在此示例中，我们使用 map 作为具有Answer和User的答案。在这里，我们将键和值对都用作对象。答案具有自己的信息，例如answerId，答案和postedDate，用户具有自己的信息，例如userId，用户名，emailId。
像前面的示例一样，它是论坛的示例其中 一个问题可以有多个答案。
Question.java
此类包含三个属性，即getters和setters方法和displayInfo()方法，用于显示信息
package com.nhooo;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.Map.Entry;
public class Question {
private int id;
private String name;
private Map<Answer,User> answers;
//getters and setters
public void displayInfo(){
System.out.println("question id:"+id);
System.out.println("question name:"+name);
System.out.println("Answers....");
Set<Entry<Answer, User>> set=answers.entrySet();
Iterator<Entry<Answer, User>> itr=set.iterator();
while(itr.hasNext()){
Entry<Answer, User> entry=itr.next();
Answer ans=entry.getKey();
User user=entry.getValue();
System.out.println("Answer Information:");
System.out.println(ans);
System.out.println("Posted By:");
System.out.println(user);
}
}
}
Answer.java
package com.nhooo;
import java.util.Date;
public class Answer {
private int id;
private String answer;
private Date postedDate;
public Answer() {}
public Answer(int id, String answer, Date postedDate) {
super();
this.id = id;
this.answer = answer;
this.postedDate = postedDate;
}
public String toString(){
return "Id:"+id+" Answer:"+answer+" Posted Date:"+postedDate;
}
}
User.java
package com.nhooo;
public class User {
private int id;
private String name,email;
public User() {}
public User(int id, String name, String email) {
super();
this.id = id;
this.name = name;
this.email = email;
}
public String toString(){
return "Id:"+id+" Name:"+name+" Email Id:"+email;
}
}
applicationContext.xml
条目 element 的 key-ref 和 value-ref 属性用于在地图中定义bean的引用。
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd"> <bean id="answer1" class="com.nhooo.Answer"> <property name="id" value="1"></property> <property name="answer" value="Java is a Programming Language"></property> <property name="postedDate" value="12/12/2001"></property> </bean> <bean id="answer2" class="com.nhooo.Answer"> <property name="id" value="2"></property> <property name="answer" value="Java is a Platform"></property> <property name="postedDate" value="12/12/2003"></property> </bean> <bean id="user1" class="com.nhooo.User"> <property name="id" value="1"></property> <property name="name" value="Arun Kumar"></property> <property name="email" value="arun@gmail.com"></property> </bean> <bean id="user2" class="com.nhooo.User"> <property name="id" value="2"></property> <property name="name" value="Varun Kumar"></property> <property name="email" value="Varun@gmail.com"></property> </bean> <bean id="q" class="com.nhooo.Question"> <property name="id" value="1"></property> <property name="name" value="What is Java?"></property> <property name="answers"> <map> <entry key-ref="answer1" value-ref="user1"></entry> <entry key-ref="answer2" value-ref="user2"></entry> </map> </property> </bean> </beans>
Test.java
此类从applicationContext.xml文件获取Bean，并调用displayInfo()方法以显示信息。
package com.nhooo;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
public class Test {
public static void main(String[] args) {
Resource r=new ClassPathResource("applicationContext.xml");
BeanFactory factory=new XmlBeanFactory(r);
Question q=(Question)factory.getBean("q");
q.displayInfo();
}
}