Persist List of String with JPA

Sometimes you might want to store a List of string as one column field in your database. The following code snippet helped me achieve this. First define the Entity Class as shown below

public class Customer implements Serializable {
    
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "id", nullable = false)
    private Integer id;
    @Basic(optional = false)
    @NotNull
    @Size(min = 1, max = 245)
    @Column(name = "firstname", length = 245)
    private String firstname;
    
    @Basic(optional = true)
    @Column(name = "middlename", length = 245)
    private String middlename;
    
    @Basic(optional = true)
    @NotNull
    @Size(min = 1, max = 245)
    @Column(name = "lastname", length = 245)
    private String lastname;
    
    @Basic(optional = true)
    @NotNull
    @Size(min = 1, max = 245)
    @Column(name = "primary_email", length = 245)
    private String primaryEmail;
    
    @Size(max = 245)
    @Column(name = "previousCourse", length = 245)
    List<String> previousCourse;

Next, Add a converter to convert the database column to a list of string in the java Object and like wise the Java object will be stored in the database column as Physics;Biology;Chemistry. The following code below shows the Converter class

import java.util.Arrays;
import java.util.List;

import javax.persistence.AttributeConverter;
import javax.persistence.Converter;

import static java.util.Collections.*;


@Converter
public class StringListConverter implements AttributeConverter<List<String>, String> {

    private static final String SPLIT_CHAR = ";";

    @Override
    public String convertToDatabaseColumn(List<String> stringList) {
        return stringList != null ? String.join(SPLIT_CHAR, stringList) : "";
    }

    @Override
    public List<String> convertToEntityAttribute(String string) {
        return string != null ? Arrays.asList(string.split(SPLIT_CHAR)) : emptyList();
    }
}

Finally, use the Converter in the entity field like this

    @Column(name = "previousCourse", length = 245)
    @Convert(converter = StringListConverter.class)
    List<String> previousCourse;

Another way to do this is to use the @ElementCollection in JPA.