Reading Parameter
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Handling The Client Request: FORM DATA Objectives
Reading individual request parameters Reading entire set of request parameter Handling missing and malformed data Filtering special characters out of request parameter Automatically filling in a data object with request parameter values. Dealing with incomplete form submission.
Reading single values:
To read a request parameter, you simply call the getParameter() methods of HttpServletRequest, supplying casesensitive parameter name. An empty String is returned if parameter exists but it does not have any value. Null is returned if there was no such parameter.
getParameterValues()
If same parameter name might appear in the form data more than once, you should call getParameterValues() instead of getParameter() The return value of getParameterValues is null for non existent parameter names and is a none element array when
getParameterNames() and getParameterMap()
The getParameterNames() returns an empty Enumeration(not null) . Enumeration is an interface that merely guarantees that actual class will have hasMoreElements and nextElement. An alternative to getParameterNames is getParameterMap. This method returns a Map.
Reading input in multiple character sets: setCharacterEncoding()
By default request.getParameter interprets inp1ut using the server’s current character set. To change the default use setCharacterEncoding() method of ServletRequest.
Using default values when parameters are missing
The value is null The value is an empty string The value is not empty string of wrong format.
Handling The Client Request: FORM DATA Objectives
Reading individual request parameters Reading entire set of request parameter Handling missing and malformed data Filtering special characters out of request parameter Automatically filling in a data object with request parameter values. Dealing with incomplete form submission.
Reading single values:
To read a request parameter, you simply call the getParameter() methods of HttpServletRequest, supplying casesensitive parameter name. An empty String is returned if parameter exists but it does not have any value. Null is returned if there was no such parameter.
getParameterValues()
If same parameter name might appear in the form data more than once, you should call getParameterValues() instead of getParameter() The return value of getParameterValues is null for non existent parameter names and is a none element array when
getParameterNames() and getParameterMap()
The getParameterNames() returns an empty Enumeration(not null) . Enumeration is an interface that merely guarantees that actual class will have hasMoreElements and nextElement. An alternative to getParameterNames is getParameterMap. This method returns a Map.
Reading input in multiple character sets: setCharacterEncoding()
By default request.getParameter interprets inp1ut using the server’s current character set. To change the default use setCharacterEncoding() method of ServletRequest.
Using default values when parameters are missing
The value is null The value is an empty string The value is not empty string of wrong format.
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