package com.cn.unit.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.http.HttpServletRequest;

import org.apache.commons.lang.StringUtils;
import org.springframework.web.multipart.MultipartHttpServletRequest;
import org.springframework.web.multipart.commons.CommonsMultipartResolver;

/**
 * 過濾器
 * Created by adonis on 2020/12/12
 */
public class SafeFilter implements Filter{
 
 // 配置信息對象
 public FilterConfig filterConfig;
 
 /**
 * 初始化
 * 與我們編寫的Servlet程序一樣，F(xiàn)ilter的創(chuàng)建和銷毀由WEB服務器負責。 
 * Web應用程序啟動時，Web服務器將創(chuàng)建Filter的實例對象，并調用其init方法，讀取web.xml配置，
 * 完成對象的初始化功能，從而為后續(xù)的用戶請求作好攔截的準備工作。
 * Filter對象只會創(chuàng)建一次，init方法也只會執(zhí)行一次。
 * 開發(fā)人員通過init方法的參數(shù)，可獲得代表當前Filter配置信息的FilterConfig對象。
 */
  @Override
  public void init(FilterConfig filterConfig) throws ServletException {
   filterConfig = config;
 }
 
 /**
   * 攔截請求
   * 這個方法完成實際的過濾操作。當客戶請求訪問與過濾器關聯(lián)的URL的時候，Servlet過濾器將先執(zhí)行doFilter方法。
   * FilterChain參數(shù)用于訪問后續(xù)過濾器。
   */
  @Override
  public void doFilter(ServletRequest request, ServletResponse response,
             FilterChain chain) throws IOException, ServletException {
    HttpServletRequest httpRequest = (HttpServletRequest) request;
    String enctype = httpRequest.getContentType();
    if(StringUtils.isNotBlank(enctype) && enctype.contains("multipart/form-data")){
     // 上傳文件
     CommonsMultipartResolver commonsMultipartResolver = new CommonsMultipartResolver(
     httpRequest.getSession().getServletContext());
   MultipartHttpServletRequest multipartRequest = commonsMultipartResolver.resolveMultipart(httpRequest);
   XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper(multipartRequest);
   chain.doFilter(xssRequest, response);
    }else{
     // 普通表單和Ajax
     XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper((HttpServletRequest) request);
     chain.doFilter(xssRequest, response);
    }
  }
  
  /**
   * 銷毀
   * Filter對象創(chuàng)建后會駐留在內存，當Web應用移除或服務器停止時才銷毀。在Web容器卸載Filter對象之前被調用。
   * 該方法在Filter的生命周期中僅執(zhí)行一次。在這個方法中，可以釋放過濾器使用的資源。
   */
  @Override
  public void destroy() {
   this.filterConfig = null;
 }
 
}

package com.cn.unit.filter;

import java.util.Map;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

/**
 * 用戶請求包裝類
 * Created by adonis on 2020/12/12
 */
public class SafeHttpServletRequestWrapper extends HttpServletRequestWrapper{

  public SafeHttpServletRequestWrapper(HttpServletRequest request) { 
    super(request);
  }
  
  @Override 
  public String getParameter(String name) { 
    String value = super.getParameter(name); 
    if (value != null) { 
      value = xssEncode(value); 
    } 
    return value; 
  }
  @Override
  public String[] getParameterValues(String name) {
    String[] value = super.getParameterValues(name);
    if(value != null){
      for (int i = 0; i < value.length; i++) {
        value[i] = xssEncode(value[i]);
      }
    }
    return value;
  }
 @Override
  public Map getParameterMap() {
    return super.getParameterMap();
  }
  
 /**
 * 請求頭不過濾
 */
  @Override 
  public String getHeader(String name) { 
   return super.getHeader(name);
  } 
  
