Spring Boot 2.X(九)：Spring MVC - 拦截器（Interceptor）

朝雾轻寒

发布于 2019-10-24 23:29:34

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发布于 2019-10-24 23:29:34

文章被收录于专栏：Spring Boot 2.X 系列Spring Boot 2.X 系列

拦截器

1.简介

Spring MVC 中的拦截器（Interceptor）类似于 Servlet 开发中的过滤器 Filter，它主要用于拦截用户请求并作相应的处理,它也是 AOP 编程思想的体现,底层通过动态代理模式完成。

2.定义实现类

拦截器有两种实现方式： 1.实现 HandlerInterceptor 接口 2.继承 HandlerInterceptorAdapter 抽象类（看源码最底层也是通过 HandlerInterceptor 接口实现）

3.HandlerInterceptor方法介绍

????????@Override
????????public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
????????????????throws Exception {
????????????//进行逻辑判断，如果ok就返回true，不行就返回false，返回false就不会处理请求
????????????return true;
????????}
????????@Override
????????public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
????????????????ModelAndView modelAndView) throws Exception {
????????}
????????@Override
????????public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
????????????????throws Exception {
????????}

preHandle：在业务处理器处理请求之前被调用。预处理，可以进行编码、安全控制、权限校验等处理； postHandle：在业务处理器处理请求执行完成后，生成视图之前执行。 afterCompletion：在 DispatcherServlet 完全处理完请求后被调用，可用于清理资源等。

4.应用场景

1.日志记录：记录请求信息的日志，以便进行信息监控、信息统计、计算PV（Page View）等； 2.登录鉴权：如登录检测，进入处理器检测检测是否登录； 3.性能监控：检测方法的执行时间； 4.其他通用行为。

5.与 Filter 过滤器的区别

1.拦截器是基于java的反射机制的，而过滤器是基于函数回调。 2.拦截器不依赖于servlet容器，而过滤器依赖于servlet容器。 3.拦截器只能对Controller请求起作用，而过滤器则可以对几乎所有的请求起作用。 4.拦截器可以访问action上下文、值栈里的对象，而过滤器不能访问。 5.在Controller的生命周期中，拦截器可以多次被调用，而过滤器只能在容器初始化时被调用一次。 6.拦截器可以获取IOC容器中的各个bean，而过滤器不行。这点很重要，在拦截器里注入一个service，可以调用业务逻辑。

具体实现

单个拦截器

1.新建拦截器

????public class Test1Interceptor implements HandlerInterceptor{

????@Override
??? public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
????????????throws Exception {
???????System.out.println("执行preHandle方法-->01");
???????return true;
????}
?????@Override
?????public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
?????????????ModelAndView modelAndView) throws Exception {
????????System.out.println("执行postHandle方法-->02");
?????}
?????@Override
?????public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
?????????????throws Exception {
?????????System.out.println("执行afterCompletion方法-->03");
?????}
}

2.配置拦截器

@Configuration
public class WebMvcConfig extends WebMvcConfigurationSupport {
????/*
?????* 拦截器配置
?????*/
????@Override
????public void addInterceptors(InterceptorRegistry registry) {
????????// 注册自定义拦截器，添加拦截路径和排除拦截路径
????????registry.addInterceptor(new Test1Interceptor()) // 添加拦截器
????????????????.addPathPatterns("/**") // 添加拦截路径
????????????????.excludePathPatterns(// 添加排除拦截路径
????????????????????????"/hello").order(0);//执行顺序
???????super.addInterceptors(registry);
?????}

}

3.测试拦截器

@RestController
public class TestController {
????@RequestMapping("/hello")
????public String getHello() {
????????System.out.println("这里是Hello");
????????return "hello world";
????}

????@RequestMapping("/test1")
????public String getTest1() {
????????System.out.println("这里是Test1");
 ?????? return "test1 content";
????}
????@RequestMapping("/test2")
????public String getTest2() {
????????System.out.println("这里是Test2");
????????return "test2 content";
????}
}

