[TOC]
本篇介绍了StandardHost中使用的三个Valve：StandardHostValve，ErrorReportValve，ErrorDispatcherValve
StandardHostValve
StandardHostValve的核心就一个invoke方法。里面就是根据Request匹配Context，并将Request传递给匹配到的Context。
public void invoke(Request request, Response response, ValveContext valveContext)
throws IOException, ServletException {
if (!(request.getRequest() instanceof HttpServletRequest) ||
!(response.getResponse() instanceof HttpServletResponse)) {
return;
}
//选择一个Context子容器继续处理Request
StandardHost host = (StandardHost) getContainer();
Context context = (Context) host.map(request, true);
if (context == null) {
((HttpServletResponse) response.getResponse()).sendError
(HttpServletResponse.SC_INTERNAL_SERVER_ERROR,sm.getString("standardHost.noContext"));
return;
}
// 为当前线程绑定ClassLoader
Thread.currentThread().setContextClassLoader
(context.getLoader().getClassLoader());
//更新session最后的访问时间
HttpServletRequest hreq = (HttpServletRequest) request.getRequest();
String sessionId = hreq.getRequestedSessionId();
if (sessionId != null) {
Manager manager = context.getManager();
if (manager != null) {
Session session = manager.findSession(sessionId);
if ((session != null) && session.isValid())
session.access();
}
}
// 请求context继续处理Request
context.invoke(request, response);
}
ErrorReportValve
- 一般工作在Host上的Valve，当关联Context时，也能够正常工作
- 当ErrorReportValve在Response没有状态码且已经写入Header才不会继续向下调用
Valve的核心方法invoke：
- invoke(Request request, Response response,ValveContext context)
public void invoke(Request request, Response response, ValveContext context)
throws IOException, ServletException {
//调用ValveContext中的InvokeNext方法，即先执行下一个Valve
context.invokeNext(request, response);
ServletRequest sreq = (ServletRequest) request;
Throwable throwable = (Throwable) sreq.getAttribute(Globals.EXCEPTION_ATTR);
ServletResponse sresp = (ServletResponse) response;
//commit状态代表response已经有status code且被写入了header
if (sresp.isCommitted()) {
return;
}
if (throwable != null) {
// The response is an error
response.setError();
//重置response
try {
sresp.reset();
} catch (IllegalStateException e) {
}
ServletResponse sresponse = (ServletResponse) response;
if (sresponse instanceof HttpServletResponse)
((HttpServletResponse) sresponse).sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
}
//设置暂停标志位位false
response.setSuspended(false);
try {
//返回错误页面
report(request, response, throwable);
} catch (Throwable tt) {
tt.printStackTrace();
}
}
- report方法是将response中的错误信息拼接为html，设置到response中
protected void report(Request request, Response response, Throwable throwable) throws IOException {
//不是HttpResponse直接返回
if (!(response instanceof HttpResponse))
return;
HttpResponse hresponse = (HttpResponse) response;
//不是HttpServletResponse直接返回
if (!(response instanceof HttpServletResponse))
return;
HttpServletResponse hres = (HttpServletResponse) response;
int statusCode = hresponse.getStatus();
String message = RequestUtil.filter(hresponse.getMessage());
if (message == null)
message = "";
if (statusCode < 300)
return;
if (statusCode == HttpServletResponse.SC_NOT_MODIFIED)
return;
//对于异常的处理
Throwable rootCause = null;
if (throwable != null) {
if (throwable instanceof ServletException)
rootCause = ((ServletException) throwable).getRootCause();
}
// Do nothing if there is no report for the specified status code
String report = null;
try {
report = sm.getString("http." + statusCode, message);
} catch (Throwable t) {
;
}
if (report == null)
return;
StringBuffer sb = new StringBuffer();
sb.append("<html><head><title>");
sb.append(ServerInfo.getServerInfo()).append(" - ");
sb.append(sm.getString("errorReportValve.errorReport"));
sb.append("</title>");
