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在做web项目开发时，我们有时候需要做一些前置的拦截判断处理，比如非法参数校验，防攻击拦截，统一日志处理等，而请求参数如果是form表单提交还好处理；对于json这种输入流的数据就会有问题，统一处理如果读取了数据流就会将流进行关闭，这就会导致接下来的业务处理无法读取数据流。为了解决这个问题，需要将request中的输入流包装为可以重复读取的数据流，具体的操作如下：
自定义一个类继承HttpServletRequestWrapper，并实现它里面的相关方法：

import cn.hutool.core.io.IoUtil;
import jakarta.servlet.ReadListener;
import jakarta.servlet.ServletInputStream;
import jakarta.servlet.http.HttpServletRequest;
import jakarta.servlet.http.HttpServletRequestWrapper;import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStreamReader;/*** @Author xingo* @Date 2024/1/26*/
public class RepeatableReadRequestWrapper extends HttpServletRequestWrapper {private final byte[] body;public RepeatableReadRequestWrapper(HttpServletRequest request) throws IOException {super(request);request.setCharacterEncoding("UTF-8");body = IoUtil.readBytes(request.getInputStream());}@Overridepublic BufferedReader getReader() throws IOException {return new BufferedReader(new InputStreamReader(getInputStream()));}@Overridepublic ServletInputStream getInputStream() throws IOException {final ByteArrayInputStream bis = new ByteArrayInputStream(body);return new ServletInputStream() {@Overridepublic int read() throws IOException {return bis.read();}@Overridepublic boolean isFinished() {return false;}@Overridepublic boolean isReady() {return false;}@Overridepublic void setReadListener(ReadListener readListener) {}};}}

封装成这个类就是为了解决需要重复读取输入流的地方就使用这个包装类替换原有的request对象。再定义一个过滤器用于模拟统一处理请求参数，下面就简单模拟在参数中取用户名的过滤器：

import com.fasterxml.jackson.databind.JsonNode;
import jakarta.servlet.*;
import jakarta.servlet.annotation.WebFilter;
import jakarta.servlet.http.HttpServletRequest;
import org.springframework.core.Ordered;
import org.springframework.core.annotation.Order;
import org.springframework.http.MediaType;
import org.springframework.stereotype.Component;import java.io.IOException;
import java.util.Objects;/*** @Author xingo* @Date 2024/1/26*/
@Order(value = Ordered.LOWEST_PRECEDENCE - 1)
@Component
@WebFilter(filterName = "paramsFilter", urlPatterns = "/*")
public class CheckParamsFilter implements Filter {private ServletContext context;static final String checkKey = "userName";@Overridepublic void init(FilterConfig filterConfig) throws ServletException {Filter.super.init(filterConfig);context = filterConfig.getServletContext();}@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain chain) throws IOException, ServletException {HttpServletRequest request = (HttpServletRequest) servletRequest;ServletRequest requestWrapper = null;String userName = null;String contentType = request.getContentType();if(contentType != null && contentType.contains(MediaType.APPLICATION_JSON_VALUE)) {try {// 对于需要读取输入流的先对request进行包装处理，这样后续再次需要读取数据流时就可以正常读到requestWrapper = new RepeatableReadRequestWrapper(request);JsonNode jsonNode = JacksonUtils.getObjectMapper().readTree(requestWrapper.getInputStream());if(jsonNode.get(checkKey) != null) {userName = jsonNode.get(checkKey).asText();}} catch (Exception e) {e.printStackTrace();}} else {try {if(request.getParameter(checkKey) != null) {userName = request.getParameter(checkKey);}} catch (Exception e) {e.printStackTrace();}}if(userName != null) {// 这里判断用户名检查成功就放行、否则就返回失败信息，在放行处理时需要判断是否需要传递包装requestif(this.check(userName)) {chain.doFilter(Objects.requireNonNullElse(requestWrapper, servletRequest), servletResponse);}servletResponse.setContentType("application/json; charset=utf-8");servletResponse.getWriter().print(JacksonUtils.toJSONString(ApiResult.fail(400, "信息验证失败")));return;}chain.doFilter(Objects.requireNonNullElse(requestWrapper, servletRequest), servletResponse);}@Overridepublic void destroy() {Filter.super.destroy();}private boolean check(String userName) {return "admin".equals(userName);}
}