Question

I’m creating a Spring-based Scala project. One of my objects needs a simple Map[String, String] injected in to it. I have the following code:

applicationContext.xml

<?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:p="http://www.springframework.org/schema/p"
  xmlns:context="http://www.springframework.org/schema/context"
  xmlns:util="http://www.springframework.org/schema/util"
  xmlns:device="http://www.springframework.org/schema/mobile/device"
  xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd
        http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.0.xsd
        http://www.springframework.org/schema/mobile/device http://www.springframework.org/schema/mobile/device/spring-mobile-device-1.0.xsd">

  <util:map id="validHosts">
    <entry key="host1.domain.com" value="queue-1" />
    <entry key="host2.domain.com" value="queue-2" />
  </util:map>

</beans>

HostMapper.Scala

import scala.collection.JavaConversions._

import org.springframework.beans.factory.annotation.Autowired
import org.springframework.stereotype.Component

@Component
class HostMapper() {

  @Autowired private var validHosts:java.util.Map[String, String] = null

}

When running this app, I get the following error on startup:

org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [java.lang.String] found for dependency [map with value type java.lang.String]: expected at least 1 bean which qualifies as autowire candidate for this dependency.

I attempted explicitly declaring the key and value types as java.lang.String, but that had no effect. Any ideas what I might be doing wrong?

Answer 1

I did not know this myself and found this actually:

As a specific consequence of this semantic difference, beans which are themselves defined as a collection or map type cannot be injected via @Autowired since type matching is not properly applicable to them. Use @Resource for such beans, referring to the specific collection/map bean by unique name

And I tested this and instead of

 @Autowired

I used:

 @Resource
 private Map<String, String> validHosts;


 <util:map id="validHosts" key-type="java.lang.String" value-type="java.lang.String">
    <entry key="host1.domain.com" value="queue-1" />
    <entry key="host2.domain.com" value="queue-2" />
</util:map>

And it worked.