java configures multiple filter priorities and several common filter operations

Directory Filter Configuration: Common Filter 1: Common Filter 2: Sensitive Word Filter Tool Class

If there is no accident in a project, there will be more than two filters, but if it is not configured directly, it will be executed according to your filter name, which may lead to some performance or logical problems. Then, controlling the execution order under 1 is what we must do.

java encapsulates an FilterRegistrationBean object, which can be compared to a container. Filters are put into this object, and attributes such as priority setting and filtering rule setting can be carried out on this object. Here are several commonly used filters and filter configurations.

Filter configuration:

package cn.ask.filter;
import javax.servlet.DispatcherType; 
import org.springframework.boot.web.servlet.FilterRegistrationBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.filter.DelegatingFilterProxy;
 
/**
 * Title:      FilterConfig
 * @date       2018 Year 10 Month 25 Day 
 * @version    V1.0
 * Description:  Filter configuration 
 */
@SuppressWarnings("all")
@Configuration
public class FilterConfig {
	/**
	 * @Description  Prevent xss Attack filter 
	 * @date 2018 Year 8 Month 16 Sunday afternoon 4:55:44
	 */
	@Bean
	public FilterRegistrationBean xssFilterRegistration() {
		FilterRegistrationBean registration = new FilterRegistrationBean();
		registration.setDispatcherTypes(DispatcherType.REQUEST);
		registration.setFilter(new XssFilter());
		registration.addUrlPatterns("/*");
		registration.setName("xssFilter");
        //order The smaller the number, the more it executes first 
		registration.setOrder(1);
		return registration;
	}
	
	/**  
	* @Description  Get login information  
	* @date 2018 Year 10 Month 25 Sunday morning 9:14:48
	*/
	@Bean
	public FilterRegistrationBean cookieRegistration() {
		FilterRegistrationBean registration = new FilterRegistrationBean();
		registration.setDispatcherTypes(DispatcherType.REQUEST);
		registration.setFilter(new CookieFilter());
		registration.addUrlPatterns("/*");
		registration.setName("firstFilter");
		registration.setOrder(2);
		return registration;
	}	
}

Common Filter 1:

sso Single Sign-On (use cookie to record cross-site data)

package cn.ask.filter; 
import java.io.IOException;
import java.net.URLDecoder; 
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.Cookie;
import javax.servlet.http.HttpServletRequest; 
import org.apache.commons.lang3.StringUtils;
 
/**
 * Servlet Filter implementation class FirstFilter
 */
public class CookieFilter implements Filter {
 
    /**
     * Default constructor. 
     */
    public CookieFilter() {
        // TODO Auto-generated constructor stub
    }
 
	/**
	 * @see Filter#destroy()
	 */
	public void destroy() {
		// TODO Auto-generated method stub
	}
 
	/**
	 * @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
	 */
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
		HttpServletRequest req = (HttpServletRequest) request;
		String tokenHeader = req.getHeader("token");
		if(StringUtils.isBlank(tokenHeader)) {
			Cookie[] cookies = req.getCookies();
			if (cookies != null && cookies.length > 0) {
				for (int i = 0; i < cookies.length; i++) {
					String name = cookies[i].getName();
					String value = cookies[i].getValue();
					if ("user_accesstoken".equals(name)) { //  Users token
						req.setAttribute("token", URLDecoder.decode(value, "utf-8"));
					}
					if ("user_avatar".equals(name)) { //  Head portrait 
						req.setAttribute("avatar", URLDecoder.decode(value, "utf-8"));
					}
					if ("user_nickname".equals(name)) { //  Nickname 
						req.setAttribute("nickname", URLDecoder.decode(value, "utf-8"));
					}
					String token = (String) req.getAttribute("token");
					if (StringUtils.isBlank(token)) {
						req.setAttribute("isLogin", "no");
					} else {
						req.setAttribute("isLogin", "yes");
					}
				}
			}else {
				req.removeAttribute("token");
				req.removeAttribute("avatar");
				req.removeAttribute("nickname");
				req.setAttribute("isLogin", "no");
			}
		} else {
			req.setAttribute("token", tokenHeader);
		}
		
		chain.doFilter(request, response);
	}
 
	/**
	 * @see Filter#init(FilterConfig)
	 */
	public void init(FilterConfig fConfig) throws ServletException {
		// TODO Auto-generated method stub
	} 
}

