Spring Mapstruct simple guide from scratch

Mapping Entity/DTO objects with Mapstruct

ActivityType and Activity mappings are achieved with Mapstruct:

1. Pom.xml

.....

<<dependency>

<groupId>org.mapstruct</groupId> <artifactId>mapstruct-jdk8</artifactId> <version>1.3.0.Final</version> </dependency> <build> <plugins> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-compiler-plugin</artifactId> <version>3.8.1</version> <configuration> <source>1.8</source> <target>1.8</target> <annotationProcessorPaths> <path> <groupId>org.mapstruct</groupId> <artifactId>mapstruct-processor</artifactId> <version>${org.mapstruct.version}</version> </path> </annotationProcessorPaths> </configuration> </plugin> </plugins> </build>

2. Entity class

@Entity @Table(name = "day_activity") public class DayActivity implements Serializable { private static final long serialVersionUID = 1L; @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; @Column(name = "todo_kg") private String todoKg; @Column(name = "todo_sets") private String todoSets; @Column(name = "todo_reps") private String todoReps; @Column(name = "logged_reps") private String loggedReps; @Column(name = "date") @NotNull private LocalDate logDate; @ManyToOne @JsonIgnoreProperties("dayActivities") private ActivityType activitytype; @ManyToOne @JsonIgnoreProperties("dayActivities") private Activity activity; public DayActivity() {} public DayActivity(String amountFactor, LocalDate logDate, String loggedReps, String todoKg, String todoReps, String todoSets, Activity activity, ActivityType activityType) { this.logDate = logDate; this.loggedReps = loggedReps; this.todoKg = todoKg; this.todoSets = todoSets; this.todoReps = todoReps; this.activity = activity; this.activitytype = activityType; } // getters, setters... }

3. DTO class

@JsonIgnoreProperties(ignoreUnknown = true) public class DayActivityDTO implements Serializable { private String id; private String activityId; private String activityTypeId; private String todoKg; private String todoSets; private String todoReps; private String loggedReps; private LocalDate logDate; private String activityTypeTitle; private String activitySubType; // getters, setters... }

4. Mapper class

@Mapper(unmappedTargetPolicy = org.mapstruct.ReportingPolicy.IGNORE, componentModel = "spring") public abstract class DayActivityMapper { @Mappings({ @Mapping(source = "activitytype", target = "activityTypeId", qualifiedByName = "actTypeToId"), @Mapping(source = "activitytype", target = "activityTypeTitle", qualifiedByName = "actTypeToTitle"), @Mapping(source = "activity", target = "activitySubType", qualifiedByName = "actToSubType"), @Mapping(source = "activity", target = "activityId", qualifiedByName = "actToActId") }) public abstract DayActivityDTO toDto(DayActivity entity); @Named("actTypeToId") static String actTypeToId(ActivityType activityType) { return Long.toString(activityType.getId()); } @Named("actTypeToTitle") static String actTypeToTitleMethod(ActivityType activityType) { return activityType.getTitle(); } @Named("actToSubType") static String actToSubTypeMethod(Activity activity) { return activity.getActivitySubType(); } @Named("actToActId") static String actToActIdMethod(Activity activity) { return Long.toString(activity.getId()); } public List<DayActivityDTO> toDtos(List<DayActivity> entities) { List<DayActivityDTO> result = new ArrayList<>(); for (DayActivity d : entities) { result.add(this.toDto(d)); } return result; } }

5. Usage in Service layer

In your ServiceImpl:

// Declare Mapper class private final DayActivityMapper dayActivityMapper; // Inject dependency public YourServiceImpl(DayActivityMapper dayActivityMapper) { this.dayActivityMapper = dayActivityMapper; } // Use in method: // Get entities list List<DayActivity> dayActivities = // get your entities.. // Map to DTOs List<DayActivityDTO> dayActivityDTOs = dayActivityMapper.toDtos(dayActivities);

6. Generate mapper implementations in target folder

mvn clean install