在一对多关系中,我们习惯把一的一方称之为主表,把多的一方称之为从表。在数据库中建立一对多的关系,需要使用数据库的外键约束。
什么是外键?
指的是从表中有一列,取值参照主表的主键,这一列就是外键。
package com.ytkj.entity; import javax.persistence.*; import java.io.Serializable; import java.util.ArrayList; import java.util.List; /** * @Entity * 作用:指定当前类是实体类。 * @Table * 作用:指定实体类和表之间的对应关系。 * 属性: * name:指定数据库表的名称 * @Id * 作用:指定当前字段是主键。 * @GeneratedValue * 作用:指定主键的生成方式。。 * 属性: * strategy :指定主键生成策略。 * @Column * 作用:指定实体类属性和数据库表之间的对应关系 * 属性: * name:指定数据库表的列名称。 * unique:是否唯一 * nullable:是否可以为空 * inserttable:是否可以插入 * updateable:是否可以更新 * columnDefinition: 定义建表时创建此列的DDL * secondaryTable: 从表名。如果此列不建在主表上(默认建在主表),该属性定义该列所在从表的名字搭建开发环境[重点] * @OneToMany: * 作用:建立一对多的关系映射 * 属性: * targetEntityClass:指定多的多方的类的字节码 * mappedBy:指定从表实体类中引用主表对象的名称。 * 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:用于定义主键字段和外键字段的对应关系。 * 属性: * name:指定外键字段的名称 * 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。 * * cascade:配置级联操作 * CascadeType.MERGE 级联更新 * CascadeType.PERSIST 级联保存: * CascadeType.REFRESH 级联刷新: * CascadeType.REMOVE 级联删除: * CascadeType.ALL 包含所有 * * 客户实体类 * 配置映射关系 * 实体类和表映射 * 实体类属性和表字段映射 */ @Entity @Table(name = "cst_customer") public class Customer implements Serializable { /** * 声明主键配置 */ @Id /** * 配置主键的生成策略 */ @GeneratedValue(strategy = GenerationType.IDENTITY) /** * 指定实体类属性和数据库表之间的对应关系 */ @Column(name ="cust_id") private Long custId;//客户主键 @Column(name = "cust_name") private String custName;//客户名称 @Column(name ="cust_source" ) private String custSource;//客户来源 @Column(name = "cust_industry") private String custIndustry;//客户行业 @Column(name ="cust_level") private String custLevel;//客户级别 @Column(name ="cust_address") private String custAddress;//客户地址 @Column(name = "cust_phone") private String custPhone;//客户电话 //配置客户和联系人的关系(一个客户有多个联系人,一对多) /** * 使用注解的形式配置多表关系 * 1.声明关系 * @OneToMany :配置一对多 * targetEntity:对方对象的字节码对象 * 2.使用外键 * @JoinColumn * name:外键字段名称 * referencedColumnName:参照的主表的主键字段名称 * 在主表客户实体类上(一的乙方)添加了外键的配置,所以对于客户而言,也具备了维护外键 * * cascade:配置级联操作 * CascadeType.MERGE 级联更新 * CascadeType.PERSIST 级联保存: * CascadeType.REFRESH 级联刷新: * CascadeType.REMOVE 级联删除: * CascadeType.ALL 包含所有 */ @OneToMany(targetEntity =LinkMan.class,cascade = CascadeType.ALL) @JoinColumn(name = "lkm_cust_id",referencedColumnName = "cust_id") private List<LinkMan> linkMans=new ArrayList<>(); public Long getCustId() { return custId; } public void setCustId(Long custId) { this.custId = custId; } public String getCustName() { return custName; } public void setCustName(String custName) { this.custName = custName; } public String getCustSource() { return custSource; } public void setCustSource(String custSource) { this.custSource = custSource; } public String getCustIndustry() { return custIndustry; } public void setCustIndustry(String custIndustry) { this.custIndustry = custIndustry; } public String getCustLevel() { return custLevel; } public void setCustLevel(String custLevel) { this.custLevel = custLevel; } public String getCustAddress() { return custAddress; } public void setCustAddress(String custAddress) { this.custAddress = custAddress; } public String getCustPhone() { return custPhone; } public void setCustPhone(String custPhone) { this.custPhone = custPhone; } public List<LinkMan> getLinkMans() { return linkMans; } public void setLinkMans(List<LinkMan> linkMans) { this.linkMans = linkMans; } @Override public String toString() { return "Customer{" + "custId=" + custId + ", custName=‘" + custName + ‘\‘‘ + ", custSource=‘" + custSource + ‘\‘‘ + ", custIndustry=‘" + custIndustry + ‘\‘‘ + ", custLevel=‘" + custLevel + ‘\‘‘ + ", custAddress=‘" + custAddress + ‘\‘‘ + ", custPhone=‘" + custPhone + ‘\‘‘ + ‘}‘; } }
