Using enum in the application context

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.

Code:

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<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>

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Hi Martin,

Quote:

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Originally Posted by sylvestris

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?

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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:

Code:

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<?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>

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

Code:

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package com.abc;

public enum Colour {
        RED, GREEN, BLUE;
}

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Code:

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package com.abc;

public interface ColourMapper {}

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Code:

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package com.abc;

public class RedMapper implements ColourMapper {}

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Code:

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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);
        }
}

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Code:

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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());
        }
}

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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

Hi Sam, thanks for the detailed instructions.

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

Quote:

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Originally Posted by ramat123

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

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

Regards,

Sam