ModelMapper: Map object which has nested collection to flat object - java

I have a class with a nested list and I want to map this object into list of flat objects using ModelMapper.
public class A {
private String str;
private String str2;
private List<B> blist;
// Setters and getters
}
public class B {
private String str3;
private String str4;
// Setters and getters
}
public class C {
private String str;
private String str2;
private String str3;
private String str4;
// Setters and getters
}
I want to convert an object of class A into a list of objects of class C

Related

Modelmapper skip a object field

I have four class
public class A {
private String field1;
private String field2;
private B b;
// setter and getter
}
public class B {
private String fieldB1;
private String fieldB2;
// setter and getter
}
public class ADto {
private String field1;
private String field2;
private BDto b;
// setter and getter
}
public class BDto {
private String fieldB1;
private String fieldB2;
// setter and getter
}
I want to use modelmapper to populate dto objects
ModelMapper modelMapper = new ModelMapper();
modelMapper.typeMap(A.class, ADto.class, "LAZY")
.addMappings(mapper -> mapper.skip(ADto::setB))
.addMappings(mapper -> mapper.skip(ADto::setField2));
modelMapper.map(a, ADto.class, "LAZY");
I use typeMapName to be able to have more mappers
The mapper correctly skips field2 but instead ignores the skip for B, what am I wrong?
Thanks

Why in my code do I have this inheritance problem? Create an object passing a specialized type instead of declared abstract super type

Working on a Java application I am finding the following problem related to inheritance.
I have the following situation:
1) I defined an abstract class named TrendFromExcelAbstract. This class contains some basic fields common to other classes which extend it and represent different tabs of an Excel file (but this is not important now):
public abstract class TrendFromExcelAbstract {
private Long id;
private String date;
private String time;
private String excelDocumentName;
private String excelDocumentSheet;
public TrendFromExcelAbstract() {
super();
}
public TrendFromExcelAbstract(Long id, String date, String time, String excelDocumentName,
String excelDocumentSheet) {
super();
this.id = id;
this.date = date;
this.time = time;
this.excelDocumentName = excelDocumentName;
this.excelDocumentSheet = excelDocumentSheet;
}
................................................................
................................................................
GETTER AND SETTER METHODS
................................................................
................................................................
}
Then I have a class named CompVibrAndTempDTO extending the previous abstract class:
public class CompVibrAndTempDTO extends TrendFromExcelAbstract {
// Temperature reading point
private String tempReadingPointA;
private String tempReadingPointB;
private String tempReadingPointC;
private String tempReadingPointD;
private String tempReadingPointE;
private String tempReadingPointF;
private String tempReadingPointG;
private String tempReadingPointH;
private String tempReadingPointI;
private String tempReadingPointJ;
private String tempReadingPointK;
private String tempReadingPointL;
private String tempReadingPointM;
private String tempReadingPointN;
private String tempReadingPointO;
private String tempReadingPointP;
// Vibration reading point
private String vibrReadingPointA;
private String vibrReadingPointB;
private String vibrReadingPointC;
private String vibrReadingPointD;
private String vibrReadingPointE;
private String vibrReadingPointF;
private String vibrReadingPointG;
private String vibrReadingPointH;
private String vibrReadingPointI;
private String vibrReadingPointJ;
private String vibrReadingPointK;
private String vibrReadingPointL;
public CompVibrAndTempDTO() {
super();
}
public CompVibrAndTempDTO(Long id, String date, String time, String excelDocumentName, String excelDocumentSheet,
String tempReadingPointA, String tempReadingPointB, String tempReadingPointC, String tempReadingPointD,
String tempReadingPointE, String tempReadingPointF, String tempReadingPointG, String tempReadingPointH,
String tempReadingPointI, String tempReadingPointJ, String tempReadingPointK, String tempReadingPointL,
String tempReadingPointM, String tempReadingPointN, String tempReadingPointO, String tempReadingPointP,
String vibrReadingPointA, String vibrReadingPointB, String vibrReadingPointC, String vibrReadingPointD,
String vibrReadingPointE, String vibrReadingPointF, String vibrReadingPointG, String vibrReadingPointH,
String vibrReadingPointI, String vibrReadingPointJ, String vibrReadingPointK, String vibrReadingPointL) {
........................................................................................................................
........................................................................................................................
........................................................................................................................
}
........................................................................................................................
........................................................................................................................
GETTER AND SETTER METHODS
........................................................................................................................
........................................................................................................................
}
Then I have another DTO class named ExcelTabGeneralInfoDTO like this:
public class ExcelTabGeneralInfoDTO {
private String excelDocumentName;
private String excelSheetName;
private List<TrendFromExcelAbstract> trendOfTabList;
public ExcelTabGeneralInfoDTO() {
super();
}
public ExcelTabGeneralInfoDTO(String excelDocumentName, String excelSheetName,
List<TrendFromExcelAbstract> trendOfTabList) {
super();
this.excelDocumentName = excelDocumentName;
this.excelSheetName = excelSheetName;
this.trendOfTabList = trendOfTabList;
}
..................................................................
..................................................................
GETTER AND SETTER METHODS
..................................................................
..................................................................
}
As you can see this class contains this list field:
private List<TrendFromExcelAbstract> trendOfTabList;
The idea is that this field represents a list of any objects that derive from TrendFromExcelAbstract
The problem is that in another class I am trying to do something like this:
public List<ExcelTabGeneralInfoDTO> getCompVibrAndTempTab() {
List<CompVibrAndTempDTO> tabTrendList = excelRepo.findCompVibrAndTempTab();
String excelDocumentName;
String excelSheetName;
if(tabTrendList.size() >=0 ) {
excelDocumentName = tabTrendList.get(0).getExcelDocumentName();
excelSheetName = tabTrendList.get(0).getExcelDocumentSheet();
}
ExcelTabGeneralInfoDTO result = new ExcelTabGeneralInfoDTO(excelDocumentName, excelSheetName, tabTrendList);
return result;
}
So basically at this line:
ExcelTabGeneralInfoDTO result = new ExcelTabGeneralInfoDTO(excelDocumentName, excelSheetName, tabTrendList);
I am trying to create a new ExcelTabGeneralInfoDTO, passing to it the tabTrendList list having type List.
I get the following error message:
Description Resource Path Location Type
The constructor ExcelTabGeneralInfoDTO(String, String, List<CompVibrAndTempDTO>) is undefined ExcelServiceImpl.java /energy-prg-be/src/main/java/com/springboot/excelapi/services line 425 Java Problem
Description Resource Path Location Type
Type mismatch: cannot convert from List<ExcelTabGeneralInfoDTO> to List<CompVibrAndTempDTO> ExcelResource.java /energy-prg-be/src/main/java/com/springboot/excelapi/resources line 167 Java Problem
My idea is that I can use the more general type (ExcelTabGeneralInfoDTO) and then pass the child type (CompVibrAndTempDTO). But it seems that my assumption is false. What is wrong? What am I missing? Why can't I do something like this? How can I fix it?