  /** 
   * 將容易引起注入的關鍵字的半角字符直接替換成全角字符
   * @param value 過濾前的值
   * @return 過濾后的值
   */ 
  private static String xssEncode(String value) { 
    if (value == null || value.isEmpty()) {
      return value;
    }
    // 防SQL注入轉義
 value = StringEscapeUtils.escapeSql(value);
 
 // HTML防注入，個人建議使用第三種
    // 1.防HTML注入轉義(HtmlUtils工具類，漢字不轉義，雙引號轉義，存在JSON封裝需要反轉義)
    value = HtmlUtils.htmlEscape(value);
    /*
    // 2.防HTML注入轉義(StringEscapeUtils工具類，漢字也轉義，取出時需要反轉義)
    // value = StringEscapeUtils.escapeHtml(value);
    // 3.字符串替換法（通過各種循環(huán)替換字符串測試，最終還是replace替換效果最佳）
    value = value.replaceAll("<", "＜");
    value = value.replaceAll(">", "＞");
    value = value.replaceAll("'", "＇");
    value = value.replaceAll(";", "﹔");
    value = value.replaceAll("&", "＆");
    value = value.replaceAll("%", "﹪");
    value = value.replaceAll("#", "＃");
    value = value.replaceAll("select", "seleᴄt");// "c"→"ᴄ"
    value = value.replaceAll("truncate", "trunᴄate");// "c"→"ᴄ"
    value = value.replaceAll("exec", "exeᴄ");// "c"→"ᴄ"
    value = value.replaceAll("join", "jᴏin");// "o"→"ᴏ"
    value = value.replaceAll("union", "uniᴏn");// "o"→"ᴏ"
    value = value.replaceAll("drop", "drᴏp");// "o"→"ᴏ"
    value = value.replaceAll("count", "cᴏunt");// "o"→"ᴏ"
    value = value.replaceAll("insert", "ins℮rt");// "e"→"℮"
    value = value.replaceAll("update", "updat℮");// "e"→"℮"
    value = value.replaceAll("delete", "delet℮");// "e"→"℮"
    
    value = value.replaceAll("script", "sᴄript");// "c"→"ᴄ"
    value = value.replaceAll("cookie", "cᴏᴏkie");// "o"→"ᴏ"
    value = value.replaceAll("iframe", "ifram℮");// "e"→"℮"
    value = value.replaceAll("onmouseover", "onmouseov℮r");// "e"→"℮"
    value = value.replaceAll("onmousemove", "onmousemov℮");// "e"→"℮"*/
    return value;
  } 
}

<!-- 配置過濾器防止SQL注入XSS注入 -->
<filter>
  <filter-name>XssSqlFilter</filter-name>
  <filter-class>com.cn.unit.filter.SafeFilter</filter-class>
</filter>
<filter-mapping>
  <filter-name>XssSqlFilter</filter-name>
  <url-pattern>/*</url-pattern>
</filter-mapping>

<init-param>
 <param-name>excludeFilter</param-name><!-- 靜態(tài)資源不進行過濾，如js、css文件 -->
 <param-value>/document/;/ligentres/</param-value>
</init-param>

public FilterConfig filterConfig;
public String[] excludeFilterArray;
@Override
public void init(FilterConfig config) throws ServletException {
 filterConfig = config;
  // 讀取web配置文件中的靜態(tài)資源所在路徑
 String excludeFilter = filterConfig.getInitParameter("excludeFilter");
 excludeFilterArray = excludeFilter.split(";");
}

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
  HttpServletRequest httpRequest = (HttpServletRequest) request;
  String uri = httpRequest.getRequestURI();
  // 靜態(tài)資源直接跳過,不進行過濾
  if(uri==null||this.isContains(uri, excludeFilterArray)) {
   chain.doFilter(request, response);
   return;
  }
  ......
}

// 判斷數(shù)組是否包含某一元素
public boolean isContains(String uri, String[] regx) {
  boolean result = false;
  for (int i = 0; i < regx.length; i++) {
   if (uri.indexOf(regx[i]) != -1) {
   return true;
   }
  }
  return result;
}