使用 xml 文件映射 Hibernate Map

2024 年 8 月 29 日 | 阅读 2 分钟

Hibernate 允许您将 Map 元素与 RDBMS 映射。众所周知，list 和 map 是基于索引的集合。对于 map，索引列用作键，元素列用作值。

使用 xml 文件在集合映射中映射 Map 的示例

您需要创建以下页面来映射 map 元素。

Question.java
question.hbm.xml
hibernate.cfg.xml
StoreTest.java
FetchTest.java

Question.java

package com.javatpoint;

import java.util.Map;

public class Question {
private int id;
private String name,username;
private Map<String,String> answers;

public Question() {}
public Question(String name, String username, Map<String, String> answers) {
	super();
	this.name = name;
	this.username = username;
	this.answers = answers;
}
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 getUsername() {
	return username;
}
public void setUsername(String username) {
	this.username = username;
}
public Map<String, String> getAnswers() {
	return answers;
}
public void setAnswers(Map<String, String> answers) {
	this.answers = answers;
}
}

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.javatpoint.Question" table="question736">
<id name="id">
<generator class="native"></generator>
</id>
<property name="name"></property>
<property name="username"></property>

<map name="answers" table="answer736" cascade="all">
<key column="questionid"></key>
<index column="answer" type="string"></index>
<element column="username" type="string"></element>
</map>
</class>

</hibernate-mapping>                  

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">update</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"/>
    </session-factory>

</hibernate-configuration>

StoreTest.java

package com.javatpoint;  
  
import java.util.HashMap;  
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 StoreTest {  
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();  
  
HashMap<String,String> map1=new HashMap<String,String>();  
map1.put("Java is a programming language","John Milton");  
map1.put("Java is a platform","Ashok Kumar");  
  
HashMap<String,String> map2=new HashMap<String,String>();  
map2.put("Servlet technology is a server side programming","John Milton");  
map2.put("Servlet is an Interface","Ashok Kumar");  
map2.put("Servlet is a package","Rahul Kumar");  
  
Question question1=new Question("What is Java?","Alok",map1);  
Question question2=new Question("What is Servlet?","Jai Dixit",map2);  
  
session.persist(question1);  
session.persist(question2);  
  
t.commit();  
session.close();  
System.out.println("successfully stored");  
}  
}  

输出

FetchTest.java

package com.javatpoint;  
import java.util.*;

import javax.persistence.TypedQuery;

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 FetchTest {  
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();  
          
 TypedQuery query=session.createQuery("from Question ");  
 List<Question> list=query.getResultList();  
          
 Iterator<Question> iterator=list.iterator();  
 while(iterator.hasNext()){  
  Question question=iterator.next();  
  System.out.println("question id:"+question.getId());  
  System.out.println("question name:"+question.getName());  
  System.out.println("question posted by:"+question.getUsername());  
  System.out.println("answers.....");  
  Map<String,String> map=question.getAnswers();  
  Set<Map.Entry<String,String>> set=map.entrySet();  
              
  Iterator<Map.Entry<String,String>> iteratoranswer=set.iterator();  
  while(iteratoranswer.hasNext()){  
   Map.Entry<String,String> entry=(Map.Entry<String,String>)iteratoranswer.next();  
   System.out.println("answer name:"+entry.getKey());  
   System.out.println("answer posted by:"+entry.getValue());  
  }  
 }  
session.close();  
}  
}  

输出

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