Commonly used filters 2:

xss filtering and anti-html injection filtering (including filtering sensitive words)

package cn.ask.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;  
/**
 * Title:      XssFilter
 * @date       2018 Year 8 Month 16 Day 
 * @version    V1.0
 * Description: xss Filter 
 */
public class XssFilter implements Filter {
 
	@Override
	public void init(FilterConfig config) throws ServletException {
	}
 
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
		XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper((HttpServletRequest) request);
		chain.doFilter(xssRequest, response);
	}
 
	@Override
	public void destroy() {
	} 
}

package cn.ask.filter;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map;
import javax.servlet.ReadListener;
import javax.servlet.ServletInputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper; 
import org.apache.commons.io.IOUtils;
import org.apache.commons.lang3.StringUtils;
import org.springframework.http.HttpHeaders;
import org.springframework.http.MediaType; 
 
/**
 * Title:      XssHttpServletRequestWrapper
 * @date       2018 Year 8 Month 16 Day 
 * @version    V1.0
 * Description:  XSS Filtration treatment 
 */
public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {
    /** Unpackaged HttpServletRequest (Special scenes need to be filtered by yourself */
    HttpServletRequest orgRequest;
    /**html Filter */
    private final static HtmlFilter HTMLFILTER = new HtmlFilter();
 
    public XssHttpServletRequestWrapper(HttpServletRequest request) {
        super(request);
        orgRequest = request;
    }
 
    @Override
    public ServletInputStream getInputStream() throws IOException {
        // Non json Type, returning directly 
        if(!super.getHeader(HttpHeaders.CONTENT_TYPE).equalsIgnoreCase(MediaType.APPLICATION_JSON_VALUE)){
            return super.getInputStream();
        }
 
        // Is empty, return directly 
        String json = IOUtils.toString(super.getInputStream(), "utf-8");
        if (StringUtils.isBlank(json)) {
            return super.getInputStream();
        }
 
        //xss Filter 
        json = xssEncode(json);
        final ByteArrayInputStream bis = new ByteArrayInputStream(json.getBytes());
        return new ServletInputStream() {
            @Override
            public boolean isFinished() {
                return true;
            }
 
            @Override
            public boolean isReady() {
                return true;
            }
 
            @Override
            public void setReadListener(ReadListener readListener) {
 
            }
 
            @Override
            public int read() throws IOException {
                return bis.read();
            }
        };
    } 
    @Override
    public String getParameter(String name) {
        String value = super.getParameter(xssEncode(name));
        if (StringUtils.isNotBlank(value)) {
            value = xssEncode(value);
        }
        return value;
    } 
    @Override
    public String[] getParameterValues(String name) {
        String[] parameters = super.getParameterValues(name);
        if (parameters == null || parameters.length == 0) {
            return null;
        }
 
        for (int i = 0; i < parameters.length; i++) {
            parameters[i] = xssEncode(parameters[i]);
        }
        return parameters;
    } 
    @Override
    public Map<String,String[]> getParameterMap() {
        Map<String,String[]> map = new LinkedHashMap<>();
        Map<String,String[]> parameters = super.getParameterMap();
        for (String key : parameters.keySet()) {
            String[] values = parameters.get(key);
            for (int i = 0; i < values.length; i++) {
                values[i] = xssEncode(values[i]);
            }
            map.put(key, values);
        }
        return map;
    } 
    @Override
    public String getHeader(String name) {
        String value = super.getHeader(xssEncode(name));
        if (StringUtils.isNotBlank(value)) {
            value = xssEncode(value);
        }
        return value;
    }
    // Rich text content release 
    private String xssEncode(String input) {
    	if(!input.startsWith("<p")&&!input.startsWith("<ol")&&!input.startsWith("<ul")&&!input.startsWith("<hr/>")) {
    		input=HTMLFILTER.filter(input);
    	}
        // Sensitive word filtering 
        input=SensitiveWordUtils.getSensitiveWordUtils().replaceSensitiveWord(input, '*', 2);
        return input;        
    } 
    /**
     *  Get the most primitive request
     */
    public HttpServletRequest getOrgRequest() {
        return orgRequest;
    } 
    /**
     *  Get the most primitive request
     */
    public static HttpServletRequest getOrgRequest(HttpServletRequest request) {
        if (request instanceof XssHttpServletRequestWrapper) {
            return ((XssHttpServletRequestWrapper) request).getOrgRequest();
        } 
        return request;
    } 
}

