一、过滤器
新建如下的 Controller：
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| @RestController
public class UserController {
@GetMapping("user/{id}")
public void get(@PathVariable String id) {
System.out.println(id);
}
}
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过滤器的实现：定义一个类实现 Filter ，并重写其中的方法
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| @Component
@WebFilter(urlPatterns = "/*")
public class TimeFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("Initialization");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
System.out.println("++++++++ Start ++++++++");
Long start = new Date().getTime();
filterChain.doFilter(servletRequest, servletResponse);
System.out.println("Filter costs: ");
System.out.println(new Date().getTime() - start);
System.out.println("++++++++ End ++++++++");
}
@Override
public void destroy() {
System.out.println("Filter is over");
}
}
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init 方法：是对项目启动时，进行的初始化
doFilter 方法：当执行一个请求的时候，进行过滤
destroy 方法：当这个项目关闭时，该过滤器也被销毁了
浏览器运行：http://localhost:8080/user/666
结果：
在这个过程中出现了一点问题：
当我们进行下面这种过滤一部分的情况下：
TimeFilter
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| @Component
@WebFilter(urlPatterns = {"/user/*"})
public class TimeFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println(filterConfig.getServletContext().getContextPath());
System.out.println("Initialization........");
}
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
System.out.println("++++++++ Start ++++++++");
Long start = new Date().getTime();
filterChain.doFilter(servletRequest, servletResponse);
System.out.println("Filter costs: ");
System.out.println(new Date().getTime() - start);
System.out.println("++++++++ End ++++++++");
}
@Override
public void destroy() {
System.out.println("Filter is over");
}
}
|
UserController
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| @RestController
public class UserController {
@GetMapping("user/{id}")
public void get(@PathVariable String id) {
System.out.println("userID：" +id);
}
}
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HelloController
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| @RestController
public class HelloController {
@RequestMapping("hello")
public String hello() {
return "hello";
}
}
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此时我们过滤的是 /user 后面所有的请求，但是结果是 UserController 和 HelloController 都进入了过滤器中：
最终解决方案：去掉在 TimeFilter 中的 @Component 注解，在启动类上加上 @ServletComponentScan 注解即可：
在上面我们使用了注解的方式进行过滤：
@WebFilter(urlPatterns = “/*”)
第二种方式：
去掉 @Component 和 *@WebFilter(urlPatterns = {“/user/“})** 注解，并配置如下的配置类：
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| @Configuration
public class WebConfig {
@Bean
public FilterRegistrationBean timeFilter() {
FilterRegistrationBean filterRegistrationBean = new FilterRegistrationBean();
TimeFilter timeFilter = new TimeFilter();
filterRegistrationBean.setFilter(timeFilter);
List<String> urlList = new ArrayList<>();
urlList.add("/user/*");
filterRegistrationBean.setUrlPatterns(urlList);
return filterRegistrationBean;
}
}
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二、拦截器
编写一个拦截器类实现 HandlerInterceptor ，如下：
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| public class TimeInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("处理拦截之前");
request.setAttribute("startTime", new Date().getTime());
System.out.println(((HandlerMethod) handler).getBean().getClass().getName());
System.out.println(((HandlerMethod) handler).getMethod().getName());
return true;
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
System.out.println("开始处理拦截");
Long start = (Long) request.getAttribute("startTime");
System.out.println("【拦截器】耗时 " + (new Date().getTime() - start));
}
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
System.out.println("处理拦截之后");
Long start = (Long) request.getAttribute("startTime");
System.out.println("【拦截器】耗时 " + (new Date().getTime() - start));
System.out.println("异常信息 " + ex);
}
}
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preHandle 方法在处理拦截之前执行
postHandle 方法只有当被拦截的方法没有抛出异常成功时才会处理
afterCompletion 方法无论被拦截的方法抛出异常与否都会执行
将我们写好的拦截器注册到容器中：
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| @Configuration
public class InterceptorConfig implements WebMvcConfigurer {
@Autowired
TimeInterceptor timeInterceptor;
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(timeInterceptor).addPathPatterns("/user/*");
}
}
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同样分别运行：http://localhost:8080/user/888 和 http://localhost:8080/hello
可以看见结果如下：
只是对 user/888 进行拦截了，对 hello 没有进行拦截
三、过滤器与拦截器的对比
我们再将前面的过滤器加入其中，可以得到如下结果：
有一张已经整理好执行顺序图：
