code: public void checkMethodReturnType(Class<?> returnType, StatementMetaData metaData) {
          if (returnType != void.class && !Number.class.isAssignableFrom(returnType)) {
              throw new InvalidDataAccessApiUsageException(
                  "error return type, only support int/long/double/float/void type for method with @ReturnGeneratedKeys:"
                                                           + metaData.getMethod());
          }
      }
docs: 检查DAO返回的类型是否合格
  
  @param returnType DAO方法的返回类型（如果方法声明的返回类型是泛型，框架会根据上下文信息解析为运行时实际应该返回的真正类型)
  
  @throws InvalidDataAccessApiUsageException DAO方法的返回类型不合格