一对多注解

@OneToMany

作用

• 建立一对多的关系映射

属性

• targetEntityClass：指定多的方的类的字节码

• mappedBy：指定从表实体类中引用主表对象的名称,在哪方出现,哪方不维护外键

• cascade：指定要使用的级联操作

• fetch：指定是否采用延迟加载

• orphanRemoval：是否使用孤儿删除

@ManyToOne

作用

• 建立多对一的关系

属性

• targetEntityClass：指定一的一方实体类字节码

• cascade：指定要使用的级联操作

• fetch：指定是否采用延迟加载

• optional：关联是否可选。如果设置为false，则必须始终存在非空关系

@JoinColumn

作用

• 定义主键字段和外键字段的对应关系，维护外键

属性

• name：指定表中的外键字段的名称

• referencedColumnName：指定引用主表的主键字段名称

• unique：是否唯一，默认值不唯一

• nullable：是否允许为空，默认值允许

• insertable：是否允许插入，默认值允许

• updatable：是否允许更新，默认值允许

• columnDefinition：列的定义信息

 

import java.util.HashSet;
import java.util.Set;import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.OneToMany;
import javax.persistence.Table;/*** @ClassName: Customer* @Description:jpa的所有的注解都在一个叫javax.persistence包下* @author jsz* @date 2018年8月20日*/
@Entity // 指定当前类是实体类,写上此注解用于在创建SessionFactory/EntityManager时,加载映射配置
@Table(name = "cst_customer") // 指定实体类和表之间的对应关系
public class Customer {@Id@Column(name = "cust_id")@GeneratedValue(strategy = GenerationType.IDENTITY)private Long cust_id;@Column(name = "cust_name")private String cust_name;@Column(name = "cust_source")private String cust_source;@Column(name = "cust_industry")private String cust_industry;@Column(name = "cust_level")private String cust_level;@Column(name = "cust_address")private String cust_address;@Column(name = "cust_phone")private String cust_phone;/** targetEntity:* mappedBy:当前java类在对方的属性名,在哪里出现,那方不维护外键*/@OneToMany(targetEntity=LinkMan.class,mappedBy="customer",cascade=CascadeType.REMOVE)private Set<LinkMan> linkMans = new HashSet<LinkMan>();public Customer() {}public Customer(Long cust_id, String cust_name) {this.cust_id = cust_id;this.cust_name = cust_name;}public Set<LinkMan> getLinkMans() {return linkMans;}public void setLinkMans(Set<LinkMan> linkMans) {this.linkMans = linkMans;}public Long getCust_id() {return cust_id;}public void setCust_id(Long cust_id) {this.cust_id = cust_id;}public String getCust_name() {return cust_name;}public void setCust_name(String cust_name) {this.cust_name = cust_name;}public String getCust_source() {return cust_source;}public void setCust_source(String cust_source) {this.cust_source = cust_source;}public String getCust_industry() {return cust_industry;}public void setCust_industry(String cust_industry) {this.cust_industry = cust_industry;}public String getCust_level() {return cust_level;}public void setCust_level(String cust_level) {this.cust_level = cust_level;}public String getCust_address() {return cust_address;}public void setCust_address(String cust_address) {this.cust_address = cust_address;}public String getCust_phone() {return cust_phone;}public void setCust_phone(String cust_phone) {this.cust_phone = cust_phone;}@Overridepublic String toString() {return "Customer [cust_id=" + cust_id + ", cust_name=" + cust_name + ", cust_source=" + cust_source+ ", cust_industry=" + cust_industry + ", cust_level=" + cust_level + ", cust_address=" + cust_address+ ", cust_phone=" + cust_phone + "]";}}

import javax.persistence.CascadeType;
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.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.Table;@Entity
@Table(name = "cst_linkman")
public class LinkMan {@Id@Column(name = "lkm_id")@GeneratedValue(strategy = GenerationType.IDENTITY)private Long lkm_id;// '联系人编号(主键)',@Column(name = "lkm_name")private String lkm_name;// '联系人姓名',@Column(name = "lkm_gender")private String lkm_gender;// '联系人性别',@Column(name = "lkm_phone")private String lkm_phone;// '联系人办公电话',@Column(name = "lkm_mobile")private String lkm_mobile;// '联系人手机',@Column(name = "lkm_email")private String lkm_email;// '联系人邮箱',@Column(name = "lkm_qq")private String lkm_qq;// '联系人qq',@Column(name = "lkm_position")private String lkm_position;// '联系人职位',@Column(name = "lkm_memo")private String lkm_memo;// '联系人备注',@ManyToOne(targetEntity=Customer.class,cascade=CascadeType.PERSIST)@JoinColumn(name="lkm_cust_id",referencedColumnName="cust_id")private Customer customer;public Long getLkm_id() {return lkm_id;}public void setLkm_id(Long lkm_id) {this.lkm_id = lkm_id;}public String getLkm_name() {return lkm_name;}public void setLkm_name(String lkm_name) {this.lkm_name = lkm_name;}public String getLkm_gender() {return lkm_gender;}public void setLkm_gender(String lkm_gender) {this.lkm_gender = lkm_gender;}public String getLkm_phone() {return lkm_phone;}public void setLkm_phone(String lkm_phone) {this.lkm_phone = lkm_phone;}public String getLkm_mobile() {return lkm_mobile;}public void setLkm_mobile(String lkm_mobile) {this.lkm_mobile = lkm_mobile;}public String getLkm_email() {return lkm_email;}public void setLkm_email(String lkm_email) {this.lkm_email = lkm_email;}public String getLkm_qq() {return lkm_qq;}public void setLkm_qq(String lkm_qq) {this.lkm_qq = lkm_qq;}public String getLkm_position() {return lkm_position;}public void setLkm_position(String lkm_position) {this.lkm_position = lkm_position;}public String getLkm_memo() {return lkm_memo;}public void setLkm_memo(String lkm_memo) {this.lkm_memo = lkm_memo;}public Customer getCustomer() {return customer;}public void setCustomer(Customer customer) {this.customer = customer;}}

 

import static org.junit.Assert.*;import javax.persistence.EntityManager;
import javax.persistence.EntityTransaction;import org.junit.Test;import com.itheima.domain.Customer;
import com.itheima.domain.LinkMan;
import com.itheima.utils.JPAUtils;public class Demo02 {/*** @MethodName:test01* @Description:级联保存,保存联系人的时候,保存客户* @throws Exception*/@Testpublic void test01() throws Exception {EntityManager manger = JPAUtils.getEntityManager();EntityTransaction tx = manger.getTransaction();tx.begin();Customer c1 = new Customer();c1.setCust_name("张三");LinkMan l1 = new LinkMan();l1.setLkm_name("tom01");LinkMan l2 = new LinkMan();l2.setLkm_name("tom02");l1.setCustomer(c1);l2.setCustomer(c1);manger.persist(l1);manger.persist(l2);tx.commit();manger.close();}/*** @MethodName:test02* @Description:级联删除,删除用户时,删除关联的联系人* @throws Exception*/@Testpublic void test02() throws Exception {EntityManager manger = JPAUtils.getEntityManager();EntityTransaction tx = manger.getTransaction();tx.begin();Customer customer = manger.find(Customer.class, 2l);manger.remove(customer);tx.commit();manger.close();}}