jfinal學習筆記02 源碼解讀JFinalFilter

當運行起來後，咱們能夠看看如此短小精悍的神器的原理是什麼？確定會有人有疑惑。下面咱們來初步學習一下。

首先看web.xml ， 能夠看到他只有一個filter(過濾器)。 能夠確定他的核心是filter(過濾器)構成的。

/**
 * JFinal framework filter
 */
public class JFinalFilter implements Filter {
	
	private Handler handler;
	private String encoding;
	private JFinalConfig jfinalConfig;
	private Constants constants;
	private static final JFinal jfinal = JFinal.me();
	private static Log log;
	private int contextPathLength;

	//方法在 Filter 生命週期中僅執行一次，web 容器在調用 init 方法時
	public void init(FilterConfig filterConfig) throws ServletException {
        //從web.xml裏讀取configClass參數，並初始化jfinalConfig這個類
		createJFinalConfig(filterConfig.getInitParameter("configClass"));
		//初始化一些參數配置
		if (jfinal.init(jfinalConfig, filterConfig.getServletContext()) == false) {
			throw new RuntimeException("JFinal init error!");
		}
		
		handler = jfinal.getHandler();
		constants = Config.getConstants();
		encoding = constants.getEncoding();
		jfinalConfig.afterJFinalStart();
		
		String contextPath = filterConfig.getServletContext().getContextPath();
		contextPathLength = (contextPath == null || "/".equals(contextPath) ? 0 : contextPath.length());
	}
	
	public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest)req;
		HttpServletResponse response = (HttpServletResponse)res;
		request.setCharacterEncoding(encoding);
		
		String target = request.getRequestURI();
		if (contextPathLength != 0) {
			target = target.substring(contextPathLength);
		}
		
		boolean[] isHandled = {false};
		try {
			handler.handle(target, request, response, isHandled);
		}
		catch (Exception e) {
			if (log.isErrorEnabled()) {
				String qs = request.getQueryString();
				log.error(qs == null ? target : target + "?" + qs, e);
			}
		}
		
		if (isHandled[0] == false) {
			chain.doFilter(request, response);
		}
	}
	
	public void destroy() {
		jfinalConfig.beforeJFinalStop();
		jfinal.stopPlugins();
	}
	
	private void createJFinalConfig(String configClass) {
		if (configClass == null) {
			throw new RuntimeException("Please set configClass parameter of JFinalFilter in web.xml");
		}
		
		Object temp = null;
		try {
			temp = Class.forName(configClass).newInstance();
		} catch (Exception e) {
			throw new RuntimeException("Can not create instance of class: " + configClass, e);
		}
		
		if (temp instanceof JFinalConfig) {
			jfinalConfig = (JFinalConfig)temp;
		} else {
			throw new RuntimeException("Can not create instance of class: " + configClass + ". Please check the config in web.xml");
		}
	}
	
	static void initLog() {
		log = Log.getLog(JFinalFilter.class);
	}
}

概念解讀

Filter  ： http://www.javashuo.com/article/p-kjjxrnqw-hv.html