500 Internal Server Error; when using POST method in springBoot rest api - spring

Question

I used Spring Boot, POST method for create a new score for my player.
In POST method, I check if the player and game exists then create new score and also add score and its related date into the history of my score's class.
Each score has history which contains score and its date. the history has type list of History's class
The History Class:
package thesisMongoProject;
import java.util.Date;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
#Document(collection = "history")
public class History {
#Id
private String score;
private Date date;
public History(String score, Date date) {
super();
this.score = score;
this.date = date;
}
public String getScore() {
return score;
}
public void setScore(String score) {
this.score = score;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
#Override
public String toString() {
return "History [score=" + score + ", date=" + date + "]";
}
}
The Score Class:
package thesisMongoProject;
import java.util.Date;
import java.util.List;
import javax.validation.constraints.NotBlank;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
import com.fasterxml.jackson.annotation.JsonView;
#Document(collection = "score")
public class Score {
#Id
#NotBlank
#JsonView(Views.class)
private String score;
#NotBlank
#JsonView(Views.class)
private String player;
#NotBlank
#JsonView(Views.class)
private String code;
#JsonView(Views.class)
private Date date;
private List<History> history;
public Score(#NotBlank String score, String player, String code, List<History> history, Date date) {
super();
this.score = score;
this.player = player;
this.code = code;
this.history = history;
this.date = date;
}
public String getScore() {
return score;
}
public void setScore(String score) {
this.score = score;
}
public String getPlayer() {
return player;
}
public void setPlayer(String player) {
this.player = player;
}
public String getCode() {
return code;
}
public void setCode(String code) {
this.code = code;
}
public List<History> getHistory() {
return history;
}
public void setHistory(List<History> history) {
this.history = history;
}
public Date getDate() {
return date;
}
public void setDate(Date date) {
this.date = date;
}
#Override
public String toString() {
return "Score [score=" + score + ", player=" + player + ", code=" + code + ", history=" + history + ", date="
+ date + "]";
}
}
And the POST method:
#RestController
#RequestMapping("/score")
public class ScoreController {
#Autowired
private ScoreRepository srepo;
#Autowired
private PlayerRepository prepo;
#Autowired
private GamesRepository grepo;
#Autowired
private HistoryRepository hrepo;
private List<History> history;
private History h = null;
//Create Score
#PostMapping
public ResponseEntity<?> createScore(#RequestBody #JsonView(Views.class) #Valid Score score) {
//check player exist
Player p = prepo.findByNickname(score.getPlayer());
//check game's cod exist
Games g = grepo.findByCode(score.getCode());
//check score exist
Score s = srepo.findByScore(score.getScore());
// = hrepo.findByScore(score.getScore());
if(s != null)
{
return ResponseEntity.status(409).body("Conflict!!");
}else if((p != null) && (g != null)) {
h.setScore(score.getScore());
h.setDate(score.getDate());
hrepo.save(h);
history.add(h);
//history.add(hrepo.findById(score.getScore()).get());
score.setHistory(history);
srepo.save(score);
return ResponseEntity.status(201).body("Created!");
}
else {
return ResponseEntity.status(400).body("Bad Request!");
}
}
In my POST method I tried to setScore and setDate for an object of History class, and then I saved them by hrepo which is history Repository and then I added this to the history variable of type List<History>, after that I setHistory of my score class with srepo, Score repository . But when I execute my program, in PostMan I have 500 Internal Server Error and in the console I have this Error:
java.lang.NullPointerException: null
at thesisMongoProject.controller.ScoreController.createScore(ScoreController.java:63) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
which is exactly the line that I setScore of object h, h.setScore(score.getScore());
I cannot understand what is my mistake.

Answer 1

Initialize both, you should not get NPE after that
private List<History> history=new ArrayList<>();
private History h = new History();

Answer 2

field h in this line
private History h = null;
may be local variable like below.
}else if((p != null) && (g != null)) {
History h = new History(); //add local variable here.
h.setScore(score.getScore());