SpringBoot使用攔截器

SpringBoot的攔截器只能攔截流經DispatcherServlet的請求，對於自定義的Servlet無法進行攔截。
SpringMVC中的攔截器有兩種：HandlerInterceptor和WebMvcInterceptor。這兩個接口都定義了請求之前、請求之中、請求之后三個函數，以HandlerInterceptor為例進行說明：

• 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的函數返回值都是boolean，一旦返回false，就不再處理這個請求，所以它真正具有攔截功能。而WebMvcInterceptor作用只是進行初始化，它的三個函數都是void類型的。

要想使用HandlerInterceptor需要如下幾個步驟：

實現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

過去可以用xml配置，現在更傾向於用java代碼配置

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