The ‘MapFactoryBean’ object provides developer a way to create a concrete Map collection class (HashMap and TreeMap) in Spring’s bean configuration file.

Example

Here’s a MapFactoryBean example, it will instantiate a HashMap at runtime.

package com.mkyong.common;
 
import java.util.Map;
 
public class Customer 
{
	private Map maps;
 
	public Map getMaps() {
		return maps;
	}
 
	public void setMaps(Map maps) {
		this.maps = maps;
	}
 
	@Override
	public String toString() {
		return "Customer [maps=" + maps + "]" + 
		       " Type=[" + maps.getClass() + "]";
	}
 
}

Spring’s bean configuration file.

<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-2.5.xsd">
 
<bean id="CustomerBean" class="com.mkyong.common.Customer">
	<property name="maps">
	   <bean class="org.springframework.beans.factory.config.MapFactoryBean">
		<property name="targetMapClass">
			<value>java.util.HashMap</value>
		</property>
		<property name="sourceMap">
			<map>
				<entry key="Key1" value="1" />
				<entry key="Key2" value="2" />
				<entry key="Key3" value="3" />
			</map>
		</property>
	   </bean>
	</property>
</bean>
 
</beans>

Alternatively, you also can use the util schema and <util:map> to achieve the same thing.

<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/util
http://www.springframework.org/schema/util/spring-util-2.5.xsd">
 
	<bean id="CustomerBean" class="com.mkyong.common.Customer">
		<property name="maps">
			<util:map map-class="java.util.HashMap">
				<entry key="Key1" value="1" />
				<entry key="Key2" value="2" />
				<entry key="Key3" value="3" />
			</util:map>
		</property>
	</bean>
 
</beans>

Remember to include the util schema, else you will hit the following error

Caused by: org.xml.sax.SAXParseException: 
The prefix "util" for element "util:map" is not bound.

Run it…

package com.mkyong.common;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
 
public class App 
{
    public static void main( String[] args )
    {
    	ApplicationContext context = 
    	  new ClassPathXmlApplicationContext(new String[] {"Spring-Customer.xml"});
 
    	Customer cust = (Customer)context.getBean("CustomerBean");
    	System.out.println(cust);
 
    }
}

Ouput

Customer [maps={Key2=2, Key1=1, Key3=3}] Type=[class java.util.HashMap]

You have instantiated and injected a HashMap into Cutomer’s maps property at runtime.

This article was posted in Spring category.

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