ExcelTabGeneralInfoDTO does not have a defined constructor for List<CompVibrAndTempDTO>, only for List<TrendFromExcelAbstract>. Try declaring tabTrendList as a List<TrendFromExcelAbstract> and see if it works.

Java 8 sort multiple objects

public class B {
private String name;
private String value;
//Setters and Get
}
public class C {
private String name;
private String value;
//Setters and Get Methods
}
public class D {
private String name;
private String value;
//Setters and Get
}
public class A {
private B b;
private C c;
private D d;
// Setters and Get
}
public class Example{
List<A> a = new Array List<A>();
//Lets assume a will contain objects of class B, C and D
a .sort( Comparator.comparing(A::getB().getName).thenComparing(A::getC().getName));
}
Sort field from one pojo , then sort field by next pojo.
Need to understand how to sort in this situation. Can we use
Comparator.comparing ()in this case?

You can't use method refences like that, but you could just use lambda expressions:
a.sort(Comparator.comparing((A x) -> x.getB().getName())
.thenComparing(x -> x.getC().getName()));

How to refactor this simple class fields

I have a very basic OOP question. I have two classes as follows
public class Class1 {
private String field1;
private String field2;
private List<String> field3;
// constructors
}
public class Class2 {
private String field1;
private String field2;
private List<Object1> field3;
// constructors
}
The only reason i had to create class2 was because the List in class1 can either be a List of Strings or a List of Object2. Is there a way to et rid of Class2, and have field3 behave as a List of String and also as a List of Object2.
I know i can do something like
public class Class1 {
private String field1;
private String field2;
private List<String> field3;
private List<Object1> field4;
// constructors which are initializing null to either field 3 or field 4
}
But the above doesnt seem clean, as an object instantiated with either list should not have any reference in it of the other List.

Use generics:
public class Class1<TField3> {
private String field1;
private String field2;
private List<TField3> field3;
// constructors
}
Class1<String> stringObj = new Class1<>();

JSON to java object returing LinkedHashMap

I have below json string :-
{"name":"Test","sortlist":[],"filterlist":[{"fieldname":"regions_id","operator":"equals","value":{"id":1,"code":"HIGH","description":"HIGH Region","comment":"High Region","active":true}}]}
and Java class as below :-
#JsonSerialize
#JsonDeserialize
public class ItemFilter implements Serializable {
private String name;
private List<FieldFilter> filterlist = new ArrayList<FieldFilter>();
}
public class FieldFilter implements Serializable {
private static final long serialVersionUID = 1L;
private String fieldname;
private String operator;
private Object value;
}
and my convert method as below :-
public static ItemFilter convertItemFilter(String item) {
ObjectMapper mapper = new ObjectMapper();
try {
ItemFilter itemFilter = mapper.readValue(item, new TypeReference<ItemFilter>(){});
return itemFilter;
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
ItemFilter domain is getting converted correctly but in private Object value; field i am getting LinkedHashMap i want to get an simple object and later i will type cast it.
Can someone please guide me how to escape LinkedHashMap and get an simple Java Object in variable?
i cant use hard coding Object type because its a generic pojo which can have any object type. hard coding will make this pojo very bigger and frontend also need to change for it. So that why i have used Object as data type.

The following class structure should return the JSON to "YourObject"
public class YourObject{
private String name;
private List<String> sortList;
private List<Filter> filterList;
public static class Filter{
private String fieldname;
private String operator;
private Value value;
}
public static class Value{
private Integer id;
private String code;
private String description;
private String comment;
private Boolean active;
}
}
Then use the following to read it into the object:
YourObject itemFilter = mapper.readValue(item, YourObject.class);

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