Question

人实体通过personBankAssociation与银行实体有多对多关系保存人员实体时我得到的错误是 Hibernate：/ *将SampleJavaProject.Entity.Bank * / insert插入test.Bank（金额，名称）值（？，？）线程“main”java.lang.NullPointerException中的异常在SampleJavaProject.Entity.PersonBankAssociation.setPerson（PersonBankAssociation.java:97）在SampleJavaProject.HibernateTransaction.PersonBankApp.main（PersonBankApp.java:57）

/**
 * 
 */
package SampleJavaProject.Entity;

import java.io.Serializable;
import java.util.Calendar;
import java.util.Set;

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.OneToMany;
import javax.persistence.Table;

/**
 * @author Siddhant_S
 * 
 */
@Entity
@Table(name = "person", schema = "test")
public class Person implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="person_id")
    private int id;
    private String name;
    @Column(precision = 2)
    private double amount;
    private Calendar birthDate;
    private String street;
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "pk.person")
    private Set<PersonBankAssociation> bank;

    /**
     * 
     */
    public Person() {
    }

    /**
     * @param name
     * @param amount
     * @param birthDate
     * @param street
     * @param bank
     */
    public Person(String name, double amount, Calendar birthDate, String street) {
        this.name = name;
        this.amount = amount;
        this.birthDate = birthDate;
        this.street = street;
        this.bank = bank;
    }

    /**
     * @return the id
     */
    public int getId() {
        return id;
    }

    /**
     * @param id
     *            the id to set
     */
    public void setId(int id) {
        this.id = id;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name
     *            the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the amount
     */
    public double getAmount() {
        return amount;
    }

    /**
     * @param amount
     *            the amount to set
     */
    public void setAmount(double amount) {
        this.amount = amount;
    }

    /**
     * @return the birthDate
     */
    public Calendar getBirthDate() {
        return birthDate;
    }

    /**
     * @param birthDate
     *            the birthDate to set
     */
    public void setBirthDate(Calendar birthDate) {
        this.birthDate = birthDate;
    }

    /**
     * @return the street
     */
    public String getStreet() {
        return street;
    }

    /**
     * @param street
     *            the street to set
     */
    public void setStreet(String street) {
        this.street = street;
    }

    /**
     * @return the bank
     */
    public Set<PersonBankAssociation> getBank() {
        return bank;
    }

    /**
     * @param bank
     *            the bank to set
     */
    public void setBank(Set<PersonBankAssociation> bank) {
        this.bank = bank;
    }
}

Bank entity

/**
 * 
 */
package SampleJavaProject.Entity;

import java.io.Serializable;
import java.util.Set;

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.OneToMany;
import javax.persistence.Table;

/**
 * @author Siddhant_S
 * 
 */
@Entity
@Table(name = "Bank", schema = "test")
public class Bank implements Serializable {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="bank_id")
    private int id;
    private String name;
    @Column(precision = 2)
    private double amount;
    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY, mappedBy = "pk.bank")
    private Set<PersonBankAssociation> associations;

    /**
     * 
     */
    public Bank() {
    }

    /**
     * @param name
     * @param amount
     * @param associations
     */
    public Bank(String name, double amount) {
        this.name = name;
        this.amount = amount;
    }

    /**
     * @return the id
     */
    public int getId() {
        return id;
    }

    /**
     * @param id
     *            the id to set
     */
    public void setId(int id) {
        this.id = id;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name
     *            the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the amount
     */
    public double getAmount() {
        return amount;
    }

    /**
     * @param amount
     *            the amount to set
     */
    public void setAmount(double amount) {
        this.amount = amount;
    }

    /**
     * @return the associations
     */
    public Set<PersonBankAssociation> getAssociations() {
        return associations;
    }

    /**
     * @param associations
     *            the associations to set
     */
    public void setAssociations(Set<PersonBankAssociation> associations) {
        this.associations = associations;
    }
}

Association


/**
 * 
 */
package SampleJavaProject.Entity;

import java.io.Serializable;

import javax.persistence.AssociationOverride;
import javax.persistence.AssociationOverrides;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.JoinColumn;
import javax.persistence.Table;
import javax.persistence.Transient;

/**
 * @author Siddhant_S
 * 
 */
@Entity
@Table(name = "Person_Bank_Association", schema = "test")
@AssociationOverrides({
        @AssociationOverride(name = "pk.person", joinColumns = @JoinColumn(name = "person_id")),
        @AssociationOverride(name = "pk.bank", joinColumns = @JoinColumn(name = "bank_id")) })
public class PersonBankAssociation implements Serializable {
    @EmbeddedId
    private PersonBankId pk;
    private String name;
    private double amount;
    /**
     * 
     */
    public PersonBankAssociation() {
    }
    /**
     * @param name
     * @param amount
     */
    public PersonBankAssociation(String name, double amount) {
        this.name = name;
        this.amount = amount;
    }
    /**
     * @return the pk
     */
    public PersonBankId getPk() {
        return pk;
    }
    /**
     * @param pk
     *            the pk to set
     */
    public void setPk(PersonBankId pk) {
        this.pk = pk;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name
     *            the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the amount
     */
    public double getAmount() {
        return amount;
    }

