@Target({TYPE})
@Retention(RUNTIME)
public @interface TableShard {

    Class<? extends TableShardStrategy> shardStrategy();
}

public interface TableShardStrategy {
    String getTableShardName(String tableName);
}

public class DateTableShardStrategy implements TableShardStrategy {

    public static final String PATTERN = "yyyyMM";

    @Override
    public String getTableShardName(String tableName) {
        YearMonth yearMonth = Optional.ofNullable(ProcessContextHolder.get()).orElse(ProcessInfo.builder().yearMonth(TimeUtils.getYearMonth()).build()).getYearMonth();
        String date = DateTimeFormatter.ofPattern(PATTERN).format(yearMonth);
        return tableName + "_" + date;
    }
}

@Intercepts({
        @Signature(
                type = StatementHandler.class,
                method = "prepare",
                args = {Connection.class, Integer.class}
        )
})
@Slf4j
@Component
@ConditionalOnProperty(value = "table.shard.enabled", havingValue = "true") //加上了table.shard.enabled 該配置才會生效
public class MybatisStatementInterceptor implements Interceptor {

    private static final ReflectorFactory defaultReflectorFactory = new DefaultReflectorFactory();
    public static final String DELEGATE_BOUND_SQL_SQL = "delegate.boundSql.sql";
    public static final String DELEGATE_MAPPED_STATEMENT = "delegate.mappedStatement";

    @Override
    public Object intercept(Invocation invocation) throws Throwable {
        StatementHandler statementHandler = (StatementHandler) invocation.getTarget();
        MetaObject metaObject = MetaObject.forObject(statementHandler,
                SystemMetaObject.DEFAULT_OBJECT_FACTORY,
                SystemMetaObject.DEFAULT_OBJECT_WRAPPER_FACTORY,
                defaultReflectorFactory
        );

        MappedStatement mappedStatement = (MappedStatement)
                metaObject.getValue(DELEGATE_MAPPED_STATEMENT);

        Class<?> clazz = getTableClass(mappedStatement);
        if (clazz == null) {
            return invocation.proceed();
        }
        TableShard tableShard = clazz.getAnnotation(TableShard.class); //獲取表實體類上的注解
        Table table = clazz.getAnnotation(Table.class);
        if (tableShard != null && table != null) { //如果注解存在就執(zhí)行分表策略
            String tableName = table.name();
            Class<? extends TableShardStrategy> strategyClazz = tableShard.shardStrategy();
            TableShardStrategy strategy = strategyClazz.getDeclaredConstructor().newInstance();
            String tableShardName = strategy.getTableShardName(tableName);
            String sql = (String) metaObject.getValue(DELEGATE_BOUND_SQL_SQL);
            metaObject.setValue(DELEGATE_BOUND_SQL_SQL, sql.replaceAll(tableName, tableShardName.toUpperCase())); //替換表名
        }
        return invocation.proceed();
    }

    private Class<?> getTableClass(MappedStatement mappedStatement) throws ClassNotFoundException {
        String className = mappedStatement.getId();
        className = className.substring(0, className.lastIndexOf('.')); //獲取到BaseMapper的實現(xiàn)類
        Class<?> clazz = Class.forName(className);
        if (BaseMapper.class.isAssignableFrom(clazz)) {
            return (Class<?>) ((ParameterizedType) (clazz.getGenericInterfaces()[0])).getActualTypeArguments()[0]; //獲取表實體類
            //public interface XXXMapper extends BaseMapper<XXX> 其實就是獲取到泛型中的具體表實體類
            return null;
    }

    @Override
    public Object plugin(Object target) {
        if (target instanceof StatementHandler) {
            return Plugin.wrap(target, this);
        } else {
            return target;
        }
    }

}