[英]Java- ToString() in a Java Bean generated with Hibernate caused StackOverflowError
我是这个论坛的新手,所以我希望我没做错任何事情。我一个月前开始学习Java,但是我有一个小问题。 我有2个实体,我想打印带有其轨道的CD,但是我有这个异常:线程“ main”中的异常java.lang.StackOverflowError
我不知道如何解决此问题。我发布了代码和实体:
TbTrack
package it.tgi.cd.entities2;
// default package
// Generated 11-mag-2015 16.29.34 by Hibernate Tools 4.0.0
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;
/**
* TbTrack generated by hbm2java
*/
@Entity
@Table(name = "tb_track", catalog = "db_cd_store")
public class TbTrack implements java.io.Serializable {
private Integer idTrack;
private TbCd tbCd;
private String title;
public TbTrack() {
}
public TbTrack(TbCd tbCd, String title) {
this.tbCd = tbCd;
this.title = title;
}
@Override
public String toString() {
return "idTrack=" + idTrack + ", tbCd=" + tbCd + ", title=" + title;
}
@Id
@GeneratedValue(strategy = IDENTITY)
@Column(name = "id_track", unique = true, nullable = false)
public Integer getIdTrack() {
return this.idTrack;
}
public void setIdTrack(Integer idTrack) {
this.idTrack = idTrack;
}
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "id_cd", nullable = false)
public TbCd getTbCd() {
return this.tbCd;
}
public void setTbCd(TbCd tbCd) {
this.tbCd = tbCd;
}
@Column(name = "title", nullable = false, length = 45)
public String getTitle() {
return this.title;
}
public void setTitle(String title) {
this.title = title;
}
}
TBCD
package it.tgi.cd.entities2;
// default package
// Generated 11-mag-2015 16.29.34 by Hibernate Tools 4.0.0
import java.util.HashSet;
import java.util.Set;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
/**
* TbCd generated by hbm2java
*/
@Entity
@Table(name = "tb_cd", catalog = "db_cd_store")
public class TbCd implements java.io.Serializable {
private int idCd;
private String title;
private Set<TbTrack> tbTracks = new HashSet<TbTrack>(0);
public TbCd() {
}
public TbCd(int idCd, String title) {
this.idCd = idCd;
this.title = title;
}
@Override
public String toString() {
return "idCd=" + idCd + ", title=" + title + ", track= " + tbTracks;
}
public TbCd(int idCd, String title, Set<TbTrack> tbTracks) {
this.idCd = idCd;
this.title = title;
this.tbTracks = tbTracks;
}
@Id
@Column(name = "id_cd", unique = true, nullable = false)
public int getIdCd() {
return this.idCd;
}
public void setIdCd(int idCd) {
this.idCd = idCd;
}
@Column(name = "title", nullable = false, length = 45)
public String getTitle() {
return this.title;
}
public void setTitle(String title) {
this.title = title;
}
@OneToMany(fetch = FetchType.LAZY, mappedBy = "tbCd")
public Set<TbTrack> getTbTracks() {
return this.tbTracks;
}
public void setTbTracks(Set<TbTrack> tbTracks) {
this.tbTracks = tbTracks;
}
}
CDDAO2
package it.tgi.cd.dao2;
import it.tgi.cd.connection2.DBConnection2;
import it.tgi.cd.entities2.TbCd;
import java.util.Iterator;
import java.util.List;
import org.hibernate.Query;
import org.hibernate.Session;
public class CDDAO2 {
public static void searchCD(String title) {
Session session = DBConnection2.openConnection();
String query = "FROM TbCd where title='" + title + "'";
Query _query = session.createQuery(query);
List<TbCd> list = _query.list();
System.out.println(list);
DBConnection2.closeConnection(session);
}
}
你能帮我吗? 谢谢!
您要在轨道类中添加CD 字符串 ,并且要在CD类中添加所有轨道字符串 。
这是无限递归:CD字符串包含一个轨道字符串(以及其他),此轨道字符串包含CD字符串(与开始时相同!),而CD字符串又包含轨道字符串,依此类推。
解决方法是不包括在该方法的曲目TbCd.toString()
或不包括该方法中的CD TbTrack.toString()
我建议使用后者,因为组装CD字符串时可能打算包含所有轨道:
public class TbCd implements java.io.Serializable {
@Override
public String toString() {
return "idCd=" + idCd + ", title=" + title + ", track= " + tbTracks;
}
}
public class TbTrack implements java.io.Serializable {
@Override
public String toString() {
return "idTrack=" + idTrack + ", title=" + title;
}
}
当您这样做时,它非常简单:
@Override
public String toString() {
return "idCd=" + idCd + ", title=" + title + ", track= " + tbTracks;
}
它尝试打印您的TbTrack对象集,该对象还将覆盖toString方法,以便:
@Override
public String toString() {
return "idTrack=" + idTrack + ", tbCd=" + tbCd + ", title=" + title;
}
那么发生了什么:
它打印轨道列表,每个轨道的toString方法都被调用,该方法再次打印CD“ tbCD”,它试图一次又一次地打印轨道uupps STACKOVERFLOW已达到!!!
从TbTrack类的toString中删除“ tbCD = + tbCD”,一切正常。 而是打印例如titel;)
简单的解决方法是:
@Override
public String toString() {
return "idTrack=" + idTrack + ", tbCd.Title=" + tbCd.title + ", title=" + title;
}
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