Working with Set,List,Map and Properties as attributes

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We have seen examples of having a classA as one of the attributes of another classB. We also have cases wherein the attributes of the class are a List of another object(classA).

Example File : Bill

public class Bill {

private List<ABC> abc;
}

 
File : ABC

Public class ABC{

Private double amount;
Private double discount;
}

 
For such cases, the value for the List or any other similar collection needs to be injected through framework, which involves a slight syntactical change.

Step 1 :

File : Amount.java
 

package com.simpleCodeStuffs;

public class Amount {

private double bill;

public double getBill() {
return bill;
}

public void setBill(double bill) {
this.bill = bill;
}

@Override
public String toString(){
return("amount "+bill);
}
}

Step 2 :

CollectionBean is a class, which has a list,set,map,properties of another Object as its attributes. Just to enhance the understanding, we take it that CollectionBean may have a List of any Object as its attributes. Hence the attributes are defined as List of Object and likewise.
 
File : CollectionBean.java
 

package com.simpleCodeStuffs;

import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.Set;

public class CollectionBean {
	private List<String> stringListVariable;
	private List<Object> listVariable;
	private Set<Object> setVariable;
	private Map<Object, Object> mapVariable;
	private Properties propVariable;
	
	
	public List<String> getStringListVariable() {
		return stringListVariable;
	}
	public void setStringListVariable(List<String> stringListVariable) {
		this.stringListVariable = stringListVariable;
	}
	public List<Object> getListVariable() {
		return listVariable;
	}
	public void setListVariable(List<Object> listVariable) {
		this.listVariable = listVariable;
	}
	public Set<Object> getSetVariable() {
		return setVariable;
	}
	public void setSetVariable(Set<Object> setVariable) {
		this.setVariable = setVariable;
	}
	public Map<Object, Object> getMapVariable() {
		return mapVariable;
	}
	public void setMapVariable(Map<Object, Object> mapVariable) {
		this.mapVariable = mapVariable;
	}
	public Properties getPropVariable() {
		return propVariable;
	}
	public void setPropVariable(Properties propVariable) {
		this.propVariable = propVariable;
	}
}

Step 3 : Main class to print the details of the attributes

 
File : MainClass.java
 

package com.simpleCodeStuffs;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import com.simpleCodeStuffs.Amount;
import com.simpleCodeStuffs.CollectionBean;

public class MainClass {
	 public static void main(String[] args) {
	      ApplicationContext context = 
		             new ClassPathXmlApplicationContext("Beans.xml");
	      CollectionBean bean=(CollectionBean)context.getBean("testBean");
	      Amount amt=(Amount)context.getBean("amount");
	      System.out.println("List of String:t"+bean.getStringListVariable());
	      System.out.println("List          :t"+bean.getListVariable());
	      System.out.println("set           :t"+bean.getSetVariable());
	      System.out.println("Map           :t"+bean.getMapVariable());
	      System.out.println("Properties    :t"+bean.getPropVariable());
	   }
}

Step 4 :

 
This is the main change. For each of the collection variables, the way in which the value is injected in the configuration metadata has a syntax change.

File : Beans.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-3.0.xsd">

	<bean id="testBean" class="com.simpleCodeStuffs.CollectionBean">
		<property name="stringListVariable">
			<list>
				<value>A Simple</value>
				<value>List</value>
				<value>Of</value>
				<value>String</value>
			</list>
		</property>
		<property name="listVariable">
			<list>
				<value>1</value>
				<value>List of Objects</value>
				<ref bean="amount" />
				<bean class="com.simpleCodeStuffs.Amount">
					<property name="bill">
						<value>45.9</value>
					</property>
				</bean>
			</list>
		</property>
		<property name="setVariable">
			<set>
				<value>2</value>
				<value>Set of Objects</value>
				<ref bean="amount" />
				<bean class="com.simpleCodeStuffs.Amount">
					<property name="bill">
						<value>09.5</value>
					</property>
				</bean>
			</set>
		</property>
		<property name="mapVariable">
			<map>
				<entry key="a" value="3" />
				<entry key="b" value="Map of Objects" />
				<entry key="c" value-ref="amount" />
				<entry key="d">
					<bean class="com.simpleCodeStuffs.Amount">
						<property name="bill">
							<value>76.5</value>
						</property>
					</bean>
				</entry>
			</map>
		</property>
		<property name="propVariable">
			<props>
				<prop key="a">4</prop>
				<prop key="b">properties</prop>

			</props>
		</property>
	</bean>

	<bean id="amount" class="com.simpleCodeStuffs.Amount">
		<property name="bill">
			<value>56.9</value>
		</property>
	</bean>

</beans>

The first example shown, “stringListVariable” is simply to state the means by which multiple values of a simple Data type can be injected into the list. The other variables take values of type Object. Hence, first an Integer, then a String is inserted.
The third one is to show how a reference to another bean can be inserted as a value to the list/set/map. The fourth one shows how an inner bean can be defined and the value inserted to the list/set/map. Note here that, while defining an inner bean, there is no need to mention the beanId as it has limited scope to only the outer bean which defines it.

Step 5 : Run the application. The output appears as :-

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