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POSpring injects a one-element Set instead of an empty Set
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  1. POSpring injects a one-element Set instead of an empty Set
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    copied!<p>We have an application where we are trying to inject an empty <code>java.util.HashSet</code> into a member of type <code>java.util.Set</code>, in a class which itself is a <code>@Component</code>. Spring seems to inject a <code>HashSet</code> with one element of the containing type. Any idea why Spring doesn't just inject an empty set?</p> <p><strong>Set element class:</strong></p> <pre><code>@Component public class SetElement { private String value; public String getValue() { return value; } } </code></pre> <p><strong>Class that contains a Set as a member:</strong></p> <pre><code>@Component public class MyClassWithSet { @Autowired private Set&lt;SetElement&gt; setOfElements; protected void setStringSet(Set&lt;SetElement&gt; stringSet) { this.setOfElements = stringSet; } public Set&lt;SetElement&gt; getStringSet() { return Collections.unmodifiableSet(setOfElements); } } </code></pre> <p><strong>Spring.xml</strong></p> <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt; &lt;beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context" 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-3.0.xsd "&gt; &lt;bean id="setOfElements" class="java.util.HashSet" /&gt; &lt;context:component-scan base-package="com.vikdor.db " /&gt; &lt;/beans&gt; </code></pre> <p><strong>Sample test case to confirm the behavior</strong></p> <pre><code>@RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = { "classpath:META-INF/spring.xml" }) public class SpringSetTest { @Autowired private MyClassWithSet myClassWithSet; @Test public void test() { assertNotNull(myClassWithSet); assertNotNull(myClassWithSet.getStringSet()); assertTrue(myClassWithSet.getStringSet().isEmpty()); } } </code></pre>
 

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