- standardWrapperValue 是 StanderWrapper运行时使用的基础阀
- standardWrapperValue 会在这里通过 StanderWrapper 加载Servlet，并且调用里面的service方法
- standardWrapperValue 会在这里完成设置的Filter中的过滤方法的调用，并且在调用完成之后，会再次调用Servlet的service方法
[TOC]
StandardWrapperValue的主要作用
StandardWrapperValue是Wrapper的标准阀，用在Pipleline流程中的最后一个valve执行。当Request请求到达Context的时候，继续传递给Wrapper，首先是调用StandardWrapper的Invoke方法(ContainerBase父类中)，如下.
public void invoke(Request request, Response response)
throws IOException, ServletException {
pipeline.invoke(request, response);
}
pipeline就是与容器关联的一系列处理流程，StandardWrapperValve在初始化的时候就被加入到了pipeline中。而下面调用的pipeline的invoke方法，就是调用里面的各种Valve的invoke方法。
下面就是是StandedWrapperValve的核心逻辑，invoke方法：
public void invoke(Request request, Response response,
ValveContext valveContext)
throws IOException, ServletException {
// Initialize local variables we may need
boolean unavailable = false;
Throwable throwable = null;
StandardWrapper wrapper = (StandardWrapper) getContainer();
ServletRequest sreq = request.getRequest();
ServletResponse sres = response.getResponse();
Servlet servlet = null;
HttpServletRequest hreq = null;
if (sreq instanceof HttpServletRequest)
hreq = (HttpServletRequest) sreq;
HttpServletResponse hres = null;
if (sres instanceof HttpServletResponse)
hres = (HttpServletResponse) sres;
// Check for the application being marked unavailable
if (!((Context) wrapper.getParent()).getAvailable()) {
//503
hres.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
sm.getString("standardContext.isUnavailable"));
unavailable = true;
}
// Check for the servlet being marked unavailable
if (!unavailable && wrapper.isUnavailable()) {
log(sm.getString("standardWrapper.isUnavailable",
wrapper.getName()));
if (hres == null) {
; // NOTE - Not much we can do generically
} else {
long available = wrapper.getAvailable();
if ((available > 0L) && (available < Long.MAX_VALUE))
hres.setDateHeader("Retry-After", available);
hres.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
sm.getString("standardWrapper.isUnavailable",
wrapper.getName()));
}
unavailable = true;
}
// Allocate a servlet instance to process this request
try {
if (!unavailable) {
//通过Wrapper获取Servlet实例，内部已经调用了service(request, response)方法，对req与res进行了字段赋值
//下面是对Response和Request进行后续的处理
servlet = wrapper.allocate();
}
} catch (ServletException e) {
log(sm.getString("standardWrapper.allocateException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
servlet = null;
} catch (Throwable e) {
log(sm.getString("standardWrapper.allocateException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
servlet = null;
}
// Acknowlege the request
try {
response.sendAcknowledgement();
} catch (IOException e) {
sreq.removeAttribute(Globals.JSP_FILE_ATTR);
log(sm.getString("standardWrapper.acknowledgeException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
} catch (Throwable e) {
log(sm.getString("standardWrapper.acknowledgeException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
servlet = null;
}
// Create the filter chain for this request
// 创建对于Request与Response的过滤链
ApplicationFilterChain filterChain =
createFilterChain(request, servlet);
// Call the filter chain for this request
// NOTE: This also calls the servlet's service() method
try {
String jspFile = wrapper.getJspFile();
if (jspFile != null)
sreq.setAttribute(Globals.JSP_FILE_ATTR, jspFile);
else
sreq.removeAttribute(Globals.JSP_FILE_ATTR);
if ((servlet != null) && (filterChain != null)) {
//使用过滤链过滤Request与Response
filterChain.doFilter(sreq, sres);
}
sreq.removeAttribute(Globals.JSP_FILE_ATTR);
} catch (IOException e) {
sreq.removeAttribute(Globals.JSP_FILE_ATTR);
log(sm.getString("standardWrapper.serviceException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
} catch (UnavailableException e) {
sreq.removeAttribute(Globals.JSP_FILE_ATTR);
log(sm.getString("standardWrapper.serviceException",
wrapper.getName()), e);
wrapper.unavailable(e);
long available = wrapper.getAvailable();
if ((available > 0L) && (available < Long.MAX_VALUE))
hres.setDateHeader("Retry-After", available);
