通过重写AbstractRoutingDataSource类中方法determineTargetDataSource，determineCurrentLookupKey，afterPropertiesSet实现动态DataSource。
determineTargetDataSource：获取动态DataSource
determineCurrentLookupKey：获取动态数据源名称
afterPropertiesSet：重写该方法，防止调用父类方法，自己管理多数据源
本例适用场景：多租户SAAS系统，基于数据库schema或者数据库实例完全隔离的系统。系统中有一个master数据库，会配置其他各个租户数据源的连接信息，这个是由系统配置统一维护。任何request请求都会标记该租户信息，然后由后台拦截初始化ThreadLocal变量。DynamicDataSource中根据ThreadLocal切换不同的数据源。
数据源标记ThreadLocal
public class DynamicDataSourceHolder {
private static final ThreadLocal<String> contextHolder = new InheritableThreadLocal<>();
public static void setDataSource(String dataSource) {
contextHolder.set(dataSource);
}
public static String getDataSource() {
return contextHolder.get();
}
public static void clearDataSource() {
contextHolder.remove();
}
}
@Component
public class SpringBeanHelper implements ApplicationContextAware {
private static ApplicationContext context;
public static <T> T getBean(Class<T> requiredClass) {
return context.getBean(requiredClass);
}
@Override
public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
this.context= applicationContext;
}
}
拦截请求设置ThreadLocal
@Configuration
public class DBInterceptor implements HandlerInterceptor{
private static final Logger logger= LoggerFactory.getLogger(DBInterceptor.class);
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object arg2) throws Exception {
//这里只是简单从请求参数中获取，真实场景可能会从header中租户id或者域名区分
String db= request.getParameter("db");
if(StringUtils.isNoneEmpty(db)) {
logger.info("db is: {}",db);
DynamicDataSourceHolder.setDataSource(db);
return true;
}
logger.error("db is empty");
response.getWriter().print("no authority.");
return false;
}
@Override
public void afterCompletion(HttpServletRequest arg0, HttpServletResponse arg1, Object arg2, Exception arg3)
throws Exception {
DynamicDataSourceHolder.clearDataSource();
logger.info("clear db holder.");
}
@Override
public void postHandle(HttpServletRequest arg0, HttpServletResponse response, Object arg2, ModelAndView arg3)
throws Exception {}
}
动态数据源实现
@Configuration
public class DynamicDataSource extends AbstractRoutingDataSource{
private static final Logger logger= LoggerFactory.getLogger(DynamicDataSource.class);
@Value("${jdbc.master.database}")
private String masterDataBase;
@Value("${jdbc.driver}")
private String driver;
@Value("${jdbc.url}")
private String url;
@Value("${jdbc.username}")
private String username;
@Value("${jdbc.password}")
private String password;
//保存动态创建的数据源
private static final Map<String,DataSource> targetDataSource = new HashMap<>();
//主数据库初始化
@PostConstruct
private void init() {
DataSource dataSource= (DataSource) DataSourceBuilder.create(Thread.currentThread().getContextClassLoader())
.driverClassName(driver)
.url(url)
.username(username)
.password(password).build();
dataSource.setMaxActive(1000);
dataSource.setMaxIdle(200);
dataSource.setMinIdle(200);
dataSource.setMaxWait(10000);
putDataSource(masterDataBase, dataSource);
}
@Override
protected DataSource determineTargetDataSource() {
// 根据数据库选择方案，拿到要访问的数据库
String dataSourceName = determineCurrentLookupKey();
// 根据数据库名字，从已创建的数据库中获取要访问的数据库
DataSource dataSource = targetDataSource.get(dataSourceName);
if(null == dataSource) {
//从已创建的数据库中获取要访问的数据库，如果没有则创建一个
dataSource = this.selectDataSource(dataSourceName);
}
return dataSource;
}
@Override
protected String determineCurrentLookupKey() {
String dataSourceName = DynamicDataSourceHolder.getDataSource();
return dataSourceName;
}
/**
* 该方法为同步方法，防止并发创建两个相同的数据库
* @param dbname
* @return
*/
private synchronized DataSource selectDataSource(String dbname) {
// 双重检查
DataSource obj = this.targetDataSource.get(dbname);
if (null != obj) {
return obj;
}
// 为空则创建数据库
DataSource dataSource = this.setDataSource(dbname);
if (null != dataSource) {
// 将新创建的数据库保存到map中
putDataSource(dbname, dataSource);
return dataSource;
}
throw new RuntimeException("创建数据源失败！");
}
private void putDataSource(String dbname, DataSource dataSource) {
this.targetDataSource.put(dbname, dataSource);
}
/**
* 查询对应数据库的信息
* @param dbname
* @return
*/
private DataSource setDataSource(String dbname) {
String oriSource = DynamicDataSourceHolder.getDataSource();
// 先切换回主库
DynamicDataSourceHolder.setDataSource(masterDataBase);
// 查询所需信息
CenterDatabase database = getDataBaseService().getById(dbname);
if(database==null){
throw new RuntimeException("获取目标数据库连接信息失败。");
}
// 切换回目标库
DynamicDataSourceHolder.setDataSource(oriSource);
DataSource dataSource = (DataSource)DataSourceBuilder.create(Thread.currentThread().getContextClassLoader())
.driverClassName(database.driver)
.url(database.parseMysqlURL())
.username(database.username)
.password(database.password).build();
dataSource.setMaxActive(3000);
dataSource.setMaxIdle(6);
dataSource.setMaxWait(5000);
return dataSource;
}
@Override
public void afterPropertiesSet() {
//do nothing just for override. becauseof targetDataSource management by self.
}
private DatabaseService getDataBaseService(){
return SpringBeanHelper.getBean(DatabaseService.class);
}
}
Mybatis配置
@Configuration
public class MybatisConfig implements TransactionManagementConfigurer {
//mybatis 配置路径
private static String MYBATIS_CONFIG = "mybatis-config.xml";
//mybatis mapper resource 路径
private static String MAPPER_PATH = "/mapper/**.xml";
private String typeAliasPackage = "com.test.mapper";
@Autowired
private DynamicDataSource dataSource;
@Override
public PlatformTransactionManager annotationDrivenTransactionManager() {
return new DataSourceTransactionManager(dataSource);
}
@Bean(name = "sqlSessionFactory")
public SqlSessionFactory sqlSessionFactoryBean() throws Exception {
SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
bean.setConfigLocation(new ClassPathResource(MYBATIS_CONFIG));
//添加mapper 扫描路径
PathMatchingResourcePatternResolver pathMatchingResourcePatternResolver = new PathMatchingResourcePatternResolver();
String packageSearchPath = ResourcePatternResolver.CLASSPATH_ALL_URL_PREFIX + MAPPER_PATH;
bean.setMapperLocations(pathMatchingResourcePatternResolver.getResources(packageSearchPath));
//设置datasource
bean.setDataSource(dataSource);
//设置typeAlias 包扫描路径
bean.setTypeAliasesPackage(typeAliasPackage);
return bean.getObject();
}
@Bean
public SqlSessionTemplate sqlSessionTemplate(SqlSessionFactory sqlSessionFactory) {
return new SqlSessionTemplate(sqlSessionFactory);
}
}
说明：以上方案在使用多实例数据库的时候问题不大。但如果考虑使用单实例数据库，多schema的方案需要注意的各个租户数据库连接问题，防止有的租户占用大量连接，浪费资源。
