceMap.put(DataSourceKey.salve.name() + "1", slave());
//设置目标数据源
dynamicRoutingDataSource.setTargetDataSources(dataSourceMap);
//将数据源的key放在集合中判断是否正常
DynamicDataSourceContextHolder.slaveDataSourceKeys.addAll(dataSourceMap.keySet());
//实现负载均衡算法 将 Slave 数据源的 key 放在集合中，用于轮循
DynamicDataSourceContextHolder.slaveDataSourceKeys.addAll(dataSourceMap.keySet());
DynamicDataSourceContextHolder.slaveDataSourceKeys.remove(DataSourceKey.migration.name());
return dynamicRoutingDataSource;
}
/**
* 设置工厂类
*/
@Bean
public SqlSessionFactoryBean sqlSessionFactoryBean() {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(dynamicDataSource());
//此处设置为了解决找不到mapper文件的问题
try {
sqlSessionFactoryBean.setMapperLocations(new PathMatchingResourcePatternResolver().getResources("classpath:mapper/*Mapper.xml"));
} catch (IOException e) {
e.printStackTrace();
}
return sqlSessionFactoryBean;
}
/**
* 事物管理器
*/
@Bean("transactionManager")
public DataSourceTransactionManager transactionManager() {
return new DataSourceTransactionManager(dynamicDataSource());
}
}
8、启动类
/**
* springboot入口类,此类需要在所有用到的package上层 exclude =
* {DataSourceAutoConfiguration.class}
* 禁用springboot默认加载的application.properties单数据源配置
*/
@SpringBootApplication(exclude = {DataSourceAutoConfiguration.class})
public class StartApp {
public static void main(String[] args) {
SpringApplication.run(StartApp.class);
}
}
9、测试
mapper接口
@Mapper
public interface UserDataSourceMapper {
public List<TbUser> findUser();
}
mapper文件
<?xml version="1.0" encoding="utf-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
"http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.yehui.mapper.UserDataSourceMapper">
<select id="findUser" resultType="com.yehui.entity.TbUser">
select * from tb_user
</select>
</mapper>
service类
@Service public class UserServiceImpl implements UserService { @Autowired private UserDataSourceMapper userMapper; @Override @DBSource("slave")//使用数据源打上注解即可 public List<TbUser> findUser() { return userMapper.findUser(); } }
controller类
@RestController
public class UserController {
@Autowired
private UserService userService;
@RequestMapping("/findUser")
public List<TbUser> findUser(){
return userService.findUser();
}
}
效果:
如图所示，则动态数据源配置成功