休眠：java.lang.IllegalArgumentException：无法设置int字段

Question

Im试图使用休眠在MySQL数据库中插入一个条目。但是我收到了一个IllegalArgumentException。 id是数据库中的主键，我检查了autoincrement选项。

org.hibernate.property.access.spi.PropertyAccessException: Error accessing field [public int com.nexus.tutorial.Items.id] by reflection for persistent property [com.nexus.tutorial.Items#id] : Items [name=test, price=20.0, lagerstand=5, anfver=ankauf, position=0,0,0]
...
...
...
Caused by: java.lang.IllegalArgumentException: Can not set int field com.nexus.tutorial.Items.id to com.nexus.tutorial.Items
        at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:167)
        at sun.reflect.UnsafeFieldAccessorImpl.throwSetIllegalArgumentException(UnsafeFieldAccessorImpl.java:171)
        at sun.reflect.UnsafeFieldAccessorImpl.ensureObj(UnsafeFieldAccessorImpl.java:58)
        at sun.reflect.UnsafeIntegerFieldAccessorImpl.getInt(UnsafeIntegerFieldAccessorImpl.java:56)
        at java.lang.reflect.Field.getInt(Field.java:574)
        at org.hibernate.property.access.spi.GetterFieldImpl.get(GetterFieldImpl.java:62)

public class HibernateUpdate {

    public static void update(Items item) {

        SessionFactory factory = new Configuration()
                .configure("C:\\Users\\N3XUS\\AppData\\\\Roaming\\.minecraft\\config\\hibernate.cfg.xml")
                .addAnnotatedClass(Items.class)
                .buildSessionFactory();

        Session session = factory.getCurrentSession();

        try {
            System.out.println("Creating new Items");
            session.beginTransaction();
            //List<Items> itemList = session.createQuery("from Items").list();
            session.save(item);
            session.getTransaction().commit();

        }finally {
            factory.close();
        }
    }

}

这就是我所说的方法：

HibernateUpdate.update(new Items("test", 20.00, 5,"ankauf","0,0,0"));

这是我的模特：

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="items")
public class Items {

    @Id
    @Column(name="id")
    public int id;

    @Column(name="name")
    public String name;

    @Column(name="price")
    public double price;

    @Column(name="lagerstand")
    public int lagerstand;

    @Column(name="anfver")
    public String anfver;

    @Column(name="position")
    public String position;

    public Items() {

    }

    public Items(String name, double price, int lagerstand, String anfver, String position) {
        this.name = name;
        this.price = price;
        this.lagerstand = lagerstand;
        this.anfver = anfver;
        this.position = position;
    }

    public int getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public double getPrice() {
        return price;
    }

    public void setPrice(double price) {
        this.price = price;
    }

    public int getLagerstand() {
        return lagerstand;
    }

    public void setLagerstand(int lagerstand) {
        this.lagerstand = lagerstand;
    }

    public String getAnfver() {
        return anfver;
    }

    public void setAnfver(String anfver) {
        this.anfver = anfver;
    }

    public String getPosition() {
        return position;
    }

    public void setPosition(String position) {
        this.position = position;
    }

    @Override
    public String toString() {
        return "Items [name=" + name + ", price=" + price + ", lagerstand=" + lagerstand + ", anfver=" + anfver
                + ", position=" + position + "]";
    }

}

我知道修饰符应该是私有的。我正在使用最新版本的JDBC并从maven存储库中休眠。

    compile 'org.hibernate:hibernate-agroal:5.3.10.Final'
compile group: 'mysql', name: 'mysql-connector-java', version: '8.0.15'

Answer 1

您必须使用GeneratedValue来确保您的ID是自动递增的：

@Id @GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name="id")
public int id;

此后，您的ID将自动递增，您可以添加商品：

HibernateUpdate.update(new Items("test", 20.00, 5,"ankauf","0,0,0"));

  

建议：您的偏好设置属性必须是私有的或受保护的，并且   从getter和setter中可以访问它们。