@EqualsAndHashCode(callSuper = false)
@Data
@FieldDefaults(level = AccessLevel.PRIVATE)
public class TenantConfigEntity {
    /**
     * 租户id
     **/
    Integer tenantId;
    /**
     * 租户名称
     **/
    String tenantName;
    /**
     * 租户名称key
     **/
    String tenantKey;
    /**
     * 数据库url
     **/
    String dbUrl;
    /**
     * 数据库用户名
     **/
    String dbUser;
    /**
     * 数据库密码
     **/
    String dbPassword;
    /**
     * 数据库public_key
     **/
    String dbPublicKey;
}

public class DataSourceUtil {
    private static final String DATA_SOURCE_BEAN_KEY_SUFFIX = "_data_source";
    private static final String JDBC_URL_ARGS = "?useUnicode=true&characterEncoding=UTF-8&useOldAliasMetadataBehavior=true&zeroDateTimeBehavior=convertToNull";
    private static final String CONNECTION_PROPERTIES = "config.decrypt=true;config.decrypt.key=";
    /**
     * 拼接数据源的spring bean key
     */
    public static String getDataSourceBeanKey(String tenantKey) {
        if (!StringUtils.hasText(tenantKey)) {
            return null;
        }
        return tenantKey + DATA_SOURCE_BEAN_KEY_SUFFIX;
    }
    /**
     * 拼接完整的JDBC URL
     */
    public static String getJDBCUrl(String baseUrl) {
        if (!StringUtils.hasText(baseUrl)) {
            return null;
        }
        return baseUrl + JDBC_URL_ARGS;
    }
    /**
     * 拼接完整的Druid连接属性
     */
    public static String getConnectionProperties(String publicKey) {
        if (!StringUtils.hasText(publicKey)) {
            return null;
        }
        return CONNECTION_PROPERTIES + publicKey;
    }
}

public class DataSourceContextHolder {
    private static final ThreadLocal<String> dataSourceKey = new InheritableThreadLocal<>();
    public static void setDataSourceKey(String tenantKey) {
        dataSourceKey.set(tenantKey);
    }
    public static String getDataSourceKey() {
        return dataSourceKey.get();
    }
    public static void clearDataSourceKey() {
        dataSourceKey.remove();
    }
}

public class DynamicDataSource extends AbstractRoutingDataSource {
    @Autowired
    private ApplicationContext applicationContext;
    @Lazy
    @Autowired
    private DynamicDataSourceSummoner summoner;
    @Lazy
    @Autowired
    private TenantConfigDAO tenantConfigDAO;
    @Override
    protected String determineCurrentLookupKey() {
        String tenantKey = DataSourceContextHolder.getDataSourceKey();
        return DataSourceUtil.getDataSourceBeanKey(tenantKey);
    }
    @Override
    protected DataSource determineTargetDataSource() {
        String tenantKey = DataSourceContextHolder.getDataSourceKey();
        String beanKey = DataSourceUtil.getDataSourceBeanKey(tenantKey);
        if (!StringUtils.hasText(tenantKey) || applicationContext.containsBean(beanKey)) {
            return super.determineTargetDataSource();
        }
        if (tenantConfigDAO.exist(tenantKey)) {
            summoner.registerDynamicDataSources();
        }
        return super.determineTargetDataSource();
    }
}