package cn.ask.filter; 
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
import java.util.logging.Logger;
import java.util.regex.Matcher;
import java.util.regex.Pattern; 
/**
 * Title:      HTMLFilter
 * @date       2018 Year 8 Month 16 Day 
 * @version    V1.0
 * Description:  Prevent html Injection 
 */
public final class HtmlFilter { 
    /** regex flag union representing /si modifiers in php **/
    private static final int REGEX_FLAGS_SI = Pattern.CASE_INSENSITIVE | Pattern.DOTALL;
    private static final Pattern P_COMMENTS = Pattern.compile("<!--(.*?)-->", Pattern.DOTALL);
    private static final Pattern P_COMMENT = Pattern.compile("^!--(.*)--$", REGEX_FLAGS_SI);
    private static final Pattern P_TAGS = Pattern.compile("<(.*?)>", Pattern.DOTALL);
    private static final Pattern P_END_TAG = Pattern.compile("^/([a-z0-9]+)", REGEX_FLAGS_SI);
    private static final Pattern P_START_TAG = Pattern.compile("^([a-z0-9]+)(.*?)(/?)$", REGEX_FLAGS_SI);
    private static final Pattern P_QUOTED_ATTRIBUTES = Pattern.compile("([a-z0-9]+)=([\"'])(.*?)\\2", REGEX_FLAGS_SI);
    private static final Pattern P_UNQUOTED_ATTRIBUTES = Pattern.compile("([a-z0-9]+)(=)([^\"\\s']+)", REGEX_FLAGS_SI);
    private static final Pattern P_PROTOCOL = Pattern.compile("^([^:]+):", REGEX_FLAGS_SI);
    private static final Pattern P_ENTITY = Pattern.compile("&#(\\d+);?");
    private static final Pattern P_ENTITY_UNICODE = Pattern.compile("&#x([0-9a-f]+);?");
    private static final Pattern P_ENCODE = Pattern.compile("%([0-9a-f]{2});?");
    private static final Pattern P_VALID_ENTITIES = Pattern.compile("&([^&;]*)(?=(;|&|$))");
    private static final Pattern P_VALID_QUOTES = Pattern.compile("(>|^)([^<]+?)(<|$)", Pattern.DOTALL);
    private static final Pattern P_END_ARROW = Pattern.compile("^>");
    private static final Pattern P_BODY_TO_END = Pattern.compile("<([^>]*?)(?=<|$)");
    private static final Pattern P_XML_CONTENT = Pattern.compile("(^|>)([^<]*?)(?=>)");
    private static final Pattern P_STRAY_LEFT_ARROW = Pattern.compile("<([^>]*?)(?=<|$)");
    private static final Pattern P_STRAY_RIGHT_ARROW = Pattern.compile("(^|>)([^<]*?)(?=>)");
    private static final Pattern P_AMP = Pattern.compile("&");
    private static final Pattern P_QUOTE = Pattern.compile("<");
    private static final Pattern P_LEFT_ARROW = Pattern.compile("<");
    private static final Pattern P_RIGHT_ARROW = Pattern.compile(">");
    private static final Pattern P_BOTH_ARROWS = Pattern.compile("<>");
    private static final String SS="#//";
 
    /** @xxx could grow large... maybe use sesat's ReferenceMap */
    private static final ConcurrentMap<String,Pattern> P_REMOVE_PAIR_BLANKS = new ConcurrentHashMap<String, Pattern>();
    private static final ConcurrentMap<String,Pattern> P_REMOVE_SELF_BLANKS = new ConcurrentHashMap<String, Pattern>();
 
    /** set of allowed html elements, along with allowed attributes for each element **/
    private final Map<String, List<String>> vAllowed;
    /** counts of open tags for each (allowable) html element **/
    private final Map<String, Integer> vTagCounts = new HashMap<String, Integer>();
 
    /** html elements which must always be self-closing (e.g. "<img />") **/
    private final String[] vSelfClosingTags;
    /** html elements which must always have separate opening and closing tags (e.g. "<b></b>") **/
    private final String[] vNeedClosingTags;
    /** set of disallowed html elements **/
    private final String[] vDisallowed;
    /** attributes which should be checked for valid protocols **/
    private final String[] vProtocolAtts;
    /** allowed protocols **/
    private final String[] vAllowedProtocols;
    /** tags which should be removed if they contain no content (e.g. "<b></b>" or "<b />") **/
    private final String[] vRemoveBlanks;
    /** entities allowed within html markup **/
    private final String[] vAllowedEntities;
    /** flag determining whether comments are allowed in input String. */
    private final boolean stripComment;
    private final boolean encodeQuotes;
    private boolean vDebug = false;
    /**
     * flag determining whether to try to make tags when presented with "unbalanced"
     * angle brackets (e.g. "<b text </b>" becomes "<b> text </b>").  If set to false,
     * unbalanced angle brackets will be html escaped.
     */
    private final boolean alwaysMakeTags;
 
