Using enum in the application context

[sylvestris]

Hi everyone, I want to use enums as keys in a map within the context.xml. The following doesn't work. Any ideas on what I should do ? Thanks. Martin.

<bean id="mybean" class="com.abc.MyBean">
   <property name="mappers">
      <map>
         <entry>
            <key>
               <bean class="com.abc.Colour.RED"/>
            </key>
            <value>
               <bean class="com.abc.RedMapper"/>
            </value>
         </entry>
      </map>
   </property>
</bean>

[Sam Brannen]

Hi Martin,

I want to use enums as keys in a map within the context.xml. The following doesn't work. Any ideas on what I should do?

Yes. First and foremost, "com.abc.Colour.RED" is not a class. So that configuration could never work.

You need to access the RED enum constant as a static field. This can be achieved with the util namespace as follows:

<?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:util="http://www.springframework.org/schema/util"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
		http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd">

	<util:constant id="red" static-field="com.abc.Colour.RED" />

	<bean id="redMapper" class="com.abc.RedMapper" />

	<bean id="mybean" class="com.abc.MyBean">
		<property name="mappers">
			<map>
				<entry key-ref="red" value-ref="redMapper" />
			</map>
		</property>
	</bean>

</beans>

To prove that it works, I threw together a mini unit test using the following classes:

package com.abc;

public enum Colour {
	RED, GREEN, BLUE;
}

package com.abc;

public interface ColourMapper {}

package com.abc;

public class RedMapper implements ColourMapper {}

package com.abc;

import java.util.HashMap;
import java.util.Map;

public class MyBean {

	private final Map<Colour, ColourMapper> mappers = new HashMap<Colour, ColourMapper>();

	public Map<Colour, ColourMapper> getMappers() {
		return this.mappers;
	}

	public void setMappers(Map<Colour, ColourMapper> mappers) {
		this.mappers.putAll(mappers);
	}
}

package com.abc;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertNotNull;
import static org.junit.Assert.assertTrue;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration
public class EnumColourMapperTests {

	@Autowired
	private MyBean myBean;

	@Test
	public void colourMappingConfig() {
		assertNotNull(myBean);
		assertEquals(1, myBean.getMappers().size());
		assertTrue(myBean.getMappers().containsKey(Colour.RED));
		assertEquals(RedMapper.class.getName(), myBean.getMappers().get(Colour.RED).getClass().getName());
	}
}

If you want to try out this code, simply store the XML application context configuration listed at the top of this post in your classpath as com/abc/EnumColourMapperTests-context.xml. Then run the unit test.

Regards,

Sam

[sylvestris]

Hi Sam, thanks for the detailed instructions.

[ramat123]

Is it s spring 3.x option only? I am using 2.0.7.

[Sam Brannen]

Is it s spring 3.x option only? I am using 2.0.7.

The util namespace was introduced in Spring 2.0. See the util schema section of the reference manual for details.

Regards,

Sam