当我点击任何链接时,它应该在JSF,Primefaces的同一个新窗口中打开

Use <h:commandLink> instead of <p:commandLink>.

I tried your code and make a little change like this:

<h:commandLink id="sidlink" action="#{studentController.selectStudent(studData)}" target="_blank">  
    <h:outputText value="#{studData.studentId}" styleClass="txtlink" />
</h:commandLink>

I changed <p:commandLink> to <h:commandLink>, and call a method in the backing bean to set the selected Student.(For the New Window should need the student information.)

Here is the code of studentController.selectStudent :

private Student selectedStu;

public String selectStudent(Student stu) {
    selectedStu = stu;
    return "/studentinfo.xhtml";
}

And the following is the code of New Window?

 <h:form>
    <h:commandLink value="Another Link" action="/anotherinfo.xhtml" target="_self"/>
    <br/>
    Student: <h:outputText value="#{studentController.selectedStu.studentName}"/>
 </h:form>

Which is just showing name of the selected Student, and another link you want.
Note that the target attribute is _self because you want the new page show in the same window.

Finally, the anotherinfo.xhtml is just an empty page I created via NetBeans, so there's no need to post it.

And here's what you may see:

After clicking the id of "Johnson" :

After clicking "Another Link" :

Update

As @User2561626 explain what he/she intended to, I update my answer as follow:
If you want a New Window pop up in stead of New Tab, you should change the code like:

<p:commandLink id="sidlink" actionListener="#{studentController.selectStudent(studData)}" oncomplete="window.open('studentinfo.xhtml', 'newwindow', ');">  
    <h:outputText value="#{studData.studentId}" styleClass="txtlink" />
</p:commandLink>

I change <h:commandLink> back to <p:commandLink>, make action as actionListener because we want to set the selected Student first, finally I add window.open in oncomplete attribute so that the new page will open in a new window but not tab.
Of course we need to edit the method studentController.selectStudent(), like this:

public void selectStudent(Student stu) {
    selectedStu = stu;
}

As you can see, the return type is void now, and the only thing this method do is just set the selected Student.
Hope this may help.