    /** Default constructor.
     *
     */
    public HtmlFilter() {
        vAllowed = new HashMap<>();
 
        final ArrayList<String> aAtts = new ArrayList<String>();
        aAtts.add("href");
        aAtts.add("target");
        vAllowed.put("a", aAtts);
 
        final ArrayList<String> imgAtts = new ArrayList<String>();
        imgAtts.add("src");
        imgAtts.add("width");
        imgAtts.add("height");
        imgAtts.add("alt");
        vAllowed.put("img", imgAtts);
 
        final ArrayList<String> noAtts = new ArrayList<String>();
        vAllowed.put("b", noAtts);
        vAllowed.put("strong", noAtts);
        vAllowed.put("i", noAtts);
        vAllowed.put("em", noAtts);
 
        vSelfClosingTags = new String[]{"img"};
        vNeedClosingTags = new String[]{"a", "b", "strong", "i", "em"};
        vDisallowed = new String[]{};
        /**no ftp*/
        vAllowedProtocols = new String[]{"http", "mailto", "https"};
        vProtocolAtts = new String[]{"src", "href"};
        vRemoveBlanks = new String[]{"a", "b", "strong", "i", "em"};
        vAllowedEntities = new String[]{"amp", "gt", "lt", "quot"};
        stripComment = true;
        encodeQuotes = true;
        alwaysMakeTags = true;
    } 
    /** Set debug flag to true. Otherwise use default settings. See the default constructor.
     *
     * @param debug turn debug on with a true argument
     */
    public HtmlFilter(final boolean debug) {
        this();
        vDebug = debug; 
    } 
    /** Map-parameter configurable constructor.
     *
     * @param conf map containing configuration. keys match field names.
     */
    @SuppressWarnings("unchecked")
	public HtmlFilter(final Map<String,Object> conf) {
 
        assert conf.containsKey("vAllowed") : "configuration requires vAllowed";
        assert conf.containsKey("vSelfClosingTags") : "configuration requires vSelfClosingTags";
        assert conf.containsKey("vNeedClosingTags") : "configuration requires vNeedClosingTags";
        assert conf.containsKey("vDisallowed") : "configuration requires vDisallowed";
        assert conf.containsKey("vAllowedProtocols") : "configuration requires vAllowedProtocols";
        assert conf.containsKey("vProtocolAtts") : "configuration requires vProtocolAtts";
        assert conf.containsKey("vRemoveBlanks") : "configuration requires vRemoveBlanks";
        assert conf.containsKey("vAllowedEntities") : "configuration requires vAllowedEntities";
 
        vAllowed = Collections.unmodifiableMap((HashMap<String, List<String>>) conf.get("vAllowed"));
        vSelfClosingTags = (String[]) conf.get("vSelfClosingTags");
        vNeedClosingTags = (String[]) conf.get("vNeedClosingTags");
        vDisallowed = (String[]) conf.get("vDisallowed");
        vAllowedProtocols = (String[]) conf.get("vAllowedProtocols");
        vProtocolAtts = (String[]) conf.get("vProtocolAtts");
        vRemoveBlanks = (String[]) conf.get("vRemoveBlanks");
        vAllowedEntities = (String[]) conf.get("vAllowedEntities");
        stripComment =  conf.containsKey("stripComment") ? (Boolean) conf.get("stripComment") : true;
        encodeQuotes = conf.containsKey("encodeQuotes") ? (Boolean) conf.get("encodeQuotes") : true;
        alwaysMakeTags = conf.containsKey("alwaysMakeTags") ? (Boolean) conf.get("alwaysMakeTags") : true;
    } 
    private void reset() {
        vTagCounts.clear();
    } 
    private void debug(final String msg) {
        if (vDebug) {
            Logger.getAnonymousLogger().info(msg);
        }
    } 
    //---------------------------------------------------------------
    /**my versions of some PHP library functions*/
    public static String chr(final int decimal) {
        return String.valueOf((char) decimal);
    }
 
