A great solution to consider in this scenario is using Filters:
1. Develop a filter that wraps the original request with new parameters:
@WebFilter("/scripts/*")
public class CustomFilter implements Filter
{
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException,
ServletException
{
String version=request.getParameter("version");
if (version == null)
{
Map<String, String[]> myParameters=new HashMap<>(request.getParameterMap());
request=new EnhancedHttpServletRequest((HttpServletRequest)request, myParameters);
}
chain.doFilter(request, response);
}
// ... implement rest of the Filter logic...
}
2. Implement the request wrapper:
public class EnhancedHttpServletRequest extends HttpServletRequestWrapper
{
private final Map<String, String[]> parameters;
public EnhancedHttpServletRequest(HttpServletRequest request, Map<String, String[]> parameters)
{
super(request);
this.parameters=parameters;
}
@Override
public String getParameter(String name)
{
String[] values=parameters.get(name);
return values!=null && values.length > 0
? values[0]
: null;
}
@Override
public Map<String, String[]> getParameterMap()
{
return parameters;
}
}
Update
If you need to override the getQueryString method, you can do it like this:
@Override
public String getQueryString()
{
String queryString;
try
{
queryString=super.getQueryString();
if (queryString == null)
{
queryString="?";
}
for (Map.Entry<String, String[]> param : getParameterMap().entrySet())
{
queryString+="&";
for (String value : param.getValue())
{
queryString+=URLEncoder.encode(param.getKey(), "UTF-8") + "=" + URLEncoder.encode(value, "UTF-8");
}
}
}
catch (UnsupportedEncodingException e)
{
throw new java.lang.RuntimeException("Unhandled exception", e);
}
return queryString;
}
}