Empty join table for ManyToMany Relationship

Question

A similar question with a different issue has been answered before. I have a bidirectional @ManyToMany relationship using Hibernate. The data persists to the separate entity tables, but the id column that maps to the entity tables is empty. I have tried the suggestions in Empty Join Table resulting from JPA ManyToMany, ManyToMany relationship, deleting records from relationship table and Hibernate Many-to-many association: left hand side collection contains elements, but right hand side collection is empty, but have not had success so far. Below is my code for completeness (I am still learning java and the spring framework, so I apologise for any rookie mistakes in advance):

CaseStudy Class

 @Entity
public class CaseStudy {

    @Id
    @GeneratedValue (strategy = GenerationType.AUTO)
    private Long caseStudyId;
    private String location;
    private String equipment;
    private String issue;
    private String solution;
    private String benefit;
    private float upper_dissolved_Oxygen;
    private float lower_dissolved_Oxygen;
    private float upper_pH;
    private float lower_pH;
    private float upper_temp;
    private float lower_temp;
    private float upper_conductivity;
    private float lower_conductivity;

    @CreationTimestamp
    private Date created;

    @ManyToOne
    @JsonBackReference
    private User user;

    private int likes;

    @ManyToMany(mappedBy="casestudyList", fetch = FetchType.EAGER)
    private List<WaterQuality> waterQualityList  = new List<WaterQuality>();

    @OneToMany(mappedBy = "casestudy", fetch = FetchType.EAGER)
    private List<Comment> commentList;

    public Long getCaseStudyId() {
        return caseStudyId;
    }


    public void setCaseStudyId(Long caseStudyId) {
        this.caseStudyId = caseStudyId;
    }


    public String getLocation() {
        return location;
    }


    public void setLocation(String location) {
        this.location = location;
    }


    public String getIssue() {
        return issue;
    }


    public void setIssue(String issue) {
        this.issue = issue;
    }


    public String getSolution() {
        return solution;
    }


    public void setSolution(String solution) {
        this.solution = solution;
    }


    public String getBenefit() {
        return benefit;
    }


    public void setBenefit(String benefit) {
        this.benefit = benefit;
    }


    public Date getCreated() {
        return created;
    }


    public void setCreated(Date created) {
        this.created = created;
    }


    public User getUser() {
        return user;
    }


    public void setUser(User user) {
        this.user = user;
    }


    public int getLikes() {
        return likes;
    }


    public void setLikes(int likes) {
        this.likes = likes;
    }


    public List<Comment> getCommentList() {
        return commentList;
    }


    public void setCommentList(List<Comment> commentList) {
        this.commentList = commentList;
    }


    public String getEquipment() {
        return equipment;
    }


    public void setEquipment(String equipment) {
        this.equipment = equipment;
    }


    public float getUpper_dissolved_Oxygen() {
        return upper_dissolved_Oxygen;
    }


    public void setUpper_dissolved_Oxygen(float upper_dissolved_Oxygen) {
        this.upper_dissolved_Oxygen = upper_dissolved_Oxygen;
    }


    public float getLower_dissolved_Oxygen() {
        return lower_dissolved_Oxygen;
    }


    public void setLower_dissolved_Oxygen(float lower_dissolved_Oxygen) {
        this.lower_dissolved_Oxygen = lower_dissolved_Oxygen;
    }


    public float getUpper_pH() {
        return upper_pH;
    }


    public void setUpper_pH(float upper_pH) {
        this.upper_pH = upper_pH;
    }


    public float getLower_pH() {
        return lower_pH;
    }


    public void setLower_pH(float lower_pH) {
        this.lower_pH = lower_pH;
    }


    public float getUpper_temp() {
        return upper_temp;
    }


    public void setUpper_temp(float upper_temp) {
        this.upper_temp = upper_temp;
    }


    public float getLower_temp() {
        return lower_temp;
    }


    public void setLower_temp(float lower_temp) {
        this.lower_temp = lower_temp;
    }


    public float getUpper_conductivity() {
        return upper_conductivity;
    }


    public void setUpper_conductivity(float upper_conductivity) {
        this.upper_conductivity = upper_conductivity;
    }


    public float getLower_conductivity() {
        return lower_conductivity;
    }


    public void setLower_conductivity(float lower_conductivity) {
        this.lower_conductivity = lower_conductivity;
    }

    public List<WaterQuality> getWaterQualityList() {
        return waterQualityList;
    }


    public void setWaterQualityList(List<WaterQuality> waterQualityList) {
        this.waterQualityList = waterQualityList;
    }


