Mapstruct: Can't map property "java.lang.String mail" to "java.util.ArrayList<java.lang.String> listMail"

[amineRS2i]

I have a client sources like below :

    @Entity
    @Table(name="client")
     public class Client implements Serializable {

         @Id
         @Column(name="code_client", nullable = false, length=10)
         private String codeClient;

         @Column(name="mail", length=100)
         private String mail;`
       } 

and target is :

 public class CompteClient{ 

    private String codeClient;
    private ArrayList<String> listMail;
 }

The mapper class :

@Mapper
 public interface ClientMapper {

public static ClientMapper INSTANCE = Mappers.getMapper(ClientMapper.class );

 @Mappings({
     @Mapping(source="codeClient", target="codeClient"),
     @Mapping(source="mail",qualifiedBy=FirstElement.class, target="listMail"
})
CompteClient clientToCompteClient(Client client);`

To map a mail (string) to listMail(List) i need set mail to the first element of listMail, i have created an annotation FirstElement like :

       @Qualifier
       @Target(ElementType.METHOD)
       @Retention(RetentionPolicy.SOURCE)
       public @interface FirstElement {
     }

and the classe where i can set to the first element :
public class IterableNonInterableUtil {

   @FirstElement
    public <T> T first( List<T> in ) {
         if ( in != null && !in.isEmpty() ) {
           return in.get( 0 );
        }
        else {
             return null;
        }
   }

`

when i run the maven command : generate-sources, i have this error message :

[ERROR] diagnostic: C:\Users\mameharzi\Documents\Sap workspace\mblog-services-sap\src\main\java\fr\rs2i\mblog\sap\mapper\ClientMapper.java:33: error: Can't map property "java.lang.String mail" to "java.util.ArrayList listMail". Consider to declare/implement a mapping method: "java.util.ArrayList map(java.lang.String value)".
CompteClient clientToCompteClient(Client client);

CAN YOU HELP ME PLEASE TO RESOLVE THIS PROBLEM ??!!

[agudian]

Well, you're trying to map from String to ArrayList<String>, so you'll have to provide a method that takes String as an argument and returns an ArrayList<String>. Your method first does the opposite of that... :smile:

One more note: When creating @Qualifier annotations, better use @Retention(RetentionPolicy.CLASS) - there are several cases where SOURCE won't be enough. We tried to fix that in our latest versions of documentations and examples and hopefully found all spots.

[gunnarmorling]

As Andreas is saying, all you need is reversing the logic of that qualified method and let it create an ArrayList from a single string.

Or you use an inline expression, e.g. like so:

@Mapping(target = "listMail", expression = "java(Collections.singletonList(client.getMail()))")

I'm going to close this one as "Not a bug".

[amineRS2i]

Think you for your help

[lo-rodriguez]

Unsatisfied by the explanation

[filiphr]

@lo-rodriguez you are commenting on a 4 year old issue which has been answered and the explanation has been accepted by the original poster.

If something is not clear I would suggest that you create a Stackoverflow question or write in the Gitter room