title: When to use merge() before save()?
body: <p>I am just curious when to use <code>merge()</code> method before saving an object in hibernate.
  I saw an example that uses <code>merge()</code> before saving with an object that has a many to many relationship with another object.</p>
  
  <p><strong>Example</strong> for using merge: <code>Role</code> has <code>ManyToMany</code> with <code>Permission</code> and it sets <code>List</code> of <code>Permission</code> in the <code>Role</code> object before saving.</p>
  
  <p>So is that's only that case, when the saved object has relation with other objects?</p>
  
  <p>I need good explanation and use cases.</p>