ConcurrentHashMap卡在我的Java Web应用程序的无限循环中吗？

Question

I am new to web development in general but so far am doing basic stuff so I don't know why this doesn't work. My servlet receives a request to add new users to my database, but before that I first want to check the values using regular expressions.

So my idea was to have all the parameter names and regex patterns in a hashmap, and then iterate that map, get the parameter from the request object and return an array(for now) containing only the invalid fields. However, it seems that I might get stuck in an infinite loop because I can't find a different explanation why this doesn't work.

I am not sure if this has anything to do with threads as I will only read it and never modify it at runtime, but I switched from HashMap to Concurrent anyway. It seemed too simple to go wrong. So here it is:

public class FormValidator {

    public ArrayList<String> Validate(HttpServletRequest request) {
        ArrayList<String> invalidFields = new ArrayList<String>();
        ConcurrentHashMap<String, String> fieldRegexMap = new ConcurrentHashMap<String, String>();
        fieldRegexMap.put("username", ".{8,}");
        fieldRegexMap.put("email", "(^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+$)");
        fieldRegexMap.put("password", "^(?=.*[A-Za-z])(?=.*\\d)(?=.*[$@$!%*#?&])[A-Za-z\\d$@$!%*#?&]{8,10}$");
        //fieldRegexMap.put("confirmPassword", "^(?=.*[A-Za-z])(?=.*\\d)(?=.*[$@$!%*#?&])[A-Za-z\\d$@$!%*#?&]{8,10}$");
        fieldRegexMap.put("firstname", ".{1,20}");
        fieldRegexMap.put("lastname", ".{4,20}");
        fieldRegexMap.put("DOB", "^(?:(?:31(\\/|-|\\.)(?:0?[13578]|1[02]))\\1|(?:(?:29|30)(\\/|-|\\.)(?:0?[1,3-9]|1[0-2])\\2))(?:(?:1[6-9]|[2-9]\\d)?\\d{2})$|^(?:29(\\/|-|\\.)0?2\\3(?:(?:(?:1[6-9]|[2-9]\\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:0?[1-9]|1\\d|2[0-8])(\\/|-|\\.)(?:(?:0?[1-9])|(?:1[0-2]))\\4(?:(?:1[6-9]|[2-9]\\d)?\\d{2})$\\");

        fieldRegexMap.put("city", ".{2,20}");
        fieldRegexMap.put("address", ".{2,20}");
        fieldRegexMap.put("profession", ".{2,20}");
        fieldRegexMap.put("interests", ".{,100}");
        fieldRegexMap.put("moreinfo", ".{,500}");

        //Get all parameters from the request and validate them key:parametername value:regex
        for (Map.Entry<String, String> entry : fieldRegexMap.entrySet()) {
            if (!(request.getParameter(entry.getKey()).matches(entry.getValue()))) {
                invalidFields.add(entry.getKey());
            }

        }

        return invalidFields;
    }
}

Then my servlet's doPost calls ProcessRequest:

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {

        ArrayList<String> results = new ArrayList<String>();

        out.println("<h1>Servlet lqRegisterServlet at " + 
        request.getContextPath() + "</h1>");

        out.println("<h2>Method: " + request.getMethod() + "</h2>");
        out.println("This Shows up");

        FormValidator validator = new FormValidator();

        out.println("Everything shows up to this point!");
        results = validator.Validate(request);
        out.println("This does not show");
        for (String param : results) {

            out.println("<p>Field:" + param + "</p>");
        }

    }
    response.getOutputStream().println("This is servlet response");
}

I don't know if this is the best way to check the fields, this is a project for me to learn java web development. But it's the only way I could think of that made sense to me and seemed reusable. I plan to create and populate the hashmap outside the validate function.