hres.sendError(HttpServletResponse.SC_SERVICE_UNAVAILABLE,
sm.getString("standardWrapper.isUnavailable",
wrapper.getName()));
// Do not save exception in 'throwable', because we
// do not want to do exception(request, response, e) processing
} catch (ServletException e) {
sreq.removeAttribute(Globals.JSP_FILE_ATTR);
log(sm.getString("standardWrapper.serviceException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
} catch (Throwable e) {
sreq.removeAttribute(Globals.JSP_FILE_ATTR);
log(sm.getString("standardWrapper.serviceException",
wrapper.getName()), e);
throwable = e;
exception(request, response, e);
}
// Release the filter chain (if any) for this request
try {
if (filterChain != null)
//释放过滤链
filterChain.release();
} catch (Throwable e) {
log(sm.getString("standardWrapper.releaseFilters",
wrapper.getName()), e);
if (throwable == null) {
throwable = e;
exception(request, response, e);
}
}
// Deallocate the allocated servlet instance
try {
if (servlet != null) {
//释放servlet
wrapper.deallocate(servlet);
}
} catch (Throwable e) {
log(sm.getString("standardWrapper.deallocateException",
wrapper.getName()), e);
if (throwable == null) {
throwable = e;
exception(request, response, e);
}
}
// If this servlet has been marked permanently unavailable,
// unload it and release this instance
try {
if ((servlet != null) &&
(wrapper.getAvailable() == Long.MAX_VALUE)) {
//回收所有的Servlet
wrapper.unload();
}
} catch (Throwable e) {
log(sm.getString("standardWrapper.unloadException",
wrapper.getName()), e);
if (throwable == null) {
throwable = e;
exception(request, response, e);
}
}
}
上面的代码看着挺长的，对照代码主要做了下面几件事：
- 通过Wrapper获取Servlet实例，内部已经调用了service(request, response)方法，对req与res进行了字段赋值
- 给请求发送确认，这时还是空实现
- 创建对于Request与Response的过滤链
- 使用过滤链过滤Request与Response
- 释放servlet，释放的STM类型的servlet会被放入的stack中，以后会被再次使用
- 根据情况决定是否回收所有的Servlet
1. 就是通过Wrapper加载Servlet，并且调用了Servlet的Service方法。
这里的的Wrapper是指Wrapper的标准实现：StandardWrapper。里面的allocate方法会通过ClassLoader来加载一个Servlet。
具体的逻辑看StandWrapper
2. 给请求发送确认，这时还是空实现
Send an acknowledgment of a request.发送一个请求的确认。在tomcat4版本还是空实现
3. 创建对于Request与Response的过滤链
过滤链的过滤项是在Wrapper的父容器Context(StanderContext)中设置的。StanderContext提供了FilterMap[]数组来存储各个过滤项。Filter使用户可以改变一个request和修改一个response，它不是一个servlet，也不能产生response，它能够在一个request到达servlet之前预处理request，也可以在response离开servlet时处理response。
How Tomcat Works - Chapter 11 - Standard Wrapper
Tomcat Filter 源码分析
private FilterMap filterMaps[] = new FilterMap[0];
那么FilterMap到底是什么呢？下面是FilterMap的定义,里面只包含了是三个字段：
private String filterName = null; //当成功匹配时，执行名字为filterName的筛选器
private String servletName = null; //用于匹配Request的name,对应的StandardWrapper设置的Name
private String urlPattern = null; //用于匹配Request中的RequestURL，最终要对应一个StanderWrapper
而在StanderWrapperValue中，通过父容器StanderderContext获取到这个FielterMap[]数组，通过下面的代码构建过滤链：
private ApplicationFilterChain createFilterChain(Request request,
Servlet servlet) {
if (servlet == null)
return (null);
// 创建并且初始化一个过滤链对象ApplicationFilterChain
ApplicationFilterChain filterChain = new ApplicationFilterChain();
filterChain.setServlet(servlet);
StandardWrapper wrapper = (StandardWrapper) getContainer();
filterChain.setSupport(wrapper.getInstanceSupport());
// 获取Context的过滤mappings
StandardContext context = (StandardContext) wrapper.getParent();
FilterMap filterMaps[] = context.findFilterMaps();
if ((filterMaps == null) || (filterMaps.length == 0))
return (filterChain);
// 获取我们需要的匹配 fliter mappings 的信息
String requestPath = null;
if (request instanceof HttpRequest) {
HttpServletRequest hreq = (HttpServletRequest) request.getRequest();
String contextPath = hreq.getContextPath(); //设置的一个context对用的mapper匹配路径
if (contextPath == null) {
contextPath = "";
}
String requestURI = ((HttpRequest) request).getDecodedRequestURI();
//去掉RequestURI中的contextPath
if (requestURI.length() >= contextPath.length()) {
requestPath = requestURI.substring(contextPath.length());
}
}
String servletName = wrapper.getName();
int n = 0;
// 根据RequestURI匹配FilterMaps中的过滤项，添加到filterChain中
