Tomcat中的Filter
Filter
说明
filter 是 Servlet 规范
filter 是在 容器后，执行 Servlet.service方法之前执行
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接口
package javax.servlet;
public interface FilterChain {
void doFilter(ServletRequest request, ServletResponse response)
throws IOException, ServletException;
}实现
public final class ApplicationFilterChain implements FilterChain {
private int pos = 0;
private int n = 0;
@Override
public void doFilter(ServletRequest request, ServletResponse response)
throws IOException, ServletException {
// 判断是否开启安全管理器
if( Globals.IS_SECURITY_ENABLED ) {
final ServletRequest req = request;
final ServletResponse res = response;
try {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedExceptionAction<Void>() {
@Override
public Void run()
throws ServletException, IOException {
internalDoFilter(req,res);
return null;
}
}
);
} catch( PrivilegedActionException pe) {
throw new ServletException(e.getMessage(), e);
}
} else {
internalDoFilter(request,response);
}
}
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 {
// 调用具体Filter 的 doFilter 方法。
filter.doFilter(request, response, this);
}
} catch (IOException | ServletException | RuntimeException e) {
throw e;
} catch (Throwable e) {
throw new ServletException(sm.getString("filterChain.filter"), e);
}
return;
}
// 调用servlet实例
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) {
throw new ServletException(sm.getString("filterChain.servlet"), e);
} finally {
if (ApplicationDispatcher.WRAP_SAME_OBJECT) {
lastServicedRequest.set(null);
lastServicedResponse.set(null);
}
}
}
}- Line：63
// 列如：CorsFilter
@Override
public void doFilter(final ServletRequest servletRequest,
final ServletResponse servletResponse,
final FilterChain filterChain) {
switch (requestType) {
case SIMPLE:
// Handles a Simple CORS request.
this.handleSimpleCORS(request, response, filterChain);
break;
case ACTUAL:
// Handles an Actual CORS request.
this.handleSimpleCORS(request, response, filterChain);
break;
default:
// Handles a CORS request that violates specification.
this.handleInvalidCORS(request, response, filterChain);
break;
}
}
private void handleNonCORS(final HttpServletRequest request,
final HttpServletResponse response,
final FilterChain filterChain) {
addStandardHeaders(request, response);
// 调用下一个 Filter，回到 ApplicationFilterChain.doFilter
filterChain.doFilter(request, response);
}- LIne101：servlet.service(request, response);
// 调用 DispatcherServlet.service方法Filter注入
// org.apache.catalina.core.StandardContext
@Override
protected synchronized void startInternal() throws LifecycleException {
// 准备好环境
// Configure and call application filters
if (ok) {
if (!filterStart()) {
log.error(sm.getString("standardContext.filterFail"));
ok = false;
}
}
}
private HashMap<String, ApplicationFilterConfig> filterConfigs =
new HashMap<>();
public boolean filterStart() {
// Instantiate and record a FilterConfig for each defined filter
boolean ok = true;
synchronized (filterConfigs) {
filterConfigs.clear();
// 从 web.xml 解析的 filter 数据中添加到 Map集合中
for (Entry<String,FilterDef> entry : filterDefs.entrySet()) {
String name = entry.getKey();
try {
ApplicationFilterConfig filterConfig =
new ApplicationFilterConfig(this, entry.getValue());
filterConfigs.put(name, filterConfig);
} catch (Throwable t) {
ok = false;
}
}
}
return ok;
}调用流程
- 在收到请求后，执行 Pipeline，走到 StandardWrapperValve
// org.apache.catalina.core.StandardWrapperValve
@Override
public final void invoke(Request request, Response response) {
// Create the filter chain for this request
ApplicationFilterChain filterChain =
ApplicationFilterFactory.createFilterChain(request, wrapper, servlet);
}// org.apache.catalina.core.ApplicationFilterFactory
public static ApplicationFilterChain createFilterChain(ServletRequest request,
Wrapper wrapper, Servlet servlet) {
// If there is no servlet to execute, return null
if (servlet == null)
return null;
// Create and initialize a filter chain object
ApplicationFilterChain filterChain = null;
if (request instanceof Request) {
Request req = (Request) request;
if (Globals.IS_SECURITY_ENABLED) {
// Security: Do not recycle
filterChain = new ApplicationFilterChain();
} 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.setServletSupportsAsync(wrapper.isAsyncSupported());
// 从 Context 中获取所有的 FilterMap 映射信息
StandardContext context = (StandardContext) wrapper.getParent();
FilterMap filterMaps[] = context.findFilterMaps();
// 没有配置 filter，返回 null
if ((filterMaps == null) || (filterMaps.length == 0))
return (filterChain);
// Acquire the information we will need to match filter mappings
DispatcherType dispatcher =
(DispatcherType) request.getAttribute(Globals.DISPATCHER_TYPE_ATTR);
String requestPath = null;
// 获取请求 路径：index.html
Object attribute = request.getAttribute(Globals.DISPATCHER_REQUEST_PATH_ATTR);
if (attribute != null){
requestPath = attribute.toString();
}
String servletName = wrapper.getName();
// Add the relevant path-mapped filters to this filter chain
for (int i = 0; i < filterMaps.length; i++) {
if (!matchDispatcher(filterMaps[i] ,dispatcher)) {
continue;
}
// 匹配 url-pattern
if (!matchFiltersURL(filterMaps[i], requestPath))
continue;
// 根据 配置的 filter-name 找到 filterConfig
ApplicationFilterConfig filterConfig = (ApplicationFilterConfig)
context.findFilterConfig(filterMaps[i].getFilterName());
if (filterConfig == null) {
continue;
}
filterChain.addFilter(filterConfig);
}
// 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))
continue;
ApplicationFilterConfig filterConfig = (ApplicationFilterConfig)
context.findFilterConfig(filterMaps[i].getFilterName());
if (filterConfig == null) {
// FIXME - log configuration problem
continue;
}
filterChain.addFilter(filterConfig);
}
return filterChain;
}
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