public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...");
        return true;
    }

參數(shù)：

■ request：請求對象

■ response：響應(yīng)對象

■ handler：被調(diào)用的處理器對象，本質(zhì)上是一個方法對象，對反射技術(shù)中的Method對象進(jìn)行再包裝

返回值：

■ 返回值為false，被攔截的處理器將不執(zhí)行

后置處理

public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }

參數(shù)：

modeAanView：如果處理器執(zhí)行完成具有返回結(jié)果，可以讀取到對應(yīng)數(shù)據(jù)與頁面信息，并進(jìn)行調(diào)整

完成后處理

public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }

參數(shù)：

ex：如果處理器執(zhí)行過程中出現(xiàn)異常對象，可以針對異常情況進(jìn)行單獨(dú)處理

二、攔截器鏈配置

配置第一個攔截器

@Component
//定義攔截器類，實(shí)現(xiàn)HandlerInterceptor接口
//注意當(dāng)前類必須受Spring容器控制
public class ProjectInterceptor implements HandlerInterceptor {
    @Override
    //原始方法調(diào)用前執(zhí)行的內(nèi)容
    //返回值類型可以攔截控制的執(zhí)行，true放行，false終止
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        String contentType = request.getHeader("Content-Type");
        HandlerMethod hm = (HandlerMethod)handler;
        System.out.println("preHandle..."+contentType);
        return true;
    }
 
    @Override
    //原始方法調(diào)用后執(zhí)行的內(nèi)容
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...");
    }
 
    @Override
    //原始方法調(diào)用完成后執(zhí)行的內(nèi)容
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...");
    }
}

配置第二個攔截器

@Component
public class ProjectInterceptor2 implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        System.out.println("preHandle...222");
        return true;
    }
 
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
        System.out.println("postHandle...222");
    }
 
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
        System.out.println("afterCompletion...222");
    }
}

當(dāng)配置多個攔截器時(shí)，形成攔截器鏈

@Configuration
@ComponentScan({"com.itheima.controller"})
@EnableWebMvc
//實(shí)現(xiàn)WebMvcConfigurer接口可以簡化開發(fā)，但具有一定的侵入性
public class SpringMvcConfig implements WebMvcConfigurer {
    @Autowired
    private ProjectInterceptor projectInterceptor;
    @Autowired
    private ProjectInterceptor2 projectInterceptor2;
 
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        //配置多攔截器
        registry.addInterceptor(projectInterceptor).addPathPatterns("/books","/books/*");
        registry.addInterceptor(projectInterceptor2).addPathPatterns("/books","/books/*");
    }
}

三個攔截器構(gòu)成的攔截器鏈圖例