Error in servlet url pattern matching implementation

Question

I'm implementing the Servlet URL pattern matching follow the Servlet Specification. My matching method:

public static boolean match(String pattern, String str, boolean isCaseSensitive) {
        char[] patArr = pattern.toCharArray();
        char[] strArr = str.toCharArray();
        int patIdxStart = 0;
        int patIdxEnd = patArr.length - 1;
        int strIdxStart = 0;
        int strIdxEnd = strArr.length - 1;

        boolean containsStar = false;
        for (int i = 0; i < patArr.length; i++) {
            if (patArr[i] != '*') {
                continue;
            }
            containsStar = true;
            break;
        }

        if (!containsStar) {
            if (patIdxEnd != strIdxEnd) {
                return false;
            }
            for (int i = 0; i <= patIdxEnd; i++) {
                char ch = patArr[i];
                if (ch == '?')
                    continue;
                if ((isCaseSensitive) && (ch != strArr[i])) {
                    return false;
                }
                if ((!isCaseSensitive)
                        && (Character.toUpperCase(ch) != Character
                                .toUpperCase(strArr[i]))) {
                    return false;
                }
            }

            return true;
        }

        if (patIdxEnd == 0) {
            return true;
        }

        char ch;
        while (((ch = patArr[patIdxStart]) != '*')
                && (strIdxStart <= strIdxEnd)) {
            if (ch != '?') {
                if ((isCaseSensitive) && (ch != strArr[strIdxStart])) {
                    return false;
                }
                if ((!isCaseSensitive)
                        && (Character.toUpperCase(ch) != Character
                                .toUpperCase(strArr[strIdxStart]))) {
                    return false;
                }
            }
            patIdxStart++;
            strIdxStart++;
        }

        if (strIdxStart > strIdxEnd) {
            for (int i = patIdxStart; i <= patIdxEnd; i++) {
                if (patArr[i] != '*') {
                    return false;
                }
            }
            return true;
        }

        while (((ch = patArr[patIdxEnd]) != '*') && (strIdxStart <= strIdxEnd)) {
            if (ch != '?') {
                if ((isCaseSensitive) && (ch != strArr[strIdxEnd])) {
                    return false;
                }
                if ((!isCaseSensitive)
                        && (Character.toUpperCase(ch) != Character
                                .toUpperCase(strArr[strIdxEnd]))) {
                    return false;
                }
            }
            patIdxEnd--;
            strIdxEnd--;
        }

        if (strIdxStart > strIdxEnd) {
            for (int i = patIdxStart; i <= patIdxEnd; i++) {
                if (patArr[i] != '*') {
                    return false;
                }
            }
            return true;
        }

        while ((patIdxStart != patIdxEnd) && (strIdxStart <= strIdxEnd)) {
            int patIdxTmp = -1;
            for (int i = patIdxStart + 1; i <= patIdxEnd; i++) {
                if (patArr[i] != '*') {
                    continue;
                }
                patIdxTmp = i;
                break;
            }

            if (patIdxTmp == patIdxStart + 1) {
                patIdxStart++;
                continue;
            }

            int patLength = patIdxTmp - patIdxStart - 1;
            int strLength = strIdxEnd - strIdxStart + 1;
            int foundIdx = -1;
            for (int i = 0; i <= strLength - patLength; i++) {
                int j = 0;
                while (true)
                    if (j < patLength) {
                        ch = patArr[(patIdxStart + j + 1)];
                        if (ch != '?') {
                            if ((isCaseSensitive)
                                    && (ch != strArr[(strIdxStart + i + j)])) {
                                break;
                            }
                            if ((!isCaseSensitive)
                                    && (Character.toUpperCase(ch) != Character
                                            .toUpperCase(strArr[(strIdxStart
                                                    + i + j)])))
                                break;
                        } else {
                            j++;
                            continue;
                        }

                    } else {
                        foundIdx = strIdxStart + i;
                        break;
                    }
            }

            if (foundIdx == -1) {
                return false;
            }

            patIdxStart = patIdxTmp;
            strIdxStart = foundIdx + patLength;
        }

        for (int i = patIdxStart; i <= patIdxEnd; i++) {
            if (patArr[i] != '*') {
                return false;
            }
        }
        return true;
    }

But when I test with case below:

String pattern = "*.a*";
String path = "/index.abc";
String matches = match(pattern, path, true) ? "matches" : "unmatches";
System.out.println(path + " " + matches + " " + pattern);

The test case runs forever and cannot stop. I have 2 questions:

Is pattern "*.a*" valid with Servlet URL pattern matching spec?
How to fix this error to break the infinite loop?

