Springboot中使用拦截器、过滤器、监听器

在Spring Boot中，你可以通过以下方式实现拦截器、过滤器和监听器：

1. 拦截器（Interceptor）: 使用Spring MVC的HandlerInterceptor。

import org.springframework.stereotype.Component;
import org.springframework.web.servlet.HandlerInterceptor;
 
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
@Component
public class CustomInterceptor implements HandlerInterceptor {
    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) {
        // 在请求处理之前进行调用
        return true; // 如果返回false，则停止流程，api不会被调用
    }
 
    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler, ModelAndView modelAndView) {
        // 请求处理之后进行调用，但是在视图被渲染之前
    }
 
    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex) {
        // 在整个请求结束之后调用，也就是在DispatcherServlet渲染了视图执行
    }
}

然后注册拦截器：

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
@Configuration
public class WebConfig implements WebMvcConfigurer {
 
    @Autowired
    private CustomInterceptor customInterceptor;
 
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        registry.addInterceptor(customInterceptor)
                .addPathPatterns("/**"); // 拦截所有请求
    }
}

2. 过滤器（Filter）: 实现javax.servlet.Filter接口。

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
 
public class CustomFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // 过滤器初始化
    }
 
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) 
            throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        // 可以在调用chain.doFilter(request, response)之前进行你想要的操作
        chain.doFilter(request, response); // 继续执行其他的过滤器或servlet
        // 可以在调用chain.doFilter(request, response)之后进行你想要的操作
    }
 
    @Override
    public void destroy() {
        // 过滤器销毁
    }
}