使用注解Hibernate多对多示例 Hibernate多对多|Hibernate

【使用注解Hibernate多对多示例】在上一节中, 我们使用XML文件执行了多对多映射。在这里, 我们将使用注释执行此任务。
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, 我们将通过列表在问题和答案之间生成多对多关系。
1）创建持久性类
Question.java

package com.srcmini; import java.util.List; import javax.persistence.*; @Entity @Table(name="ques1123") public class Question { @Id @GeneratedValue(strategy=GenerationType.AUTO) private int id; private String qname; @ManyToMany(targetEntity = Answer.class, cascade = { CascadeType.ALL }) @JoinTable(name = "q_ans1123", joinColumns = { @JoinColumn(name = "q_id") }, inverseJoinColumns = { @JoinColumn(name = "ans_id") }) 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 javax.persistence.*; @Entity @Table(name="ans1123") public class Answer { @Id @GeneratedValue(strategy=GenerationType.AUTO) private int id; private String answername; private String postedBy; 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; }}

2）在pom.xml文件中添加项目信息和配置。
打开pom.xml文件, 然后单击源。现在, 在< dependencies> … . < / dependencies> 标记之间添加以下依赖关系。

< dependency> < groupId> org.hibernate< /groupId> < artifactId> hibernate-core< /artifactId> < version> 5.3.1.Final< /version> < /dependency>

< dependency> < groupId> com.oracle< /groupId> < artifactId> ojdbc14< /artifactId> < version> 10.2.0.4.0< /version> < /dependency>

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。

< ?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 class="com.srcmini.Question"/> < mapping class="com.srcmini.Answer"/> < /session-factory> < /hibernate-configuration>

4）创建类来存储数据
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 an1=new Answer(); an1.setAnswername("Java is a programming language"); an1.setPostedBy("Ravi Malik"); Answer an2=new Answer(); an2.setAnswername("Java is a platform"); an2.setPostedBy("Sudhir Kumar"); Question q1=new Question(); q1.setQname("What is Java?"); ArrayList< Answer> l1=new ArrayList< Answer> (); l1.add(an1); l1.add(an2); 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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