我的java web应用程序中的ConcurrentHashMap陷入了无限循环？
我的java web应用程序中的ConcurrentHashMap陷入了无限循环？
提问于 2017-11-23 06:29:15
一般来说，我对web开发是个新手，但到目前为止，我还在做一些基本的事情，所以我不知道为什么这不起作用。我的servlet收到一个向数据库添加新用户的请求，但在此之前，我希望首先使用正则表达式检查这些值。
因此，我的想法是将所有参数名称和正则表达式模式放在一个散列映射中，然后迭代该映射，从请求对象中获取参数，并返回一个仅包含无效字段的数组(目前)。然而，似乎我可能会陷入无限循环，因为我找不到不同的解释为什么这不起作用。
我不确定这是否与线程有关，因为我只会读取它，而不会在运行时修改它，但我还是从HashMap切换到了并发。这似乎太简单了，不会出错。所以就是这样：
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;
}
}然后我的servlet的doPost调用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");
}我不知道这是否是检查字段的最好方法，这是一个让我学习java web开发的项目。但这是我能想到的唯一对我有意义的方法，而且看起来是可重用的。我计划在validate函数之外创建和填充hashmap。
谢谢您抽时间见我
回答 1
Stack Overflow用户
发布于 2017-11-23 07:30:00
servlet调用没有卡住，但失败并出现错误，因为至少DOB的正则表达式是错误的。我通过编写一个简短的main方法找到了这一点：
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()));
});
}这将导致以下输出：
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)之所以看不到这一点，是因为您已经向客户端发送了响应。因为服务器已经返回了一个HTTP 200响应码，所以它不能将其更改为HTTP 500，因此在到达这一点时只需关闭与客户端的连接。不过，您应该会在服务器的日志中看到一些错误消息。
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原文链接：
https://stackoverflow.com/questions/47444846
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