Hibernate06_ID生成策略

第一种native , id自增， 相当于primary key auto_increment;

Book实体类

package com.chb.model;

public class Book {
    private int id;
    private String name;
    private double price;

    public Book() {}

    public Book(int id, String name, double price) {
        super();
        this.id = id;
        this.name = name;
        this.price = price;
    }


    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;
    }



}

Book.hbm.xml

测试成功：

查看数据库， 可以发现id自动为1

二、生成策略为assign

修改Book.hbm.xml

使用DROP TABLE book_table 将数据库中的book_table删除

ID生成策略改为assigned， 第一次执行，ID自动为1

再次执行测试， 报如下错误。因为id需要开发人员自己指定。

ERROR: Duplicate entry '0' for key 'PRIMARY'

三、生成策略为uuid

Book.hbm.xml

将Book实体类的id改为String

package com.chb.model;

public class Book {
    private String id;
    private String name;
    private double price;

    public Book() {}

    public Book(String id, String name, double price) {
        super();
        this.id = id;
        this.name = name;
        this.price = price;
    }


    public String getId() {
        return id;
    }
    public void setId(String 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;
    }



}

删除数据库中的book_table

测试