@Slf4j
@Component
public class DynamicDataSourceSummoner implements ApplicationListener<ContextRefreshedEvent> {
    // 跟spring-data-source.xml的默认数据源id保持一致
    private static final String DEFAULT_DATA_SOURCE_BEAN_KEY = "defaultDataSource";
    @Autowired
    private ConfigurableApplicationContext applicationContext;
    @Autowired
    private DynamicDataSource dynamicDataSource;
    @Autowired
    private TenantConfigDAO tenantConfigDAO;
    private static boolean loaded = false;
    /**
     * Spring加载完成后执行
     */
    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        // 防止重复执行
        if (!loaded) {
            loaded = true;
            try {
                registerDynamicDataSources();
            } catch (Exception e) {
                log.error("数据源初始化失败, Exception:", e);
            }
        }
    }
    /**
     * 从数据库读取租户的DB配置,并动态注入Spring容器
     */
    public void registerDynamicDataSources() {
        // 获取所有租户的DB配置
        List<TenantConfigEntity> tenantConfigEntities = tenantConfigDAO.listAll();
        if (CollectionUtils.isEmpty(tenantConfigEntities)) {
            throw new IllegalStateException("应用程序初始化失败,请先配置数据源");
        }
        // 把数据源bean注册到容器中
        addDataSourceBeans(tenantConfigEntities);
    }
    /**
     * 根据DataSource创建bean并注册到容器中
     */
    private void addDataSourceBeans(List<TenantConfigEntity> tenantConfigEntities) {
        Map<Object, Object> targetDataSources = Maps.newLinkedHashMap();
        DefaultListableBeanFactory beanFactory = (DefaultListableBeanFactory) applicationContext.getAutowireCapableBeanFactory();
        for (TenantConfigEntity entity : tenantConfigEntities) {
            String beanKey = DataSourceUtil.getDataSourceBeanKey(entity.getTenantKey());
            // 如果该数据源已经在spring里面注册过,则不重新注册
            if (applicationContext.containsBean(beanKey)) {
                DruidDataSource existsDataSource = applicationContext.getBean(beanKey, DruidDataSource.class);
                if (isSameDataSource(existsDataSource, entity)) {
                    continue;
                }
            }
            //  组装bean
            AbstractBeanDefinition beanDefinition = getBeanDefinition(entity, beanKey);
            //  注册bean
            beanFactory.registerBeanDefinition(beanKey, beanDefinition);
            //  放入map中，注意一定是刚才创建bean对象
            targetDataSources.put(beanKey, applicationContext.getBean(beanKey));
        }
        //  将创建的map对象set到 targetDataSources；
        dynamicDataSource.setTargetDataSources(targetDataSources);
        //  必须执行此操作，才会重新初始化AbstractRoutingDataSource 中的 resolvedDataSources，也只有这样，动态切换才会起效
        dynamicDataSource.afterPropertiesSet();
    }
    /**
     * 组装数据源spring bean
     */
    private AbstractBeanDefinition getBeanDefinition(TenantConfigEntity entity, String beanKey) {
        BeanDefinitionBuilder builder = BeanDefinitionBuilder.genericBeanDefinition(DruidDataSource.class);
        builder.getBeanDefinition().setAttribute("id", beanKey);
        // 其他配置继承defaultDataSource
        builder.setParentName(DEFAULT_DATA_SOURCE_BEAN_KEY);
        builder.setInitMethodName("init");
        builder.setDestroyMethodName("close");
        builder.addPropertyValue("name", beanKey);
        builder.addPropertyValue("url", DataSourceUtil.getJDBCUrl(entity.getDbUrl()));
        builder.addPropertyValue("username", entity.getDbUser());
        builder.addPropertyValue("password", entity.getDbPassword());
        builder.addPropertyValue("connectionProperties", DataSourceUtil.getConnectionProperties(entity.getDbPublicKey()));
        return builder.getBeanDefinition();
    }
    /**
     * 判断Spring容器里面的DataSource与数据库的DataSource信息是否一致
     * 备注:这里没有判断public_key,因为另外三个信息基本可以确定唯一了
     */
    private boolean isSameDataSource(DruidDataSource existsDataSource, TenantConfigEntity entity) {
        boolean sameUrl = Objects.equals(existsDataSource.getUrl(), DataSourceUtil.getJDBCUrl(entity.getDbUrl()));
        if (!sameUrl) {
            return false;
        }
        boolean sameUser = Objects.equals(existsDataSource.getUsername(), entity.getDbUser());
        if (!sameUser) {
            return false;
        }
        try {
            String decryptPassword = ConfigTools.decrypt(entity.getDbPublicKey(), entity.getDbPassword());
            return Objects.equals(existsDataSource.getPassword(), decryptPassword);
        } catch (Exception e) {
            log.error("数据源密码校验失败,Exception:{}", e);
            return false;
        }
    }
}

@Slf4j
@Aspect
@Component
@Order(1) // 请注意：这里order一定要小于tx:annotation-driven的order，即先执行DynamicDataSourceAspectAdvice切面，再执行事务切面，才能获取到最终的数据源
@EnableAspectJAutoProxy(proxyTargetClass = true)
public class DynamicDataSourceAspectAdvice {
    @Around("execution(* a.b.c.*.controller.*.*(..))")
    public Object doAround(ProceedingJoinPoint jp) throws Throwable {
        ServletRequestAttributes sra = (ServletRequestAttributes) RequestContextHolder.getRequestAttributes();
        HttpServletRequest request = sra.getRequest();
        HttpServletResponse response = sra.getResponse();
        String tenantKey = request.getHeader("tenant");
        // 前端必须传入tenant header, 否则返回400
        if (!StringUtils.hasText(tenantKey)) {
            WebUtils.toHttp(response).sendError(HttpServletResponse.SC_BAD_REQUEST);
            return null;
        }
        log.info("当前租户key:{}", tenantKey);
        DataSourceContextHolder.setDataSourceKey(tenantKey);
        Object result = jp.proceed();
        DataSourceContextHolder.clearDataSourceKey();
        return result;
    }
}