    public static String htmlSpecialChars(final String s) {
        String result = s;
        result = regexReplace(P_AMP, "&amp;", result);
        result = regexReplace(P_QUOTE, "&quot;", result);
        result = regexReplace(P_LEFT_ARROW, "&lt;", result);
        result = regexReplace(P_RIGHT_ARROW, "&gt;", result);
        return result;
    } 
    //---------------------------------------------------------------
    /**
     * given a user submitted input String, filter out any invalid or restricted
     * html.
     *
     * @param input text (i.e. submitted by a user) than may contain html
     * @return "clean" version of input, with only valid, whitelisted html elements allowed
     */
    public String filter(final String input) {
        reset();
        String s = input;
 
        debug("************************************************");
        debug("              INPUT: " + input);
 
        s = escapeComments(s);
        debug("     escapeComments: " + s);
 
        s = balanceHTML(s);
        debug("        balanceHTML: " + s);
 
        s = checkTags(s);
        debug("          checkTags: " + s);
 
        s = processRemoveBlanks(s);
        debug("processRemoveBlanks: " + s);
 
        s = validateEntities(s);
        debug("    validateEntites: " + s);
 
        debug("************************************************\n\n");
        return s;
    } 
    public boolean isAlwaysMakeTags(){
        return alwaysMakeTags;
    } 
    public boolean isStripComments(){
        return stripComment;
    } 
    private String escapeComments(final String s) {
        final Matcher m = P_COMMENTS.matcher(s);
        final StringBuffer buf = new StringBuffer();
        if (m.find()) {
        	/**(.*?)*/
            final String match = m.group(1); 
            m.appendReplacement(buf, Matcher.quoteReplacement("<!--" + htmlSpecialChars(match) + "-->"));
        }
        m.appendTail(buf); 
        return buf.toString();
    } 
    private String balanceHTML(String s) {
        if (alwaysMakeTags) {
            //
            // try and form html
            //
            s = regexReplace(P_END_ARROW, "", s);
            s = regexReplace(P_BODY_TO_END, "<$1>", s);
            s = regexReplace(P_XML_CONTENT, "$1<$2", s);
 
        } else {
            //
            // escape stray brackets
            //
            s = regexReplace(P_STRAY_LEFT_ARROW, "&lt;$1", s);
            s = regexReplace(P_STRAY_RIGHT_ARROW, "$1$2&gt;<", s);
 
            //
            // the last regexp causes '<>' entities to appear
            // (we need to do a lookahead assertion so that the last bracket can
            // be used in the next pass of the regexp)
            //
            s = regexReplace(P_BOTH_ARROWS, "", s);
        } 
        return s;
    } 
    private String checkTags(String s) {
        Matcher m = P_TAGS.matcher(s);
 