PMV · Accepted Answer · 2017-04-28 08:29:32Z

Here is my Java Servlet Specification 3.1 (April 2013) Mapping Requests to Servlets implementation.

/**
 * Java Servlet Specification 3.1 (April 2013)
 * Mapping Requests to Servlets (Chapter 12) implementation.
 *
 * This class is thread safe.
 */
public class ServletMappingMatcher {
    private final String[] patterns;
    private final String[] welcomePages;

    public ServletMappingMatcher(String... patterns) {
        this(patterns, new String[0]);
    }

    public ServletMappingMatcher(String[] patterns, String[] welcomePages) {
        this.patterns = patterns;
        this.welcomePages = welcomePages;
    }

    public String getPatternForPath(String path) {
        for (String pattern : patterns) {
            if (matches(pattern, path)) {
                return pattern;
            }
        }

        return null;
    }

    private boolean matches(String pattern, String path) {
        if (isPathMapping(pattern)) {
            return pathMatches(pattern, path);
        } else if (isExtensionPattern(pattern)) {
            return extensionMatches(pattern, path);
        } else if (isApplicationContextRoot(pattern)) {
            return matchesApplicationContextRoot(path);
        } else if (isDefaultServlet(pattern)) {
            return matchesDefaultServlet(path);
        }

        return strictlyMatches(pattern, path);
    }

    private boolean isPathMapping(String pattern) {
        return pattern.startsWith("/") && pattern.endsWith("/*");
    }

    private boolean isExtensionPattern(String pattern) {
        return pattern.startsWith("*.");
    }

    private boolean isApplicationContextRoot(String pattern) {
        return pattern.isEmpty();
    }

    private boolean isDefaultServlet(String pattern) {
        return pattern.equals("/");
    }

    private boolean pathMatches(String pattern, String path) {
        return path.startsWith(pattern.substring(0, pattern.length() - 1)) ||
                path.equals(pattern.substring(0, pattern.length() - 2));
    }

    private boolean extensionMatches(String pattern, String path) {
        return path.endsWith(pattern.substring(1));
    }

    private boolean matchesApplicationContextRoot(String path) {
        return path.equals("/");
    }

    private boolean strictlyMatches(String pattern, String path) {
        return path.equals(pattern);
    }

    private boolean matchesDefaultServlet(String path) {
        if (path.endsWith("/")) {
            return true;
        }

        for (String welcomePage : welcomePages) {
            if (path.endsWith("/" + welcomePage)) {
                return true;
            }
        }

        return false;
    }
}

And JUnit tests:

import org.junit.Assert;
import org.junit.Test;

public class ServletMappingMatcherTest {
    @Test
    public void testsFromSpec() {
        final String servlet1Pattern = "/foo/bar/*";
        final String servlet2Pattern = "/baz/*";
        final String servlet3Pattern = "/catalog";
        final String servlet4Pattern = "*.bop";
        final String defaultServlet = "/";

        final String[] patterns = {servlet1Pattern, servlet2Pattern, servlet3Pattern, servlet4Pattern, defaultServlet};
        final String[] welcomePages = {"index.html"};

        final ServletMappingMatcher matcher = new ServletMappingMatcher(patterns, welcomePages);

        Assert.assertEquals(servlet1Pattern, matcher.getPatternForPath("/foo/bar/index.html"));
        Assert.assertEquals(servlet1Pattern, matcher.getPatternForPath("/foo/bar/index.bop"));
        Assert.assertEquals(servlet2Pattern, matcher.getPatternForPath("/baz"));
        Assert.assertEquals(servlet2Pattern, matcher.getPatternForPath("/baz/index.html"));
        Assert.assertEquals(servlet3Pattern, matcher.getPatternForPath("/catalog"));
        Assert.assertEquals(defaultServlet, matcher.getPatternForPath("/catalog/index.html"));
        Assert.assertEquals(servlet4Pattern, matcher.getPatternForPath("/catalog/rececar.bop"));
        Assert.assertEquals(servlet4Pattern, matcher.getPatternForPath("/index.bop"));
    }
}

Barcelona · Accepted Answer · 2015-05-18 01:32:27Z

0

I fixed it, in the while(true) loop add below line to break the loop:

[...]
while(true) {
     if (ch != '?') {
          if(...) {
             //...
             break;
          }

          if(...) {
             //...
             break;
          }
          j++;  // Add this line to avoid infinite loop
     }
}

answered May 18, 2015 at 1:32

Barcelona

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