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I am building a REST API using Spring boot and hibernate. Now I want to create a POST method that gets a JSON. After some validations, I want to save this object as a new entity in my DB. I was wondering how to convert the map of attributes to a new User entity? I have the following classes:

User.java

@Entity
@Table(name="users")
@JsonIdentityInfo(generator= ObjectIdGenerators.IntSequenceGenerator.class, property="id")
public class User {
    
    @Transient
    Logger logger = LogManager.getLogger(getClass());

    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int ID;
    
    @NotNull
    private String username;
    
    @NotNull
    private String Last_Name;
    @NotNull
    private String First_Name;

    private String Title;

//...

}

UserController.java

@PostMapping("/user") 
public ResponseEntity test(@RequestBody Map<String,Object> object) throws Exception {
    try {
        userService.createAccount(object);
    } catch (IllegalArgumentException e) {
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getMessage());
    }
    return ResponseEntity.ok("Account was added successfully");
}

UserService.java

public void createAccount(Map<String, Object> accountObject) throws Exception {
        logger.trace("Entering createAccount(). account=" +accountObject);
        User user = new User( ??? );
        userRepository.save(user);
  }
            

I was thinking of creating a new constructor in User.java that maps every MapEntry to a field, but I was wondering if there is a better approach?

public User(Map<String, Object> fieldsMapping) {
        this(
            getValue(fieldsMapping, "username", String.class),
            getValue(fieldsMapping, "last_name", String.class),
            getValue(fieldsMapping, "first_name", String.class),
        );
    }

    // Helper method for type-safe value extraction.
    private static <T> T getValue(Map<String, Object> map, String key, Class<T> clazz) {
        Object value = map.get(key);
        if (value == null) {
            return null;
        }
        return clazz.cast(value);
    }

I am building a REST API using Spring boot and hibernate. Now I want to create a POST method that gets a JSON. After some validations, I want to save this object as a new entity in my DB. I was wondering how to convert the map of attributes to a new User entity? I have the following classes:

User.java

@Entity
@Table(name="users")
@JsonIdentityInfo(generator= ObjectIdGenerators.IntSequenceGenerator.class, property="id")
public class User {
    
    @Transient
    Logger logger = LogManager.getLogger(getClass());

    
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private int ID;
    
    @NotNull
    private String username;
    
    @NotNull
    private String Last_Name;
    @NotNull
    private String First_Name;

    private String Title;

//...

}

UserController.java

@PostMapping("/user") 
public ResponseEntity test(@RequestBody Map<String,Object> object) throws Exception {
    try {
        userService.createAccount(object);
    } catch (IllegalArgumentException e) {
        return ResponseEntity.status(HttpStatus.BAD_REQUEST).body(e.getMessage());
    }
    return ResponseEntity.ok("Account was added successfully");
}

UserService.java

public void createAccount(Map<String, Object> accountObject) throws Exception {
        logger.trace("Entering createAccount(). account=" +accountObject);
        User user = new User( ??? );
        userRepository.save(user);
  }
            

I was thinking of creating a new constructor in User.java that maps every MapEntry to a field, but I was wondering if there is a better approach?

public User(Map<String, Object> fieldsMapping) {
        this(
            getValue(fieldsMapping, "username", String.class),
            getValue(fieldsMapping, "last_name", String.class),
            getValue(fieldsMapping, "first_name", String.class),
        );
    }

    // Helper method for type-safe value extraction.
    private static <T> T getValue(Map<String, Object> map, String key, Class<T> clazz) {
        Object value = map.get(key);
        if (value == null) {
            return null;
        }
        return clazz.cast(value);
    }

• java
• spring
• spring-boot

Share Improve this question Follow asked Feb 23 at 12:43 Ziv AvivZiv Aviv 7111 silver badge77 bronze badges 3

• why dont use some UserDto instead of Map<String,Object> object as request body? – Geii Lvov Commented Feb 23 at 13:00
• @GeiiLvov my manager wants the same method to be used for the creation of both User and some other entity. During the request, the method should determine what object to create depends on some "type" field in the request body that will be set to either user or the second entity. So I did not know how to implement this behavior using DTO's – Ziv Aviv Commented Feb 23 at 13:16
• Looks weird to use /user path to something else, but anyway my advice would be not to create a constructor in User class, but creating a mapper class – Geii Lvov Commented Feb 23 at 15:57

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1 Answer 1

Sorted by: Reset to default 3

You can use Jackson's ObjectMapper to convert a map of values to another class. But be sure to use @JsonIgnoreProperties(ignoreUnknown = true) in your User class, otherwise it will give you errors if unecessary properties are present. Example:

Map<String, Object> request = new HashMap<>();
request.put("username", "myName");
request.put("Last_Name", "myLastName");

ObjectMapper objectMapper = new ObjectMapper();
User user = objectMapper.convertValue(request, User.class);

Also you need to make sure about the Json mappings using @JsonProperty annotation.

Just for reference, I don't think it's a good idea to do this based on the comments you gave saying you intend to map /users to two different entities, I would advise creating two distinct endpoints using two distinct DTOs, and the caller decides which one to use.

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