Hibernate的注解

数据库mysql：user50表和order50表是一对多的关系

order50表有   外键： user_id

user类:

package com.c50.entity;

import java.util.Date;
import java.util.HashSet;
import java.util.Set;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

import org.hibernate.annotations.Cache;
import org.hibernate.annotations.CacheConcurrencyStrategy;
import org.hibernate.annotations.Cascade;
import org.hibernate.annotations.CascadeType;
import org.hibernate.annotations.GenericGenerator;

//代表此类参与ORM映射，此注解必须要有
@Entity
//代表user这个类映射了一个表user50，如果表名和类名一样，此注解可以省略
@Table(name="user50")
//读写缓存权限
@Cache(usage=CacheConcurrencyStrategy.READ_WRITE)
public class User {
    //主键，此注解必须要有
    @Id
    //数据库表中主键列名为id,如果实体类属性名和列名相同，此注解可以省略
    @Column(name="id")
    //主键的维护策略
    @GenericGenerator(name="inc50",strategy="increment")
    @GeneratedValue(generator="inc50")
    private Integer userID;
    private String name;
    private Integer age;
    @Column(name="birth")
    //此属性是日期类型，time:只保存时间       date:只保存日期         timestamp:(默认)日期+时间
    @Temporal(TemporalType.DATE)
    private Date birthday;
    //关系属性
    //mappedBy="对方中映射着外键的关系属性"=="order类中关系属性为user"
    //延迟加载：fetch = FetchType.LAZY
    @OneToMany(mappedBy="user",fetch=FetchType.LAZY)
    //ALL:增删改都可以级联(cascade)
    //save-update:增加和更新可以级联
    //delete:删除可以级联
    //如果不设置，则增删改都不可以级联
    //注意：查询例外，不受级联权限的控制，默认级联。
    @Cascade(value=CascadeType.DELETE)
    private Set<Order> orders=new HashSet<Order>();

    public Set<Order> getOrders() {
        return orders;
    }

    public void setOrders(Set<Order> orders) {
        this.orders = orders;
    }

    public User(){}

    public User(Integer userID, String name, Integer age, Date birthday) {
        super();
        this.userID = userID;
        this.name = name;
        this.age = age;
        this.birthday = birthday;
    }

    public Integer getUserID() {
        return userID;
    }
    public void setUserID(Integer userID) {
        this.userID = userID;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public Date getBirthday() {
        return birthday;
    }
    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "User [userID=" + userID + ", name=" + name + ", age=" + age
                + ", birthday=" + birthday + "]";
    }

}

order类：

package com.c50.entity;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;
import javax.persistence.Table;

import org.hibernate.annotations.GenericGenerator;

@Entity
@Table(name="order50")
public class Order {
    @Id
    @GenericGenerator(name="inc50",strategy="increment")
    @GeneratedValue(generator="inc50")
    private Integer id;
    private Double price;
    private String note;
    //关系属性
    @ManyToOne
    //数据库中order表，外键名为user_id，指向user表
    @JoinColumn(name="user_id")
    private User user;

    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public Double getPrice() {
        return price;
    }
    public void setPrice(Double price) {
        this.price = price;
    }
    public String getNote() {
        return note;
    }
    public void setNote(String note) {
        this.note = note;
    }
    @Override
    public String toString() {
        return "Order [id=" + id + ", price=" + price + ", note=" + note + "]";
    }
    public Order(){}
    public Order(Integer id, Double price, String note) {
        super();
        this.id = id;
        this.price = price;
        this.note = note;
    }

}