"message": "无法从类型 [java.lang.String] 转换为类型 [java.lang.Long] 以获取值 'count'；对于输入字符串：\\"count\\""

Question

I need count users in mysql using spring boot to display a statistic

my code content 3 class and interface :

////////////////interface////////////////////
public interface UserRepository extends JpaRepository<User, Long>

String count(String name);

////////////////service////////////////////
public String count(String username);

@Override
public String count(String username) {
    return userRepository.count(username);
}

//////////////////iontroller////////////
@GetMapping("/count")
public String count(String username) {
    return userService.count(username);
}

result in postman:

"message": "Failed to convert from type [java.lang.String] to type [java.lang.Long] for value 'count'; nested exception is java.lang.NumberFormatException: For input string: \"count\""

Answer 1

In the repository you need to use countBy clause with searching field name and return long as return type. Assuming in User entity username is a field.

long countByUsername(String username);