title: Creating custom Authentication entry point for form login
body: <p>I have a form login entry point currently defined like so:</p>
  
  <pre class="lang-xml prettyprint-override"><code>&lt;form-login login-page="/spring/login" 
              login-processing-url="/spring/login"
              authentication-failure-url="/spring/loginfail" 
              default-target-url="/spring/loginsuccess" 
              always-use-default-target="true" /&gt;
  </code></pre>
  
  <p>This works just fine but I want to convert it into a custom authentication entry point. I have a class that extends  <code>LoginUrlAuthenticationEntryPoint</code> which gets called when authentication is needed.</p>
  
  <p>My question is: <em>How do I support POSTing the username/password using this pattern?</em>  </p>
  
  <p>When I remove the form-login block I get a POST not supported error.  I guess since I can no longer define the login-processing-url, where do I post the credentials so that Spring Security can perform the authentication?</p>