Constructor注入(具有相关对象)示例

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，两个构造函数和用于显示信息的displayInfo()方法。

示例

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;
public Question() {}
public Question(int id, String name, Map<Answer, User> answers) {
    super();
    this.id = id;
    this.name = name;
    this.answers = answers;
}
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

示例

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

示例

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。

示例

<?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">
<constructor-arg value="1"></constructor-arg>
<constructor-arg value="Java is a Programming Language"></constructor-arg>
<constructor-arg value="12/12/2001"></constructor-arg>
</bean>
<bean id="answer2" class="com.nhooo.Answer">
<constructor-arg value="2"></constructor-arg>
<constructor-arg value="Java is a Platform"></constructor-arg>
<constructor-arg value="12/12/2003"></constructor-arg>
</bean>
<bean id="user1" class="com.nhooo.User">
<constructor-arg value="1"></constructor-arg>
<constructor-arg value="Arun Kumar"></constructor-arg>
<constructor-arg value="arun@gmail.com"></constructor-arg>
</bean>
<bean id="user2" class="com.nhooo.User">
<constructor-arg value="2"></constructor-arg>
<constructor-arg value="Varun Kumar"></constructor-arg>
<constructor-arg value="Varun@gmail.com"></constructor-arg>
</bean>
<bean id="q" class="com.nhooo.Question">
<constructor-arg value="1"></constructor-arg>
<constructor-arg value="What is Java?"></constructor-arg>
<constructor-arg>
<map>
<entry key-ref="answer1" value-ref="user1"></entry>
<entry key-ref="answer2" value-ref="user2"></entry>
</map>
</constructor-arg>
</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。

示例

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();
    
}
}

Spring Bean继承 Constructor注入和Map示例

Constructor注入(具有相关对象)示例

Spring 教程