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
* Push User-defined application context object into engine context map.
	 * 
	 * @param map
	 * @param request
	 * @return
	 */
	public static Map pushAppContext( Map map, HttpServletRequest request )
	{
		if ( map == null )
			map = new HashMap( );
		
		String appContextKey = (String) request
				.getAttribute( ATTR_APPCONTEXT_KEY );
		
		if ( appContextKey != null )
			map.put( appContextKey, request
					.getAttribute( ATTR_APPCONTEXT_VALUE ) );
		return map;
	}
	/**
	 * Returns the encoding for export data.
	 * 
	 * @param request
	 * @return
	 */
	public static String getExportEncoding( HttpServletRequest request )
	{
		String encoding = getParameter( request, PARAM_EXPORT_ENCODING );
		
		if ( encoding == null )