title: Alphanumeric password validation in xsd
body: <p>Hi I need to validate password for only alphanumeric chars( should present both alphabets and numbers from 0..9) . I mean it should contain at least one digit and remaining alphabets</p>
  
  <p>The regex I use is like this : </p>
  
  <pre><code>     &lt;xsd:simpleType name="PasswordType"&gt;
           &lt;xsd:restriction base="xsd:string"&gt;
               &lt;xsd:pattern value="?!^[0-9]*$)(?!^[a-zA-Z]*$)^([a-zA-Z0-9]{8,20})$"/&gt;
           &lt;/xsd:restriction&gt;
      &lt;/xsd:simpleType&gt;
  </code></pre>
  
  <p>but eclipse complains the error :
  <i> InvalidRegex: Pattern value '?!^[0-9]<em>$)(?!^[a-zA-Z]</em>$)^([a-zA-Z0-9]{8,20})$' is not a valid regular expression. The reported error was: 
   'Unexpected meta character.'.</i></p>
  
  <p>Could anybody help how to solve this issue?</p>
  
  <p>Thanks</p>