package com.ytkj.entity; import javax.persistence.*; import java.io.Serializable; /** * 联系人实体类 */ @Entity @Table(name = "cst_linkman") public class LinkMan implements Serializable { /** * 主键 */ @Id @GeneratedValue(strategy= GenerationType.IDENTITY) @Column(name="lkm_id") private Long lkmId; @Column(name="lkm_name") private String lkmName; @Column(name="lkm_gender") private String lkmGender; @Column(name="lkm_phone") private String lkmPhone; @Column(name="lkm_mobile") private String lkmMobile; @Column(name="lkm_email") private String lkmEmail; @Column(name="lkm_position") private String lkmPosition; @Column(name="lkm_memo") private String lkmMemo; /** * 配置联系人到客户的多对一的关系 * 1.配置表关系 * @ManyToOne * 配置多对一关系 * targetEntity:对方实体类字节码 * 2.配置外键 * name:外键字段名称 * referencedColumnName:参照的主表的主键字段名称 * @return */ @ManyToOne(targetEntity = Customer.class) @JoinColumn(name = "lkm_cust_id",referencedColumnName = "cust_id") private Customer customer; public Long getLkmId() { return lkmId; } public void setLkmId(Long lkmId) { this.lkmId = lkmId; } public String getLkmName() { return lkmName; } public void setLkmName(String lkmName) { this.lkmName = lkmName; } public String getLkmGender() { return lkmGender; } public void setLkmGender(String lkmGender) { this.lkmGender = lkmGender; } public String getLkmPhone() { return lkmPhone; } public void setLkmPhone(String lkmPhone) { this.lkmPhone = lkmPhone; } public String getLkmMobile() { return lkmMobile; } public void setLkmMobile(String lkmMobile) { this.lkmMobile = lkmMobile; } public String getLkmEmail() { return lkmEmail; } public void setLkmEmail(String lkmEmail) { this.lkmEmail = lkmEmail; } public String getLkmPosition() { return lkmPosition; } public void setLkmPosition(String lkmPosition) { this.lkmPosition = lkmPosition; } public String getLkmMemo() { return lkmMemo; } public void setLkmMemo(String lkmMemo) { this.lkmMemo = lkmMemo; } public Customer getCustomer() { return customer; } public void setCustomer(Customer customer) { this.customer = customer; } @Override public String toString() { return "LinkMan{" + "lkmId=" + lkmId + ", lkmName=‘" + lkmName + ‘\‘‘ + ", lkmGender=‘" + lkmGender + ‘\‘‘ + ", lkmPhone=‘" + lkmPhone + ‘\‘‘ + ", lkmMobile=‘" + lkmMobile + ‘\‘‘ + ", lkmEmail=‘" + lkmEmail + ‘\‘‘ + ", lkmPosition=‘" + lkmPosition + ‘\‘‘ + ", lkmMemo=‘" + lkmMemo + ‘\‘‘ + ‘}‘; } }
package com.ytkj.dao; import com.ytkj.entity.Customer; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.JpaSpecificationExecutor; import org.springframework.data.jpa.repository.Modifying; import org.springframework.data.jpa.repository.Query; /** * JpaRepository<实体类类型,主键类型>:用来完成基本CRUD操作 * JpaSpecificationExecutor<实体类类型>:用于复杂查询(分页等查询操作) */ public interface CustomerDao extends JpaRepository<Customer,Long>, JpaSpecificationExecutor<Customer> { }
package com.ytkj.dao; import com.ytkj.entity.LinkMan; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.jpa.repository.JpaSpecificationExecutor; public interface LinkManDao extends JpaRepository<LinkMan,Integer>, JpaSpecificationExecutor<LinkMan> { }
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:context="http://www.springframework.org/schema/context" xmlns:jdbc="http://www.springframework.org/schema/jdbc" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:jpa="http://www.springframework.org/schema/data/jpa" xmlns:task="http://www.springframework.org/schema/task" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd http://www.springframework.org/schema/jdbc http://www.springframework.org/schema/jdbc/spring-jdbc.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx.xsd http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa.xsd"> <!--spring和spring-data-jpa的整合--> <!--1.创建entityManagerFactory对象交给spring管理--> <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> <!