拦截器
什么是拦截器
作用：SpringMVC 用于拦截 Controller 的路由请求。
本质：AOP 面向切面编程。
场景：权限检查（登录拦截，接口安全校验）、日志记录（推荐使用原生 AOP）、性能监控（接口访问的执行时间）、通用行为（获取 Cookie 信息，获取用户信息等）。
拦截器的配置
SpringMVC中的拦截器用于拦截控制器方法的执行
SpringMVC中的拦截器需要实现HandlerInterceptor
SpringMVC的拦截器必须在SpringMVC的配置文件中进行配置：
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| <bean class="com.atguigu.interceptor.FirstInterceptor"></bean>
<ref bean="firstInterceptor"></ref>
<mvc:interceptor>
<mvc:mapping path="/**"/>
<mvc:exclude-mapping path="/testRequestEntity"/>
<ref bean="firstInterceptor"></ref>
</mvc:interceptor>
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拦截器的三个抽象方法
SpringMVC中的拦截器有三个抽象方法：
preHandle：控制器方法执行之前执行preHandle()，其boolean类型的返回值表示是否拦截或放行，返回true为放行，即调用控制器方法；返回false表示拦截，即不调用控制器方法
postHandle：控制器方法执行之后执行postHandle()
afterCompletion：处理完视图和模型数据，渲染视图完毕之后执行afterCompletion()
多个拦截器的执行顺序
- 若每个拦截器的preHandle()都返回true
此时多个拦截器的执行顺序和拦截器在SpringMVC的配置文件的配置顺序有关：
preHandle()会按照配置的顺序执行，而postHandle()和afterCompletion()会按照配置的反序执行
- 若某个拦截器的preHandle()返回了false
preHandle()返回false和它之前的拦截器的preHandle()都会执行，postHandle()都不执行，返回false的拦截器之前的拦截器的afterCompletion()会执行
完整代码
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<mvc:interceptors>
<ref bean="firstInterceptor"></ref>
<ref bean="secondInterceptor"></ref>
</mvc:interceptors>
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| @Component
public class FirstInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("FirstInterceptor--preHandle");
return true;
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
System.out.println("FirstInterceptor--postHandle");
}
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
System.out.println("FirstInterceptor--afterCompletion");
}
}
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| @Component
public class SecondInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
System.out.println("SecondInterceptor--preHandle");
return true;
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
System.out.println("SecondInterceptor--postHandle");
}
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
System.out.println("SecondInterceptor--afterCompletion");
}
}
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| @Controller
public class TestController {
@RequestMapping("/testInterceptor")
public String testInterceptor(){
return "success";
}
}
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| <!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<h1>首页</h1>
<a th:href="@{/testInterceptor}">测试拦截器</a><br>
</body>
</html>`
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| <!DOCTYPE html>
<html lang="en" xmlns:th="http://www.thymeleaf.org">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
success
</body>
</html>
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| FirstInterceptor--preHandle
SecondInterceptor--preHandle
SecondInterceptor--postHandle
FirstInterceptor--postHandle
SecondInterceptor--afterCompletion
FirstInterceptor--afterCompletion
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- 若FirstInterceptor-preHandle返回True,SecondInterceptor--preHandle返回False,结果为
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| FirstInterceptor--preHandle
SecondInterceptor--preHandle
FirstInterceptor--afterCompletion
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自定义拦截器✨✨
- 定义一个自定义拦截实现 HandlerInterceptor 接口，重写三个方法。
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| @Slf4j
public class LoginInterceptor implements HandlerInterceptor {
@Override
public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
log.info("1-----preHandle----->");
return true;
}
@Override
public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) throws Exception {
log.info("3-----postHandle----->");
}
@Override
public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) throws Exception {
log.info("4-----afterCompletion----->");
}
}
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- 定义一个配置类实现 WebMvcConfigurer 接口，重写 addInterceptors 方法，注册拦截器并定义规则。
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| @Configuration
public class WebMvcConfiguration implements WebMvcConfigurer {
@Bean
public LoginInterceptor getLoginInterceptor() {
return new LoginInterceptor();
}
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(getLoginInterceptor()).addPathPatterns("/api/**");
}
}
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- 定义测试接口。
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| @RestController
@Slf4j
public class HelloController {
@GetMapping("/api/hello")
public String hello() {
log.info("2-----hello----->");
return "hello";
}
}
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- 结果
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| 2022-04-25 23:21:05.142 INFO 19276 --- [nio-8888-exec-5] c.f.i.config.LoginInterceptor : 1-----preHandle----->
2022-04-25 23:21:05.143 INFO 19276 --- [nio-8888-exec-5] c.f.i.controller.HelloController : 2-----hello----->
2022-04-25 23:21:05.148 INFO 19276 --- [nio-8888-exec-5] c.f.i.config.LoginInterceptor : 3-----postHandle----->
2022-04-25 23:21:05.148 INFO 19276 --- [nio-8888-exec-5] c.f.i.config.LoginInterceptor : 4-----afterCompletion----->
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单个拦截器执行流程
多个拦截器的执行流程
参考：https://frxcat.fun/