        final StringBuffer buf = new StringBuffer();
        while (m.find()) {
            String replaceStr = m.group(1);
            replaceStr = processTag(replaceStr);
            m.appendReplacement(buf, Matcher.quoteReplacement(replaceStr));
        }
        m.appendTail(buf); 
        s = buf.toString(); 
        // these get tallied in processTag
        // (remember to reset before subsequent calls to filter method)
        for (String key : vTagCounts.keySet()) {
            for (int ii = 0; ii < vTagCounts.get(key); ii++) {
                s += "</" + key + ">";
            }
        } 
        return s;
    } 
    private String processRemoveBlanks(final String s) {
        String result = s;
        for (String tag : vRemoveBlanks) {
            if(!P_REMOVE_PAIR_BLANKS.containsKey(tag)){
                P_REMOVE_PAIR_BLANKS.putIfAbsent(tag, Pattern.compile("<" + tag + "(\\s[^>]*)?></" + tag + ">"));
            }
            result = regexReplace(P_REMOVE_PAIR_BLANKS.get(tag), "", result);
            if(!P_REMOVE_SELF_BLANKS.containsKey(tag)){
                P_REMOVE_SELF_BLANKS.putIfAbsent(tag, Pattern.compile("<" + tag + "(\\s[^>]*)?/>"));
            }
            result = regexReplace(P_REMOVE_SELF_BLANKS.get(tag), "", result);
        } 
        return result;
    } 
    private static String regexReplace(final Pattern regexPattern, final String replacement, final String s) {
        Matcher m = regexPattern.matcher(s);
        return m.replaceAll(replacement);
    } 
    private String processTag(final String s) {
        // ending tags
        Matcher m = P_END_TAG.matcher(s);
        if (m.find()) {
            final String name = m.group(1).toLowerCase();
            if (allowed(name)) {
                if (!inArray(name, vSelfClosingTags)) {
                    if (vTagCounts.containsKey(name)) {
                        vTagCounts.put(name, vTagCounts.get(name) - 1);
                        return "</" + name + ">";
                    }
                }
            }
        }
        // starting tags
        m = P_START_TAG.matcher(s);
        if (m.find()) {
            final String name = m.group(1).toLowerCase();
            final String body = m.group(2);
            String ending = m.group(3);
            //debug( "in a starting tag, name='" + name + "'; body='" + body + "'; ending='" + ending + "'" );
            if (allowed(name)) {
                String params = "";
                final Matcher m2 = P_QUOTED_ATTRIBUTES.matcher(body);
                final Matcher m3 = P_UNQUOTED_ATTRIBUTES.matcher(body);
                final List<String> paramNames = new ArrayList<String>();
                final List<String> paramValues = new ArrayList<String>();
                while (m2.find()) {
                	/**([a-z0-9]+)*/
                    paramNames.add(m2.group(1)); 
                    /**(.*?)*/
                    paramValues.add(m2.group(3)); 
                }
                while (m3.find()) {
                	/**([a-z0-9]+)*/
                    paramNames.add(m3.group(1));
                    /**([^\"\\s']+)*/
                    paramValues.add(m3.group(3)); 
                }
                String paramName, paramValue;
                for (int ii = 0; ii < paramNames.size(); ii++) {
                    paramName = paramNames.get(ii).toLowerCase();
                    paramValue = paramValues.get(ii);
                    if (allowedAttribute(name, paramName)) {
                        if (inArray(paramName, vProtocolAtts)) {
                            paramValue = processParamProtocol(paramValue);
                        }
                        params += " " + paramName + "=\"" + paramValue + "\"";
                    }
                }
                if (inArray(name, vSelfClosingTags)) {
                    ending = " /";
                }
                if (inArray(name, vNeedClosingTags)) {
                    ending = "";
                }
                if (ending == null || ending.length() < 1) {
                    if (vTagCounts.containsKey(name)) {
                        vTagCounts.put(name, vTagCounts.get(name) + 1);
                    } else {
                        vTagCounts.put(name, 1);
                    }
                } else {
                    ending = " /";
                }
                return "<" + name + params + ending + ">";
            } else {
                return "";
            }
        }
        // comments
        m = P_COMMENT.matcher(s);
        if (!stripComment && m.find()) {
            return  "<" + m.group() + ">";
        }
        return "";
    } 
    private String processParamProtocol(String s) {
        s = decodeEntities(s);
        final Matcher m = P_PROTOCOL.matcher(s);
        if (m.find()) {
            final String protocol = m.group(1);
            if (!inArray(protocol, vAllowedProtocols)) {
                // bad protocol, turn into local anchor link instead
                s = "#" + s.substring(protocol.length() + 1, s.length());
                if (s.startsWith(SS)) {
                    s = "#" + s.substring(3, s.length());
                }
            }
        } 
        return s;
    } 
    private String decodeEntities(String s) {
        StringBuffer buf = new StringBuffer();
 
        Matcher m = P_ENTITY.matcher(s);
        while (m.find()) {
            final String match = m.group(1);
            final int decimal = Integer.decode(match).intValue();
            m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
        }
        m.appendTail(buf);
        s = buf.toString();
 
        buf = new StringBuffer();
        m = P_ENTITY_UNICODE.matcher(s);
        while (m.find()) {
            final String match = m.group(1);
            final int decimal = Integer.valueOf(match, 16).intValue();
            m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
        }
        m.appendTail(buf);
        s = buf.toString();
 
        buf = new StringBuffer();
        m = P_ENCODE.matcher(s);
        while (m.find()) {
            final String match = m.group(1);
            final int decimal = Integer.valueOf(match, 16).intValue();
            m.appendReplacement(buf, Matcher.quoteReplacement(chr(decimal)));
        }
        m.appendTail(buf);
        s = buf.toString();
 
        s = validateEntities(s);
        return s;
    } 
    private String validateEntities(final String s) {
        StringBuffer buf = new StringBuffer();
 
