zuul 源码调用过程
1 Zuulservlet 装入tomcat容器
zuul 请求过程是怎么被怎么理的，上一编我们看到ZuulServerlet实例化并被封装进ServletRegistrationBean，且托管到spring容器里，那么该servlet是怎么放进tomcat里的,注意ServletRegistrationBean 实现 ServletContextInitializer
@Bean
@ConditionalOnMissingBean(name = "zuulServlet")
public ServletRegistrationBean zuulServlet() {
ServletRegistrationBean servlet = new ServletRegistrationBean(new ZuulServlet(),
this.zuulProperties.getServletPattern());
// The whole point of exposing this servlet is to provide a route that doesn't
// buffer requests.
servlet.addInitParameter("buffer-requests", "false");
return servlet;
}从 ServletRegistrationBean 的getServlet 方法看一下调用链
EmbeddedWebApplicationContext 这一块在spring-boot 原理有详细分析
真正把ZuulServlet装入Servlet容器里
2 ZuulServlet源码
zuulservlet 源码并不复杂，主要处理各种zuulfilter 的执行，先看一副图执行流程图
首先先说明Zuulfilter 有四种 pre(前置),route(路由定位)，post(执行后)，erro（出错），执行流程如上图，执行代码如下面
private ZuulRunner zuulRunner;
@Override
public void init(ServletConfig config) throws ServletException {
super.init(config);
String bufferReqsStr = config.getInitParameter("buffer-requests");
boolean bufferReqs = bufferReqsStr != null && bufferReqsStr.equals("true") ? true : false;
zuulRunner = new ZuulRunner(bufferReqs);
}
@Override
public void service(javax.servlet.ServletRequest servletRequest, javax.servlet.ServletResponse servletResponse) throws ServletException, IOException {
try {
//省去一些代码
try {
//执行前置过滤器
preRoute();
} catch (ZuulException e) {
//实现前置过滤器出错，则执行出错过滤器
error(e);
//执行后置过滤，下面差不多不用说明了
postRoute();
return;
}
try {
route();
} catch (ZuulException e) {
error(e);
postRoute();
return;
}
try {
postRoute();
} catch (ZuulException e) {
error(e);
return;
}
} catch (Throwable e) {
error(new ZuulException(e, 500, "UNHANDLED_EXCEPTION_" + e.getClass().getName()));
} finally {
RequestContext.getCurrentContext().unset();
}
}
/** * executes "post" ZuulFilters * * @throws ZuulException */
void postRoute() throws ZuulException {
zuulRunner.postRoute();
}
/** * executes "route" filters * * @throws ZuulException */
void route() throws ZuulException {
zuulRunner.route();
}
/** * executes "pre" filters * * @throws ZuulException */
void preRoute() throws ZuulException {
zuulRunner.preRoute();
}
/** * initializes request * * @param servletRequest * @param servletResponse */
void init(HttpServletRequest servletRequest, HttpServletResponse servletResponse) {
zuulRunner.init(servletRequest, servletResponse);
}
/** * sets error context info and executes "error" filters * * @param e */
void error(ZuulException e) {
RequestContext.getCurrentContext().setThrowable(e);
zuulRunner.error();
}4 ZuulFilter 执行实现
跟踪源码发现核处理在FilterProcessor 类上，但逻辑也不复杂
public Object runFilters(String sType) throws Throwable {
//省去一些代码
boolean bResult = false;
//据filter类型，获取排过序的filter
List<ZuulFilter> list = FilterLoader.getInstance().getFiltersByType(sType);
if (list != null) {
for (int i = 0; i < list.size(); i++) {
ZuulFilter zuulFilter = list.get(i);
//处理filter执行
Object result = processZuulFilter(zuulFilter);
if (result != null && result instanceof Boolean)
bResult |= ((Boolean) result);
}
}
}
return bResult;
}
/** * Processes an individual ZuulFilter. This method adds Debug information. Any uncaught Thowables are caught by this method and converted to a ZuulException with a 500 status code. * * @param filter * @return the return value for that filter * @throws ZuulException */
public Object processZuulFilter(ZuulFilter filter) throws ZuulException {
RequestContext ctx = RequestContext.getCurrentContext();
boolean bDebug = ctx.debugRouting();
final String metricPrefix = "zuul.filter-";
long execTime = 0;
String filterName = "";
try {
long ltime = System.currentTimeMillis();
filterName = filter.getClass().getSimpleName();
RequestContext copy = null;
Object o = null;
Throwable t = null;
if (bDebug) {
Debug.addRoutingDebug("Filter " + filter.filterType() + " " + filter.filterOrder() + " " + filterName);
copy = ctx.copy();
}
//真正执行ZuulFilter内存方法
ZuulFilterResult result = filter.runFilter();
ExecutionStatus s = result.getStatus();
execTime = System.currentTimeMillis() - ltime;
switch (s) {
case FAILED:
t = result.getException();
ctx.addFilterExecutionSummary(filterName, ExecutionStatus.FAILED.name(), execTime);
break;
case SUCCESS:
o = result.getResult();
ctx.addFilterExecutionSummary(filterName, ExecutionStatus.SUCCESS.name(), execTime);
if (bDebug) {
Debug.addRoutingDebug("Filter {" + filterName + " TYPE:" + filter.filterType() + " ORDER:" + filter.filterOrder() + "} Execution time = " + execTime + "ms");
Debug.compareContextState(filterName, copy);
}
break;
default:
break;
}
if (t != null) throw t;
usageNotifier.notify(filter, s);
return o;
} catch (Throwable e) {
if (bDebug) {
Debug.addRoutingDebug("Running Filter failed " + filterName + " type:" + filter.filterType() + " order:" + filter.filterOrder() + " " + e.getMessage());
}
usageNotifier.notify(filter, ExecutionStatus.FAILED);
if (e instanceof ZuulException) {
throw (ZuulException) e;
} else {
ZuulException ex = new ZuulException(e, "Filter threw Exception", 500, filter.filterType() + ":" + filterName);
ctx.addFilterExecutionSummary(filterName, ExecutionStatus.FAILED.name(), execTime);
throw ex;
}
}
}ZuulFilter 执行源码
public ZuulFilterResult runFilter() {
ZuulFilterResult zr = new ZuulFilterResult();
if (!isFilterDisabled()) {
//是否执行
if (shouldFilter()) {
Tracer t = TracerFactory.instance().startMicroTracer("ZUUL::" + this.getClass().getSimpleName());
try {
//执行，run方法就是具体filter 实现的run方法
Object res = run();
zr = new ZuulFilterResult(res, ExecutionStatus.SUCCESS);
} catch (Throwable e) {
t.setName("ZUUL::" + this.getClass().getSimpleName() + " failed");
zr = new ZuulFilterResult(ExecutionStatus.FAILED);
zr.setException(e);
} finally {
t.stopAndLog();
}
} else {
zr = new ZuulFilterResult(ExecutionStatus.SKIPPED);
}
}
return zr;
}