JFinal学习笔记

一切都从web.xml开始说起：

当服务器初始化的时候会初始化web.xml里面的相关配置信息。下面我们来看一个重要的过滤器配置：JFinalFilter。下面是相关的配置信息

<filter>

<filter-name>jfinal</filter-name>

<filter-class>com.jfinal.core.JFinalFilter</filter-class>

<init-param>

<param-name>configClass</param-name>

<param-value>demo.DemoConfig</param-value>

</init-param>

</filter>

<filter-mapping>

<filter-name>jfinal</filter-name>

<url-pattern>/*</url-pattern>

</filter-mapping>

</filter>

这就意味着所有的请求都要经过JFinalFiter过滤了

从中我们可以看到在web.xml之中配置了一个名为JFinalFilter的过滤器。下面我们来看看JFinalFiter的源码。

public final 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 Logger log;

private int contextPathLength;

//系统在初始化Servlet的时候自动调用该方法

public void init(FilterConfig filterConfig) throws ServletException {

//创建JFianlConfig对象

createJFinalConfig(filterConfig.getInitParameter("configClass"));

//所有的初始化操作都在这里进行了，以后会再次提到这里！

if (jfinal.init(jfinalConfig, filterConfig.getServletContext()) == false)

throw new RuntimeException("JFinal init error!");

handler = jfinal.getHandler();

constants = Config.getConstants();

encoding = constants.getEncoding();

jfinalConfig.afterJFinalStart();

//得到项目根路径

String contextPath = filterConfig.getServletContext().getContextPath();

//如果项目路径为null或者只有一个'/',就定义项目路径的长度为0，否则还是其原来的长度。

contextPathLength = (contextPath == null || "/".equals(contextPath) ? 0 : contextPath.length());

}

//request和response的作用不用过多介绍了。这个FilterChain的左右主要是用来连续调用下一个Filter时候使用的，下面给出了FilterChain的作用介绍

/**

* A FilterChain is an object provided by the servlet container to the developer

* giving a view into the invocation chain of a filtered request for a resource. Filters

* use the FilterChain to invoke the next filter in the chain, or if the calling filter

* is the last filter in the chain, to invoke the resource at the end of the chain.

*

* @see Filter

* @since Servlet 2.3

**/

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)

//得到其ServletPath以及相关的参数

target = target.substring(contextPathLength);

boolean[] isHandled = {false};

try {

//idHandler用来判断该Target是否应该被相应的handler处理

//这是整个Filter的最核心方法

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");

try {

Object temp = Class.forName(configClass).newInstance();

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");

} catch (InstantiationException e) {

throw new RuntimeException("Can not create instance of class: " + configClass, e);

} catch (IllegalAccessException e) {

throw new RuntimeException("Can not create instance of class: " + configClass, e);

} catch (ClassNotFoundException e) {

throw new RuntimeException("Class not found: " + configClass + ". Please config it in web.xml", e);

}

}

static void initLogger() {

log = Logger.getLogger(JFinalFilter.class);

}

}

让我们重点看看这个handler的由来。

首先由handler = jfinal.getHandler();知道这个handler是由jfinal对象得来的，现在让我们看看jfinal的部分源码：

public final class JFinal {

private Constants constants;

private ActionMapping actionMapping;

private Handler handler;。。。。。定义了其他成员变量

Handler getHandler() {

return handler;

}

private static final JFinal me = new JFinal();

//初始化JFinal时候调用的方法(在上面已经提到过这一点)

boolean init(JFinalConfig jfinalConfig, ServletContext servletContext) {

this.servletContext = servletContext;

this.contextPath = servletContext.getContextPath();

initPathUtil();

Config.configJFinal(jfinalConfig); // start plugin and init logger factory in this method

constants = Config.getConstants();

initActionMapping();

initHandler();

initRender();

initOreillyCos();

initI18n();

initTokenManager();

return true;

}

private void initHandler() {

Handler actionHandler = new ActionHandler(actionMapping, constants);

handler = HandlerFactory.getHandler(Config.getHandlers().getHandlerList(), actionHandler);

}

}

由这里我们知道handler是由HandlerFactory的getHandler方法得来的。

让我们再次看看HandlerFactory的部分源码以探个究竟：

public class HandlerFactory {

private HandlerFactory() {

}

/**

* Build handler chain

*/

public static Handler getHandler(List<Handler> handlerList, Handler actionHandler) {

Handler result = actionHandler;

for (int i=handlerList.size()-1; i>=0; i--) {

Handler temp = handlerList.get(i);

temp.nextHandler = result;

result = temp;

}

return result;

}

}

显然这里返回的是一个actionHandler为首handler chain。

让我们再来看看这个：

Handler actionHandler = new ActionHandler(actionMapping, constants);

handler = HandlerFactory.getHandler(Config.getHandlers().getHandlerList(), actionHandler);

此处传进去并不是简单的handler，而是他的字类ActionHandler，并且传进去了有两个参数，一个是ActionMapping类的变量，一个是constants。对于后者将就是一些常量的设置所以不进行过多介绍。让我们先看看ActionMapping之后再来看这个ActionHandler。

final class ActionMapping {

private static final String SLASH = "/";

private Routes routes;

private Interceptors interceptors;

private final Map<String, Action> mapping = new HashMap<String, Action>();