}

WaterQuality Class

    @Entity
public class WaterQuality {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long waterQualityId;
    private String description;
    private String status;
    private float dissolved_Oxygen;
    private float pH;
    private float temp;
    private float conductivity;

    @CreationTimestamp
    private Date publishDate;

    @ManyToOne
    @JsonBackReference
    private User user;

    @ManyToMany(targetEntity = CaseStudy.class, cascade = {CascadeType.ALL})
    @JoinTable(
               joinColumns = {@JoinColumn(name="water_quality_id")},
               inverseJoinColumns = {@JoinColumn(name="case_study_id")})
    private Set<CaseStudy> casestudyList = new HashSet<CaseStudy>();

    public Long getWaterQualityId() {
        return waterQualityId;
    }

    public void setWaterQualityId(Long waterQualityId) {
        this.waterQualityId = waterQualityId;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public String getStatus() {
        return status;
    }

    public void setStatus(String status) {
        this.status = status;
    }

    public float getDissolved_Oxygen() {
        return dissolved_Oxygen;
    }

    public void setDissolved_Oxygen(float dissolved_Oxygen) {
        this.dissolved_Oxygen = dissolved_Oxygen;
    }

    public float getpH() {
        return pH;
    }

    public void setpH(float pH) {
        this.pH = pH;
    }

    public float getTemp() {
        return temp;
    }

    public void setTemp(float temp) {
        this.temp = temp;
    }

    public float getConductivity() {
        return conductivity;
    }

    public void setConductivity(float conductivity) {
        this.conductivity = conductivity;
    }

    public Date getPublishDate() {
        return publishDate;
    }

    public void setPublishDate(Date publishDate) {
        this.publishDate = publishDate;
    }

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public Set<CaseStudy> getCasestudyList() {
        return casestudyList;
    }

    public void setCasestudyList(Set<CaseStudy> casestudyList) {
        this.casestudyList = casestudyList;
    }

    public List<CaseStudy> getDissolvedOxygenalert() {
        List<CaseStudy> dissolvedOxygenalert = casestudyList.stream()           //convert list to stream
                .filter(casestudy -> casestudy.getUpper_dissolved_Oxygen() < getDissolved_Oxygen() ||  casestudy.getLower_dissolved_Oxygen() > getDissolved_Oxygen())
                .collect(Collectors.toList());          //collect the output and convert streams to a List
        System.out.print(dissolvedOxygenalert);
        return dissolvedOxygenalert;
    }


}

I have tried deleting the database and creating it again, but it hasn't solved the problem so far.

Below is the code for persisting the data to the database +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

CaseStudy Service Implementation

import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.scrunch.data.dao.CaseStudyDao;
import com.scrunch.data.model.CaseStudy;
import com.scrunch.data.model.User;
import com.scrunch.data.service.CaseStudyService;

@Service
public class CaseStudyServiceImpl implements CaseStudyService{

@Autowired
private CaseStudyDao casestudyDao;

public CaseStudy save(CaseStudy casestudy) {
    return casestudyDao.save(casestudy);
}

public Set<CaseStudy> findByUser(User user) {
    return casestudyDao.findByUser(user);
}

public CaseStudy findByCaseStudyId(Long caseStudyId) {
    return casestudyDao.findByCaseStudyId(caseStudyId);
}

public Set<CaseStudy> findAll() {
    return casestudyDao.findAll();
}
}

WaterQuality Service Implementation

import java.util.Date;
import java.util.List;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import com.scrunch.data.dao.WaterQualityDao;
import com.scrunch.data.model.User;
import com.scrunch.data.model.WaterQuality;
import com.scrunch.data.service.WaterQualityService;

@Service
public class WaterQualityServiceImpl implements WaterQualityService{

//  private static final Logger LOGGER =     LoggerFactory.getLogger(WaterQualityServiceImpl.class);

@Autowired
private WaterQualityDao waterQualityDao;


@Override
public List<WaterQuality> listAllWaterQualityByUserAndDescription(
        User user, String description) {
    return waterQualityDao.findAllWaterQualityByUserAndDescriptionContaining(user, description);
}

@Override
public WaterQuality save(WaterQuality waterQuality) {
    return waterQualityDao.save(waterQuality);
}

