JFinal实现原理
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。