sb.append("<STYLE><!--");
sb.append("H1{font-family : sans-serif,Arial,Tahoma;color : white;background-color : #0086b2;} ");
sb.append("H3{font-family : sans-serif,Arial,Tahoma;color : white;background-color : #0086b2;} ");
sb.append("BODY{font-family : sans-serif,Arial,Tahoma;color : black;background-color : white;} ");
sb.append("B{color : white;background-color : #0086b2;} ");
sb.append("HR{color : #0086b2;} ");
sb.append("--></STYLE> ");
sb.append("</head><body>");
sb.append("<h1>");
sb.append(sm.getString("errorReportValve.statusHeader",
"" + statusCode, message)).append("</h1>");
sb.append("<HR size=\"1\" noshade>");
sb.append("<p><b>type</b> ");
if (throwable != null) {
sb.append(sm.getString("errorReportValve.exceptionReport"));
} else {
sb.append(sm.getString("errorReportValve.statusReport"));
}
sb.append("</p>");
sb.append("<p><b>");
sb.append(sm.getString("errorReportValve.message"));
sb.append("</b> <u>");
sb.append(message).append("</u></p>");
sb.append("<p><b>");
sb.append(sm.getString("errorReportValve.description"));
sb.append("</b> <u>");
sb.append(report);
sb.append("</u></p>");
if (throwable != null) {
StringWriter stackTrace = new StringWriter();
throwable.printStackTrace(new PrintWriter(stackTrace));
sb.append("<p><b>");
sb.append(sm.getString("errorReportValve.exception"));
sb.append("</b> <pre>");
sb.append(stackTrace.toString());
sb.append("</pre></p>");
if (rootCause != null) {
stackTrace = new StringWriter();
rootCause.printStackTrace(new PrintWriter(stackTrace));
sb.append("<p><b>");
sb.append(sm.getString("errorReportValve.rootCause"));
sb.append("</b> <pre>");
sb.append(stackTrace.toString());
sb.append("</pre></p>");
}
}
sb.append("<HR size=\"1\" noshade>");
sb.append("<h3>").append(ServerInfo.getServerInfo()).append("</h3>");
sb.append("</body></html>");
//向response中写入生成的report数据
try {
Writer writer = response.getReporter();
if (writer != null) {
Locale locale = Locale.getDefault();
try {
hres.setContentType("text/html");
hres.setLocale(locale);
} catch (Throwable t) {
if (debug >= 1)
log("status.setContentType", t);
}
writer.write(sb.toString());
writer.flush();
}
} catch (IOException e) {
;
} catch (IllegalStateException e) {
;
}
}
ErrorDispatcherValve
ErrorDispatcherValve阀主要是根据异常状态和状态码，去匹配合适的ErrorPage进行重定向。
- invoke(Request request, Response response, ValveContext context)
public void invoke(Request request, Response response,
ValveContext context)
throws IOException, ServletException {
// 通过ValveContext先调用下一个Valve
context.invokeNext(request, response);
response.setSuspended(false);
ServletRequest sreq = request.getRequest();
Throwable t = (Throwable) sreq.getAttribute(Globals.EXCEPTION_ATTR);
if (t != null) {
throwable(request, response, t);
} else {
status(request, response);
}
}
invoke方法会根据Request中参数中的EXCEPTION_ATTR值，来获取到Throwable对象。
如果存在Throwable对象，就进入异常处理流程。否者进入到状态码处理流程。
- void throwable(Request request, Response response, Throwable throwable)
protected void throwable(Request request, Response response, Throwable throwable) {
Context context = request.getContext();
if (context == null)
return;
//异常信息
Throwable realError = throwable;
if (realError instanceof ServletException) {
realError = ((ServletException) realError).getRootCause();
if (realError == null) {
realError = throwable;
}
}
//查找异常对应的ErrorPage
ErrorPage errorPage = findErrorPage(context, realError);
//当找到errorPage时，设置Request与Response的各种参数
if (errorPage != null) {
response.setAppCommitted(false);
ServletRequest sreq = request.getRequest();
ServletResponse sresp = response.getResponse();
sreq.setAttribute(Globals.STATUS_CODE_ATTR, new Integer(HttpServletResponse.SC_INTERNAL_SERVER_ERROR));
