request parameter를 서버단에서 추가하기

filter단에서 request parameter에 기본적으로 셋팅하고 싶은 정보가 있을때 사용한다.  

AddParamHttpRequest.java

public class AddParamHttpRequest extends HttpServletRequestWrapper {

	private final Map modifiableParameters;
	private Map allParameters = null;

	/**
	 * Create a new request wrapper that will merge additional parameters into
	 * the request object without prematurely reading parameters from the
	 * original request.
	 * 
	 * @param request
	 * @param additionalParams
	 */
	public AddParamHttpRequest(final HttpServletRequest request,
			final Map additionalParams) {
		super(request);
		modifiableParameters = new TreeMap();
		modifiableParameters.putAll(additionalParams);
	}

	@Override
	public String getParameter(final String name) {
		String[] strings = getParameterMap().get(name);
		if (strings != null) {
			return strings[0];
		}
		return super.getParameter(name);
	}

	@Override
	public Map getParameterMap() {
		if (allParameters == null) {
			allParameters = new TreeMap();
			allParameters.putAll(super.getParameterMap());
			allParameters.putAll(modifiableParameters);
		}
		// Return an unmodifiable collection because we need to uphold the
		// interface contract.
		return Collections.unmodifiableMap(allParameters);
	}

	@Override
	public Enumeration getParameterNames() {
		return Collections.enumeration(getParameterMap().keySet());
	}

	@Override
	public String[] getParameterValues(final String name) {
		return getParameterMap().get(name);
	}
}