Home  >  Spring

Spring Collection Merging Example

By Arvind Rai, November 04, 2021
The Spring container supports merging collections. We can create a parent element using <list/>, <map/>, <set/> or <props/> elements and they can have child <list/>, <map/>, <set/> or <props/> elements overriding values from the parent collection. The elements in child collection are the result of merging the elements of the parent and child collections.
Merging parent and child collections can be controlled by merge property. The value merge="true" will allow child collection to inherit parent collection.



Collection Merging Example

spring-config.xml
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="parentCollection" class="com.concretepage.bean.MyCollection">
       <property name="mySet">
	 <set>
             <value>AAAA</value>
             <value>BBBB</value>
         </set>
       </property>
    </bean>
    <bean id="childCollection" parent="parentCollection">
       <property name="mySet">
	 <set merge="true">
             <value>CCCC</value>
             <value>DDDD</value>
         </set>
       </property>
    </bean>
</beans> 
MyCollection.java
package com.concretepage.bean;
import java.util.Set;
public class MyCollection {
	private Set<String> mySet;
	public Set<String> getMySet() {
		return mySet;
	}
	public void setMySet(Set<String> mySet) {
		this.mySet = mySet;
	}
} 
Run Application.
SpringDemo.java
package com.concretepage;
import java.util.Iterator;
import java.util.Set;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.concretepage.bean.MyCollection;
public class SpringDemo {
   public static void main(String[] args) {
	AbstractApplicationContext  context = new ClassPathXmlApplicationContext("spring-config.xml");
	MyCollection myCollection=(MyCollection)context.getBean("parentCollection");
        //access parent collection 
        System.out.println("---Elements in parent bean---");		
        Set<String> parentSet=myCollection.getMySet();
        Iterator<String> itrP= parentSet.iterator();
        while(itrP.hasNext()){
        	System.out.println(itrP.next());
        }
        MyCollection concreteChild=(MyCollection)context.getBean("childCollection");
        //access child collection 
        System.out.println("---Elements in child bean---");        
        Set<String> setC=concreteChild.getMySet();
        Iterator<String> itrC= setC.iterator();
        while(itrC.hasNext()){
        	System.out.println(itrC.next());
        } 
        context.close();
  }
} 
Find the output.
---Elements in parent bean---
AAAA
BBBB
---Elements in child bean---
AAAA
BBBB
CCCC
DDDD 

Reference

Spring Collection Merging

Download Source Code

POSTED BY
ARVIND RAI
ARVIND RAI










©2022 concretepage.com | Privacy Policy | Contact Us