Develop Reference

How to implement group by with sum of multiple fields in java

Controller class:
#RestController
#RequestMapping(value = "/api/v1/")
public class TestController {
#Autowired
TestService testService;
#GetMapping(value = "test")
public List<Bean> getDetails() {
return testService.getDetails();
}
}
Service class:
#Service
public class TestService {
#Autowired
BeanRepository beanRepository;
public List<Bean> getDetails() {
List<Bean> res = new ArrayList<>();
try{
List<BeanEntity> beans = beanRepository.findAllApplications();
for(BeanEntity beanEntity : beans) {
Bean bean = new Bean();
BeanUtils.copyProperties(beanEntity, bean);
if(beanEntity.getDesc().contains("Motor") || beanEntity.getDesc().contains("Nut")){
bean.setName("A");
} else if (beanEntity.getDesc().contains("Bolt") || beanEntity.getDesc().contains("Engine")) {
bean.setName("B");
} else {
bean.setName("C");
}
res.add()
}
} catch(Exception e) {
throw new e;
}
}
}
Entity class:
#Getter
#Setter
#NoArgConstructor
#AllArgConstructor
#Entity
public class BeanEntity implements Serializable {
private static final long serialVersionID = 3269743987697633760L;
#Id
#Column(name = "ApplicationID", nullable = false, unique = true)
public String application_id;
#Column(name= "Description")
public String desc;
#Column(name = "Status")
public String status;
#Column(name ="Approved")
public int approved;
#Column(name ="Declined")
public int declined;
}
Bean class:
#Getter
#Setter
#NoArgConstructor
#AllArgConstructor
public class Bean {
public String application_id;
public String desc;
public String status;
public int approved;
public int declined;
public String name;
}
Repository class:
#Repository
public interface BeanRepository extends JpaRepository<BeanEntity, String> {
#Query(name = "select * from abc", nativeQuery = true)
List<BeanEntity> findAllApplications();
}
Below is the Current Response i am getting from above code:
[
{
"application_id" : "12345",
"desc": "Motor",
"status": "active",
"approved": 1,
"declined": 0,
"name": "A"
},
{
"application_id" : "14785",
"desc": "Nut",
"status": "active",
"approved": 0,
"declined": 1,
"name": "A"
},
{
"application_id" : "15974",
"desc": "Bolt",
"status": "not-active",
"approved": 1,
"declined": 0,
"name": "B"
},
{
"application_id" : "36985",
"desc": "Engine",
"status": "active",
"approved": 1,
"declined": 0,
"name": "B"
},
{
"application_id" : "78945",
"desc": "Filter",
"status": "active",
"approved": 1,
"declined": 0,
"name": "C"
},
{
"application_id" : "45612",
"desc": "AC",
"status": "active",
"approved": 0,
"declined": 1,
"name": "C"
}
]
Expected Response i am looking for:
[
{
"name": "A",
"approved": 1,
"declined": 1
},
{
"name": "B",
"approved": 2,
"declined": 0
},
{
"name": "C",
"approved": 1,
"declined": 1
}
]
I am in beginner phase of learning java, How to implement group by with sum of multiple fields in java.
Can someone help me how i can achieve the expected response.

Infinite Loop Created When I want to Create an Organization Diagram Using Java Spring Boot

