[SalesForce] Using a CommandButton/CommandLink to Open a New Tab/Window

You can use the key prefix in conjunction with the RecordType parameter in a custom controller or extension. The basic idea is below. The developer name should be stable and not change between orgs. Also, once in production the ID doesn't change in sandboxes refreshed from production, so if you are already working with a record type that is in production you could use the ID.

You can adapt this code to be more specific or to not be an extension. The main thing is the format of the URL and the idea that the RecordType ID is retrieved in a relatively stable way.

public class BypassRecTypeController {
    private sObject rec;
    private String recTypeDevName;

    public BypassRecTypeController(ApexPages.StandardController controller) {
        rec = controller.getRecord();

        // might get this some other way...
        recTypeDevName = ApexPages.currentPage().getParameters().get('recTypeDevName');
    }

    public PageReference bypass() {
        // Get the key prefix to use as part of the url
        // Alternatively, if you know the SObject you could have something like
        // Account.SObjectType.getDescribe() hard coded.
        Schema.DescribeSObjectResult dsr = rec.getSObjectType().getDescribe();
        String keyPrefix = dsr.getKeyPrefix();

        // Get the record type to add on to the query string
        Id recTypeId = [Select Id From RecordType Where DeveloperName = :recTypeDevName].Id;

        PageReference pageRef = new PageReference('/' + keyPrefix + '/e?RecordType=' + recTypeId);

        return pageRef;
    }

}

I'd say "you don't".

In the end PageReference will be an URL and it's up to browser how will it open it. So - if anything - you control it in Visualforce, not in Apex. Can you post your commandButton's definition?

Do you need to submit some data to the server and then open up a new window? In that case maybe some kind of <apex:commandButton oncomplete="..."> will work. If you need to "go to this page or another" - maybe actionFunction that'd be examining the returned PageReference? Is it more of onclick or oncomplete scenario anyway?

If it's a straightforward "just open me a new window" - maybe you don't need the whole action and parameters passed? In that case a plain outputLink or even <a> tag will work (styled with CSS class "btn" for good measure). Links don't pass params like buttons do though; check Why does apex:param assignTo work with apex:commandLink but not apex:commandButton? for workarounds.

EDIT after some explanation in comments

Experiment with this code sample:

<apex:page>
    <apex:form>
    <apex:pageBlock>
        <apex:pageBlockButtons>
            <apex:commandLink value="Generate PDF (new tab most likely)" action="/apex/testpdfpage" styleClass="btn" immediate="true"
                target="_blank" style="text-decoration:none" />
            <a href="/apex/testpdfpage" class="btn" style="text-decoration:none" 
                onclick="window.open(this.href, 'mywin', 'height=400,width=300'); return false;" >Pure HTML version, should be a popup</a>
        </apex:pageBlockButtons>
    </apex:pageBlock>
    </apex:form>
</apex:page>

It seeems that target="_blank" is ignored (Chrome and Firefox will spawn new tab instead of new window) so you need Javascript & window.open. I've included commandLink and plain anchor tag, you can of course mix & match them with onclick etc or use outputLink even...

Also probably a reference to {!$Page.testpdfpage} will be a bit better as if you'll ever try to delete the page SF will stop you saying that this page is used somewhere.