springboot拦截器之Filter（一）

filter实际上就是一个过滤器

1使用Servlet3.0的注解进行配置

2启动类中家@ServletComponentScan,进行扫描

3新建一个Filter类，implements Filter，并且实现对应的接口

4@WebFilter(urlPatterns = "/api/*",filterName = "LogginFilter")  标记一个类为filter，被spring扫描

urlPatterns 是拦截规则，支持正则  

5控制filterChain.doFilter方法的调用，来实现是否支持放行，不放行，web应该返回resp.sendRedirect("/index.html");

场景：权限的控制，用户的登陆（非前后端分离）

6代码：

6.1目录结构

 6.2添加注解

@SpringBootConfiguration
@EnableAutoConfiguration
@ComponentScan
@ServletComponentScan
public class Springboot2Application extends SpringBootServletInitializer {

@Override
protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
return application.sources(Springboot2Application.class);
}

public static void main(String[] args) {
SpringApplication.run(Springboot2Application.class, args);
}
}

6.3新建Filter

package com.example.demo.filter;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebFilter(urlPatterns = "/api/*",filterName = "LogginFilter")
public class LogginFilter implements Filter{

/**
* 容器加载的时候调用
*/
@Override
public void init(FilterConfig filterConfig)throws ServletException {
System.out.println("init loginFilter");
}

/**
* 容器拦截的时候调用
*/
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse serletResponse, FilterChain filterChain)
throws IOException, ServletException {
System.out.println("doliter loginFilter");
HttpServletRequest rec=(HttpServletRequest)servletRequest;
HttpServletResponse resp=(HttpServletResponse) serletResponse;
String username=rec.getParameter("username");
if("李明".equals(username)) {
filterChain.doFilter(servletRequest, serletResponse);
}else {
resp.sendRedirect("/index.html");
return;
}
}

/**
* 容器销毁的时候调用
*/
@Override
public void destroy() {
System.out.println("destroy loginFilter");
}

}

6.4新建controller

package com.example.demo.controller.login;

import java.util.HashMap;
import java.util.Map;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class LoginController {

private Map<String,Object> params=new HashMap<>();

@RequestMapping(value="/api/v1/account")
public Object account() {
params.put("money", "1000");
return params;
}
}

6.5访问地址：http://localhost:8080//api/v1/account?username=李明