我正在与hibernate合作，尝试与SQL进行映射。
每次我尝试运行代码时，都会收到错误消息：
org.hibernate.AnnotationException: mappedBy reference an unknown
target entity property: Catalog.primaryKey.suppliers in
Suppliers.catalogSet There is an error:java.lang.NullPointerException
我已经进行了三次检查，以确保正确映射了所有内容，但是我必须丢失某些内容。有谁知道为什么我的给定代码会得到一个空指针？这些是我的班级代码：
导入javax.persistence。*;
@Entity
@Table(name = "catalog")
@AssociationOverrides({
@AssociationOverride(name = "primaryKey.suppliers",
joinColumns = @JoinColumn(name = "sid")),
@AssociationOverride(name = "primaryKey.parts",
joinColumns = @JoinColumn(name = "pid"))
})
public class Catalog {
//Composite ID
private CatalogId primaryKey = new CatalogId();
//Additional Column
private String cost;
@EmbeddedId
public CatalogId getPrimaryKey() {
return primaryKey;
}
public void setPrimaryKey(CatalogId primaryKey) {
this.primaryKey = primaryKey;
}
@Transient
public Suppliers getSuppliers(){
return getPrimaryKey().getSupplier();
}
public void setSuppliers(Suppliers supplier){
getPrimaryKey().setSupplier(supplier);
}
@Transient
public Parts getParts(){
return getPrimaryKey().getParts();
}
public void setParts(Parts part){
getPrimaryKey().setParts(part);
}
@Column(name = "cost")
public String getCost() {
return cost;
}
public void setCost(String cost) {
this.cost = cost;
}
}
import java.io.Serializable;
import javax.persistence.*;
@Embeddable
public class CatalogId implements Serializable{
private Suppliers suppliers;
private Parts parts;
@ManyToOne (cascade = CascadeType.ALL)
public Suppliers getSupplier() {
return suppliers;
}
public void setSupplier(Suppliers suppliers) {
this.suppliers = suppliers;
}
@ManyToOne(cascade = CascadeType.ALL)
public Parts getParts() {
return parts;
}
public void setParts(Parts parts) {
this.parts = parts;
}
}
import java.util.*;
import javax.persistence.*;
@Entity
@Table(name = "suppliers")
public class Suppliers {
private long sid;
private String sname;
private String address;
private Set<Catalog> catalogSet = new HashSet<Catalog>();
public Suppliers(String sname, String address) {
this.sname = sname;
this.address = address;
}
public Suppliers() {
}
@Id
@GeneratedValue
@Column(name = "sid")
public long getSid() {
return this.sid;
}
public void setSid(long sid) {
this.sid = sid;
}
@Column(name= "sname")
public String getSname() {
return this.sname;
}
public void setSname(String sname) {
this.sname = sname;
}
@Column(name = "address")
public String getAddress() {
return this.address;
}
public void setAddress(String address) {
this.address = address;
}
@OneToMany(mappedBy = "primaryKey.suppliers", cascade = CascadeType.ALL)
public Set<Catalog> getCatalogSet() {
return catalogSet;
}
public void setCatalogSet(Set<Catalog> catalogSet) {
this.catalogSet = catalogSet;
}
public void addRecipe(Catalog catalog){
this.catalogSet.add(catalog);
}
}
import java.util.*;
import javax.persistence.*;
@Entity
@Table(name = "parts")
public class Parts {
private long pid;
private String pname;
private String color;
private Set<Catalog> catalogSet = new HashSet<Catalog>();
public Parts(String pname, String color) {
super();
this.pname = pname;
this.color = color;
}
public Parts() {
super();
}
@Id
@GeneratedValue
@Column(name = "pid")
public long getPid() {
return pid;
}
public void setPid(long pid) {
this.pid = pid;
}
@Column(name = "pname")
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
@Column(name = "color")
public String getColor() {
return color;
}
public void setColor(String color) {
this.color = color;
}
@OneToMany(mappedBy = "primaryKey.parts", cascade = CascadeType.ALL)
public Set<Catalog> getCatalogSet() {
return this.catalogSet;
}
public void setCatalogSet(Set<Catalog> catalogSet) {
this.catalogSet = catalogSet;
}
public void addCatalog(Catalog catalog){
this.catalogSet.add(catalog);
}
}
这是我的（未完成的查询代码）：
import org.hibernate.*;