Thank you for your time

Answer 1

You servlet-call isn't stuck but fails with an error because at least the regular expression for DOB is wrong. I found that out by writing a short main method:

public static void main(String[] args) {
    ArrayList<String> invalidFields = null;
    ConcurrentHashMap<String, String> fieldRegexMap = new ConcurrentHashMap<String, String>();
    fieldRegexMap.put("username", ".{8,}");
    fieldRegexMap.put("email", "(^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+$)");
    fieldRegexMap.put("password", "^(?=.*[A-Za-z])(?=.*\\d)(?=.*[$@$!%*#?&])[A-Za-z\\d$@$!%*#?&]{8,10}$");
    //fieldRegexMap.put("confirmPassword", "^(?=.*[A-Za-z])(?=.*\\d)(?=.*[$@$!%*#?&])[A-Za-z\\d$@$!%*#?&]{8,10}$");
    fieldRegexMap.put("firstname", ".{1,20}");
    fieldRegexMap.put("lastname", ".{4,20}");
    fieldRegexMap.put("DOB", "^(?:(?:31(\\/|-|\\.)(?:0?[13578]|1[02]))\\1|(?:(?:29|30)(\\/|-|\\.)(?:0?[1,3-9]|1[0-2])\\2))(?:(?:1[6-9]|[2-9]\\d)?\\d{2})$|^(?:29(\\/|-|\\.)0?2\\3(?:(?:(?:1[6-9]|[2-9]\\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:0?[1-9]|1\\d|2[0-8])(\\/|-|\\.)(?:(?:0?[1-9])|(?:1[0-2]))\\4(?:(?:1[6-9]|[2-9]\\d)?\\d{2})$\\");

    fieldRegexMap.put("city", ".{2,20}");
    fieldRegexMap.put("address", ".{2,20}");
    fieldRegexMap.put("profession", ".{2,20}");
    fieldRegexMap.put("interests", ".{,100}");
    fieldRegexMap.put("moreinfo", ".{,500}");

    fieldRegexMap.entrySet().stream()
        .forEach(elem -> {
            System.out.println(elem.getKey());
            System.out.println(Pattern.compile(elem.getValue()));
        });
}

This results into the following output:

profession
.{2,20}
password
^(?=.*[A-Za-z])(?=.*\d)(?=.*[$@$!%*#?&])[A-Za-z\d$@$!%*#?&]{8,10}$
firstname
.{1,20}
address
.{2,20}
city
.{2,20}
DOB
Exception in thread "main" java.util.regex.PatternSyntaxException: Unexpected internal error near index 325
^(?:(?:31(\/|-|\.)(?:0?[13578]|1[02]))\1|(?:(?:29|30)(\/|-|\.)(?:0?[1,3-9]|1[0-2])\2))(?:(?:1[6-9]|[2-9]\d)?\d{2})$|^(?:29(\/|-|\.)0?2\3(?:(?:(?:1[6-9]|[2-9]\d)?(?:0[48]|[2468][048]|[13579][26])|(?:(?:16|[2468][048]|[3579][26])00))))$|^(?:0?[1-9]|1\d|2[0-8])(\/|-|\.)(?:(?:0?[1-9])|(?:1[0-2]))\4(?:(?:1[6-9]|[2-9]\d)?\d{2})$\
                                                                                                                                                                                                                                                                                                                                     ^
    at java.util.regex.Pattern.error(Pattern.java:1955)
    at java.util.regex.Pattern.compile(Pattern.java:1702)
    at java.util.regex.Pattern.<init>(Pattern.java:1351)
    at java.util.regex.Pattern.compile(Pattern.java:1028)
    at IntArraySplitter.lambda$0(IntArraySplitter.java:30)
    at IntArraySplitter$$Lambda$1/1995265320.accept(Unknown Source)
    at java.util.concurrent.ConcurrentHashMap$EntrySpliterator.forEachRemaining(ConcurrentHashMap.java:3606)
    at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
    at IntArraySplitter.main(IntArraySplitter.java:28)

The reason why you don't see this is the fact that you already send a response to the client. Because the server already returned an HTTP 200 response code it can't change that to HTTP 500 and therefor just closes the connection to the client when reaching this point. You should see some error message in the server's log, though.