ActionMapping(Routes routes, Interceptors interceptors) {

this.routes = routes;

this.interceptors = interceptors;

}

在ActionMapping中定义了一个路由(routes)和一个Interceptors,这个routes类里面主要的核心是两个Map,内容如下(截取了部分源码过来)：

//每一个访问路径(controllerKey)都对应有一个相应的controller，并作为一对Entry放到map中

private final Map<String, Class<? extends Controller>> map = new HashMap<String, Class<? extends Controller>>();

//每一个访问路径(controllerKey)都对应一个在项目中的实际存放路径(WEB-INF/index.jsp等等)，并作为一对Entry放到viewPathMap中

private final Map<String, String> viewPathMap = new HashMap<String, String>();

因此我们知道这个ActionHandler就是处理一些关于ActionMapping中对应的ControllerKey与Controller.class的事情。

所以现在既然这些都已经清楚了，我们可以看看ActionHandler的庐山真面目了。

在ActionHandler中我们可以看到这样一行注释：

/**

* handle

* 1: Action action = actionMapping.getAction(target)

* 2: new ActionInvocation(...).invoke()

* 3: render(...)

*/

这就解释了handle方法需要做的事情了，首先是根据ActionMapping获得相应的Action，然后利用反射进行方法的调用，最后把结果映射到相应的页面上去。这就是核心的三个步骤了，接下来让我们详细的读一下这个源码：

final class ActionHandler extends Handler {

private final boolean devMode;

private final ActionMapping actionMapping;

private static final RenderFactory renderFactory = RenderFactory.me();

private static final Logger log = Logger.getLogger(ActionHandler.class);

public ActionHandler(ActionMapping actionMapping, Constants constants) {

this.actionMapping = actionMapping;

this.devMode = constants.getDevMode();

}

/**

* handle

* 1: Action action = actionMapping.getAction(target)

* 2: new ActionInvocation(...).invoke()

* 3: render(...)

*/

//这里进行了核心的handle方法描述：

这里的target为以下格式:http://localhost:8080/ContextPath/ControllerKey/MethodName/parameters

public final void handle(String target, HttpServletRequest request, HttpServletResponse response, boolean[] isHandled) {

if (target.indexOf(".") != -1) {

return ;

}

isHandled[0] = true;

String[] urlPara = {null};

Action action = actionMapping.getAction(target, urlPara);

//判断Action是否为空

if (action == null) {

if (log.isWarnEnabled()) {

String qs = request.getQueryString();

log.warn("404 Action Not Found: " + (qs == null ? target : target + "?" + qs));

}

renderFactory.getErrorRender(404).setContext(request, response).render();

return ;

}

//Action不为空时候：

try {

//得到对应的Controller

Controller controller = action.getControllerClass().newInstance();

controller.init(request, response, urlPara[0]);

if (devMode) {

boolean isMultipartRequest = ActionReporter.reportCommonRequest(controller, action);

//利用反射执行相关的Action

new ActionInvocation(action, controller).invoke();

if (isMultipartRequest) ActionReporter.reportMultipartRequest(controller, action);

}

else {

new ActionInvocation(action, controller).invoke();

}

Render render = controller.getRender();

if (render instanceof ActionRender) {

String actionUrl = ((ActionRender)render).getActionUrl();

if (target.equals(actionUrl))

throw new RuntimeException("The forward action url is the same as before.");

else

handle(actionUrl, request, response, isHandled);

return ;

}

if (render == null)

render = renderFactory.getDefaultRender(action.getViewPath() + action.getMethodName());

render.setContext(request, response, action.getViewPath()).render();

}

catch (RenderException e) {

if (log.isErrorEnabled()) {

String qs = request.getQueryString();

log.error(qs == null ? target : target + "?" + qs, e);

}

}

catch (ActionException e) {

int errorCode = e.getErrorCode();

if (errorCode == 404 && log.isWarnEnabled()) {

String qs = request.getQueryString();

log.warn("404 Not Found: " + (qs == null ? target : target + "?" + qs));

}

else if (errorCode == 401 && log.isWarnEnabled()) {

String qs = request.getQueryString();

log.warn("401 Unauthorized: " + (qs == null ? target : target + "?" + qs));

}

else if (errorCode == 403 && log.isWarnEnabled()) {

String qs = request.getQueryString();

log.warn("403 Forbidden: " + (qs == null ? target : target + "?" + qs));

}

else if (log.isErrorEnabled()) {

String qs = request.getQueryString();

log.error(qs == null ? target : target + "?" + qs, e);

}

e.getErrorRender().setContext(request, response).render();

}

catch (Exception e) {

if (log.isErrorEnabled()) {

String qs = request.getQueryString();

log.error(qs == null ? target : target + "?" + qs, e);

}

renderFactory.getErrorRender(500).setContext(request, response).render();

}

}

}

到这里，我们简单了看了一下JFinal的实现原理。