JPA（六）：映射关联关系------映射单向一对多的关联关系

映射单向一对多的关联关系

新建项目项目请参考《JPA（五）：映射关联关系------映射单向多对一的关联关系》中的例子进行修改（需要清空数据中的表，因为本例子还是使用customer，order表来测试，但是关联关系发生了变化）：

Customer.java

package com.dx.jpa.singlemanytoone;

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

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.OneToMany;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;
import javax.persistence.Transient;

@Entity
@Table(name = "jpa_customer")
public class Customer {
    private Integer id;
    private String fullName;
    private Integer age;
    private Date birth;
    private Date createDate;
    private Set<Order> orders = new HashSet<>();

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    public Integer getId() {
        return id;
    }

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

    @Column(name = "FULL_NAME", length = 64, nullable = false)
    public String getFullName() {
        return fullName;
    }

    public void setFullName(String fullName) {
        this.fullName = fullName;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    @Temporal(TemporalType.DATE)
    public Date getBirth() {
        return birth;
    }

    public void setBirth(Date birth) {
        this.birth = birth;
    }

    @Temporal(TemporalType.TIMESTAMP)
    public Date getCreateDate() {
        return createDate;
    }

    public void setCreateDate(Date createDate) {
        this.createDate = createDate;
    }

    // 映射一对多的关联关系
    // @JoinColumn 用来映射一对多的关联关系
    // @OneToMany 用来映射外键列
    @JoinColumn(name = "CUSTOMER_ID")
    @OneToMany()
    public Set<Order> getOrders() {
        return orders;
    }

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

    // 帮助方法，不希望保存到数据库，但是需要动态获取Customer对象的属性。
    @Transient
    public String getCustomerInfo() {
        return "username:" + fullName + ",age:" + age;
    }
}

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