        // validate entities throughout the string
        Matcher m = P_VALID_ENTITIES.matcher(s);
        while (m.find()) {
        	/**([^&;]*)*/
            final String one = m.group(1);
            /**(?=(;|&|$))*/
            final String two = m.group(2);
            m.appendReplacement(buf, Matcher.quoteReplacement(checkEntity(one, two)));
        }
        m.appendTail(buf); 
        return encodeQuotes(buf.toString());
    } 
    private String encodeQuotes(final String s){
        if(encodeQuotes){
            StringBuffer buf = new StringBuffer();
            Matcher m = P_VALID_QUOTES.matcher(s);
            while (m.find()) {
            	/**(>|^)*/
                final String one = m.group(1);
                /**([^<]+?)*/
                final String two = m.group(2); 
                /**(<|$)*/
                final String three = m.group(3);
                m.appendReplacement(buf, Matcher.quoteReplacement(one + regexReplace(P_QUOTE, "&quot;", two) + three));
            }
            m.appendTail(buf);
            return buf.toString();
        }else{
            return s;
        }
    } 
    private String checkEntity(final String preamble, final String term) {
 
        return ";".equals(term) && isValidEntity(preamble)
                ? '&' + preamble
                : "&amp;" + preamble;
    } 
    private boolean isValidEntity(final String entity) {
        return inArray(entity, vAllowedEntities);
    } 
    private static boolean inArray(final String s, final String[] array) {
        for (String item : array) {
            if (item != null && item.equals(s)) {
                return true;
            }
        }
        return false;
    } 
    private boolean allowed(final String name) {
        return (vAllowed.isEmpty() || vAllowed.containsKey(name)) && !inArray(name, vDisallowed);
    } 
    private boolean allowedAttribute(final String name, final String paramName) {
        return allowed(name) && (vAllowed.isEmpty() || vAllowed.get(name).contains(paramName));
    }
}

Sensitive word filtering tool class

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Serializable;
import java.util.*; 
import org.springframework.core.io.ClassPathResource;
 
/**
 * Title:      SensitiveWordUtils
 * @author:    gaodeqiang
 * @date       2018年12月12日
 * @version    V1.0
 * Description: 敏感词过滤
 */
@SuppressWarnings("all")
public class SensitiveWordUtils implements Serializable { 
	private static final long serialVersionUID = 1L; 
	private SensitiveWordUtils() {
	}
 
	private static SensitiveWordUtils sensitiveWordUtils = null;
 
	public synchronized static SensitiveWordUtils getSensitiveWordUtils() {
		if (sensitiveWordUtils == null) {
			sensitiveWordUtils = new SensitiveWordUtils();
		}
		return sensitiveWordUtils;
	} 
	private static Set<String> sensitiveWordSet = null; 
	static {
		try {
			readResource("keywords.txt");
		} catch (Exception e) {
			e.printStackTrace();
		}
		// 初始化敏感词库
		initSensitiveWordMap();
	} 
	private static final int MinMatchTYpe = 1; // 最小匹配规则，如：敏感词库["中国","中国人"]，语句："我是中国人"，匹配结果：我是[中国]人
	private static final int MaxMatchType = 2; // 最大匹配规则，如：敏感词库["中国","中国人"]，语句："我是中国人"，匹配结果：我是[中国人] 
	private static HashMap sensitiveWordMap = new HashMap<>();
 
	/**
	 * @author gaodeqiang
	 * @Description 读取资源文件
	 * @date 2018年12月13日上午9:29:01
	 */
	private static void readResource(String name) throws Exception {
		ClassPathResource resource = new ClassPathResource(name);
		InputStream inputStream = resource.getInputStream();
		InputStreamReader read = new InputStreamReader(inputStream, "utf-8");
		// 初始化set集合
		sensitiveWordSet = new HashSet<String>();
		// 缓冲区读取流
		BufferedReader bufferedReader = new BufferedReader(read);
		// 循环读取文件中内容，每次读取1行内容
		String txt = null;
		while ((txt = bufferedReader.readLine()) != null) {
			// 读取文件，将文件内容放入到set中
			sensitiveWordSet.add(txt);
		}
		read.close();
	} 
	/**
	 * @author gaodeqiang
	 * @Description 初始化敏感词库，构建DFA算法模型
	 * @date 2018年12月13日上午9:30:08
	 */
	private static void initSensitiveWordMap() {
		// 初始化敏感词容器，减少扩容操作
		sensitiveWordMap = new HashMap(sensitiveWordSet.size());
		String key;
		Map nowMap;
		Map<String, String> newWorMap;
		// 迭代sensitiveWordSet
		Iterator<String> iterator = sensitiveWordSet.iterator();
		while (iterator.hasNext()) {
			// 关键字
			key = iterator.next();
			nowMap = sensitiveWordMap;
			for (int i = 0; i < key.length(); i++) {
				// 转换成char型
				char keyChar = key.charAt(i);
				// 库中获取关键字
				Object wordMap = nowMap.get(keyChar);
				// 如果存在该key，直接赋值，用于下1个循环获取
				if (wordMap != null) {
					nowMap = (Map) wordMap;
				} else {
					// 不存在则，则构建1个map，同时将isEnd设置为0，因为他不是最后1个
					newWorMap = new HashMap<>();
					// 不是最后1个
					newWorMap.put("isEnd", "0");
					nowMap.put(keyChar, newWorMap);
					nowMap = newWorMap;
				}
 
