How to convert string to DTO in Java-CodePudding

How to convert string to DTO.

I am doing some db fetch and getting String.

List<String> tempString = myRepo.getData(str);

I am getting string here like this

{"LastName": "Ben",  "FirstName": "David", "EmailAddress": "[email protected]"}

now I want to convertto dto.

my dto will be like this.

@Data
@NoArgsConstructor
@AllArgsConstructor
@Component
public class UserDTO {

   
    @JsonProperty("FirstName")
    private String firstName;

    @JsonProperty("LastName")
    private String lastName;

    @JsonProperty("EmailAddress")
    private String email;


}

Now here is what I am trying but not getting sucees, anything I am missing here.

ObjectMapper mapper = new ObjectMapper();
UserDTO userdeto;
try{
    userdeto= mapper.readValue(tempString.get(i), UserDTO.class);
}

but this is wrong here I. any other way to get this.

CodePudding user response：

Using Java 8

It seems that you are getting list of String from the database, you can convert the list of string into list of UserDTO by this approach.

Approach Here:

Here I have stream the list of string and convert each String into UserDTO type using the map() operation and collecting it as a list of UserDTO.

where, tempString is the list that you are preparing from the db (it is hardcoded in my case for the solution purpose)

    public class Test {
    public static void main(String[] args) {
        List<String> tempString = new ArrayList<>();
        tempString.add("{\"LastName\": \"Ben\",  \"FirstName\": \"David\", \"EmailAddress\": \"[email protected]\"}");
        tempString.add("{\"LastName\": \"Ben2\",  \"FirstName\": \"David1\", \"EmailAddress\": \"[email protected]\"}");
        tempString.add("{\"LastName\": \"Ben3\",  \"FirstName\": \"David2\", \"EmailAddress\": \"[email protected]\"}");

        ObjectMapper mapper = new ObjectMapper();

        List<UserDTO> userDtoList = tempString.stream().map(x -> {
            UserDTO userDto = null;
            try {
                userDto = mapper.readValue(x, UserDTO.class);
            } catch (JsonProcessingException e) {
                System.out.println("exception" e);
            }
            return userDto;
        }).collect(Collectors.toList());

        System.out.println(userDtoList);
    }
}

Output:

[UserDTO(firstName=David, lastName=Ben, [email protected]), UserDTO(firstName=David1, lastName=Ben2, [email protected]), UserDTO(firstName=David2, lastName=Ben3, [email protected])]

CodePudding user response：

Since you are using spring you can directly convert to List UserDTO from the repository itself if you can extend your Repository from JpaRepository.

@Repository
public interface UserRepository extends JpaRepository<User, Long> {
  @Query("SELECT new com.UserDTO(u.firstName, u.lastName, u.email) FROM USER u WHERE u.user_id= :UserId ")
        List<UserDTO> getData(@Param("userId")  userId);
}

You need to have a matching constructor in your DTO and need provide full package name in the query.