Java URI 正则表达式耗时过长

Question

我的 Java 应用程序中有一个 servlet 过滤器，以确保用户使用最新的文章和类别 URI。问题是，根据分析器的结果，这个过滤器需要（自己）大约 40% 的请求总时间（即使是简单的 URI“/”）（内部操作是不平凡的，它的动态网页带有巨大的菜单，文章排名等）。

public class NameFilter implements Filter {

    private ArticleServiceIface articleService;
    private CategoryServiceIface categoryService;
    private UrlRewriteServiceIface urlRewriteService;
    private Pattern pattern = Pattern.compile("^(?>.*?)/(article|category)/(\\d+)/(?>.*)$");

    public void init(FilterConfig filterConfig) throws ServletException {
        ApplicationContext ctx = WebApplicationContextUtils.getRequiredWebApplicationContext(filterConfig.getServletContext());
        articleService = (ArticleServiceIface) ctx.getBean("articleService");
        categoryService = (CategoryServiceIface) ctx.getBean("categoryService");
        urlRewriteService = (UrlRewriteServiceIface) ctx.getBean("urlRewriteService");
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        String uri = ((HttpServletRequest) request).getRequestURI();
        Matcher matcher = pattern.matcher(uri);
        String currUri;
        if (matcher.matches()) {
            if (matcher.group(1).equals("article")) {
                Long articleId = Long.valueOf(matcher.group(2));

                ArticleDTO a = articleService.getById(articleId);
                currUri = urlRewriteService.getUrl(a.getId());
            } else {
                Long categoryId = Long.valueOf(matcher.group(2));

                CategoryDTO c = categoryService.getById(categoryId);
                currUri = urlRewriteService.getCategoryUrl(c.getId());
            }
        } else { //does not match neighter article nor category
            chain.doFilter(request, response);
            return;
        }
        if (currUri.equals(uri)) {
            chain.doFilter(request, response);
        } else {
            HttpServletResponse res = (HttpServletResponse) response;
            res.setStatus(HttpServletResponse.SC_MOVED_PERMANENTLY);
            res.setHeader("Location", currUri);
            res.getWriter().close();
        }


    }

    public void destroy() {
    }
}

我花了几个小时调试和分析它，尝试了许多不同的方法来制定正则表达式，但结果总是一样的。

瓶颈似乎在matches方法中，它被递归调用，在某些时候它出于某种原因迭代地调用模式匹配（几千次）......

感谢您的任何建议。

编辑：Profiler results（对我来说似乎很奇怪...根据调试器，这应该是解析 URI == "/" ）

---

EDIT2：当前正则表达式：

 private static Pattern pattern = Pattern.compile(".*?/(article|category)/(\\d+)/.*");

结果还是一样。我会尝试用

来衡量它

  System.out.print(System.currTimeMillis - time)

---

EDIT3：结论：它可能是 netbeans profiler 错误...

我试过这段代码和URI“/”

    long time = System.currentTimeMillis();
    if (matcher.matches()) {
        if (matcher.group(1).equals("article")) {
            Long articleId = Long.valueOf(matcher.group(2));

            ArticleDTO a = articleService.getById(articleId);
            currUri = urlRewriteService.getUrl(a.getId());
        } else {
            Long categoryId = Long.valueOf(matcher.group(2));

            CategoryDTO c = categoryService.getById(categoryId);
            currUri = urlRewriteService.getCategoryUrl(c.getId());
        }
    } else { //does not match neighter article nor category
        System.out.println(System.currentTimeMillis() - time);
        ....

输出始终为 0。因此在我看来，netbeans 分析器出于某种原因正在为该方法添加时间。

但是感谢大家的帮助和合作，我已经学会了一些正则表达式技巧。

Answer 1

实际上没有必要在你的模式中使用 Lookbehinds。以下代码适用于我并且在相当快的时间内：

long l = System.currentTimeMillis();
Pattern p = Pattern.compile("^.*?/(article|category)/(\\d+)/.*$");
Matcher m = p.matcher("/category/1012/Grafy");
System.out.println("Matches: " + m.matches());
System.out.println("Group1: " + m.group(1) + ", Group2: " + m.group(2));
System.out.println("Time taken: " + (System.currentTimeMillis()-l));

输出

Matches: true
Group1: category, Group2: 1012
Time taken: 0

编辑像这样尝试 find() 而不是 matches()：

long l = System.currentTimeMillis();
p = Pattern.compile("/(article|category)/(\\d+)/");
m = p.matcher("/en/article/123/articleName");
System.out.println("Matches: " + m.find());
System.out.println("Group1: " + m.group(1) + ", Group2: " + m.group(2));
System.out.println("Time taken: " + (System.currentTimeMillis()-l));