【Java】Zuul- 调用

Z时代
2024-01-10
分类：技术分享

ZuulServlet是HttpServlet。Servlet的生命周期包括init（仅第一次）、service、destroy。ZuulServlet的init在Zuul- 启动提过了，就是创建一个ZuulRunner对象。所以我们主要看service方法

ZuulServlet#service

这个方法就是获取一个RequestContext，如果没有则创建，是ThreadLocal类。获取后就开始调用preRoute、route、postRoute、error方法。由于这几个方法调用方式是一致的，所以下面就只讲preRoute，这个方法实际就是调用ZuulRunner#preRoute方法。

@Override
public void service(javax.servlet.ServletRequest servletRequest, javax.servlet.ServletResponse servletResponse) throws ServletException, IOException {
try {
// 给RequestContext赋值request和HttpResponse
init((HttpServletRequest) servletRequest, (HttpServletResponse) servletResponse);
// 获取RequestContext
RequestContext context = RequestContext.getCurrentContext();
context.setZuulEngineRan();
try {
preRoute();
} catch (ZuulException e) {
error(e);
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();
}}

ZuulRunner#preRoute

preRoute是单例。然后调用runFilters。在runFilters中，先从FilterLoader获取ZuulFilter集合，然后遍历处理ZuulFilter。

public void preRoute() throws ZuulException {
runFilters("pre");
//其他略
}
public Object runFilters(String sType) throws Throwable {
boolean bResult = false;
// 从FilterLoader获取ZuulFilter集合
List<ZuulFilter> list = FilterLoader.getInstance().getFiltersByType(sType);
if (list != null) {
for (int i = 0; i < list.size(); i++) {
ZuulFilter zuulFilter = list.get(i);
// 处理每个ZuulFilter
Object result = processZuulFilter(zuulFilter);
if (result != null && result instanceof Boolean) {
bResult |= ((Boolean) result);
}
}
}
return bResult;}

FilterLoader#getFiltersByType

FilterLoader也是单例。主要就是ConcurrentHashMap类型的hashFiltersByType取值，没有的话从filterRegistry获取，然后排序返回。

public List<ZuulFilter> getFiltersByType(String filterType) {
// 从ConcurrentHashMap类型的hashFiltersByType，通过filterType取ZuulFilter集合
List<ZuulFilter> list = hashFiltersByType.get(filterType);
// 如果有了，直接返回
if (list != null) return list;
list = new ArrayList<ZuulFilter>();
//没有从filterRegistry获取，并根据filterType拿到对应的ZuulFilter
Collection<ZuulFilter> filters = filterRegistry.getAllFilters();
for (Iterator<ZuulFilter> iterator = filters.iterator(); iterator.hasNext(); ) {
ZuulFilter filter = iterator.next();
if (filter.filterType().equals(filterType)) {
list.add(filter);
}
}
// 排序
Collections.sort(list); // sort by priority
hashFiltersByType.putIfAbsent(filterType, list);
return list;}

FilterProcessor#processZuulFilter

拿到ZuulFilter集合后，对每个ZuulFilter处理。主要的调用ZuulFilter的runFilter方法。

public Object processZuulFilter(ZuulFilter filter) throws ZuulException {
// 其他略
ZuulFilterResult result = filter.runFilter();
// 其他略}

ZuulFilter#runFilter

public ZuulFilterResult runFilter() {
ZuulFilterResult zr = new ZuulFilterResult();
if (!isFilterDisabled()) {
// 这个是我们需要写的，是否过滤
if (shouldFilter()) {
Tracer t = TracerFactory.instance().startMicroTracer("ZUUL::" + this.getClass().getSimpleName());
try {
// 这个是我们需要写的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;}