for (int i = 0; i < filterMaps.length; i++) {
if (!matchFiltersURL(filterMaps[i], requestPath))
continue;
ApplicationFilterConfig filterConfig = (ApplicationFilterConfig) context.findFilterConfig(filterMaps[i].getFilterName());
if (filterConfig == null) {
continue;
}
filterChain.addFilter(filterConfig);
n++;
}
// 根据StanderWrapper的Name来匹配FilterMaps中的过滤项，添加到filterChain
for (int i = 0; i < filterMaps.length; i++) {
if (!matchFiltersServlet(filterMaps[i], servletName))
continue;
ApplicationFilterConfig filterConfig = (ApplicationFilterConfig) context.findFilterConfig(filterMaps[i].getFilterName());
if (filterConfig == null) {
continue;
}
filterChain.addFilter(filterConfig);
n++;
}
return (filterChain);
}
在 createFilterChain 的过程中，调用了matchFiltersURL()，matchFiltersServlet()方法来判断FliterMap是否匹配到当前Request
- matchFiltersServlet：比较匹配ServletName
private boolean matchFiltersServlet(FilterMap filterMap,String servletName) {
if (servletName == null)
return (false);
else {
//比较的是FilterMap的ServletName与StanderWrapper的Name(即Servlet)
return (servletName.equals(filterMap.getServletName()));
}
}
- 调用了matchFiltersURL：比较匹配URL。解释在注释里面
private boolean matchFiltersURL(FilterMap filterMap, String requestPath) {
if (requestPath == null)
return (false);
String testPath = filterMap.getURLPattern();
if (testPath == null)
return (false);
// Case 1 - Exact Match 完全匹配
if (testPath.equals(requestPath))
return (true);
// Case 2 - Path Match ("/.../*")
if (testPath.equals("/*"))
return (true);
if (testPath.endsWith("/*")) {
String comparePath = requestPath;
//前缀匹配，如：匹配a/, /a/b/c:匹配顺序就是a/b/c --> /a/b --> a/ -->true
while (true) {
if (testPath.equals(comparePath + "/*"))
return (true);
int slash = comparePath.lastIndexOf('/');
if (slash < 0)
break;
comparePath = comparePath.substring(0, slash);
}
return (false);
}
// Case 3 - Extension Match 后缀匹配RequestURL '.' 出现之后的部分
if (testPath.startsWith("*.")) {
int slash = requestPath.lastIndexOf('/');
int period = requestPath.lastIndexOf('.');
if ((slash >= 0) && (period > slash))
return (testPath.equals("*." + requestPath.substring(period + 1)));
}
// Case 4 - "Default" Match
return (false); // NOTE - Not relevant for selecting filters
}
4. 使用过滤链过滤Request与Response：filterChain.doFilter(sreq, sres);
这里是调用ApplicationFilterChain的doFilter()方法，doFilter内部有调用了 internalDoFilter()方法。下面是internalDoFilter方法的实现：
private void internalDoFilter(ServletRequest request, ServletResponse response)
throws IOException, ServletException {
if (this.iterator == null)
this.iterator = filters.iterator();
//调用每一个Filter的Filter方法
if (this.iterator.hasNext()) {
ApplicationFilterConfig filterConfig =
(ApplicationFilterConfig) iterator.next();
Filter filter = null;
try {
filter = filterConfig.getFilter();
support.fireInstanceEvent(InstanceEvent.BEFORE_FILTER_EVENT,
filter, request, response);
//调用过滤方法
filter.doFilter(request, response, this);
support.fireInstanceEvent(InstanceEvent.AFTER_FILTER_EVENT,
filter, request, response);
}
return;
}
try {
support.fireInstanceEvent(InstanceEvent.BEFORE_SERVICE_EVENT,
servlet, request, response);
if ((request instanceof HttpServletRequest) &&
(response instanceof HttpServletResponse)) {
servlet.service((HttpServletRequest) request,
(HttpServletResponse) response);
} else {
//如果存在Filter，调用service方法处理request
servlet.service(request, response);
}
support.fireInstanceEvent(InstanceEvent.AFTER_SERVICE_EVENT,
servlet, request, response);
}
}
上面方法就只做了两件事：
- 调用每一个Filter的doFilter方法
- 在调用每一个Filter完成之后，调用service方法处理request。
doFilter的之后的逻辑，没有看，就不说了。
5. 释放servlet，释放的STM类型的servlet会被放入的stack中，以后会被再次使用：deallocate(Servlet servlet)
dealoocate的实现是在StanderWrapper中，在servlet完成service方法，完成对于request，response处理之后，之后就调用这个方法，完成回收工作
public void deallocate(Servlet servlet) throws ServletException {
//如果不是STM，就直接返回。STM类型的Servlet每次只有一个Servelt在执行Service方法
if (!singleThreadModel) {
countAllocated--;
return;
}
// 如果是STM，就放入到实例池中，以备后来使用
synchronized (instancePool) {
countAllocated--;
instancePool.push(servlet);
instancePool.notify();
}
}
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