DTO pattern Best way to copy properties between two objects

Question

In my application s architecture I usually send the object or list of objects from the data access layer to the web layer via the service layer  in which these objects get transformed from a DAO object to a DTO object and vice versa  The web layer don t have any access to DAO objects and the DAO layer do not use DTOs   To demonstrate  I usually write the code as    Transactional readOnly   true  public List lt UserDTO gt  getAllUserAsUserDTO         List lt UserDTO gt  userDTOs   new ArrayList lt UserDTO gt          for User user   getAllUser              userDTOs add constructUserDTO user               return userDTOs     private UserDTO constructUserDTO User user        UserDTO userDTO   new UserDTO        userDTO setFullName user getFullName         userDTO setId user getId         userDTO setUsername user getUsername         userDTO setRole user getRole         userDTO setActive user isActive         userDTO setActiveText user isActive      Active     Inactive        return userDTO      Here the user is the database entity    javax persistence Entity  Table name    USER   public class User extends Entity         Transient     private static final long serialVersionUID   -112950002831333869L       private String username      private String fullName      private boolean active      private String role         other fields      public User             super                NaturalId      Column name    USERNAME   nullable   false      public String getUsername             return username             public void setUsername String username            this username   username              Column name    FULL NAME       public String getFullName             return fullName             public void setFullName String fullName            this fullName   fullName              Column name    ACTIVE   nullable   false      public boolean isActive             return active             public void setActive boolean active            this active   active              Column name    ROLE       public String getRole             return role             public void setRole String role            this role   role            And this is the UserDTO   public class UserDTO extends BaseDTO        private static final long serialVersionUID   -3719463614753533782L       private String username      private String fullName      private String role      private String activeText      private Boolean active        other properties      public UserDTO             super               public String getUsername             return username             public void setUsername String username            this username   username             public String getFullName             return fullName             public void setFullName String fullName            this fullName   fullName             public String getRole             return role             public void setRole String role            this role   role             public String getActiveText             return activeText             public void setActiveText String activeText            this activeText   activeText             public Boolean getActive             return active             public void setActive Boolean active            this active   active            So I was wondering if this is the only way to copy properties between two objects  I guess I am not sure  Also I am using lambdaj  so is there a method in this API by which I can copy all these properties to create list of other objects   This topic may be sounds subjective  but I really want to know from you experts the ways by which the transformation of object from one form to another can be done where the maximum fields are having same string

User · Accepted Answer

You can have a look at dozer which is a

Java Bean to Java Bean mapper that recursively copies data from one object to another. Typically, these Java Beans will be of different complex types.

Another better link...

User · Answer

You can use reflection to find all the get methods in your DAO objects and call the equivalent set method in the DTO  This will only work if all such methods exist  It should be easy to find example code for this

User · Answer

Wouldn t lambdaj s project function do what you are looking for   It ll look something like this   List lt UserDTO gt  userNDtos   project users  UserDTO class  on User class  getUserName    on User class  getFullName               Define the constructor for UserDTO accordingly      Also see here for examples

User · Answer

I suggest you should use one of the mappers  libraries  Mapstruct  ModelMapper  etc  With Mapstruct your mapper will look like    Mapper public interface UserMapper            UserMapper INSTANCE   Mappers getMapper  UserMapper class          UserDTO toDto User user       The real object with all getters and setters will be automatically generated from this interface  You can use it like   UserDTO userDTO   UserMapper INSTANCE toDto user     You can also add some logic for your activeText filed using  AfterMapping annotation

User · Answer

You can use Apache Commmons Beanutils  The API is   org apache commons beanutils PropertyUtilsBean copyProperties Object dest  Object orig     It copies property values from the  origin  bean to the  destination  bean for all cases where the property names are the same    Now I am going to off topic  Using DTO is mostly considered an anti-pattern in EJB3  If your DTO and your domain objects are very alike  there is really no need to duplicate codes  DTO still has merits  especially for saving network bandwidth when remote access is involved  I do not have details about your application architecture  but if the layers you talked about are logical layers and does not cross network  I do not see the need for DTO

User · Answer

I had an application that I needed to convert from a JPA entity to DTO  and I thought about it and finally came up using org springframework beans BeanUtils copyProperties for copying simple properties and also extending and using org springframework binding convert service DefaultConversionService for converting complex properties   In detail my service was something like this    Service  seedingConverterService   public class SeedingConverterService extends DefaultConversionService implements ISeedingConverterService         PostConstruct     public void init            Converter lt Feature FeatureDTO gt  featureConverter   new Converter lt Feature  FeatureDTO gt                    Override             public FeatureDTO convert Feature f                    FeatureDTO dto   new FeatureDTO                      BeanUtils copyProperties f  dto  configurationModel                    BeanUtils copyProperties f  dto                   dto setConfigurationModelId f getConfigurationModel    null null f getConfigurationModel   getId                     return dto                                    Converter lt ConfigurationModel ConfigurationModelDTO gt  configurationModelConverter   new Converter lt ConfigurationModel ConfigurationModelDTO gt                   Override             public ConfigurationModelDTO convert ConfigurationModel c                    ConfigurationModelDTO dto   new ConfigurationModelDTO                      BeanUtils copyProperties c  dto   features                    BeanUtils copyProperties c  dto                   dto setAlgorithmId c getAlgorithm    null null c getAlgorithm   getId                     List lt FeatureDTO gt  l   c getFeatures   stream   map f- gt featureConverter convert f   collect Collectors toList                     dto setFeatures l                   return dto                                   addConverter featureConverter           addConverter configurationModelConverter

[java] DTO pattern: Best way to copy properties between two objects

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