JPA exception: Object: null is not a known entity type

Question

Hi I'm new in JPA and when I want to persist object I get these errors:

java.lang.IllegalArgumentException: Object: null is not a known entity type.
    at org.eclipse.persistence.internal.jpa.EntityManagerImpl.persist(EntityManagerImpl.java:437)
    at database.TarpineManager.persist(TarpineManager.java:31)
    at gijos.InsertToDB.insertLink(InsertToDB.java:34)
    at gijos.VilpraParser.run(VilpraParser.java:77)

There is my firs object class, which I want to do relation with other XLinksMedia class, I think problem is in

@OneToMany(mappedBy = "xParserLink", targetEntity = XLinksMedia.class, fetch=FetchType.EAGER, cascade = CascadeType.ALL)
private List<XLinksMedia> fotos; 

but I do not know what is wrong:

package database.entity;

import java.io.Serializable;
import java.util.Date;
import java.util.List;
import javax.persistence.Basic;
import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.xml.bind.annotation.XmlRootElement;

@Entity
@Table(name = "x_parser_links")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "XParserLinks.findAll", query = "SELECT x FROM XParserLinks x"),
    @NamedQuery(name = "XParserLinks.findByLinkId", query = "SELECT x FROM XParserLinks x WHERE x.linkId = :linkId"),
    @NamedQuery(name = "XParserLinks.findByPageId", query = "SELECT x FROM XParserLinks x WHERE x.pageId = :pageId"),
    @NamedQuery(name = "XParserLinks.findByLink", query = "SELECT x FROM XParserLinks x WHERE x.link = :link"),
    @NamedQuery(name = "XParserLinks.findByLevel", query = "SELECT x FROM XParserLinks x WHERE x.level = :level"),
    @NamedQuery(name = "XParserLinks.findByLinkType", query = "SELECT x FROM XParserLinks x WHERE x.linkType = :linkType"),
    @NamedQuery(name = "XParserLinks.findByCreateDate", query = "SELECT x FROM XParserLinks x WHERE x.createDate = :createDate"),
    @NamedQuery(name = "XParserLinks.findByDelDate", query = "SELECT x FROM XParserLinks x WHERE x.delDate = :delDate")})
public class XParserLinks implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "link_id")
    private Integer linkId;
    @Column(name = "page_id")
    private Integer pageId;
    @Column(name = "link")
    private String link;
    @Column(name = "level")
    private Integer level;
    @Column(name = "link_type")
    private Short linkType;
    @Column(name = "create_date")
    @Temporal(TemporalType.TIMESTAMP)
    private Date createDate;
    @Column(name = "del_date")
    @Temporal(TemporalType.TIMESTAMP)
    private Date delDate;
    @JoinColumn(name = "tev_link_id")
    @OneToOne
    private XParserLinks tevas;   
    @OneToMany(mappedBy = "xParserLink", targetEntity = XLinksMedia.class, fetch=FetchType.EAGER, cascade = CascadeType.ALL)
    private List<XLinksMedia> fotos;


    public XParserLinks() {
    }

    public XParserLinks(Integer linkId) {
        this.linkId = linkId;
    }

    public Integer getLinkId() {
        return linkId;
    }

    public void setLinkId(Integer linkId) {
        this.linkId = linkId;
    }

    public Integer getPageId() {
        return pageId;
    }

    public void setPageId(Integer pageId) {
        this.pageId = pageId;
    }

    public String getLink() {
        return link;
    }

    public void setLink(String link) {
        this.link = link;
    }

    public Integer getLevel() {
        return level;
    }

    public void setLevel(Integer level) {
        this.level = level;
    }

    public Short getLinkType() {
        return linkType;
    }

    public void setLinkType(Short linkType) {
        this.linkType = linkType;
    }

    public Date getCreateDate() {
        return createDate;
    }

    public void setCreateDate(Date createDate) {
        this.createDate = createDate;
    }

    public Date getDelDate() {
        return delDate;
    }

    public void setDelDate(Date delDate) {
        this.delDate = delDate;
    }

    public XParserLinks getTevas() {
        return tevas;
    }

    public void setTevas(XParserLinks tevas) {
        this.tevas = tevas;
    }

    public List<XLinksMedia> getFotos() {
        return fotos;
    }

    public void setFotos(List<XLinksMedia> fotos) {
        this.fotos = fotos;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (linkId != null ? linkId.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof XParserLinks)) {
            return false;
        }
        XParserLinks other = (XParserLinks) object;
        if ((this.linkId == null && other.linkId != null) || (this.linkId != null && !this.linkId.equals(other.linkId))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "database.entity.XParserLinks[ linkId=" + linkId + " ]";
    }

}

Second class for fotos object

package database.entity;

import java.io.Serializable;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.xml.bind.annotation.XmlRootElement;

@Entity
@Table(name = "x_links_media")
@XmlRootElement
@NamedQueries({
    @NamedQuery(name = "XLinksMedia.findAll", query = "SELECT x FROM XLinksMedia x"),
    @NamedQuery(name = "XLinksMedia.findByLinkId", query = "SELECT x FROM XLinksMedia x WHERE x.xLinksMediaPK.linkId = :linkId"),
    @NamedQuery(name = "XLinksMedia.findByImage", query = "SELECT x FROM XLinksMedia x WHERE x.xLinksMediaPK.image = :image")})
public class XLinksMedia implements Serializable {
    private static final long serialVersionUID = 1L;
    @EmbeddedId
    protected XLinksMediaPK xLinksMediaPK;
    @ManyToOne
    @JoinColumn(name = "link_id")
    private XParserLinks xParserLink;

    public XLinksMedia() {
    }

    public XLinksMedia(XLinksMediaPK xLinksMediaPK) {
        this.xLinksMediaPK = xLinksMediaPK;
    }

    public XLinksMedia(int linkId, String image) {
        this.xLinksMediaPK = new XLinksMediaPK(linkId, image);
    }

    public XLinksMediaPK getXLinksMediaPK() {
        return xLinksMediaPK;
    }

    public void setXLinksMediaPK(XLinksMediaPK xLinksMediaPK) {
        this.xLinksMediaPK = xLinksMediaPK;
    }

    public XParserLinks getxParserLink() {
        return xParserLink;
    }

    public void setxParserLink(XParserLinks xParserLink) {
        this.xParserLink = xParserLink;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (xLinksMediaPK != null ? xLinksMediaPK.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof XLinksMedia)) {
            return false;
        }
        XLinksMedia other = (XLinksMedia) object;
        if ((this.xLinksMediaPK == null && other.xLinksMediaPK != null) || (this.xLinksMediaPK != null && !this.xLinksMediaPK.equals(other.xLinksMediaPK))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "database.entity.XLinksMedia[ xLinksMediaPK=" + xLinksMediaPK + " ]";
    }

}

And to persist object is this method:

    obj= new XParserLinks();
    obj.setCreateDate(new Date());
    obj.setLevel(1);
    obj.setPageId(2);
    obj.setLink(link);
    obj.setLinkType((short) 2);

        TarpineManager.startTransaction();

        TarpineManager.persist(obj);

        System.out.println("NAUJAS LINKAS");
        TarpineManager.commitTransaction();

Answer 1

Just a wild guess: fotos instance variable of the entity you're trying to persist named obj is never set and therefore null. Null pointers do not seem to be a legal entity for one-to-many relations.