@Override
public List<WaterQuality> findByUser(User user) {
    return waterQualityDao.findByUser(user);
}

@Override
public WaterQuality findWaterQualityById(Long waterQualityId) {
    return waterQualityDao.findByWaterQualityId(waterQualityId);
}

@Override
public List<WaterQuality> findAll() {
    return waterQualityDao.findAll();
}
}

WaterQuality Controller

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.fasterxml.jackson.annotation.JsonIgnore;
import com.scrunch.data.model.CaseStudy;
import com.scrunch.data.model.User;
import com.scrunch.data.model.WaterQuality;
import com.scrunch.data.service.WaterQualityService;

@RestController
@RequestMapping("/rest")
public class WaterQualityResource {
private String location;
private String equipment;
private String issue;
private String solution;
private String benefit;
private float upper_dissolved_Oxygen;
private float lower_dissolved_Oxygen;
private int likes;



@Autowired
private WaterQualityService waterQualityService;

@RequestMapping(value="/waterquality/add", method=RequestMethod.POST)

public WaterQuality addWaterQuality(@RequestBody WaterQuality waterQuality) {

    waterQuality.setCasestudyList(new HashSet<CaseStudy>());

    CaseStudy casestudy = new CaseStudy();
    casestudy.setLocation(location);
    casestudy.setEquipment(equipment);
    casestudy.setIssue(issue);
    casestudy.setSolution(solution);
    casestudy.setBenefit(benefit);
    casestudy.setUpper_dissolved_Oxygen(upper_dissolved_Oxygen);
    casestudy.setLower_dissolved_Oxygen(lower_dissolved_Oxygen);


    waterQuality.getCasestudyList().add(casestudy);
    return waterQualityService.save(waterQuality);
}

Get request for all waterqualities response returns and endless loop of the same results.

     [{"waterQualityId":1,"description":"sdfdsf","status":"dsfdsf","dissolved_Oxygen":5.0,"pH":7.0,"temp":72.0,"conductivity":500.0,"publishDate":1472784062000,"dissolvedOxygenalert":[{"caseStudyId":2,"location":null,"equipment":null,"issue":null,"solution":null,"benefit":null,"upper_dissolved_Oxygen":0.0,"lower_dissolved_Oxygen":0.0,"upper_pH":0.0,"lower_pH":0.0,"upper_temp":0.0,"lower_temp":0.0,"upper_conductivity":0.0,"lower_conductivity":0.0,"created":1472784062000,"likes":0,"waterQualityList":[{"waterQualityId":1,"description":"sdfdsf","status":"dsfdsf","dissolved_Oxygen":5.0,"pH":7.0,"temp":72.0,"conductivity":500.0,"publishDate":1472784062000,"dissolvedOxygenalert":[{"caseStudyId":2,"location":null,"equipment":null,"issue":null,"solution":null,"benefit":null,"upper_dissolved_Oxygen":0.0,"lower_dissolved_Oxygen":0.0,"upper_pH":0.0,"lower_pH":0.0,"upper_temp":0.0,"lower_temp":0.0,"upper_conductivity":0.0,"lower_conductivity":0.0,"created":1472784062000,"likes":0,"waterQualityList":

I am able to get data populated to the join table, but it seems to populate endlessly. It happens when the water quality data is added.

Answer 1

It is not clear in code posted, how you are trying to save associated entity. You should persist like this...

WaterQuality waterQuality = new WaterQuality();
//Set other fields too

CaseStudy caseStudy1 = new CaseStudy();
CaseStudy caseStudy2 = new CaseStudy();
CaseStudy caseStudy3 = new CaseStudy();
CaseStudy caseStudy4 = new CaseStudy();
//Set other fileds of case study too

List<CaseStudy> caseStudyList = waterQuality.getCaseStudyList();
caseStudyList.add(caseStudy1);
caseStudyList.add(caseStudy2);
caseStudyList.add(caseStudy3);
caseStudyList.add(caseStudy4);

waterQualityService.save(waterQuality);

If you will assign WaterQuality objects to CaseStudy Entity and save CaseStudy, then associations won't be populated in JoinTable.

And one more important thing, use Set instead of List for Collection.In case of List, Suppose, You already have 100 case study for waterQuality and if you want to delete one of them, Then it will delete entire case studies first and then add all case study again except the deleted one. Use Set if your collection does not contain duplicates. If your collection contains duplicates too, Then use List with index.