title: @ElementCollection org.hibernate.MappingException: Could not determine type for: java.util.Set, at table
body: <p>I would like to store a  <code>Map&lt;String, Set&lt;String&gt;&gt;</code> with jpa. </p>
  
  <p>Here is what i have : </p>
  
  <pre><code>@ElementCollection
      @JoinTable(name="material_index_join", joinColumns=@JoinColumn(name="paire_Id"))
      @MapKeyColumn (name="material")
      @Column(name="index")
      private Map&lt;String, Set&lt;String&gt;&gt; mapMaterialIndex = new HashMap&lt;String, Set&lt;String&gt;&gt;();
  </code></pre>
  
  <p>But i get the following error :</p>
  
  <blockquote>
    <p>org.hibernate.MappingException: Could not determine type for: java.util.Set, at table: material_index_join, for columns: [org.hibernate.mapping.Column(index)]</p>
  </blockquote>
  
  <p>What can i do ?</p>
  
  <p>Tell me if you need any further information.</p>