mapstruct - Mapping fields values to properties

Question

I have requirement where I want to map field value in the source class to a field property. I was able to do it using Mapstruct using the 'expression' parameter of the @Mapper annotation

Source class:

public class ClassA {

    public ClassA() {
    }

    private String name;
    private String address;

    private ArrayList<RequestFilter> filter;

    public ArrayList<RequestFilter> getFilter() {
        return filter;
    }

    public void setFilter(ArrayList<RequestFilter> filter) {
        this.filter = filter;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

}

Target Class:

public class ClassATransform {

    public ClassATransform() {
    }

    private String name;
    private String id;
    private String address;
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getAddress() {
        return address;
    }
    public void setAddress(String address) {
        this.address = address;
    }
    public String getId() {
        return id;
    }
    public void setId(String id) {
        this.id = id;
    }
}

my mapstruct mapper looks like this:

@Mapper(imports=RequestFilter.class)
public interface ClassAMapper {

    ClassAMapper INSTANCE = Mappers.getMapper(ClassAMapper.class);

    @Mappings({
        @Mapping(target = "name", source = "name"),
        @Mapping(target= "address", source = "address"),
        @Mapping(target = "id",  expression="java(req.getFilter().get(req.getFilter().indexOf(new RequestFilter(\"id\"))).filterValue)")
    })
    ClassATransform classAToDTO(ClassA req);
}

RequestFilter.java:

public class RequestFilter {

public RequestFilter() {
}


public RequestFilter(String filterName) {
    this.filterName = filterName;
}


public String filterName;
public String filterValue;
public String filterOperator;
public String joinOperator;
@Override
public int hashCode() {
    final int prime = 31;
    int result = 1;
    result = prime * result + ((filterName == null) ? 0 : filterName.hashCode());
    return result;
}
@Override
public boolean equals(Object obj) {
    if (this == obj)
        return true;
    if (obj == null)
        return false;
    if (getClass() != obj.getClass())
        return false;
    RequestFilter other = (RequestFilter) obj;
    if (filterName == null) {
        if (other.filterName != null)
            return false;
    } else if (!filterName.equals(other.filterName))
        return false;
    return true;
    }
}

is there any other way to do the mapping without using "expression" ?

Answer 1

You can provide a custom method that would map it for you:

@Mapper
public interface ClassAMapper {

    ClassAMapper INSTANCE = Mappers.getMapper(ClassAMapper.class);

    @Mappings({
        @Mapping(target = "id", source = "req")
    })
    ClassATransform classAToDTO(ClassA req);

    default String mapToid(ClassA req) {
        // null checks
        return reg.getFilter()
                    .stream()
                    .filter( filter -> filter.filterName.equals("id"))
                    .findAny()
                    .orElse(null);
    }
}

Btw. the mappings where the source and target are the same are not needed as MapStruct will do that automatically.