springboot配置監聽器、過濾器和攔截器
監聽器:listener是servlet規範中定義的一種特殊類。用於監聽servletContext、HttpSession和servletRequest等域物件的建立和銷燬事件。監聽域物件的屬性發生修改的事件。用於在事件發生前、發生後做一些必要的處理。其主要可用於以下方面:1、統計線上人數和線上使用者2、系統啟動時載入初始化資訊3、統計網站訪問量4、記錄使用者訪問路徑。
過濾器:Filter是Servlet技術中最實用的技術,Web開發人員通過Filter技術,對web伺服器管理的所有web資源:例如Jsp, Servlet, 靜態圖片檔案或靜態 html 檔案等進行攔截,從而實現一些特殊的功能。例如實現URL級別的許可權訪問控制、過濾敏感詞彙、壓縮響應資訊等一些高階功能。它主要用於對使用者請求進行預處理,也可以對HttpServletResponse進行後處理。使用Filter的完整流程:Filter對使用者請求進行預處理,接著將請求交給Servlet進行處理並生成響應,最後Filter再對伺服器響應進行後處理。
攔截器:Interceptor 在AOP(Aspect-Oriented Programming)中用於在某個方法或欄位被訪問之前,進行攔截然後在之前或之後加入某些操作。比如日誌,安全等。一般攔截器方法都是通過動態代理的方式實現。可以通過它來進行許可權驗證,或者判斷使用者是否登陸,或者是像12306 判斷當前時間是否是購票時間。
三大器在springboot中使用時,首先實現相應的介面定義類,然後通過配置類將其加入到spring容器中,從而實現相應的功能。程式碼如下:
1、過濾器類
package com.example.demo; import java.io.IOException; import javax.servlet.Filter; import javax.servlet.FilterChain; import javax.servlet.FilterConfig; import javax.servlet.ServletException; import javax.servlet.ServletRequest; import javax.servlet.ServletResponse; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpServletResponseWrapper; public class MyFilter implements Filter { @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { System.out.println(servletRequest.getParameter("name")); HttpServletRequest hrequest = (HttpServletRequest)servletRequest; HttpServletResponseWrapper wrapper = new HttpServletResponseWrapper((HttpServletResponse) servletResponse); if(hrequest.getRequestURI().indexOf("/index") != -1 || hrequest.getRequestURI().indexOf("/asd") != -1 || hrequest.getRequestURI().indexOf("/online") != -1 || hrequest.getRequestURI().indexOf("/login") != -1 ) { filterChain.doFilter(servletRequest, servletResponse); }else { wrapper.sendRedirect("/login"); } } @Override public void destroy() { } @Override public void init(FilterConfig filterConfig) throws ServletException { } }
2、監聽器類
package com.example.demo; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener; public class MyHttpSessionListener implements HttpSessionListener { public static int online = 0; @Override public void sessionCreated(HttpSessionEvent se) { System.out.println("建立session"); online ++; } @Override public void sessionDestroyed(HttpSessionEvent se) { System.out.println("銷燬session"); } }
3、攔截器類
package com.example.demo;
import java.io.PrintWriter;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.HandlerMapping;
import org.springframework.web.servlet.ModelAndView;
public class MyInterceptor implements HandlerInterceptor {
//在請求處理之前進行呼叫(Controller方法呼叫之前
@Override
public boolean preHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o) throws Exception {
System.out.println("preHandle被呼叫");
Map map =(Map)httpServletRequest.getAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE);
System.out.println(map.get("name"));
System.out.println(httpServletRequest.getParameter("username"));
if(map.get("name").equals("zhangsan")) {
return true; //如果false,停止流程,api被攔截
}else {
PrintWriter printWriter = httpServletResponse.getWriter();
printWriter.write("please login again!");
return false;
}
}
@Override
public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {
System.out.println("postHandle被呼叫");
}
@Override
public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {
System.out.println("afterCompletion被呼叫");
}
}
4、配置類
package com.example.demo;
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.boot.web.servlet.ServletListenerRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ViewControllerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
@Configuration
public class MywebConfig implements WebMvcConfigurer {
@Override
public void addViewControllers(ViewControllerRegistry registry) {
registry.addViewController("/zxc/foo").setViewName("foo");
}
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(new MyInterceptor())
.addPathPatterns("/asd/**");
}
@SuppressWarnings({ "rawtypes", "unchecked" })
@Bean
public FilterRegistrationBean filterRegist() {
FilterRegistrationBean frBean = new FilterRegistrationBean();
frBean.setFilter(new MyFilter());
frBean.addUrlPatterns("/*");
System.out.println("filter");
return frBean;
}
@SuppressWarnings({ "rawtypes", "unchecked" })
@Bean
public ServletListenerRegistrationBean listenerRegist() {
ServletListenerRegistrationBean srb = new ServletListenerRegistrationBean();
srb.setListener(new MyHttpSessionListener());
System.out.println("listener");
return srb;
}
}
5、控制層
package com.example.demo;
import java.util.Date;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.ResponseBody;
@Controller
public class UserController {
private final Logger logger = LoggerFactory.getLogger(UserController.class);
@Value("${application.message:Hello World}")
private String message ;
@GetMapping("/asd/{name}")
public String welcome(@PathVariable String name,Map<String, Object> model) {
model.put("time", new Date());
model.put("message", this.message);
return "welcome";
}
@RequestMapping("/login")
@ResponseBody
public Object foo() {
logger.info("列印日誌----------------------");
return "login";
}
@RequestMapping("/index")
@ResponseBody
public Object index(HttpServletRequest request) {
HttpSession session = request.getSession(true);
session.setAttribute("zxc", "zxc");
return "index";
}
@RequestMapping("/online")
@ResponseBody
public Object online() {
return "當前線上人數:" + MyHttpSessionListener.online + "人";
}
}
6、程式主入口及application.properties檔案預設。
專案啟動後,首先測試過濾器,所有訪問路徑都需經過我們自定義的filter,如果路徑中包含/index、/asd、/online、/login則直接通過,否則則被重定向至/login。
然後測試監聽器,先訪問http://localhost:8080/index,建立session物件(因為 session物件建立需要顯示的呼叫getsession方法),然後訪問http://localhost:8080/online,然後換一個瀏覽器做相同操作,如下:
最後測試攔截器,程式碼展示瞭如何獲取@PathVariable註解的請求引數以及普通請求引數,首先訪問http://localhost:8080/asd/zhangsan?username=lisi,響應正常,如果訪問路徑上的名字不是zhangsan,則被攔截,例如http://localhost:8080/asd/wangwu?username=lisi,如下:
在實際專案中我們還可以在配置的時候設定過濾器、攔截器的執行順序及其它的引數,同時filter和listener還有對應的註解方式:@WebFilter和@WebListener,在使用註解方式時不要忘了在主程式加上@ServletComponentScan註解,這樣才能在程式啟動時將對應的bean載入進來。