4.单个拦截器的执行流程

通过浏览器测试： http://127.0.0.1:8080/hello 结果：

这里是Hello

http://127.0.0.1:8080/test1 、http://127.0.0.1:8080/test2 结果：

执行preHandle方法-->01
这里是Test1
执行postHandle方法-->02
执行afterCompletion方法-->03

多个拦截器

1.新建两个拦截器

Test1Interceptor

public class Test1Interceptor implements HandlerInterceptor{

????@Override
????public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
????????????throws Exception {
???????System.out.println("执行Test1Interceptor preHandle方法-->01");
???????return true;
???}
???@Override
???public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
???????????ModelAndView modelAndView) throws Exception {
??????System.out.println("执行Test1Interceptor postHandle方法-->02");
???}
???@Override
???public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
???????????throws Exception {
???????System.out.println("执行Test1Interceptor afterCompletion方法-->03");
???}
}

Test2Interceptor

public class Test2Interceptor extends HandlerInterceptorAdapter{
????public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
 ?????????? throws Exception {
??????   System.out.println("执行Test2Interceptor preHandle方法-->01");
????????return true;
????}
 ?? public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
????????????ModelAndView modelAndView) throws Exception {
???????System.out.println("执行Test2Interceptor postHandle方法-->02");
???}
????public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
????????????throws Exception {
????????System.out.println("执行Test2Interceptor afterCompletion方法-->03");
????}
}

2.配置拦截器

????@Configuration
????public class WebMvcConfig extends WebMvcConfigurationSupport {
????????/*
?????????* 拦截器配置
?????????*/
????????@Override
????????public void addInterceptors(InterceptorRegistry registry) {
????????????// 注册自定义拦截器，添加拦截路径和排除拦截路径
????????????registry.addInterceptor(new Test1Interceptor()) // 添加拦截器1
????????????????????.addPathPatterns("/**") // 添加拦截路径
????????????????????.excludePathPatterns(// 添加排除拦截路径
????????????????????????????"/hello")
????????????????????.order(0);
????????????registry.addInterceptor(new Test2Interceptor()) // 添加拦截器2
????????????????????.addPathPatterns("/**") // 添加拦截路径
????????????????????.excludePathPatterns(// 添加排除拦截路径
????????????????????????????"/test1")
????????????????????.order(1);
????????????super.addInterceptors(registry);
????????}
????}

3.测试拦截器

????@RestController
????public class TestController {
????????@RequestMapping("/hello")
????????public String getHello() {
????????????System.out.println("这里是Hello");
????????????return "hello world";
????????}
????????@RequestMapping("/test1")
????????public String getTest1() {
????????????System.out.println("这里是Test1");
????????????return "test1 content";
????????}
????????@RequestMapping("/test2")
????????public String getTest2() {
????????????System.out.println("这里是Test2");
????????????return "test2 content";
????????}
????}

4.多个拦截器的执行流程

通过浏览器测试： http://127.0.0.1:8080/test2 结果：

执行Test1Interceptor preHandle方法-->01
执行Test2Interceptor preHandle方法-->01
这里是Test2执行Test2Interceptor postHandle方法-->02
执行Test1Interceptor postHandle方法-->02
执行Test2Interceptor afterCompletion方法-->03
执行Test1Interceptor afterCompletion方法-->03

通过示例，简单的说多个拦截器执行流程就是先进后出。

简单的 token 判断示例

1.拦截器

????@Override
????????public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
????????????????throws Exception {
????????????System.out.println("执行Test1Interceptor preHandle方法-->01");
????????????String token = request.getParameter("token");
????????????if (StringUtils.isEmpty(token)) { ???????????
????????????????response.setContentType("text/html");
????????????????response.setCharacterEncoding("UTF-8");
????????????????response.getWriter().println("token不存在");
????????????????return false;
????????????}
????????????return true;
????????}

2.测试及结果

未传token：

执行Test1Interceptor preHandle方法-->01

传token：

执行Test1Interceptor preHandle方法-->01
页码：1
页码大小：10
执行Test1Interceptor postHandle方法-->02
执行Test1Interceptor afterCompletion方法-->03

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