SpringBoot攔截器

一般實(shí)現(xiàn)

定義一個攔截器類

MyInterceptor.java 實(shí)現(xiàn)HandlerInterceptor 接口

import org.json.JSONObject;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.PrintWriter;

@Component
public class MyInterceptor implements HandlerInterceptor {
    Logger logger = LoggerFactory.getLogger(MyInterceptor.class);

    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        // TODO Auto-generated method stub
        //獲取session
        logger.info("---------------------開始進(jìn)入請求地址攔截----------------------------");
        //return true;
        HttpSession session = request.getSession(true);
        if (session.getAttribute("userId") == null) {
            logger.info("------:跳轉(zhuǎn)到login頁面周荐！");
//            response.reset();

            response.setCharacterEncoding("UTF-8");
            response.setContentType("application/json; charset=utf-8");
            PrintWriter out = null;

            JSONObject res = new JSONObject();
            res.put("state", "0");
            res.put("msg", "login in first");
            res.put("output","");
            out = response.getWriter();
            out.append(res.toString());
            return false;
        } else {
            session.setAttribute("userId", session.getAttribute("userId"));
            return true;
        }
    }

    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
                           ModelAndView modelAndView) throws Exception {
        // TODO Auto-generated method stub
        logger.info("--------------處理請求完成后視圖渲染之前的處理操作---------------");
    }

    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        // TODO Auto-generated method stub
        logger.info("---------------視圖渲染之后的操作-------------------------0");
    }
}

定義一個WebConfig類,并將
WebConfig.java

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

import javax.annotation.Resource;

@Configuration
public class WebConfig implements WebMvcConfigurer{
    @Resource
    private MyInterceptor myInterceptor;
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(myInterceptor).addPathPatterns("/sensitiveword");//.excludePathPatterns("/login.html").excludePathPatterns("/*.min.js.*");
    }

}

這樣一個攔截器就實(shí)現(xiàn)了
HandlerInterceptor是一個接口，其中定義了三個default方法

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.lang.Nullable;

public interface HandlerInterceptor {
    default boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        return true;
    }

    default void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable ModelAndView modelAndView) throws Exception {
    }

    default void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, @Nullable Exception ex) throws Exception {
    }
}

WebMvcConfigurer也是一個接口璧疗，定義的方法都是default方法

import java.util.List;
import org.springframework.format.FormatterRegistry;
import org.springframework.http.converter.HttpMessageConverter;
import org.springframework.lang.Nullable;
import org.springframework.validation.MessageCodesResolver;
import org.springframework.validation.Validator;
import org.springframework.web.method.support.HandlerMethodArgumentResolver;
import org.springframework.web.method.support.HandlerMethodReturnValueHandler;
import org.springframework.web.servlet.HandlerExceptionResolver;

public interface WebMvcConfigurer {
    default void configurePathMatch(PathMatchConfigurer configurer) {
    }
    //內(nèi)容協(xié)商配置
    default void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
    }

    default void configureAsyncSupport(AsyncSupportConfigurer configurer) {
    }

    default void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
    }
    //類型轉(zhuǎn)換器和格式化器
    default void addFormatters(FormatterRegistry registry) {
    }
    //添加攔截器
    default void addInterceptors(InterceptorRegistry registry) {
    }
    //添加靜態(tài)資源，重新定義靜態(tài)資源的路徑
    default void addResourceHandlers(ResourceHandlerRegistry registry) {
    }
    //添加跨域支持
    default void addCorsMappings(CorsRegistry registry) {
    }

    default void addViewControllers(ViewControllerRegistry registry) {
    }
    //配置視圖解析器
    default void configureViewResolvers(ViewResolverRegistry registry) {
    }

    default void addArgumentResolvers(List<HandlerMethodArgumentResolver> resolvers) {
    }

    default void addReturnValueHandlers(List<HandlerMethodReturnValueHandler> handlers) {
    }
    //配置消息轉(zhuǎn)換器
    default void configureMessageConverters(List<HttpMessageConverter<?>> converters) {
    }

    default void extendMessageConverters(List<HttpMessageConverter<?>> converters) {
    }

    default void configureHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
    }

    default void extendHandlerExceptionResolvers(List<HandlerExceptionResolver> resolvers) {
    }

    @Nullable
    default Validator getValidator() {
        return null;
    }

    @Nullable
    default MessageCodesResolver getMessageCodesResolver() {
        return null;
    }
}

Servlet過濾器

Servlet過濾器提供過濾作用箕昭，能夠在調(diào)用前檢查Request對象，修改Request Header和Request內(nèi)容叶雹，在Servlet調(diào)用完成以后檢查Response對象，修改Response Header和Respones內(nèi)容
可以串聯(lián)
只有特定的URL才會觸發(fā)攔截器

public interface Filter {
        //Servlet過濾器的初始化方法换吧，Servlet容器創(chuàng)建Servlet過濾器實(shí)例后將調(diào)用這個方法折晦。在這個方法中可以讀取web.xml文件中Servlet過濾器的初始化參數(shù)
    public void init(FilterConfig filterConfig) throws ServletException;
    //完成實(shí)際的過濾操作，當(dāng)客戶請求訪問于過濾器關(guān)聯(lián)的URL時沾瓦，Servlet容器將先調(diào)用過濾器的doFilter方法满着。FilterChain參數(shù)用于訪問后續(xù)過濾器
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException;
         //Servlet容器在銷毀過濾器實(shí)例前調(diào)用該方法，這個方法中可以釋放Servlet過濾器占用的資源
    public void destroy();
}
public interface FilterConfig {
 //返回web．xml部署文件中定義的該過濾器的名稱
    String getFilterName();
 //返回調(diào)用者所處的servlet上下文
    ServletContext getServletContext();
//返回過濾器初始化參數(shù)值的字符串形式贯莺，當(dāng)參數(shù)不存在時风喇，返回nul1．name是初始化參數(shù)名
    String getInitParameter(String var1);
//以Enumeration形式返回過濾器所有初始化參數(shù)值，如果沒有初始化參數(shù)缕探，返回為空
    Enumeration<String> getInitParameterNames();
}

Servlet攔截過程

攔截器截獲客戶端請求
重新封裝ServletResponse响驴，在封裝后的ServletResponse中提供用戶自定義的輸出流
將請求后續(xù)傳遞
Web組件響應(yīng)請求
獲取ServletRespones中的輸出流
將響應(yīng)內(nèi)容通過用戶自定義的輸出流寫入到緩沖流中
修改響應(yīng)內(nèi)容清空緩沖流輸出相應(yīng)內(nèi)容

對比

filter基于filter接口中的doFilter回調(diào)函數(shù)，interceptor則基于Java本身的反射機(jī)制撕蔼；
filter是依賴于servlet容器的豁鲤，沒有servlet容器就無法回調(diào)doFilter方法，而interceptor與servlet無關(guān)鲸沮；
filter的過濾范圍比interceptor大琳骡，filter除了過濾請求外通過通配符可以保護(hù)頁面、圖片讼溺、文件等楣号，而interceptor只能過濾請求，只對action起作用怒坯，在action之前開始炫狱，在action完成后結(jié)束（如被攔截，不執(zhí)行action）剔猿；
filter的過濾一般在加載的時候在init方法聲明视译，而interceptor可以通過在xml聲明是guest請求還是user請求來辨別是否過濾；
interceptor可以訪問action上下文归敬、值棧里的對象酷含，而filter不能；
在action的生命周期中汪茧，攔截器可以被多次調(diào)用椅亚，而過濾器只能在容器初始化時被調(diào)用一次。