spring-boot在web層面使用了spring mvc的攔截器功能，并沒有做其他處理沐兵，故我們只要熟悉mvc的攔截器，自然而然可以將攔截器加入到spring-boot上
攔截器接口
package org.springframework.web.servlet;
public interface HandlerInterceptor {
boolean preHandle(
HttpServletRequest request, HttpServletResponse response,
Object handler)
throws Exception;
void postHandle(
HttpServletRequest request, HttpServletResponse response,
Object handler, ModelAndView modelAndView)
throws Exception;
void afterCompletion(
HttpServletRequest request, HttpServletResponse response,
Object handler, Exception ex)
throws Exception;
}
我們可能注意到攔截器一個有3個回調(diào)方法响迂，而一般的過濾器Filter才兩個蹋笼，這是怎么回事呢？馬上分析蜕该。
preHandle****：預處理回調(diào)方法犁柜，實現(xiàn)處理器的預處理（如登錄檢查），第三個參數(shù)為響應的處理器（如我們上一章的Controller實現(xiàn)）蛇损；
返回值：true表示繼續(xù)流程（如調(diào)用下一個攔截器或處理器）赁温；
false表示流程中斷（如登錄檢查失敗）淤齐，不會繼續(xù)調(diào)用其他的攔截器或處理器股囊，此時我們需要通過response來產(chǎn)生響應；
postHandle****：后處理回調(diào)方法更啄，實現(xiàn)處理器的后處理（但在渲染視圖之前）稚疹，此時我們可以通過modelAndView（模型和視圖對象）對模型數(shù)據(jù)進行處理或?qū)σ晥D進行處理，modelAndView也可能為null祭务。
afterCompletion****：整個請求處理完畢回調(diào)方法内狗，即在視圖渲染完畢時回調(diào)，如性能監(jiān)控中我們可以在此記錄結(jié)束時間并輸出消耗時間义锥，還可以進行一些資源清理柳沙，類似于try-catch-finally中的finally，但僅調(diào)用處理器執(zhí)行鏈中preHandle返回true的攔截器的afterCompletion拌倍。
攔截運行圖
正常流程
中斷流程
中斷流程中赂鲤，比如是HandlerInterceptor2中斷的流程（preHandle返回false），此處僅調(diào)用它之前攔截器的preHandle返回true的afterCompletion方法柱恤。
DispatcherServlet內(nèi)部工作：
//doDispatch方法
//1数初、處理器攔截器的預處理（正序執(zhí)行）
HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();
if (interceptors != null) {
for (int i = 0; i < interceptors.length; i++) {
HandlerInterceptor interceptor = interceptors[i];
if (!interceptor.preHandle(processedRequest, response, mappedHandler.getHandler())) {
//1.1、失敗時觸發(fā)afterCompletion的調(diào)用
triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);
return;
}
interceptorIndex = i;//1.2梗顺、記錄當前預處理成功的索引
}
}
//2泡孩、處理器適配器調(diào)用我們的處理器
mv = ha.handle(processedRequest, response, mappedHandler.getHandler());
//當我們返回null或沒有返回邏輯視圖名時的默認視圖名翻譯（詳解4.15.5 RequestToViewNameTranslator）
if (mv != null && !mv.hasView()) {
mv.setViewName(getDefaultViewName(request));
}
//3、處理器攔截器的后處理（逆序）
if (interceptors != null) {
for (int i = interceptors.length - 1; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
interceptor.postHandle(processedRequest, response, mappedHandler.getHandler(), mv);
}
}
//4寺谤、視圖的渲染
if (mv != null && !mv.wasCleared()) {
render(mv, processedRequest, response);
if (errorView) {
WebUtils.clearErrorRequestAttributes(request);
}
//5仑鸥、觸發(fā)整個請求處理完畢回調(diào)方法afterCompletion
triggerAfterCompletion(mappedHandler, interceptorIndex, processedRequest, response, null);
// triggerAfterCompletion方法
private void triggerAfterCompletion(HandlerExecutionChain mappedHandler, int interceptorIndex,
HttpServletRequest request, HttpServletResponse response, Exception ex) throws Exception {
// 5吮播、觸發(fā)整個請求處理完畢回調(diào)方法afterCompletion （逆序從1.2中的預處理成功的索引處的攔截器執(zhí)行）
if (mappedHandler != null) {
HandlerInterceptor[] interceptors = mappedHandler.getInterceptors();
if (interceptors != null) {
for (int i = interceptorIndex; i >= 0; i--) {
HandlerInterceptor interceptor = interceptors[i];
try {
interceptor.afterCompletion(request, response, mappedHandler.getHandler(), ex);
}
catch (Throwable ex2) {
logger.error("HandlerInterceptor.afterCompletion threw exception", ex2);
}
}
}
}
}
spring boot添加攔截器
- 方法一
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication application = new SpringApplication(Application.class);
// application.addListeners(new ApplicationListenerEnvironmentPrepared());
// application.addListeners(new ApplicationListenerFailed());
// application.addListeners(new ApplicationListenerPrepared());
// application.addListeners(new ApplicationListenerStarted());
application.run(args);
}
@Configuration
static class WebMvcConfigurer extends WebMvcConfigurerAdapter {
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new HandlerInterceptorAdapter() {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
Object handler) throws Exception {
request.getContextPath();
System.out.println("interceptor====");
return true;
}
}).addPathPatterns("/*");
}
}
}
- 方法二
@Configuration
public class WebMvcConfigurer extends WebMvcConfigurerAdapter {
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new HandlerInterceptorAdapter() {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response,
Object handler) throws Exception {
System.out.println("interceptor====222");
return true;
}
}).addPathPatterns("/*");
}
}
總結(jié)：只要能被springboot掃描到即可
