标签:code serial bsp ble cep 项目 数据表 组合 system
一、对象信息 转换为 关系信息(数据表)
1、使用SchemaExport生成关系
package com.project.test; import org.hibernate.Session; import org.hibernate.Transaction; import org.hibernate.cfg.Configuration; import org.hibernate.tool.hbm2ddl.SchemaExport; import org.junit.After; import org.junit.Before; import org.junit.Test; import com.project.pojo.User; import com.project.util.HibernateUtil; public class HibernateTest { Session session = null; Transaction beginTransaction = null; @Before public void setUp(){ session = HibernateUtil.getSession(); beginTransaction = session.beginTransaction(); } @After public void tearDown(){ HibernateUtil.closeSession(); } @Test public void testSelect(){ User u = (User) session.get(User.class, 1); System.out.println(u); } @Test public void testCreateDB(){ Configuration cfg = new Configuration().configure(); //使得hibernate映射信息转换为数据库识别的dll语言 SchemaExport se = new SchemaExport(cfg); //第一个参数:是否打印ddl语句 //第二个参数:是否将ddl到数据库中执行 se.create(true, true); } }
2、hibernate.cxf.xml 通用配置 hbm2ddl
<!-- hbm2ddl.auto 该属性用于配置是否将映射信息转换为ddl create 每次执行都会先删除后再创建表,用于测试 update 检查数据库表是否存在,如果不存在则先创建表,项目中通常上线使用 --> <property name="hbm2ddl.auto">create</property>
二、关联关系:多对一
多 对 1
student(学生)——》classes(班级)
1、classes类
package com.project.pojo; import java.io.Serializable; public class Classes implements Serializable{ private int id; private String name; private String address; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getAddress() { return address; } public void setAddress(String address) { this.address = address; } }
2、学生类
package com.project.pojo; import java.io.Serializable; public class Student implements Serializable{ private int id; private String name; private int age; private Classes classes; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public int getAge() { return age; } public void setAge(int age) { this.age = age; } public Classes getClasses() { return classes; } public void setClasses(Classes classes) { this.classes = classes; } }
3、Classes.hbm2.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <hibernate-mapping package="com.project.pojo"> <class name="Classes" table="t_class"> <id name="id" column="id" type="int"> <generator class="native"></generator> </id> <property name="name" /> <property name="address" /> </class> </hibernate-mapping>
4、Student.hbm2.xml
<?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd"> <!-- package指定类所在的包,如果不指定,那么在指定class的name时,需要指定完全限定名 --> <hibernate-mapping package="com.project.pojo"> <class name="Student" table="t_student"> <id name="id"> <generator class="native"></generator> </id> <property name="name" /> <property name="age" /> <many-to-one name="classes" column="classes_id" /> </class> </hibernate-mapping>
5、hibernate.cfg.xml
<mapping resource="com/project/pojo/Classes.hbm2.xml" /> <mapping resource="com/project/pojo/Student.hbm2.xml" />
6、测试
@Test public void testSave(){ try { Classes c1 = new Classes(); c1.setName("一年级"); c1.setAddress("B-1栋"); Classes c2 = new Classes(); c2.setName("二年级"); c2.setAddress("B-2栋"); session.save(c1); session.save(c2); Student s1 = new Student(); s1.setName("张三"); s1.setAge(20); s1.setClasses(c1); Student s2 = new Student(); s2.setName("李四"); s2.setAge(21); s2.setClasses(c2); Student s3 = new Student(); s3.setName("哈哈狗"); s3.setAge(19); s3.setClasses(c1); session.save(s1); session.save(s2); session.save(s3); ts.commit(); } catch (Exception e) { e.printStackTrace(); if(ts!=null) ts.rollback(); } }
类与类关系:依赖——》关联——》聚合——》组合 根据箭头类与类关系强度越来越高
标签:code serial bsp ble cep 项目 数据表 组合 system
原文地址:https://www.cnblogs.com/chai-blogs/p/12927279.html