I know this question can be misleading, if possible someone may correct it, I am not sure how to ask a question with this situation.
I am trying to Convert Class X into Class Y (here class Y contains fields of class X, but in different way, Eg:- Integer a, b;
inside class X , converts to Map<a, b>
in class Y while other variables stay the same.),
using streams in java 8. I am trying to return the final object to the UI part as json. The project is done in spring boot. Both Class X and Y contains the same objects, but Class Y is to make class X distinct I am not familiar with streams.
Class X
public class X {
private final String thumbnailUrl;
private final Integer duration;
private final String contentId;
private final Date reportDate;
private final Integer count;
public X(Report report, int count) {
this.thumbnailUrl = report.getContent().getThumbnailUrl();
this.duration = report.getContent().getDuration();
this.contentId = report.getContent().getContentId();
this.reportDate = report.getReportDate();
this.count = count;
}
public String getThumbnailUrl() {
return thumbnailUrl;
}
public Integer getDuration() {
return duration;
}
public String getContentId() {
return contentId;
}
public Date getReportDate() {
return reportDate;
}
public Integer getCount() {
return count;
}
}
Class Y
public class Y {
private final String thumbnailUrl;
private final Integer duration;
private final String contentId;
private final Map<Date, Integer> contentList;
public Y(X x, Map<Date, Integer> contentList) {
this.thumbnailUrl = x.getThumbnailUrl();
this.duration = x.getDuration();
this.contentId = x.getContentId();
this.contentList = contentList;
}
public String getThumbnailUrl() {
return thumbnailUrl;
}
public Integer getDuration() {
return duration;
}
public String getContentId() {
return contentId;
}
public Map<Date, Integer> getContentList() {
return contentList;
}
}
This is what I am currently getting from class X
[
{
"thumbnailUrl": "a",
"duration": 12,
"contentId": "CNT10",
"reportDate": "2020-01-20",
"count": 3
},
{
"thumbnailUrl": "a",
"duration": 12,
"contentId": "CNT10",
"reportDate": "2020-01-21",
"count": 5
},
{
"thumbnailUrl": "a",
"duration": 12,
"contentId": "CNT10",
"reportDate": "2020-01-22",
"count": 3
},
{
"thumbnailUrl": "a",
"duration": 12,
"contentId": "CNT10",
"reportDate": "2020-01-23",
"count": 4
}
]
I got the above json in postman after using this code and returning the final list.
List<X> x;
List<Y> y;
x = StreamSupport.stream(reportRepository
.reportWithRoll(a, b, c).spliterator(), false)
.map(report -> new X(report, report.getStartCount()))
.collect(Collectors.toList());
I want this to transformed into content of Class Y as below. How can I achieve this with streams in Java?
[
{
"list": [
{
"2020-01-20": 3,
"2020-01-21": 5,
"2020-01-22": 3,
"2020-01-23": 4
}
],
"thumbnailUrl": "a",
"duration": 12,
"contentId": "CNT10"
}
]
I tried this to get the above json format, but ended up getting duplicate data, for single contentId and error for multiple contentId
y = x.stream().map(
rep -> {
Map<Date, Integer> contentList = x.stream().collect(
Collectors.toMap(X::getReportDate, X::getCount)
);
Y yy = new Y(rep, contentList);
return yy;
}
).distinct().collect(Collectors.toList());
I am combining the common date and count : key value pair into a single "list" for each unique "contentId" (each unique "contentId" will have its own "thumbnailUrl" and "duration" specific to it, so when I am referring only "contentId" as unique, it will include "thumbnailUrl" and "duration", only the date and count will be multiple for each of these).
I have found a solution using stream itself, thanks to one stack overflow answer.
y = x.stream()
.map(X::getContentId)
.distinct()
.map(
contentId -> {
return reportModifier(reportViews, contentId);
}
).collect(Collectors.toList());
private Y reportModifier(List<x> x, String contentId) {
Map<Date, Integer> contentList = x.stream()
.filter(a -> a.getContentId().equals(contentId))
.collect(
Collectors.toMap(X::getReportDate, X::getCount)
);
X rv = x.stream()
.filter(a -> a.getContentId().equals(contentId))
.findFirst()
.get();
Y yy = new Y(rv, contentList);
return yy;
}
I got the following json with this
[
{
"thumbnailUrl": "a",
"duration": 12,
"contentId": "CNT10",
"contentList": {
"2020-01-21T18:30:00.000+0000": 3,
"2020-01-20T18:30:00.000+0000": 3,
"2020-01-22T18:30:00.000+0000": 3,
"2020-01-19T18:30:00.000+0000": 3
}
},
{
"thumbnailUrl": "b",
"duration": 12,
"contentId": "CNT12",
"contentList": {
"2020-01-19T18:30:00.000+0000": 3
}
},
{
"thumbnailUrl": "c",
"duration": 12,
"contentId": "CNT11",
"contentList": {
"2020-01-21T18:30:00.000+0000": 3,
"2020-01-20T18:30:00.000+0000": 3,
"2020-01-19T18:30:00.000+0000": 3
}
}
]