Wrapper组件 - 969251639/study GitHub Wiki
Wrapper其实就是一个Servlet，到了这里也就是真正Servlet入口，继续接收从context流入进来的管道数据
final class StandardWrapperValve
extends ValveBase {
...
@Override
public final void invoke(Request request, Response response)
throws IOException, ServletException {
...
// Allocate a servlet instance to process this request
try {
if (!unavailable) {
servlet = wrapper.allocate();//根据web.xml中的servletClass反射一个servlet对象出来
}
}
...
// Create the filter chain for this request
ApplicationFilterChain filterChain =
ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);//获取过滤器链
// Call the filter chain for this request
// NOTE: This also calls the servlet's service() method
try {
if ((servlet != null) && (filterChain != null)) {
// Swallow output if needed
if (context.getSwallowOutput()) {
try {
SystemLogHandler.startCapture();
if (request.isAsyncDispatching()) {
request.getAsyncContextInternal().doInternalDispatch();
} else if (comet) {
filterChain.doFilterEvent(request.getEvent());
} else {
filterChain.doFilter(request.getRequest(),
response.getResponse());
}
} finally {
String log = SystemLogHandler.stopCapture();
if (log != null && log.length() > 0) {
context.getLogger().info(log);
}
}
} else {
if (request.isAsyncDispatching()) {
request.getAsyncContextInternal().doInternalDispatch();
} else if (comet) {
filterChain.doFilterEvent(request.getEvent());
} else {
filterChain.doFilter
(request.getRequest(), response.getResponse());
}
}
}
}
...
// Deallocate the allocated servlet instance
try {
if (servlet != null) {
wrapper.deallocate(servlet);
}
}
...
}
...
}
上面的invoke方法很长，看重点部分
- 创建Servlet
public class StandardWrapper extends ContainerBase
implements ServletConfig, Wrapper, NotificationEmitter {
@Override
public Servlet allocate() throws ServletException {
...
instance = loadServlet();
...
if (!instanceInitialized) {
initServlet(instance);
}
}
}
...
}
public synchronized Servlet loadServlet() throws ServletException {
...
Servlet servlet;
...
InstanceManager instanceManager = ((StandardContext)getParent()).getInstanceManager();
...
servlet = (Servlet) instanceManager.newInstance(servletClass);
...
initServlet(servlet);
...
return servlet;
}
private synchronized void initServlet(Servlet servlet)
throws ServletException {
....
servlet.init(facade);
....
instanceInitialized = true;
}
}
- 获取可以拦截该servlet的过滤器链
public final class ApplicationFilterFactory {
...
@SuppressWarnings("deprecation")
public static ApplicationFilterChain createFilterChain
(ServletRequest request, Wrapper wrapper, Servlet servlet) {
// get the dispatcher type
DispatcherType dispatcher = null;
if (request.getAttribute(Globals.DISPATCHER_TYPE_ATTR) != null) {
dispatcher = (DispatcherType) request.getAttribute(
Globals.DISPATCHER_TYPE_ATTR);
}
String requestPath = null;
Object attribute = request.getAttribute(
Globals.DISPATCHER_REQUEST_PATH_ATTR);
if (attribute != null){
requestPath = attribute.toString();
}
// If there is no servlet to execute, return null
if (servlet == null)
return (null);
boolean comet = false;
// Create and initialize a filter chain object
ApplicationFilterChain filterChain = null;
if (request instanceof Request) {
Request req = (Request) request;
comet = req.isComet();
if (Globals.IS_SECURITY_ENABLED) {
// Security: Do not recycle
filterChain = new ApplicationFilterChain();
if (comet) {
req.setFilterChain(filterChain);
}
} else {
filterChain = (ApplicationFilterChain) req.getFilterChain();
if (filterChain == null) {
filterChain = new ApplicationFilterChain();
req.setFilterChain(filterChain);
}
}
} else {
// Request dispatcher in use
filterChain = new ApplicationFilterChain();
}
filterChain.setServlet(servlet);
filterChain.setSupport
(((StandardWrapper)wrapper).getInstanceSupport());
// Acquire the filter mappings for this Context
StandardContext context = (StandardContext) wrapper.getParent();
FilterMap filterMaps[] = context.findFilterMaps();
// If there are no filter mappings, we are done
if ((filterMaps == null) || (filterMaps.length == 0))
return (filterChain);
// Acquire the information we will need to match filter mappings
String servletName = wrapper.getName();
// Add the relevant path-mapped filters to this filter chain
// 匹配过滤器
for (int i = 0; i < filterMaps.length; i++) {
if (!matchDispatcher(filterMaps[i] ,dispatcher)) {
continue;
}
if (!matchFiltersURL(filterMaps[i], requestPath))//是否匹配拦截
continue;
ApplicationFilterConfig filterConfig = (ApplicationFilterConfig)
context.findFilterConfig(filterMaps[i].getFilterName());
if (filterConfig == null) {
// FIXME - log configuration problem
continue;
}
boolean isCometFilter = false;
if (comet) {
try {
isCometFilter = filterConfig.getFilter() instanceof CometFilter;
} catch (Exception e) {
// Note: The try catch is there because getFilter has a lot of
// declared exceptions. However, the filter is allocated much
// earlier
Throwable t = ExceptionUtils.unwrapInvocationTargetException(e);
ExceptionUtils.handleThrowable(t);
}
if (isCometFilter) {
filterChain.addFilter(filterConfig);
}
} else {
filterChain.addFilter(filterConfig);
}
}
// 匹配servlet
// Add filters that match on servlet name second
for (int i = 0; i < filterMaps.length; i++) {
if (!matchDispatcher(filterMaps[i] ,dispatcher)) {
continue;
}
if (!matchFiltersServlet(filterMaps[i], servletName))//根据servlet name匹配
continue;
ApplicationFilterConfig filterConfig = (ApplicationFilterConfig)
context.findFilterConfig(filterMaps[i].getFilterName());
if (filterConfig == null) {
// FIXME - log configuration problem
continue;
}
boolean isCometFilter = false;
if (comet) {
try {
isCometFilter = filterConfig.getFilter() instanceof CometFilter;
} catch (Exception e) {
// Note: The try catch is there because getFilter has a lot of
// declared exceptions. However, the filter is allocated much
// earlier
}
if (isCometFilter) {
filterChain.addFilter(filterConfig);
}
} else {
filterChain.addFilter(filterConfig);
}
}
// Return the completed filter chain
return (filterChain);
}
...
}
- 调用过滤器链，同时也调用Servlet的service方法执行servlet逻辑
final class ApplicationFilterChain implements FilterChain, CometFilterChain {
...
@Override
public void doFilter(ServletRequest request, ServletResponse response)
throws IOException, ServletException {
...
internalDoFilter(request,response);
...
}
private void internalDoFilter(ServletRequest request,
ServletResponse response)
throws IOException, ServletException {
// Call the next filter if there is one
if (pos < n) {//true执行filter，否则执行servlet
ApplicationFilterConfig filterConfig = filters[pos++];
Filter filter = null;
...
filter = filterConfig.getFilter();
...
filter.doFilter(request, response, this);//调用下一个filter
...
return;
}
...
servlet.service(request, response);//调用Servlet的service方法
...
}
...
}