Bug 176681 Issue about creating context-parameter path in read-only path[0601]
Description: Issue about creating context-parameter path in read-only path Build number:2.2.0.v20070308 Steps to reproduce: 1. Deploy birt. 2. Set BIRT_VIEWER_DOCUMENT_FOLDER/BIRT_VIEWER_IMAGE_DIR/.. to a read-only path. 3. Preview report. Expected result: Because the path is read-only, folders should be created in ${java.io.tmpdir} Actual result: No folders are created in ${java.io.tmpdir} and reports cannot be previewed in frameset mode.
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/utility/ParameterAccessor.java
* @param request
	 *            http request
	 * @param name
	 *            parameter name
	 * @param defaultValue
	 *            default parameter value
	 * @return parameter value
	 */
	public static String getReportParameter( HttpServletRequest request,
			String name, String defaultValue )
	{
		assert request != null && name != null;
		String value = getParameter( request, name );
		if ( value == null || value.length( ) <= 0 ) 
		
		{
			value = ""; 
		}
		Map paramMap = request.getParameterMap( );
		String ISOName = toISOString( name );
		if ( paramMap == null || !paramMap.containsKey( ISOName ) )
		{
			value = defaultValue;
		}
		Set nullParams = getParameterValues( request, PARAM_ISNULL );
		if ( nullParams != null && nullParams.contains( name ) )
		{
			value = null;
		}
		return value;