<wsse:UsernameToken>
            <wsse:Username>XXXXXXXX</wsse:Username>
            <wsse:Password>xxxxxxxxxxxx</wsse:Password></wsse:UsernameToken>
public class OasisOpenOrgWssSecuritySecext

// UserToken Class
public class UsernameToken
{
    // Constructor for UsernameToken used to pass in username and password parameters
    public UsernameToken(String username, String password)
    {
        this.Username = username;
        this.Password = password;
        this.Nonce = generateNounce();
        this.Created = generateTimestamp();
    }

    public String Username;
    public String Password;
    public String Nonce;
    public String Created;
    private String[] Username_type_info = new String[]{'Username','http://www.w3.org/2001/XMLSchema','string','0','1','false'};
    private String[] Password_type_info = new String[]{'Password','http://www.w3.org/2001/XMLSchema','string','0','1','false'};
    private String[] Nonce_type_info = new String[]{'Nonce','http://www.w3.org/2001/XMLSchema','string','0','1','false'};
    private String[] Created_type_info = new String[]{'wsu:Created','http://www.w3.org/2001/XMLSchema','string','0','1','false'};
    private String[] apex_schema_type_info = new String[]{'http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd','true','false'};
    private String[] field_order_type_info = new String[]{'Username','Password','Nonce','Created'};

    // Generate Nounce, random number base64 encoded
    public String generateNounce()
    {
        Long randomLong = Crypto.getRandomLong();
        return EncodingUtil.base64Encode(Blob.valueOf(String.valueOf(randomLong)));
    }

    // Generate timestamp in GMT
    public String generateTimestamp()
    {
        return Datetime.now().formatGmt('yyyy-MM-dd'T'hh:mm:ss'Z'');
    }
}

// SecurityHeaderType Class
public class SecurityHeaderType
{
    // Constructor for SecurityHeaderType used to pass in username and password parameters and instantiate the UsernameToken object
    public SecurityHeaderType(String username, String password)
    {
        this.UsernameToken = new OasisOpenOrgWssSecuritySecext.UsernameToken(username, password);
    }

    public String wsuNamespace = 'http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd';
    public OasisOpenOrgWssSecuritySecext.UsernameToken UsernameToken;
    private String[] UsernameToken_type_info = new String[]{'UsernameToken','http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd','UsernameToken','1','1','false'};
    private String[] wsuNamespace_att_info = new String[]{'xmlns:wsu'};
    private String[] apex_schema_type_info = new String[]{'http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd','true','false'};
    private String[] field_order_type_info = new String[]{'UsernameToken'};
}

<wsse:UsernameToken>
            <wsse:Username>XXXXXXXX</wsse:Username>
            <wsse:Password Type="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-username-token-profile-1.0#PasswordText">xxxxxxxxxxxx</wsse:Password>