sreq.setAttribute(Globals.ERROR_MESSAGE_ATTR, throwable.getMessage());
sreq.setAttribute(Globals.EXCEPTION_ATTR, realError);
Wrapper wrapper = request.getWrapper();
if (wrapper != null)
sreq.setAttribute(Globals.SERVLET_NAME_ATTR, wrapper.getName());
if (sreq instanceof HttpServletRequest)
sreq.setAttribute(Globals.EXCEPTION_PAGE_ATTR, ((HttpServletRequest) sreq).getRequestURI());
sreq.setAttribute(Globals.EXCEPTION_TYPE_ATTR, realError.getClass());
//重要！通过重定向到ErrorPage页面处理status code与exception
if (custom(request, response, errorPage)) {
try {
sresp.flushBuffer();
} catch (IOException e) {
log("Exception Processing " + errorPage, e);
}
}
}
}
ErrorDispatcherValve中的findErrorPage方法，会先根据异常获取到类名，然后到Context中查找对应的ErrorPage。
当前类名查找不到，就查找向上查找，查找父类。
- ErrorPage findErrorPage(Context context, Throwable exception)
protected static ErrorPage findErrorPage(Context context, Throwable exception) {
if (exception == null)
return (null);
//获取的异常的Class，通过class的name去查找errorPage。
Class clazz = exception.getClass();
String name = clazz.getName();
while (!"java.lang.Object".equals(clazz)) {
//通过Context获取到指定的ErrorPage
ErrorPage errorPage = context.findErrorPage(name);
if (errorPage != null)
return (errorPage);
clazz = clazz.getSuperclass();
if (clazz == null)
break;
name = clazz.getName();
}
return (null);
}
status方法主要是根据Response的状态码，来查找对应的ErrorPage
- void status(Request request, Response response)
protected void status(Request request, Response response) {
if (!(response instanceof HttpResponse))
return;
HttpResponse hresponse = (HttpResponse) response;
if (!(response.getResponse() instanceof HttpServletResponse))
return;
int statusCode = hresponse.getStatus();
String message = RequestUtil.filter(hresponse.getMessage());
if (message == null)
message = "";
//获取一个处理该status code 的通用error page
Context context = request.getContext();
if (context == null)
return;
ErrorPage errorPage = context.findErrorPage(statusCode);
if (errorPage != null) {
response.setAppCommitted(false);
ServletRequest sreq = request.getRequest();
ServletResponse sresp = response.getResponse();
sreq.setAttribute(Globals.STATUS_CODE_ATTR,new Integer(statusCode));
sreq.setAttribute(Globals.ERROR_MESSAGE_ATTR,message);
//获取到request对应的Wrapper(servlet)
Wrapper wrapper = request.getWrapper();
if (wrapper != null)
sreq.setAttribute(Globals.SERVLET_NAME_ATTR, wrapper.getName());
if (sreq instanceof HttpServletRequest)
sreq.setAttribute(Globals.EXCEPTION_PAGE_ATTR,((HttpServletRequest) sreq).getRequestURI());
//重要！通过重定向到ErrorPage页面处理status code与exception
if (custom(request, response, errorPage)) {
try {
sresp.flushBuffer();
} catch (IOException e) {
log("Exception Processing " + errorPage, e);
}
}
}
}
custom的作用主要是重定向到之前查找到的error page页面
- boolean custom(Request request, Response response, ErrorPage errorPage)
protected boolean custom(Request request, Response response, ErrorPage errorPage) {
if (!(request instanceof HttpRequest)) {
return (false);
}
HttpServletRequest hreq = (HttpServletRequest) request.getRequest();
if (!(response instanceof HttpResponse)) {
return (false);
}
HttpServletResponse hres = (HttpServletResponse) response.getResponse();
try {
//resset response
hres.reset();
//重定向到指定位置的Error Page
ServletContext servletContext = request.getContext().getServletContext();
RequestDispatcher rd = servletContext.getRequestDispatcher(errorPage.getLocation());
rd.forward(hreq, hres);
//如果我们重定向，响应再次暂停
response.setSuspended(false);
return (true);
} catch (Throwable t) {
log("Exception Processing " + errorPage, t);
return (false);
}
}
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