Difference Between Constructor and Setter Injection Setter Injection and Map Example

example of Setter injection with non-string mapping

In this example, we use map As answers with Answer and User, here we use both keys and values as objects. Answers have their own information, such as answerId, answer, and postedDate, and users have their own information, such as userId, username, and emailId.

Like the example before, it is an example of a forum, where A question can have multiple answers。

Question.java

This class contains three properties, namely getters and setters methods and displayInfo() method, which are used to display information

Example

package com.w3codebox;
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

Example

package com.w3codebox;
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

Example

package com.w3codebox;
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

entry element of key-ref and value-ref Properties are used to define bean references in the map.

Example

<?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.w3codebox.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.w3codebox.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.w3codebox.User">
<property　name="id"　value="1></property>
<property　name="name"　value="Arun　Kumar"></property>
<property　name="email"　value="[email protected]"></property>
</bean>
<bean　id="user2"　class="com.w3codebox.User">
<property　name="id"　value="2></property>
<property　name="name"　value="Varun　Kumar"></property>
<property　name="email"　value="[email protected]"></property>
</bean>
<bean　id="q"　class="com.w3codebox.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

This class retrieves a Bean from the applicationContext.xml file and calls the displayInfo() method to display information.

Example

package com.w3codebox;
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();
　　　　
}
}

Difference Between Constructor and Setter Injection Setter Injection and Map Example

Spring Tutorial

example of Setter injection with non-string mapping