Tutorial of JPA one-to-many persist

Hello everyone,

I have read the official document of Oracle, but I still have some problems about JPA relationships. Suppose that there are two tables: the header table and the item table. The DDL are following:

CREATE TABLE TMP_ZSTEST_HEADER (
MANDT VARCHAR(3) NOT NULL,
BUKRS VARCHAR(4) NOT NULL,
BELNR VARCHAR(10) NOT NULL,
GJAHR VARCHAR(4) NOT NULL,
BUTXT VARCHAR(20) NOT NULL,
WAERS VARCHAR(5) NOT NULL,
TCODE VARCHAR(20) NOT NULL,
CONSTRAINT PrimaryKey_Header PRIMARY KEY (MANDT, BUKRS, BELNR, GJAHR)
);

CREATE TABLE TMP_ZSTEST_ITEM (
MANDT VARCHAR(3) NOT NULL,
BUKRS VARCHAR(4) NOT NULL,
BELNR VARCHAR(10) NOT NULL,
GJAHR VARCHAR(4) NOT NULL,
BUZEI INTEGER DEFAULT 0 NOT NULL,
DMBTR DECIMAL(13 , 2) DEFAULT 0 NOT NULL,
COSTL VARCHAR(10) NOT NULL,
ZUONR VARCHAR(20) NOT NULL,
CONSTRAINT PrimaryKey_Item PRIMARY KEY (MANDT, BUKRS, BELNR, GJAHR, BUZEI),
CONSTRAINT Foreignkey_Header_Item FOREIGN KEY (MANDT,BUKRS,BELNR,GJAHR) REFERENCES TMP_ZSTEST_HEADER(MANDT,BUKRS,BELNR,GJAHR)
);

The Entity Classes are following:

1. TmpZstestHeader.java

package com.sap.entities;

import java.io.Serializable;
import javax.persistence.*;
import java.util.List;

/**
* The persistent class for the TMP_ZSTEST_HEADER database table.
*
*/
@Entity
@Table(name="TMP_ZSTEST_HEADER")
public class TmpZstestHeader implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private TmpZstestHeaderPK id;

private String butxt;

private String tcode;

private String waers;

//bi-directional many-to-one association to TmpZstestItem
@OneToMany(mappedBy="tmpZstestHeader", cascade={CascadeType.ALL})
private List<TmpZstestItem> tmpZstestItems;

public TmpZstestHeader() {
}

public TmpZstestHeaderPK getId() {
return this.id;
}

public void setId(TmpZstestHeaderPK id) {
this.id = id;
}

public String getButxt() {
return this.butxt;
}

public void setButxt(String butxt) {
this.butxt = butxt;
}

public String getTcode() {
return this.tcode;
}

public void setTcode(String tcode) {
this.tcode = tcode;
}

public String getWaers() {
return this.waers;
}

public void setWaers(String waers) {
this.waers = waers;
}

public List<TmpZstestItem> getTmpZstestItems() {
return this.tmpZstestItems;
}

public void setTmpZstestItems(List<TmpZstestItem> tmpZstestItems) {
this.tmpZstestItems = tmpZstestItems;
}

}

2. TmpZstestHeaderPK.java

package com.sap.entities;

import java.io.Serializable;
import javax.persistence.*;

/**
* The primary key class for the TMP_ZSTEST_HEADER database table.
*
*/
@Embeddable
public class TmpZstestHeaderPK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;

private String mandt;

private String bukrs;

private String belnr;

private String gjahr;

public TmpZstestHeaderPK() {
}
public String getMandt() {
return this.mandt;
}
public void setMandt(String mandt) {
this.mandt = mandt;
}
public String getBukrs() {
return this.bukrs;
}
public void setBukrs(String bukrs) {
this.bukrs = bukrs;
}
public String getBelnr() {
return this.belnr;
}
public void setBelnr(String belnr) {
this.belnr = belnr;
}
public String getGjahr() {
return this.gjahr;
}
public void setGjahr(String gjahr) {
this.gjahr = gjahr;
}

public boolean equals(Object other) {
if (this == other) {
return true;
}
if (!(other instanceof TmpZstestHeaderPK)) {
return false;
}
TmpZstestHeaderPK castOther = (TmpZstestHeaderPK)other;
return
this.mandt.equals(castOther.mandt)
&& this.bukrs.equals(castOther.bukrs)
&& this.belnr.equals(castOther.belnr)
&& this.gjahr.equals(castOther.gjahr);

}

public int hashCode() {
final int prime = 31;
int hash = 17;
hash = hash * prime + this.mandt.hashCode();
hash = hash * prime + this.bukrs.hashCode();
hash = hash * prime + this.belnr.hashCode();
hash = hash * prime + this.gjahr.hashCode();

return hash;
}
}

3. TmpZstestItem.java

package com.sap.entities;

import java.io.Serializable;
import javax.persistence.*;
import java.math.BigDecimal;

