Spring - How do you set Enum keys in a Map with annotations - spring

Question

I've an Enum class
public enum MyEnum{
ABC;
}
than my 'Mick' class has this property
private Map<MyEnum, OtherObj> myMap;
I've this spring xml configuration.
<util:map id="myMap">
<entry key="ABC" value-ref="myObj" />
</util:map>
<bean id="mick" class="com.x.Mick">
<property name="myMap" ref="myMap" />
</bean>
and this is fine.
I'd like to replace this xml configuration with Spring annotations.
Do you have any idea on how to autowire the map?
The problem here is that if I switch from xml config to the #Autowired annotation (on the myMap attribute of the Mick class) Spring is throwing this exception
nested exception is org.springframework.beans.FatalBeanException: Key type [class com.MyEnum] of map [java.util.Map] must be assignable to [java.lang.String]
Spring is no more able to recognize the string ABC as a MyEnum.ABC object.
Any idea?
Thanks

Answer 1

This worked for me...
My Spring application context:
<util:map id="myMap">
<entry key="#{T(com.acme.MyEnum).ELEM1}" value="value1" />
<entry key="#{T(com.acme.MyEnum).ELEM2}" value="value2" />
</util:map>
My class where the Map gets injected:
public class MyClass {
private #Resource Map<MyEnum, String> myMap;
}
The important things to note are that in the Spring context I used SpEL (Spring Expression Language) which is only available since version 3.0. And in my class I used #Resource, neither #Inject (it didn't work for me) nor #Autowired (I didn't try this). The only difference I'm aware of between #Resource and #Autowired, is that the former auto-inject by bean name while the later does it by bean type.
Enjoy!

Answer 2

This one gave me fits but I was able to piece it together using David's answer and some other links (below).
do not change the names of the properties in the MapFactoryBean declaration.
ensure that key-type attribute points to the enum that you want to use as a key in the map.
Class
#Component
public class MyClass {
private Map<MyEnum, ValueObjectInterface> valueMap;
#Autowired
public void setValueMap(final Map<MyEnum, ValueObjectInterface> valueMap) {
this.valueMap= valueMap;
}
}
Enum
public enum MyEnum{
FOO ("FOO"),
BAR ("BAR"),
BAZ ("BAZ");
}
XML Config file:
<bean id="valueMap" class="org.springframework.beans.factory.config.MapFactoryBean">
<property name="targetMapClass">
<value>java.util.HashMap</value>
</property>
<property name="sourceMap">
<map key-type="com.company.packagepath.MyEnum">
<entry key="FOO" value-ref="valueObject1" />
<entry key="BAR" value-ref="valueObject2" />
<entry key="BAZ" value-ref="valueObject3" />
</map>
</property>
</bean>
<bean id="valueObject1" class="com.company.packagepath.ValueObject1" />
<bean id="valueObject2" class="com.company.packagepath.ValueObject2" />
<bean id="valueObject3" class="com.company.packagepath.ValueObject3" />
LINKS
Code Ranch
Spring MapFactoryBean example at mkyong.com
How assign bean's property an Enum value in Spring config file?

Answer 3

Application context
<?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-3.1.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd ">
<bean id="myProvider" class="com.project.MapProvider">
<property name="myMap" ref="myMap"/>
</bean>
<util:map id="myMap" key-type="com.project.MyEnum" value-type="com.project.ValueObject">
<entry>
<key><value type="com.project.MyEnum">FOO</value></key>
<ref bean="objectValue1"/>
</entry>
</util:map>
</beans>
Java class
package com.project;
public class MapProvider {
private Map<MyEnum, ValueObject> myMap;
public void setMyMap(Map<MyEnum, ValueObject> myMap) {
this.myMap = myMap;
}
}

Answer 4

Should be:
public class Mick {
private Map<MyEnum, OtherObj> myMap;
#Autowired
public void setMyMap(Map<MyEnum, OtherObj> myMap) {
this.myMap = myMap;
}
}
Have a look at http://static.springsource.org/spring/docs/2.5.x/reference/beans.html#beans-annotation-config
Updated
The problem is that according to the util schema, you cannot specify the key or value types. You can however to implement a MapFactoryBean of your own (just inherit from org.springframework.beans.factory.config.MapFactoryBean). One ceveat - notice that the generic definition (even thought erased in runtime) doesn't get in the way.

Answer 5

The <util:map> element has key-type, resp. value-type attributes, that represents the class of the keys, resp. the values. If you specify the fully qualified class of your enum in the key-type attribute, the keys are then parsed into that enum when creating the map.
Spring verifies during injection that the map's key and value types -as declared in the class containing the map- are assignment-compatible with the key and value types of the map bean. This is actually where you get the exception from.

Answer 6

You just need to use concrete Map class as HashMap and not abstract or interface:
public class Mick {
private HashMap<MyEnum, OtherObj> myMap;
#Autowired
public void setMyMap(HashMap<MyEnum, OtherObj> myMap) {
this.myMap = myMap;
}
}
public class AppConfig
{
#Bean
public HashMap<MyEnum, OtherObj> myMap() { .. }
}

Answer 7

If you have a Map with an Enum values as keys, then consider using Java's EnumMap implementation:
https://docs.oracle.com/en/java/javase/12/docs/api/java.base/java/util/EnumMap.html
Here you also have a Baeldung post with some examples on how to use it:
https://www.baeldung.com/java-enum-map