IDEA+MAVEN 實現hiberate 一對一，一對多，多對多 操作（程式碼筆記）
阿新 • • 發佈：2018-12-17
直接上步驟：
1.修改pom.xml,新增hibernate相關包
<?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.htt.hibernate</groupId> <artifactId>Hibernate_Test</artifactId> <version>1.0-SNAPSHOT</version> <dependencies> <!-- https://mvnrepository.com/artifact/org.hibernate/hibernate-core --> <dependency> <groupId>org.hibernate</groupId> <artifactId>hibernate-core</artifactId> <version>5.3.6.Final</version> </dependency> <!-- https://mvnrepository.com/artifact/mysql/mysql-connector-java --> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>8.0.12</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.0</version> </dependency> </dependencies> </project>
2.在resources裡面新增hibernate.cfg.xml，用於連線資料庫
<?xml version='1.0' encoding='utf-8'?> <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN" "http://www.hibernate.org/dtd/hibernate-configuration-3.0.dtd"> <hibernate-configuration> <session-factory> <!-- Database connection settings --> <property name="connection.driver_class">com.mysql.jdbc.Driver</property> <property name="connection.url">jdbc:mysql://localhost:3306/javaweb?serverTimezone=UTC</property> <property name="connection.username">...</property> <property name="connection.password">...</property> <!-- JDBC connection pool (use the built-in) --> <property name="connection.pool_size">1</property> <!-- SQL dialect --> <property name="dialect">org.hibernate.dialect.MySQLDialect</property> <!-- Enable Hibernate's automatic session context management --> <property name="current_session_context_class">thread</property> <!-- Echo all executed SQL to stdout --> <property name="show_sql">true</property> <!--指定對映檔案路徑--> <!--<mapping class="UserMod" />--> <mapping resource="Grade.hbm.xml"/> <mapping resource="Student.hbm.xml"/> </session-factory> </hibernate-configuration>
3.一對多(班級和和學生)(一對一可看成特殊的一對多)
3.1 建立班級和學生的對應持久化類(//在一方定義一個多方的集合),對於建構函式，根據測試類中的需求進行構造，不過無參建構函式和包含全部引數的建構函式最好都寫上
//Grade.java package com.entity; import java.io.Serializable; import java.util.HashSet; import java.util.Set; public class Grade implements Serializable{ private int gid; private String gname; private String gdesc; //一對多時，在一方定義一個多方的集合 private Set<Student> students = new HashSet<Student>(); public Set<Student> getStudents() { return students; } public void setStudents(Set<Student> students) { this.students = students; } public int getGid() { return gid; } public void setGid(int gid) { this.gid = gid; } public String getGname() { return gname; } public void setGname(String gname) { this.gname = gname; } public String getGdesc() { return gdesc; } public void setGdesc(String gdesc) { this.gdesc = gdesc; } public Grade() { } public Grade(int gid, String gname, String gdesc,Set<Student> students) { this.gid = gid; this.gname = gname; this.gdesc = gdesc; this.students = students; } public Grade(String gname, String gdesc) { this.gname = gname; this.gdesc = gdesc; } }
//Student.java
package com.entity;
import java.io.Serializable;
public class Student implements Serializable{
private int sid;
private String sname;
private String sex;
//多對一時，在多方定義一個一方的引用
private Grade grade;
public Grade getGrade() {
return grade;
}
public void setGrade(Grade grade) {
this.grade = grade;
}
public int getSid() {
return sid;
}
public void setSid(int sid) {
this.sid = sid;
}
public String getSname() {
return sname;
}
public void setSname(String sname) {
this.sname = sname;
}
public String getSex() {
return sex;
}
public void setSex(String sex) {
this.sex = sex;
}
public Student() {
}
public Student(String sname, String sex) {
this.sname = sname;
this.sex = sex;
}
}
3.2.建立Hibrnate對應的對映類
//HibernateUtils.java