I try to do a project where I can show data Like this:
{
"vp2": {
"parentName": "ceo1",
"isParent": 0,
"hasChild": 0,
"child": []
}
}
Here My data are:
[
{
"entityName": "ceo1",
"parentId": 0,
"id": 1
},
{
"entityName": "ceo2",
"parentId": 0,
"id": 2
},
{
"entityName": "vp1",
"parentId": 1,
"id": 3
},
{
"entityName": "vp2",
"parentId": 1,
"id": 4
},
{
"entityName": "vp3",
"parentId": 1,
"id": 5
},
{
"entityName": "vp4",
"parentId": 2,
"id": 6
},
{
"entityName": "ceo3",
"parentId": 0,
"id": 7
},
{
"entityName": "ceo4",
"parentId": 0,
"id": 8
}
]
I want to show the data using map<Entity Name, DataModel>. Here DataModel's code is
#Data
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
public class DemoModel {
private String parentName;
private int isParent;
private int hasChild;
public List<Map<String, DemoModel>> child;
}
When there is no child, I get it properly. But when there is a child my function can not work. It gives infinite recursion problems. Here is my service function code
public Map<String, DemoModel> recursiveHelperFunction(int Id, List<DemoEntity> fullEntityList, List<Map<String, DemoModel>> modelList) {
Map<String, DemoModel> map = new HashMap<>();
DemoEntity demo = demoRepository.findById((long) Id).get();
DemoModel demoModel = new DemoModel();
String entityName = demo.getEntityName();
int parentId = (int) demo.getParentId();
if (Objects.equals(parentId, 0)) {
demoModel.setIsParent(1);
demoModel.setParentName("");
} else {
demoModel.setIsParent(0);
demoModel.setHasChild(0);
demoModel.setParentName(fullEntityList.get((int) demo.getParentId() - 1).getEntityName());
}
Iterator<DemoEntity> itr = fullEntityList.iterator();
while (itr.hasNext()) {
DemoEntity demo1 = itr.next();
int demo1Id = (int) demo1.getParentId();
int Id1 = (int) Id;
if (demo1Id == Id1) {
demoModel.setHasChild(1);
String demo1Entity = demo1.getEntityName();
try {
Map<String, DemoModel> map1 = recursiveHelperFunction((int) demo1.getId(), fullEntityList, modelList);
log.info("maps :{}", map1);
modelList.add(map1); //got error here
//demoModel.child.add(map1);
log.info("maps equal:??: {}", modelList.contains(map1));
} catch (Exception e) {
log.error(e.getMessage(), e);
}
}
}
demoModel.setChild(modelList);
map.put(entityName, demoModel);
return map;
}
I call this helper recursive function here:
public Map<String, DemoModel> getDataById(int Id) {
List<DemoEntity> list = demoRepository.findAll();
List<Map<String, DemoModel>> modelList = new ArrayList<>();
return recursiveHelperFunction(Id, list, modelList);
}
Here, the DemoEntity code is:
#Entity
#Data
#Getter
#Setter
#AllArgsConstructor
#NoArgsConstructor
public class DemoEntity {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private long Id;
#Column(unique = true)
private String entityName;
private long parentId;
}
How can I stop this infinite recursive problem?

Spring REST API, custom entity fields in the response

I'm working in a REST API (Java, SpringBoot, QueryDsl...) and I would like to customize the fields that I have in the result. By default I'm obtaining all fields of the entity but the fields that I need depends on the request. This should be something dynamic.
As far as I know, using projections I can obtain something like this but I have to declare previously the projection and I would like to work with something dynamic not static. On the other hand I have seen than something like GraphQL allows this behaviour but I would have to refactor everything.
Has anyone had this problem before?
This is my code:
BaseRestCRUDController
public abstract class BaseRestCRUDController<T extends EntityBase, V extends BaseDTO> {
#GetMapping("/list")
public ResponseEntity<List<V>> findAll(Predicate predicate, Pageable pageable) {
log.info("FindAll");
return new ResponseEntity(getCRUDService().findAll(predicate, pageable), HttpStatus.OK);
}
}
ExampleController
#RestController
#RequestMapping("/api/example")
public class ExampleController
extends BaseRestCRUDController<Example, ExampleDTO> {
#Autowired
private ExampleService ExampleService;
#Override
public ResponseEntity<List<ExampleDTO>> findAll(
#QuerydslPredicate(root = Example.class) Predicate predicate, Pageable pageable) {
return super.findAll(predicate, pageable);
}
#Override
protected CRUDService<Example, ExampleDTO> getCRUDService() {
return ExampleService;
}
}
Example (Entity)
public class Example {
#Id
#GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
#Column(name = "name", nullable = false)
private String name;
#Column(name = "creation_date")
private Instant creationDate;
#Column(name = "last_update")
private Instant lastUpdate;
#Column(name = "erasure_date")
private Instant erasureDate;
}
http://localhost:8080/api/example/list?name=test&page=0&size=5&sort=id,desc
http://localhost:8080/api/example/list?name=foo&page=1&size=10&sort=id,desc
http://localhost:8080/api/example/list?page=0&size=2&sort=id,asc
[
{
"id": 1,
"name": "e1",
"creationDate": "2021-11-15T23:00:00Z",
"lastUpdate": null,
"erasureDate": null
},
{
"id": 2,
"name": "e2",
"creationDate": "2021-11-15T23:00:00Z",
"lastUpdate": null,
"erasureDate": null
},
{
"id": 3,
"name": "e3",
"creationDate": "2021-11-15T23:00:00Z",
"lastUpdate": null,
"erasureDate": null
}
]
How can I obtain something like this without use projections?
http://localhost:8080/api/example/list?fields=id,name&page=1&size=10&sort=id,desc
[
{
"id": 1,
"name": "e1"
},
{
"id": 2,
"name": "e2"
},
{
"id": 3,
"name": "e3"
}
]
http://localhost:8080/api/example/list?fields=name&page=1&size=10&sort=id,desc
[
{
"name": "e1",
},
{
"name": "e2",
},
{
"name": "e3",
}
]

