使用XML的Hibernate多对多示例 Hibernate多对多|Hibernate

我们可以使用列表, 集合, 包, 地图等来映射多对多关系。在这里, 我们将使用列表进行多对多映射。在这种情况下, 将创建三个表。
多对多映射示例在此示例中, 我们将使用列表生成问题和答案之间的多对多关系。
1）创建持久性类
有两个持久性类Question.java和Answer.java。问题类包含答案类参考, 反之亦然。
Question.java

package com.srcmini; import java.util.List; public class Question { private int id; private String qname; private List< Answer> answers; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getQname() { return qname; } public void setQname(String qname) { this.qname = qname; } public List< Answer> getAnswers() { return answers; } public void setAnswers(List< Answer> answers) { this.answers = answers; } }

Answer.java

package com.srcmini; import java.util.*; public class Answer { private int id; private String answername; private String postedBy; private List< Question> questions; public int getId() { return id; } public void setId(int id) { this.id = id; } public String getAnswername() { return answername; } public void setAnswername(String answername) { this.answername = answername; } public String getPostedBy() { return postedBy; } public void setPostedBy(String postedBy) { this.postedBy = postedBy; } public List< Question> getQuestions() { return questions; } public void setQuestions(List< Question> questions) { this.questions = questions; } }

2）为持久化类创建Mapping文件
在这里, 我们创建了用来定义列表的question.hbm.xml和answer.hbm.xml文件。
question.hbm.xml

< ?xml version='1.0' encoding='UTF-8'?> < !DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 5.3//EN" "http://hibernate.sourceforge.net/hibernate-mapping-5.3.dtd"> < hibernate-mapping> < class name="com.srcmini.Question" table="ques1911"> < id name="id" type="int"> < column name="q_id" /> < generator class="increment" /> < /id> < property name="qname" /> < list name="answers" table="ques_ans1911" fetch="select" cascade="all"> < key column="q_id" /> < index column="type"> < /index> < many-to-many class="com.srcmini.Answer" column="ans_id" /> < /list> < /class> < /hibernate-mapping>

answer.hbm.xml

< ?xml version='1.0' encoding='UTF-8'?> < !DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 5.3//EN" "http://hibernate.sourceforge.net/hibernate-mapping-5.3.dtd"> < hibernate-mapping> < class name="com.srcmini.Answer" table="ans1911"> < id name="id" type="int"> < column name="ans_id" /> < generator class="increment" /> < /id> < property name="answername"/> < property name="postedBy" /> < /class> < /hibernate-mapping>

3）创建配置文件
该文件包含有关数据库和映射文件的信息。
hibernate.cfg.xml

< ?xml version='1.0' encoding='UTF-8'?> < !DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 5.3//EN" "http://hibernate.sourceforge.net/hibernate-configuration-5.3.dtd"> < hibernate-configuration> < session-factory> < property name="hbm2ddl.auto"> create< /property> < property name="dialect"> org.hibernate.dialect.Oracle9Dialect< /property> < property name="connection.url"> jdbc:oracle:thin:@localhost:1521:xe< /property> < property name="connection.username"> system< /property> < property name="connection.password"> jtp< /property> < property name="connection.driver_class"> oracle.jdbc.driver.OracleDriver< /property> < mapping resource="question.hbm.xml"/> < mapping resource="answer.hbm.xml"/> < /session-factory> < /hibernate-configuration>

4）创建类来存储数据
【使用XML的Hibernate多对多示例】StoreData.java

package com.srcmini; import java.util.ArrayList; import org.hibernate.*; import org.hibernate.boot.Metadata; import org.hibernate.boot.MetadataSources; import org.hibernate.boot.registry.StandardServiceRegistry; import org.hibernate.boot.registry.StandardServiceRegistryBuilder; public class StoreData { public static void main(String[] args) { StandardServiceRegistry ssr=new StandardServiceRegistryBuilder().configure("hibernate.cfg.xml").build(); Metadata meta=new MetadataSources(ssr).getMetadataBuilder().build(); SessionFactory factory=meta.getSessionFactoryBuilder().build(); Session session=factory.openSession(); Transaction t=session.beginTransaction(); Answer ans1=new Answer(); ans1.setAnswername("Java is a programming language"); ans1.setPostedBy("Ravi Malik"); Answer ans2=new Answer(); ans2.setAnswername("Java is a platform"); ans2.setPostedBy("Sudhir Kumar"); Question q1=new Question(); q1.setQname("What is Java?"); ArrayList< Answer> l1=new ArrayList< Answer> (); l1.add(ans1); l1.add(ans2); q1.setAnswers(l1); Answer ans3=new Answer(); ans3.setAnswername("Servlet is an Interface"); ans3.setPostedBy("Jai Kumar"); Answer ans4=new Answer(); ans4.setAnswername("Servlet is an API"); ans4.setPostedBy("Arun"); Question q2=new Question(); q2.setQname("What is Servlet?"); ArrayList< Answer> l2=new ArrayList< Answer> (); l2.add(ans3); l2.add(ans4); q2.setAnswers(l2); session.persist(q1); session.persist(q2); t.commit(); session.close(); System.out.println("success"); } }

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