package com.util;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
public class HibernateUtils {
// 1.建立工廠物件;
private static SessionFactory sessionFactory;
// 2.初始化工廠物件;
static {
sessionFactory = new Configuration().configure().buildSessionFactory();
}
//4.獲取sessionFactory
public static SessionFactory getSessionFactory(){
return sessionFactory;
}
// 3.獲得Session;
public static Session getSession() {
return sessionFactory.openSession();
}
//4.關閉session
public static void closeSession(Session session){
if (session!= null){
session.close();
}
}
}
3.3 3.建立持久化類對應的對映檔案
//Grade.hbm.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>
<class name="com.entity.Grade" table="grade">
<id name="gid" column="gid" type="java.lang.Integer">
<!--設定主鍵為自增模式-->
<generator class="increment"></generator>
</id>
<property name="gname" type="java.lang.String">
<column name="gname" length="20" not-null="true"></column>
</property>
<property name="gdesc">
<column name="gdesc"></column>
</property>
<!--配置單向的一對多關聯關係 , inverse為false表示由一方進行關聯關係的維護，設定為true表示由多方進行關聯關係的維護-->
<!--cascade代表級聯，設定為all代表對於所有操作都可以進行級聯操作。例，在班級表中新增一個班級後，該班級對應的所有學生也會新增到相應的資料庫中-->
<set name="students" table="student" inverse="false" cascade="all">
<key column="gid"></key>
<one-to-many class="com.entity.Student"/>
</set>
</class>
</hibernate-mapping>//Student.hbm.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>
<class name="com.entity.Student" table="student">
<id name="sid" column="sid" type="java.lang.Integer">
<!--設定主鍵為自增模式-->
<generator class="increment"></generator>
</id>
<property name="sname" type="java.lang.String">
<column name="sname" length="20" not-null="true"></column>
</property>
<property name="sex">
<column name="sex"></column>
</property>
<many-to-one name="grade" class="com.entity.Grade" column="gid"></many-to-one>
</class>
</hibernate-mapping>3.4 建立測試類測試
//test.java
package com.entity;
import com.util.HibernateUtils;
import org.hibernate.Session;
import org.hibernate.Transaction;
import java.util.Set;
/*單向一對多關係（班級--->學生）
* 建立關聯關係後，可以方便的從一個物件導航到另一個物件
* 當建立了雙向一對多關係後，既可以方便的由學生查詢到對應的班級資訊，也可以方便的由班級查詢到其所包含的學生資訊
* */
public class test {
public static void main(String[] args){
// add();
// findStudentsByGrade();
update();
}
//將學生新增到班級
public static void add(){
Grade g = new Grade("Java一班","Java軟體開發一班");
Student stu1 = new Student("張三","男");
Student stu2 = new Student("王蘭","女");
//如果希望在學生表中新增對應的班級編號，需要在班級中新增學生，建立關聯關係
g.getStudents().add(stu1);
g.getStudents().add(stu2);
Session session = HibernateUtils.getSession();
Transaction tx = session.beginTransaction();
session.save(g);
session.save(stu1);
session.save(stu2);
tx.commit();
HibernateUtils.closeSession(session);
}
//查詢班級中包含的學生
public static void findStudentsByGrade(){
Session session = HibernateUtils.getSession();
Grade grade = (Grade)session.get(Grade.class,1);
System.out.println(grade.getGname()+","+grade.getGdesc());
Set<Student> students = grade.getStudents();
for (Student stu:students){
System.out.println(stu.getSname()+","+stu.getSex());
}
}
//修改學生資訊
public static void update(){
Grade g = new Grade("Java二班","Java軟體開發二班");//新建一個班級
Session session = HibernateUtils.getSession();
Transaction tx = session.beginTransaction();
Student stu = (Student) session.get(Student.class,1);//獲取id為1的學生資訊，將他儲存起來
g.getStudents().add(stu);//在新建的班級中加入該學生
session.save(g);
tx.commit();
HibernateUtils.closeSession(session);
}
//刪除學生資訊
public static void delete(){
Session session = HibernateUtils.getSession();
Transaction tx = session.beginTransaction();
Student stu = (Student)session.get(Student.class,2);
session.delete(stu);
tx.commit();
HibernateUtils.closeSession(session);
}
}
4.多對多 與一對多類似，後面看情況再寫吧。。