#Ignore
private Instant creationDate;
Try this.
You can use #Ignore on getter,setter or fields.

How map List to an Object with list in mapstructs

How can I use MapStruct to create a mapper that maps a list (my source) to a object with a list (destination)?
My source classes looks like this:
class SourceB {
private String name;
private String lastname;
}
class SourceA {
private Integer id;
private List<SourceB> bs;
}
so I need to transform it to this:
class DestinationA {
private Integer id;
private DestinationAB bs;
}
class DestinationAB {
private List<DestinationB> b;
}
class DestinationB {
private String name;
private String lastname;
}
Expected sample json:
source:
{
"id": 1,
"bs": [
{
"name": "name1",
"lastname": "last1"
},
{
"name": "name2",
"lastname": "last2"
}
]
}
destination:
{
"id": 1,
"bs": {
"b": [
{
"name": "name1",
"lastname": "last1"
},
{
"name": "name2",
"lastname": "last2"
}
]
}
}

It's quite simple. Just put #Mapping annotation with specified source and destination on top of the mapping method.
#Mapper
public interface SourceMapper {
#Mapping(source = "bs", target = "bs.b")
DestinationA sourceAToDestinationA(SourceA sourceA);
}

Remove Element in Nested List with Condition From another List - Java 8

I want to remove items from a list with a conditional value that comes from another List. Here are the objects
public class Student{
private String name;
private String age;
private List<Course> listCourses;
//Setters and getters
}
public Class Course{
private String courseName;
private List<CourseDetail> listCoursesDetail;
//Setters and getters
}
public Class CourseDetail{
private String id;
private String grade;
private String professor;
//Setters and getters
}
So as you can see the object Student has a list, inside that list there is another list from the object CourseDetail. What I want to achieve is to filter or remove elements from private List<CourseDetail> listCoursesDetail where ID is not equal to id from this other object.
public class Process{
private String name;
private List<ProcessDetail> listProcessDetail;
//Setters and getters
}
public class ProcessDetail{
private String id;
//Setters and getters
}
Assume the object Process is populated as follows
{
"name": "process1",
"listProcessDetail": [
{
"id": "456"
},
{
"id": "666"
},
{
"id": "555"
}
]
}
Student is populated as follows.
{
"name": "Kevin",
"age": "22",
"listCourses": [
{
"courseName": "Math",
"listCoursesDetail": [
{
"id": "666",
"grade": "88",
"professor": "Xavier"
},
{
"id": "144",
"grade": "90",
"professor": "Marcus"
},
{
"id": "555",
"grade": "100",
"professor": "Joe"
}
]
}
]
}
The expected result will be:
{
"name": "Kevin",
"age": "22",
"listCourses": [
{
"courseName": "456",
"listCoursesDetail": [
{
"id": "666",
"grade": "88",
"professor": "Xavier"
},
{
"id": "555",
"grade": "100",
"professor": "Joe"
}
]
}
]
}
The element from listCoursesDetail with ID 144 was removed since there is no such value in the object Process.
So far I have these:
Set<String> ids = Process.getListProcessDetail().stream().map(ProcessDetail::id).collect(Collectors.toSet());
In these I stored all the ID's on a Set.
Then my attempt to remove the items:
List<Course> courses = Student.getListCourses().stream().filter(c -> c.getListCoursesDetail().stream().anyMatch(d -> ids.contains(d.getId()))).collect(Collectors.toList());
With these lines of code I get the same Student object as nothing happened.

Assuming you want to modify the existing objects, not create a clone of them with shorter lists, you'd do it like this:
student.getListCourses().forEach(c ->
c.getListCoursesDetail().removeIf(d -> ! ids.contains(d.getId())));