--数据库注入--> <property name="dataSource" ref="dataSource"/> <!--配置包的扫描--> <property name="packagesToScan" value="com.ytkj.entity"/> <!--jpa实现厂家--> <property name="persistenceProvider"> <bean class="org.hibernate.jpa.HibernatePersistenceProvider"></bean> </property> <!--JPA的供应商适配器--> <property name="jpaVendorAdapter"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> <!--配置是否自动创建数据库表--> <property name="generateDdl" value="false" /> <!--指定数据库类型--> <property name="database" value="MYSQL" /> <!--数据库方言:支持的特有语法--> <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect" /> <!--是否显示sql语句--> <property name="showSql" value="true" /> </bean> </property> <!--jpa方言:高级特性--> <property name="jpaDialect"> <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" /> </property> </bean> <!--2.创建数据连接池--> <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource"> <!--数据库信息--> <property name="driverClass" value="com.mysql.jdbc.Driver"/> <property name="jdbcUrl" value="jdbc:mysql://192.168.2.101:3306/ytkj?serverTimeZone=UTC"/> <property name="user" value="root"/> <property name="password" value="123456"/> </bean> <!--3.整合spring-data-jpa--> <jpa:repositories base-package="com.ytkj.dao" transaction-manager-ref="transacManager" entity-manager-factory-ref="entityManagerFactory"></jpa:repositories> <!--4.配置事务管理器--> <bean id="transacManager" class="org.springframework.orm.jpa.JpaTransactionManager"> <property name="entityManagerFactory" ref="entityManagerFactory" /> </bean> <!--5.声明式事务--> <tx:advice id="txAdvice" transaction-manager="transacManager"> <tx:attributes> <tx:method name="save*" propagation="REQUIRED"/> <tx:method name="insert*" propagation="REQUIRED"/> <tx:method name="update*" propagation="REQUIRED"/> <tx:method name="delete*" propagation="REQUIRED"/> <tx:method name="get*" read-only="true"/> <tx:method name="find*" read-only="true"/> <tx:method name="*" propagation="REQUIRED"/> </tx:attributes> </tx:advice> <!-- 5.aop--> <aop:config> <aop:pointcut id="pointcut" expression="execution(* com.ytkj.service.*.*(..))" /> <aop:advisor advice-ref="txAdvice" pointcut-ref="pointcut" /> </aop:config> <context:component-scan base-package="com.ytkj"/> </beans>
import com.ytkj.dao.CustomerDao; import com.ytkj.dao.LinkManDao; import com.ytkj.entity.Customer; import com.ytkj.entity.LinkMan; import org.junit.Test; import org.junit.runner.RunWith; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.test.annotation.Rollback; import org.springframework.test.context.ContextConfiguration; import org.springframework.test.context.junit4.SpringJUnit4ClassRunner; import org.springframework.transaction.annotation.Transactional; /** * 一对多测试 保存/删除操作 */ @RunWith(SpringJUnit4ClassRunner.class)//声明spring提供的单元测试环境 @ContextConfiguration(locations = "classpath:applicationContext.xml")//指定spring容器的配置信息 public class SpringdatajpaOneToManyTest { @Autowired CustomerDao customerDao; @Autowired LinkManDao linkManDao; /** * 保存操作 * 需求: * 保存一个客户和一个联系人 * 要求: * 创建一个客户对象和一个联系人对象 * 建立客户和联系人之间关联关系(双向一对多的关联关系) * 先保存客户,再保存联系人 * 问题: * 当我们建立了双向的关联关系之后,先保存主表,再保存从表时: * 会产生2条insert和1条update. * 而实际开发中我们只需要2条insert。 * */ @Test @Transactional//添加事务 @Rollback(value = false)//设置不自动回滚 public void test(){ //创建客户联系人 Customer customer=new Customer(); customer.setCustName("丁丁"); LinkMan linkMan=new LinkMan(); linkMan.setLkmName("芳芳"); /** * 配置客户到联系人关系(一对多) */ customer.getLinkMans().add(linkMan); customerDao.save(customer); linkManDao.save(linkMan); } @Test @Transactional//添加事务 @Rollback(value = false)//设置不自动回滚 public void test2(){ //创建客户联系人 Customer customer=new Customer(); customer.setCustName("丁丁1"); LinkMan linkMan=new LinkMan(); linkMan.setLkmName("芳芳1"); /** * 配置联系人到客户关系(多对一) */ linkMan.setCustomer(customer); customerDao.save(customer); linkManDao.save(linkMan); } @Test @Transactional//添加事务 @Rollback(value = false)//设置不自动回滚 public void test3(){ //创建客户联系人 Customer customer=new Customer(); customer.setCustName("丁丁3"); LinkMan linkMan=new LinkMan(); linkMan.setLkmName("芳芳3"); /** * 配置客户到联系人关系(一对多) */ customer.getLinkMans().add(linkMan); /** * 配置联系人到客户关系(多对一) */ linkMan.setCustomer(customer); customerDao.save(customer); linkManDao.save(linkMan); } /** * 级联添加 * 需要在操作主题实体类上添加cascade属性 */ @Test @Transactional//添加事务 @Rollback(value = false)//设置不自动回滚 public void test4(){ //创建客户联系人 Customer customer=new Customer(); customer.setCustName("丁丁4"); LinkMan linkMan=new LinkMan(); linkMan.setLkmName("芳芳4"); /** * 配置客户到联系人关系(一对多) */ customer.getLinkMans().add(linkMan); /** * 配置联系人到客户关系(多对一) */ linkMan.setCustomer(customer); customerDao.save(customer); } /** * 级联删除 * 需要在操作主题实体类上添加cascade属性 */ @Test @Transactional//添加事务 @Rollback(value = false)//设置不自动回滚 public void test5(){ //查询1号客户 Customer customer = customerDao.findOne(1l); //删除1号客户 customerDao.delete(customer); } }
<?xml version="1.0" encoding="UTF-8"?> <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.ytkj</groupId> <artifactId>springdatajpa</artifactId> <version>1.0-SNAPSHOT</version> <properties> <spring.version>5.1.7.RELEASE</spring.version> <hibernate.version>5.0.7.Final</hibernate.version> <slf4j.version>1.6.6</slf4j.version> <log4j.version>1.2.12</log4j.version> <c3p0.version>0.9.1.2</c3p0.version> <mysql.version>5.1.6</mysql.version> </properties> <dependencies> <!-- junit单元测试 --> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.9</version> <scope>test</scope> </dependency> <!-- spring beg --> <dependency> <groupId>org.aspectj</groupId> <artifactId>aspectjweaver</artifactId> <version>1.6.8</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aop</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-context-support</artifactId> <version>${spring.version}</version> </dependency> <!--spring对orm框架支持--> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-orm</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency> <!-- spring end --> <!-- hibernate beg --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>${hibernate.version}</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-entitymanager</artifactId> <version>${hibernate.version}</version> </dependency> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-validator</artifactId> <version>5.2.1.Final</version> </dependency> <!-- hibernate end --> <!-- c3p0 beg --> <dependency> <groupId>c3p0</groupId> <artifactId>c3p0</artifactId> <version>${c3p0.version}</version> </dependency> <!-- c3p0 end --> <!-- log end --> <dependency> <groupId>log4j</groupId> <artifactId>log4j</artifactId> <version>${log4j.version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-api</artifactId> <version>${slf4j.version}</version> </dependency> <dependency> <groupId>org.slf4j</groupId> <artifactId>slf4j-log4j12</artifactId> <version>${slf4j.version}</version> </dependency> <!-- log end --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>${mysql.version}</version> </dependency> <!--sprngdatajpa依赖--> <dependency> <groupId>org.springframework.data</groupId> <artifactId>spring-data-jpa</artifactId> <version>1.9.0.RELEASE</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>4.2.4.RELEASE</version> </dependency> <!-- el beg 使用spring data jpa 必须引入 --> <dependency> <groupId>javax.el</groupId> <artifactId>javax.el-api</artifactId> <version>2.2.4</version> </dependency> <dependency> <groupId>org.glassfish.web</groupId> <artifactId>javax.el</artifactId> <version>2.2.4</version> </dependency> <!-- el end --> </dependencies> </project>
原文地址:https://www.cnblogs.com/yscec/p/12008156.html
时间: 2024-11-07 17:09:58