Filter責任鏈模式

Filter責任鏈的創建

org.apache.catalina.core.ApplicationFilterFactory#createFilterChain,? 此方法是被org.apache.catalina.core.StandardWrapperValve#invoke調用的,? 對每個request都會創建FilterChain

public static ApplicationFilterChain createFilterChain(ServletRequest request,Wrapper wrapper, Servlet servlet) {
//傳入參數必須有一個servlet，這個servlet是在鏈的末尾被調用的. 這個servlet的查找過程是根據request的URI從web.xml配置中匹配出來的// If there is no servlet to execute, return nullif (servlet == null)return null;// Create and initialize a filter chain objectApplicationFilterChain filterChain = null;if (request instanceof Request) {//.....} else {// Request dispatcher in usefilterChain = new ApplicationFilterChain();}
// 責任鏈上綁定一個servletfilterChain.setServlet(servlet);filterChain.setServletSupportsAsync(wrapper.isAsyncSupported());// Acquire the filter mappings for this ContextStandardContext context = (StandardContext) wrapper.getParent();FilterMap filterMaps[] = context.findFilterMaps();// If there are no filter mappings, we are doneif ((filterMaps == null) || (filterMaps.length == 0))return (filterChain);// ...
//根據web.xml中filter的配置查找是否和當前request匹配// Add the relevant path-mapped filters to this filter chainfor (int i = 0; i < filterMaps.length; i++) {if (!matchDispatcher(filterMaps[i] ,dispatcher)) {continue;}if (!matchFiltersURL(filterMaps[i], requestPath))continue;ApplicationFilterConfig filterConfig = (ApplicationFilterConfig)context.findFilterConfig(filterMaps[i].getFilterName());if (filterConfig == null) {// FIXME - log configuration problemcontinue;}
// 和request URI匹配，則filter會加入到責任鏈中filterChain.addFilter(filterConfig);}/.....// Return the completed filter chainreturn filterChain;}

filterChain創建完成后就會調用doFilter啟用這個鏈,??此方法也是被org.apache.catalina.core.StandardWrapperValve#invoke調用的

org.apache.catalina.core.ApplicationFilterChain#doFilter?

 1 private void internalDoFilter(ServletRequest request,
 2                                   ServletResponse response)
 3         throws IOException, ServletException {
 4 
 5         // Call the next filter if there is one  
 6         if (pos < n) {
 7             //調用下一個filter, 每調用一次 當前pos都會++
 8             ApplicationFilterConfig filterConfig = filters[pos++];
 9             try {
10                 Filter filter = filterConfig.getFilter();
11 
12                 //...
13                     filter.doFilter(request, response, this);
14                 
15             } catch (IOException | ServletException | RuntimeException e) {
16                 throw e;
17             } catch (Throwable e) {
18                // ...
19             }
20             return;
21         }
22 
23         // We fell off the end of the chain -- call the servlet instance
24         try {
25             if (request.isAsyncSupported() && !servletSupportsAsync) {
26                 request.setAttribute(Globals.ASYNC_SUPPORTED_ATTR,
27                         Boolean.FALSE);
28             }
29             // ...  在鏈的末尾，調用具體servlet的doService
30                 servlet.service(request, response);
31             //
32         } catch (IOException | ServletException | RuntimeException e) {
33             throw e;
34         } catch (Throwable e) {
35            //...
36         } finally {
37            //...
38         }
39     }

轉載于:https://www.cnblogs.com/yszzu/p/9626167.html

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