				if (i == key.length() - 1) {
					// 最后1个
					nowMap.put("isEnd", "1");
				}
			}
		}
	} 
	/**
	 * @author gaodeqiang
	 * @Description 检查文字中是否包含敏感字符
	 * @date 2018年12月13日上午9:38:35
	 */
	private int checkSensitiveWord(String txt, int beginIndex, int matchType) {
		// 敏感词结束标识位：用于敏感词只有1位的情况
		boolean flag = false;
		// 匹配标识数默认为0
		int matchFlag = 0;
		char word;
		Map nowMap = sensitiveWordMap;
		for (int i = beginIndex; i < txt.length(); i++) {
			word = txt.charAt(i);
			// 获取指定key
			nowMap = (Map) nowMap.get(word);
			if (nowMap != null) {// 存在，则判断是否为最后1个
				// 找到相应key，匹配标识+1
				matchFlag++;
				// 如果为最后1个匹配规则,结束循环，返回匹配标识数
				if ("1".equals(nowMap.get("isEnd"))) {
					// 结束标志位为true
					flag = true;
					// 最小规则，直接返回,最大规则还需继续查找
					if (MinMatchTYpe == matchType) {
						break;
					}
				}
			} else {// 不存在，直接返回
				break;
			}
		}
		if (matchFlag < 2 || !flag) {// 长度必须大于等于1，为词
			matchFlag = 0;
		}
		return matchFlag;
	} 
	/**
	 * @author gaodeqiang
	 * @Description 判断文字是否包含敏感字符 匹配规则 1：最小匹配规则，2：最大匹配规则
	 * @date 2018年12月13日上午9:34:23
	 */
	public boolean contains(String txt, int matchType) {
		boolean flag = false;
		for (int i = 0; i < txt.length(); i++) {
			int matchFlag = checkSensitiveWord(txt, i, matchType); // 判断是否包含敏感字符
			if (matchFlag > 0) { // 大于0存在，返回true
				flag = true;
			}
		}
		return flag;
	} 
	/**
	 * @author gaodeqiang
	 * @Description 获取文字中的敏感词
	 * @date 2018年12月13日上午9:36:00
	 */
	public Set<String> getSensitiveWord(String txt, int matchType) {
		Set<String> sensitiveWordList = new HashSet<>();
 
		for (int i = 0; i < txt.length(); i++) {
			// 判断是否包含敏感字符
			int length = checkSensitiveWord(txt, i, matchType);
			if (length > 0) {// 存在,加入list中
				sensitiveWordList.add(txt.substring(i, i + length));
				i = i + length - 1;// 减1的原因，是因为for会自增
			}
		} 
		return sensitiveWordList;
	} 
	/**
	 * @author gaodeqiang
	 * @Description 替换敏感字字符
	 * @date 2018年12月13日上午9:36:34
	 */
	public String replaceSensitiveWord(String txt, char replaceChar, int matchType) {
		String resultTxt = txt;
		// 获取所有的敏感词
		Set<String> set = getSensitiveWord(txt, matchType);
		Iterator<String> iterator = set.iterator();
		String word;
		String replaceString;
		while (iterator.hasNext()) {
			word = iterator.next();
			replaceString = getReplaceChars(replaceChar, word.length());
			resultTxt = resultTxt.replaceAll(word, replaceString);
		} 
		return resultTxt;
	}
 
	/**
	 * @author gaodeqiang
	 * @Description 获取替换字符串
	 * @date 2018年12月13日上午9:37:53
	 */
	private String getReplaceChars(char replaceChar, int length) {
		String resultReplace = String.valueOf(replaceChar);
		for (int i = 1; i < length; i++) {
			resultReplace += replaceChar;
		}
		return resultReplace;
	}
}