JAVA：Filer过滤器+案例：请求IP访问限制和请求返回值修改

JAVA：Filer过滤器

介绍

Java中的Filter也被称为过滤器，它是Servlet技术的一部分，用于在web服务器上拦截请求和响应，以检查或转换其内容。
Filter的urlPatterns可以过滤特定地址http的请求，也可以利用Filter对访问请求的数据IP做限制。
文档为本人学习java过滤器过程中做的学习记录。

主要用途：

认证过滤：检查用户请求并确定是否合法。
登记日志：记录请求和响应的日志。
改变请求和响应：可以修改请求头和响应头。
数据压缩：在发送大数据前，可以压缩数据。
加密：对请求和响应进行加密和解密。

使用说明

Spring项目中，创建类继承Filter，实现init、doFilter、destroy方法；

init：只在项目启动的时候运行，用来做数据的初始化
doFilter：数据过滤，每次http请求都会过滤；filterChain.doFilter(request, servletResponse)前面的程序程序是在执行目标程序前执行，后面的程序是在目标程序后执行，若doFilter程序没有执行filterChain.doFilter，请求将会被拦截。
destroy：项目结束时运行

多个过滤器执行顺序

注意：SpringBoot项目中，多个过滤器时，@Order + @WebFilter + @ServletComponentScan 是无法实现按顺序执行过滤器的，推荐使用FilterRegistrationBean实现过滤。

原因详细分析见：https://blog.csdn.net/Zong_0915/article/details/126747302

案例（使用FilterRegistrationBean限制过滤器执行循序+限制IP+修改请求返回值）

案例：有两个过滤器：MyFilter01和MyFilter02，要求按先执行过滤器MyFilter01，再执行过滤器MyFilter02顺序。
MyFilter01实现对IP的白名单限制（限制127.0.0.1仅可以访问一次），以及请求返回值的更写。
MyFilter02仅用于体现执行顺序。

案例参考地址：
https://blog.csdn.net/zhanwuguo8346/article/details/120498756

创建过滤器：MyFilter01用于限制访问IP，修改请求返回值；


@Slf4j
public class MyFilter01 implements Filter {private Map<String, Integer> whiteIPMap;private List<String> alwaysIPList;public MyFilter01(Map<String, Integer> whiteIPMap, List<String> alwaysIPList) {this.alwaysIPList = alwaysIPList;this.whiteIPMap = whiteIPMap;}private final ObjectMapper objectMapper = new ObjectMapper();private static final Set<String> ALLOWED_PATHS = Collections.unmodifiableSet(new HashSet<>(Arrays.asList("/swagger-resources", "/v3/swagger-login", "/v2/api-docs")));private static Map<String, Integer> whiteIpMapDay = new HashMap<>();@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("（MyFilter01）项目开始时候执行：------->>>init");System.out.println("（MyFilter01）whiteIPMap：" + whiteIPMap);System.out.println("（MyFilter01）alwaysIPList：" + alwaysIPList);whiteIpMapDay.putAll(whiteIPMap);}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("（MyFilter01）项目每次http请求时候执行：------->>>doFilter.start");HttpServletRequest request = (HttpServletRequest) servletRequest;String ipAddr = getIpAddr(request);log.info("PermissionFilter 过滤器，请求ip为：{}", ipAddr);String path = request.getRequestURI().substring(request.getContextPath().length()).replaceAll("[/]+$", "");boolean contains = ALLOWED_PATHS.contains(path);servletResponse.setCharacterEncoding("utf-8");servletResponse.setContentType("text/html;charset=utf-8");if (alwaysIPList.contains(ipAddr) && contains) {filterChain.doFilter(request, servletResponse);} else {if (whiteIpMapDay.containsKey(ipAddr)) {Integer integer = whiteIpMapDay.get(ipAddr);if (integer > 0) {if (contains) {filterChain.doFilter(request, servletResponse);} else {whiteIpMapDay.put(ipAddr, (whiteIpMapDay.get(ipAddr) - 1));filterChain.doFilter(request, servletResponse);}} else {BaseResponse<Void> baseResponse = new BaseResponse<>();baseResponse.setCode(-1);baseResponse.setMessage("请求被拒绝，本IP:" + ipAddr + "每天只允许调用：" + whiteIPMap.get(ipAddr) + "次！");String response = objectMapper.writeValueAsString(baseResponse);setServletResponseMessage(servletResponse, response);}} else {BaseResponse<Void> baseResponse = new BaseResponse<>();baseResponse.setMessage("不支持本IP请求：" + ipAddr);baseResponse.setCode(-1);String response = objectMapper.writeValueAsString(baseResponse);setServletResponseMessage(servletResponse, response);}}System.out.println("（MyFilter01）项目每次http请求时候执行：------->>>doFilter.end");}@Overridepublic void destroy() {System.out.println("（MyFilter01）项目结束时候执行：------->>>destroy");}/*** 处理返回是getWriter()还是getOutputStream();* getWriter()：out对象用于处理字符流数据。* getOutputStream()：os用于输出字符流数据或者二进制的字节流数据都可以。*/private void setServletResponseMessage(ServletResponse servletResponse, String response) {try {servletResponse.getWriter().write(response);} catch (IOException e) {throw new RuntimeException(e);} catch (IllegalStateException e) {servletResponse.setContentType("text/plain;charset=UTF-8"); // 设置内容类型和编码try {ServletOutputStream outputStream = servletResponse.getOutputStream();outputStream.write(response.getBytes(StandardCharsets.UTF_8)); // 写入字节数组} catch (IOException ex) {throw new RuntimeException(ex);}}}public static String getIpAddr(HttpServletRequest request) {String ipAddress = request.getHeader("x-forwarded-for");if (ipAddress == null || ipAddress.isEmpty() || "unknown".equalsIgnoreCase(ipAddress)) {ipAddress = request.getHeader("Proxy-Client-IP");}if (ipAddress == null || ipAddress.isEmpty() || "unknown".equalsIgnoreCase(ipAddress)) {ipAddress = request.getHeader("WL-Proxy-Client-IP");}if (ipAddress == null || ipAddress.isEmpty() || "unknown".equalsIgnoreCase(ipAddress)) {ipAddress = request.getRemoteAddr();if (ipAddress.equals("127.0.0.1") || ipAddress.equals("0:0:0:0:0:0:0:1")) {//根据网卡取本机配置的IPInetAddress inet = null;try {inet = InetAddress.getLocalHost();} catch (UnknownHostException e) {e.printStackTrace();}
//                ipAddress= inet.getHostAddress();ipAddress = "127.0.0.1";}}//对于通过多个代理的情况，第一个IP为客户端真实IP,多个IP按照','分割if (ipAddress.length() > 15) { //"***.***.***.***".length() = 15if (ipAddress.indexOf(",") > 0) {ipAddress = ipAddress.substring(0, ipAddress.indexOf(","));}}return ipAddress;}}

