If the textfield is named ./contactPerson - you should be albe to get using --
As we write all components now in HTL for examples (we encourage use of HTL over JSP) - we use this syntax in HTL:
Your question is not clear,
Would appreciate if you can rephrase it
Are you thinking of doing post-AJAX call from JSP file to fetch some textfeild value?
If so refer following article:
2.Adobe Experience Manager Help | Programmatically Accessing Adobe Experience Manager Content using the JCR API to extract JCR node values.
Otherwise as mentioned by Scott, at HTL side or JSP side you can extract out the values:
<%=properties.get("contactPerson") %> [JSP]