title: How to correctly map a polygon type with postgis and hibernate-spatial?
body: <p>Assume I have the following table</p>
  
  <pre><code>CREATE TABLE foo (
    id BIGSERIAL PRIMARY KEY, 
    polygon GEOMETRY(POLYGON)
  );
  </code></pre>
  
  <p>and entity class</p>
  
  <pre><code>@Table
  @Entity
  public class Foo {
  
     @Id
     @GeneratedValue(strategy = IDENTITY)
     private Long id;
  
     private Polygon polygon;
  
  }
  </code></pre>
  
  <p>I managed to save a Foo entity, however, I can't select it them from the database. I get this exception:</p>
  
  <pre><code>java.lang.NumberFormatException: For input string: "PO"
  </code></pre>
  
  <p>Then, I added the following annotation on top of polygon field:</p>
  
  <pre><code>@Type(type = "org.hibernate.spatial.JTSGeometryType")
  </code></pre>
  
  <p>but it throws
   another exception saying that this type cannot be instantiated:</p>
  
  <pre><code>org.hibernate.MappingException: Could not instantiate Type: org.hibernate.spatial.JTSGeometryType
  </code></pre>
  
  <p>Please note that I use 5.1.0.Final version for hibernate and hibernate-spatial.</p>
  
  <p>Thank you</p>