/**
* The persistent class for the TMP_ZSTEST_ITEM database table.
*
*/
@Entity
@Table(name="TMP_ZSTEST_ITEM")
public class TmpZstestItem implements Serializable {
private static final long serialVersionUID = 1L;

@EmbeddedId
private TmpZstestItemPK id;

private String costl;

private BigDecimal dmbtr;

private String zuonr;

//bi-directional many-to-one association to TmpZstestHeader
@ManyToOne(cascade={CascadeType.ALL})
@JoinColumns({
@JoinColumn(name="BELNR", referencedColumnName="BELNR"),
@JoinColumn(name="BUKRS", referencedColumnName="BUKRS"),
@JoinColumn(name="GJAHR", referencedColumnName="GJAHR"),
@JoinColumn(name="MANDT", referencedColumnName="MANDT")
})
private TmpZstestHeader tmpZstestHeader;

public TmpZstestItem() {
}

public TmpZstestItemPK getId() {
return this.id;
}

public void setId(TmpZstestItemPK id) {
this.id = id;
}

public String getCostl() {
return this.costl;
}

public void setCostl(String costl) {
this.costl = costl;
}

public BigDecimal getDmbtr() {
return this.dmbtr;
}

public void setDmbtr(BigDecimal dmbtr) {
this.dmbtr = dmbtr;
}

public String getZuonr() {
return this.zuonr;
}

public void setZuonr(String zuonr) {
this.zuonr = zuonr;
}

public TmpZstestHeader getTmpZstestHeader() {
return this.tmpZstestHeader;
}

public void setTmpZstestHeader(TmpZstestHeader tmpZstestHeader) {
this.tmpZstestHeader = tmpZstestHeader;
}

}

4. TmpZstestItemPK.java

package com.sap.entities;

import java.io.Serializable;
import javax.persistence.*;

/**
* The primary key class for the TMP_ZSTEST_ITEM database table.
*
*/
@Embeddable
public class TmpZstestItemPK implements Serializable {
//default serial version id, required for serializable classes.
private static final long serialVersionUID = 1L;

private String mandt;

private String bukrs;

private String belnr;

private String gjahr;

private int buzei;

public TmpZstestItemPK() {
}
public String getMandt() {
return this.mandt;
}
public void setMandt(String mandt) {
this.mandt = mandt;
}
public String getBukrs() {
return this.bukrs;
}
public void setBukrs(String bukrs) {
this.bukrs = bukrs;
}
public String getBelnr() {
return this.belnr;
}
public void setBelnr(String belnr) {
this.belnr = belnr;
}
public String getGjahr() {
return this.gjahr;
}
public void setGjahr(String gjahr) {
this.gjahr = gjahr;
}
public int getBuzei() {
return this.buzei;
}
public void setBuzei(int buzei) {
this.buzei = buzei;
}

public boolean equals(Object other) {
if (this == other) {
return true;
}
if (!(other instanceof TmpZstestItemPK)) {
return false;
}
TmpZstestItemPK castOther = (TmpZstestItemPK)other;
return
this.mandt.equals(castOther.mandt)
&& this.bukrs.equals(castOther.bukrs)
&& this.belnr.equals(castOther.belnr)
&& this.gjahr.equals(castOther.gjahr)
&& (this.buzei == castOther.buzei);

}

public int hashCode() {
final int prime = 31;
int hash = 17;
hash = hash * prime + this.mandt.hashCode();
hash = hash * prime + this.bukrs.hashCode();
hash = hash * prime + this.belnr.hashCode();
hash = hash * prime + this.gjahr.hashCode();
hash = hash * prime + this.buzei;

return hash;
}
}

My Session Class is following:

Session.java

package com.sap.session;

import javax.ejb.Stateless;
import javax.persistence.*;

import com.sap.entities.*;

/**
* Session Bean implementation class Session
*/
@Stateless
public class Session implements SessionLocal {
@PersistenceUnit(unitName = "unitName")
private EntityManagerFactory emf;
private EntityManager em;
/**
* Default constructor.
*/
public Session() {
// TODO Auto-generated constructor stub
}

public void AddFromHeader(TmpZstestHeader entity){
em = emf.createEntityManager();
em.persist(entity);
em.flush();
}

public void AddFromItem(TmpZstestItem entity){
em = emf.createEntityManager();
em.persist(entity);
em.flush();
}
}

But when I run the method AddFromHeader, the exception indicates that the four columns MANDT, BUKRS, BELNR, GJAHR are not unique.

How can I do if I want to create entities in table TMP_ZSTEST_ITEM when I persist the entity of TMP_ZSTEST_HEADER?

Is there any tutorial about this?

Regards,

Zhongsheng Xu