SpringBoot使用拦截器

SpringBoot的拦截器只能拦截流经DispatcherServlet的请求，对于自定义的Servlet无法进行拦截。
SpringMVC中的拦截器有两种：HandlerInterceptor和WebMvcInterceptor。这两个接口都定义了请求之前、请求之中、请求之后三个函数，以HandlerInterceptor为例进行说明：

public boolean preHandle(HttpServletRequest req, HttpServletResponse httpServletResponse, Object o)
public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView)
public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e)

HandlerInterceptor的函数返回值都是boolean，一旦返回false，就不再处理这个请求，所以它真正具有拦截功能。而WebMvcInterceptor作用只是进行初始化，它的三个函数都是void类型的。

要想使用HandlerInterceptor需要如下几个步骤：

实现HandlerInterceptor接口

public class MyInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest req, HttpServletResponse httpServletResponse, Object o) throws Exception { 
    }

    @Override
    public void postHandle(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, ModelAndView modelAndView) throws Exception {

    }

    @Override
    public void afterCompletion(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse, Object o, Exception e) throws Exception {

    }
}

添加Configureation

过去可以用xml配置，现在更倾向于用java代码配置

@Configuration
public class MyWebMvcConfigurer extends WebMvcConfigurerAdapter {
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(new MyInterceptor()).addPathPatterns("/**");
        super.addInterceptors(registry);
    }
}