    /**
     * @param amount
     *            the amount to set
     */
    public void setAmount(double amount) {
        this.amount = amount;
    }

    /**
     * 
     * @return person
     */
    @Transient
    public Person getPerson() {
        return getPk().getPerson();
    }

    public void setPerson(Person person) {
        getPk().setPerson(person);
    }

    /**
     * 
     * @return bank
     */
    @Transient
    public Bank getBank() {
        return getPk().getBank();
    }

    public void setBank(Bank bank) {
        getPk().setBank(bank);
    }
    /* (non-Javadoc)
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((pk == null) ? 0 : pk.hashCode());
        return result;
    }
    /* (non-Javadoc)
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        PersonBankAssociation other = (PersonBankAssociation) obj;
        if (pk == null) {
            if (other.pk != null)
                return false;
        } else if (!pk.equals(other.pk))
            return false;
        return true;
    }


}

Relatation

/**
 * 
 */
package SampleJavaProject.Entity;

import java.io.Serializable;

import javax.persistence.CascadeType;
import javax.persistence.Embeddable;
import javax.persistence.FetchType;
import javax.persistence.ManyToOne;

/**
 * @author Siddhant_S
 * 
 */
@Embeddable
public class PersonBankId implements Serializable {
    @ManyToOne
    private Person person;
    @ManyToOne
    private Bank bank;

    /**
     * 
     */
    public PersonBankId() {
    }

    /**
     * @return the person
     */
    public Person getPerson() {
        return person;
    }

    /**
     * @param person
     *            the person to set
     */
    public void setPerson(Person person) {
        this.person = person;
    }

    /**
     * @return the bank
     */
    public Bank getBank() {
        return bank;
    }

    /**
     * @param bank
     *            the bank to set
     */
    public void setBank(Bank bank) {
        this.bank = bank;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#hashCode()
     */
    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((bank == null) ? 0 : bank.hashCode());
        result = prime * result + ((person == null) ? 0 : person.hashCode());
        return result;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.lang.Object#equals(java.lang.Object)
     */
    @Override
    public boolean equals(Object obj) {
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        PersonBankId other = (PersonBankId) obj;
        if (bank == null) {
            if (other.bank != null)
                return false;
        } else if (!bank.equals(other.bank))
            return false;
        if (person == null) {
            if (other.person != null)
                return false;
        } else if (!person.equals(other.person))
            return false;
        return true;
    }

}

Saving code

/**
 * 
 */
package SampleJavaProject.HibernateTransaction;

import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Set;

import org.hibernate.Session;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import SampleJavaProject.Entity.Bank;
import SampleJavaProject.Entity.Person;
import SampleJavaProject.Entity.PersonBankAssociation;
import SampleJavaProject.HibernateSession.HibernateUtil;

/**
 * @author Siddhant_S
 * 
 */
public class PersonBankApp {
    private static final Logger _logger = LoggerFactory
            .getLogger(PersonBankApp.class);
    private static final Session session = HibernateUtil.getSessionFactory()
            .openSession();

    /**
     * @return the Logger
     */
    public static Logger getLogger() {
        return _logger;
    }

    /**
     * @return the session
     */
    public static Session getSession() {
        return session;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        getSession().beginTransaction();        
        Bank bank=new Bank("SBI", 2000.00);
        getSession().save(bank);
        Calendar birthDate=GregorianCalendar.getInstance();
        birthDate.setTime(new Date());
        Person person=new Person("Siddhant", 2000.00, birthDate, "lane4");
        PersonBankAssociation associations=new PersonBankAssociation("Sbi name", 2000.00);
        associations.setPerson(person);
        associations.setBank(bank);
        person.getBank().add(associations);
        Integer personId= (Integer) getSession().save(person);
        //getSession().save(associations);
        getSession().getTransaction().commit();
        getSession().close();
        System.out.println("Person id:"+personId);
    }

}

Error getting

Hibernate: /* insert SampleJavaProject.Entity.Bank */ insert into test.Bank (amount, name) values (?, ?)
Exception in thread "main" java.lang.NullPointerException
    at SampleJavaProject.Entity.PersonBankAssociation.setPerson(PersonBankAssociation.java:97)
    at SampleJavaProject.HibernateTransaction.PersonBankApp.main(PersonBankApp.java:57)

Answer 1

您永远不会更改PersonBankAssociation.pk的默认空值。这就是为什么 getPk().setPerson(person)抛出一个NPE。

休眠 - 多对多示例 - 连接表+额外列（注释）

1 个答案: