Spring Data Jpa 多表之间的关系和操作多表的步骤(一对多)

Spring Data Jpa 多表之间的关系和操作多表的步骤

表关系

  1. 一对一
  2. 一对多:
    一的一方:主表
    多的一方:从表
    外键:需要再从表上新建一列作为外键,他的取值来源于主表的主键
  3. 多对多
    中间表:中间表中最少应该由两个字段组成,这两个字段做为外键指向两张表的主键,又组成了联合主键

实体类中的关系
4. 包含关系:可以通过实体类中的包含关系描述表关系
5. 继承关系

分析步骤
6. 明确表关系
7. 确定表关系(描述 外键 | 中间表)
8. 编写实体类,再实体类中描述表关系(包含关系)
9. 配置映射关系

完成多表操作

1.一对多操作
案例:客户和联系人案例(一对多关系)
客户:一家公司
联系人:这家公司员工
(一个客户可以具有多个联系人)
(一个联系人从属于一家公司)

分析步骤
(1) 明确表关系:
(一对多关系)
(2) 确定表关系(描述 外键 | 中间表)
主表:客户表
从表:联系人表(在从表添加外键)
(3) 编写实体类,再实体类中描述表关系(包含关系)
客户:在客户的实体类中包含一个联系人的集合
联系人: 在联系人的实体类中包含一个客户的对象
(4) 配置映射关系
使用jpa注解配置一对多映射关系

级联:
操作一个对象的同时操作他的关联对象

级联操作:

  1. 需要区分操作主题
  2. 需要在操作主题的实体类上,添加级联属性(需要添加到多表映射关系的注释上)
  3. cascada(配置级联)

级联添加:
案例:当我保存一个客户的同时保存联系人

级联删除:
案例:当我删除一个客户的同时删除此客户的所有联系人

目录信息:
Spring Data Jpa 多表之间的关系和操作多表的步骤(一对多)_第1张图片
pom文件内容

<?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>cn.itcast</groupId>
    <artifactId>jpa-day03-onetomany</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <spring.version>4.2.4.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框架的支持包   -->
        <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>

        <!--    Spring data jpa 坐标    -->
        <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>${
     spring.version}</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>

CustomerDao接口

package cn.itcast.dao;

import cn.itcast.domain.Customer;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.stereotype.Repository;

/**
 * @author JiangDong
 * @date 2020/7/16 - 10:45
 */
public interface CustomerDao extends JpaRepository<Customer,Long>, JpaSpecificationExecutor<Customer> {
     
}

LinkManDao接口

package cn.itcast.dao;

import cn.itcast.domain.LinkMan;
import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;


/**
 * @author JiangDong
 * @date 2020/7/17 - 11:43
 */

public interface LinkManDao extends JpaRepository<LinkMan,Long>, JpaSpecificationExecutor<LinkMan> {
     
}

Customer实体类

package cn.itcast.domain;

/**
 * @author JiangDong
 * @date 2020/7/12 - 22:43
 */

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

/**
 * 1. 实体类和表的映射关系
 *  @Entity
 *  @Table
 * 2. 类中属性和表中字段的对应关系
 *  @Id
 *  @GeneratedValue
 *  @Column
 */
@Entity
@Table(name ="cst_customer")
public class Customer {
     
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @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;// 客户级别

    @Column(name = "cust_level")
    private String custLevel;  // 客户所属类别

    @Column(name = "cust_address")
    private String custAddress; // 客户的联系方式

    @Column(name = "cust_phone")
    private String custPhone; // 客户地址

    // 配置客户和联系人之间的关系(一对多关系)
    /**
     * 使用注解形式配置多表关系
     *  1.声明关系
     *       @OneToMany :配置一对多关系
     *          targetEntity : 对方对象的字节码
     *  2.配置外键(中间表)
     *  @JoinColumn : 配置外键
     *      name : 外键字段名称
     *      referencedColumnName:参照的主表的主键字段名称
     *
     *  在客户实体类中(主表一方)配置了外键配置,所以对于客户而言,也具备了维护外键的作用
     */
    @OneToMany(targetEntity = LinkMan.class)
    @JoinColumn(name = "lkm_cust_id",referencedColumnName = "cust_id")
    private Set<LinkMan> linkMans = new HashSet<LinkMan>();

    public Set<LinkMan> getLinkMans() {
     
        return linkMans;
    }

    public void setLinkMans(Set<LinkMan> linkMans) {
     
        this.linkMans = linkMans;
    }

    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;
    }

    @Override
    public String toString() {
     
        return "Customer{" +
                "custId=" + custId +
                ", custName='" + custName + '\'' +
                ", custSource='" + custSource + '\'' +
                ", custIndustry='" + custIndustry + '\'' +
                ", custLevel='" + custLevel + '\'' +
                ", custAddress='" + custAddress + '\'' +
                ", custPhone='" + custPhone + '\'' +
                '}';
    }
}

LinkMan实体类

package cn.itcast.domain;

import javax.persistence.*;

@Entity
@Table(name = "cst_linkman")
public class LinkMan {
     

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "lkm_id")
    private Long lkmId; //联系人编号(主键)
    @Column(name = "lkm_name")
    private String lkmName;//联系人姓名
    @Column(name = "lkm_gender")
    private String lkmGender;//联系人性别
    @Column(name = "lkm_phone")
    private String lkmPhone;//联系人办公电话
    @Column(name = "lkm_mobile")
    private String lkmMobile;//联系人手机
    @Column(name = "lkm_email")
    private String lkmEmail;//联系人邮箱
    @Column(name = "lkm_position")
    private String lkmPosition;//联系人职位
    @Column(name = "lkm_memo")
    private String lkmMemo;//联系人备注

    /**
     * 配置联系人到客户的多对一关系
     *     使用注解的形式配置多对一关系
     *      1.配置表关系
     *          @ManyToOne : 配置多对一关系
     *              targetEntity:对方的实体类字节码
     *      2.配置外键(中间表)
     *
     * * 配置外键的过程,配置到了多的一方,就会在多的一方维护外键
     *
     */
    @ManyToOne(targetEntity = Customer.class,fetch = FetchType.LAZY)
    @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 + '\'' +
                '}';
    }
}

applicationContext.xml配置文件

<?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 的配置-->
    <!--1. 创建entityManagerFactory对象交给Spring容器管理    -->
    <bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">

        <property name="dataSource" ref="dataSource" />
        <!--配置的扫描的包(实体类所在的包) -->
        <property name="packagesToScan" value="cn.itcast.domain" />
        <!-- jpa的实现厂家 -->
        <property name="persistenceProvider">
            <bean class="org.hibernate.jpa.HibernatePersistenceProvider"/>
        </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 -->
                <property name="showSql" value="true" />
            </bean>
        </property>

        <!--jpa的方言 :高级的特性 -->
        <property name="jpaDialect" >
            <bean class="org.springframework.orm.jpa.vendor.HibernateJpaDialect" />
        </property>


        <!--
            注入jpa的配置信息
            加载jpa的基本配置信息和jpa实现方式(hibernate)的配置信息
            hibernate.hbm2ddl.auto  : 自动创建数据库表
        -->
        <property name="jpaProperties">
            <props>
                <prop key="hibernate.hbm2ddl.auto">create</prop>
            </props>
        </property>

    </bean>

    <!--2. 创建数据库连接池    -->
    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
        <property name="user" value="root"/>
        <property name="password" value=""/>
        <property name="jdbcUrl" value="jdbc:mysql://localhost:3308/itheima_spring_data_jpa"/>
        <property name="driverClass" value="com.mysql.jdbc.Driver"/>
    </bean>

    <!--3.整合spring data jpa    -->
    <jpa:repositories base-package="cn.itcast.dao" transaction-manager-ref="transactionManager" entity-manager-factory-ref="entityManagerFactory">
    </jpa:repositories>

    <!--4.配置事务管理器    -->
    <bean id="transactionManager" class="org.springframework.orm.jpa.JpaTransactionManager">
        <property name="entityManagerFactory" ref="entityManagerFactory"/>
    </bean>

    <!--5.声明式事务    -->

    <!--6.配置包扫描    -->
    <context:component-scan base-package="cn.itcast"/>
</beans>

测试类

package cn.itcast.test;

import cn.itcast.dao.CustomerDao;
import cn.itcast.dao.LinkManDao;
import cn.itcast.domain.Customer;
import cn.itcast.domain.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;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = "classpath*:applicationContext.xml")
public class OneToManyTest {
     

    @Autowired
    private CustomerDao customerDao;

    @Autowired
    private LinkManDao linkManDao;

    /**
     * 保存一个客户,保存一个联系人
     *  效果:客户和联系人作为独立的数据保存到数据库中
     *      联系人的外键为空
     *  原因?
     *      实体类中没有配置关系
     */
    @Test
    @Transactional //配置事务
    @Rollback(false) //不自动回滚
    public void testAdd() {
     
        //创建一个客户,创建一个联系人
        Customer customer = new Customer();
        customer.setCustName("百度");

        LinkMan linkMan = new LinkMan();
        linkMan.setLkmName("小李");

        /**
         * 配置了客户到联系人的关系
         *      从客户的角度上:发送两条insert语句,发送一条更新语句更新数据库(更新外键)
         * 由于我们配置了客户到联系人的关系:客户可以对外键进行维护
         */
        customer.getLinkMans().add(linkMan);

        customerDao.save(customer);
        linkManDao.save(linkMan);
    }


    @Test
    @Transactional //配置事务
    @Rollback(false) //不自动回滚
    public void testAdd1() {
     
        //创建一个客户,创建一个联系人
        Customer customer = new Customer();
        customer.setCustName("百度");

        LinkMan linkMan = new LinkMan();
        linkMan.setLkmName("小李");

        /**
         * 配置联系人到客户的关系(多对一)
         *    只发送了两条insert语句
         * 由于配置了联系人到客户的映射关系(多对一)
         *
         *
         */
        linkMan.setCustomer(customer);

        customerDao.save(customer);
        linkManDao.save(linkMan);
    }

    /**
     * 会有一条多余的update语句
     *      * 由于一的一方可以维护外键:会发送update语句
     *      * 解决此问题:只需要在一的一方放弃维护权即可
     *
     */
    @Test
    @Transactional //配置事务
    @Rollback(false) //不自动回滚
    public void testAdd2() {
     
        //创建一个客户,创建一个联系人
        Customer customer = new Customer();
        customer.setCustName("百度");

        LinkMan linkMan = new LinkMan();
        linkMan.setLkmName("小李");


        linkMan.setCustomer(customer);//由于配置了多的一方到一的一方的关联关系(当保存的时候,就已经对外键赋值)
        customer.getLinkMans().add(linkMan);//由于配置了一的一方到多的一方的关联关系(发送一条update语句)

        customerDao.save(customer);
        linkManDao.save(linkMan);
    }

    /**
     * 级联添加:保存一个客户的同时,保存客户的所有联系人
     *      需要在操作主体的实体类上,配置casacde属性
     */
    @Test
    @Transactional //配置事务
    @Rollback(false) //不自动回滚
    public void testCascadeAdd() {
     
        Customer customer = new Customer();
        customer.setCustName("百度1");

        LinkMan linkMan = new LinkMan();
        linkMan.setLkmName("小李1");

        linkMan.setCustomer(customer);
        customer.getLinkMans().add(linkMan);

        customerDao.save(customer);
    }


    /**
     * 级联删除:
     *      删除1号客户的同时,删除1号客户的所有联系人
     */
    @Test
    @Transactional //配置事务
    @Rollback(false) //不自动回滚
    public void testCascadeRemove() {
     
        //1.查询1号客户
        Customer customer = customerDao.findOne(1l);
        //2.删除1号客户
        customerDao.delete(customer);
    }
}

项目开发的六个阶段:1. 充满热情 2. 醒悟 3. 痛苦 4. 找出罪魁祸首 5. 惩罚无辜 6. 褒奖闲人

你是否也有自己喜欢的名言,欢迎分享。

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