import org.hibernate.boot.*;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import javax.swing.*;
public class HibernateHql
{
public static void main(String[] args)
{
HibernateSession hibernateSession = new HibernateSession();
SessionFactory sessionFactory;
Session session;
String option = "";
String instruction = "Enter a: Return distinct sids and snames of suppliers who supply a red part or a green part." + "\n" +
"Enter b: Return distinct pids, pnames, and the maximum cost of that part amoung all suppliers that offer the part and that maximum cost is less than 70." + "\n" +
"Enter c: Insert a new catalog row given the supplier id, the part id, and the cost fromthe user of your program." + "\n" +
"Enter d: Quit Program";
try
{
while(true)
{
option = JOptionPane.showInputDialog(instruction);
hibernateSession.setUp();
sessionFactory = hibernateSession.getSessionFactory();
session = sessionFactory.openSession();
session.beginTransaction();
if(option.equals("a"))
{
List results = session.createQuery("select distinct c from Parts p join p.catalogSet c where p.color = :color1 or p.color = :color2").setParameter("color1", "red").setParameter("color2", "green").getResultList();
String toShow = "These are suppliers who supply a red or green part:\n";
for(int i=0;i<results.size();i++)
{
Suppliers theSupplier = (Suppliers)((Catalog)results.get(i)).getSuppliers();
toShow += (i+1) + ") " + theSupplier.getSname() + "\n";
}
JOptionPane.showMessageDialog(null, toShow);
}
else if(option.equals("b"))
{
List results = session.createQuery("select max(r.cost)from Suppliers s inner join s.catalogSet r group by f").getResultList();
String toShow = "These are all parts:\n";
for(int i=0;i<results.size();i++)
{
Parts thePart = (Parts)((Catalog)results.get(i)).getParts();
String cost = ((Catalog)results.get(i)).getCost();
if(Integer.parseInt(cost) <= 70){
toShow += (i+1) + ") " + thePart.getPname() + " " + cost;
}
}
JOptionPane.showMessageDialog(null, toShow);
}
else if(option.equals("c"))
{
String allSuppliers = "SID" + "....." + "SNAME" + "\n";
List allS = session.createQuery("from Suppliers").getResultList();
for(int i=0;i<allS.size();i++)
{
Suppliers theSupplier = (Suppliers)allS.get(i);
allSuppliers += theSupplier.getSid() + "....." + theSupplier.getSname() + "\n";
}
JOptionPane.showMessageDialog(null, allSuppliers);
String supplierID = JOptionPane.showInputDialog("Enter Supplier ID: ");
String allParts = "PID" + "....." + "PNAME" + "\n";
List allP = session.createQuery("from Parts p where p.color = :color").setParameter("color", "blue").getResultList();
for(int i=0;i<allS.size();i++)
{
Parts theParts = (Parts)allP.get(i);
allParts += theParts.getPid() + "....." + theParts.getPname() + "\n";
}
JOptionPane.showMessageDialog(null, allParts);
String partsID = JOptionPane.showInputDialog("Enter Parts ID: ");
// List results = session.createQuery("select f1 from Food f1 where f1 not in (select distinct r.primaryKey.food from Ingredient i inner join i.recipeSet r where i.iname = :iname)").setParameter("iname", "Green Onion").getResultList();
// String toShow = "These foods don't have green onion:\n";
// for(int i=0;i<results.size();i++)
// {
// Food theFood = (Food)results.get(i);
// toShow += (i+1) + ") " + theFood.getFname() + "\n";
// }
// JOptionPane.showMessageDialog(null, toShow);
}
else
{
break;
}
session.getTransaction().commit();
session.close();
}
JOptionPane.showMessageDialog(null, "Good Bye");
}
catch(Exception e)
{
System.out.println("There is an error:");
System.out.println(e.toString());
}
}
}
提前感谢您的帮助！
答案 0 :(得分：0)
在Suppliers类中，您已如下映射catalogSet：
@OneToMany(mappedBy = "primaryKey.suppliers", cascade = CascadeType.ALL)
public Set<Catalog> getCatalogSet() {
return catalogSet;
}
我在Suppliers类中没有找到任何名为primaryKey的字段。我认为您应该在此处使用sid来映射catalogSet和Suppliers类之间的关系。
如果我误解了你的问题，请告诉我。