tomcat原始碼 -- servlet呼叫過程

servlet呼叫

public class Http11Processor extends AbstractProcessor {

  @Override
    public SocketState service(SocketWrapperBase<?> socketWrapper)
        throws IOException {
。。。。。
   // Process the request in the adapter
            if (!getErrorState().isError()) {
                try {
                    rp.setStage(org.apache.coyote.Constants.STAGE_SERVICE);
                    getAdapter().service(request, response);
 。。。。。

順著 getAdapter().service 一直可以找到

inal class StandardWrapperValve
    extends ValveBase {
       @Override
    public final void invoke(Request request, Response response)
        throws IOException, ServletException {
。。。。。
 try {
 // 這裡是建立Servlet的程式碼
            if (!unavailable) {
                servlet = wrapper.allocate();
            }
        } 
。。。。。
 try {
            if ((servlet != null) && (filterChain != null)) {
                // Swallow output if needed
                if (context.getSwallowOutput()) {
                    try {
                        SystemLogHandler.startCapture();
                        if (request.isAsyncDispatching()) {
                            request.getAsyncContextInternal().doInternalDispatch();
                        } else {
                            filterChain.doFilter(request.getRequest(),
                                    response.getResponse());
                        }
                    } finally {
                        String log = SystemLogHandler.stopCapture();
                        if (log != null && log.length() > 0) {
                            context.getLogger().info(log);
                        }
                    }
                } else {
                // 這裡呼叫servlet的doDispatch()
                    if (request.isAsyncDispatching()) {
                        request.getAsyncContextInternal().doInternalDispatch();
                    } else {
                        filterChain.doFilter
                            (request.getRequest(), response.getResponse());
                    }
                }

            }
        }
。。。。。

順著繼續debug

public final class ApplicationFilterChain implements FilterChain {

 private void internalDoFilter(ServletRequest request,
                                  ServletResponse response)
        throws IOException, ServletException {

        // Call the next filter if there is one
        if (pos < n) {
            ApplicationFilterConfig filterConfig = filters[pos++];
            try {
                Filter filter = filterConfig.getFilter();

                if (request.isAsyncSupported() && "false".equalsIgnoreCase(
                        filterConfig.getFilterDef().getAsyncSupported())) {
                    request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR, Boolean.FALSE);
                }
                if( Globals.IS_SECURITY_ENABLED ) {
                    final ServletRequest req = request;
                    final ServletResponse res = response;
                    Principal principal =
                        ((HttpServletRequest) req).getUserPrincipal();

                    Object[] args = new Object[]{req, res, this};
                    SecurityUtil.doAsPrivilege ("doFilter", filter, classType, args, principal);
                } else {
                    filter.doFilter(request, response, this);
                }
            } catch (IOException | ServletException | RuntimeException e) {
                throw e;
            } catch (Throwable e) {
                e = ExceptionUtils.unwrapInvocationTargetException(e);
                ExceptionUtils.handleThrowable(e);
                throw new ServletException(sm.getString("filterChain.filter"), e);
            }
            return;
        }

        // We fell off the end of the chain -- call the servlet instance
        try {
            if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
                lastServicedRequest.set(request);
                lastServicedResponse.set(response);
            }

            if (request.isAsyncSupported() && !servletSupportsAsync) {
                request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR,
                        Boolean.FALSE);
            }
            // Use potentially wrapped request from this point
            if ((request instanceof HttpServletRequest) &&
                    (response instanceof HttpServletResponse) &&
                    Globals.IS_SECURITY_ENABLED ) {
                final ServletRequest req = request;
                final ServletResponse res = response;
                Principal principal =
                    ((HttpServletRequest) req).getUserPrincipal();
                Object[] args = new Object[]{req, res};
                SecurityUtil.doAsPrivilege("service",
                                           servlet,
                                           classTypeUsedInService,
                                           args,
                                           principal);
            } else {
                servlet.service(request, response);
            }
        } catch (IOException | ServletException | RuntimeException e) {
            throw e;
        } catch (Throwable e) {
            e = ExceptionUtils.unwrapInvocationTargetException(e);
            ExceptionUtils.handleThrowable(e);
            throw new ServletException(sm.getString("filterChain.servlet"), e);
        } finally {
            if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
                lastServicedRequest.set(null);
                lastServicedResponse.set(null);
            }
        }
    }