HTTPServletRequest getParameterMap() vs getParameterNames

Question

HTTPServletRequest req, has a method getParameterMap() but, the values return a String[] instead of String, for post data as

Answer 1

If you are expecting pre determined parameters then you can use getParameter(java.lang.String name) method.

Otherwise, approaches given above can be used, but with some differences, in HTTP-request someone can send one or more parameters with the same name.

For example:

name=John, name=Joe, name=Mia

Approach 1 can be used only if you expect client sends only one parameter value for a name, rest of them will be ignored. In this example you can only read "John"

Approach 2 can be used if you expect more than one values with same name. Values will be populated as an array as you showed in the code. Hence you will be able to read all values, i.e "John","Joe","Mia" in this example

Documentation