过滤器：MyFilter02仅作日志记录。体现执行顺序

public class MyFilter02 implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("（MyFilter02）项目开始时候执行：------->>>init");}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {System.out.println("（MyFilter02）项目每次http请求时候执行：------->>>doFilter.start");filterChain.doFilter(servletRequest, servletResponse);System.out.println("（MyFilter02）项目每次http请求时候执行：------->>>doFilter.end");}@Overridepublic void destroy() {System.out.println("（MyFilter02）项目结束时候执行：------->>>destroy");}}

application.yml中设置白名单访问次数，一直有权限访问的白名单。
127.0.0.1限制仅可以访问一次。

permission:white-ip: '{"127.0.0.1": 1, "192.168.16.30": 2}'always-ip: 127.0.0.1,127.0.0.1

创建配置类：FilterConfig使用@Value读取配置文件值，注册FilterRegistrationBean到Spring容器中，并设置两个过滤器的执行顺序和过滤路径

@Configuration
public class FilterConfig { @Value("#{${permission.white-ip}}")private Map<String, Integer> whiteIPMap;@Value("#{'${permission.always-ip}'.split(',')}")private List<String> alwaysIPList;@Beanpublic FilterRegistrationBean<MyFilter01> myFilterRegistrationBean01() {FilterRegistrationBean<MyFilter01> bean = new FilterRegistrationBean<>();bean.setFilter(new MyFilter01(whiteIPMap, alwaysIPList));bean.addUrlPatterns("/api/*");bean.setOrder(1);return bean;}@Beanpublic FilterRegistrationBean<MyFilter02> myFilterRegistrationBean02() {FilterRegistrationBean<MyFilter02> bean = new FilterRegistrationBean<>();bean.setFilter(new MyFilter02());bean.addUrlPatterns("/*");bean.setOrder(2);return bean;}
}

程序中用到的BaseResponse类：

@Data
public class BaseResponse<T> implements Serializable {private int code;private T data;private String message;private String description;public BaseResponse() {}public BaseResponse(int code, T data, String message, String description) {this.code = code;this.data = data;this.message = message;this.description = description;}public BaseResponse(int code, T data, String message) {this(code, data, message, "");}public BaseResponse(int code, T data) {this(code, data, "", "");}public BaseResponse(ErrorCodeEnum errorCode) {this(errorCode.getCode(), null, errorCode.getMessage(), errorCode.getDescription());}
}