Spring MapFactoryBean example

The ‘MapFactoryBean‘ class provides developer a way to create a concrete Map collection class (HashMap and TreeMap) in Spring’s bean configuration file.
Here’s a MapFactoryBean example, it will instantiate a HashMap at runtime,, and inject it into a bean property.

package com.mkyong.common;
import java.util.Map;
public class Customer { 
    private Map maps; 
    //...
}

Spring’s bean configuration file.

<?xml version="1.0"?>
<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 util schema and <util:map> to achieve the same thing.

<?xml version="1.0"?>
<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("SpringBeans.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 a HashMap and injected it into Customer’s map property at runtime.