开发者

Where can I find a Java Servlet Filter that applies regex to the output? [closed]

As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 10 years ago. 开发者_运维知识库

I'm hoping someone has already written this:

A servlet filter that can be configured with regular expression search/replace patterns and applies them to the HTML output.

Does such a thing exist?


I couldn't find one, so I wrote one:

RegexFilter.java

package com.example;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;

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.HttpServletResponse;

/**
 * Applies search and replace patterns. To initialize this filter, the
 * param-names should be "search1", "replace1", "search2", "replace2", etc.
 */
public final class RegexFilter implements Filter {
    private List<Pattern> searchPatterns;
    private List<String> replaceStrings;

    /**
     * Finds the search and replace strings in the configuration file. Looks for
     * matching searchX and replaceX parameters.
     */
    public void init(FilterConfig filterConfig) {
        Map<String, String> patternMap = new HashMap<String, String>();

        // Walk through the parameters to find those whose names start with
        // search
        Enumeration<String> names = (Enumeration<String>) filterConfig.getInitParameterNames();
        while (names.hasMoreElements()) {
            String name = names.nextElement();
            if (name.startsWith("search")) {
                patternMap.put(name.substring(6), filterConfig.getInitParameter(name));
            }
        }
        this.searchPatterns = new ArrayList<Pattern>(patternMap.size());
        this.replaceStrings = new ArrayList<String>(patternMap.size());

        // Walk through the parameters again to find the matching replace params
        names = (Enumeration<String>) filterConfig.getInitParameterNames();
        while (names.hasMoreElements()) {
            String name = names.nextElement();
            if (name.startsWith("replace")) {
                String searchString = patternMap.get(name.substring(7));
                if (searchString != null) {
                    this.searchPatterns.add(Pattern.compile(searchString));
                    this.replaceStrings.add(filterConfig.getInitParameter(name));
                }
            }
        }
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        // Wrap the response in a wrapper so we can get at the text after calling the next filter
        PrintWriter out = response.getWriter();
        CharResponseWrapper wrapper = new CharResponseWrapper((HttpServletResponse) response);
        chain.doFilter(request, wrapper);

        // Extract the text from the completed servlet and apply the regexes
        String modifiedHtml = wrapper.toString();
        for (int i = 0; i < this.searchPatterns.size(); i++) {
            modifiedHtml = this.searchPatterns.get(i).matcher(modifiedHtml).replaceAll(this.replaceStrings.get(i));
        }

        // Write our modified text to the real response
        response.setContentLength(modifiedHtml.getBytes().length);
        out.write(modifiedHtml);
        out.close();
    }

    public void destroy() {
        this.searchPatterns = null;
        this.replaceStrings = null;
    }
}

CharResponseWrapper.java

package com.example;

import java.io.CharArrayWriter;
import java.io.PrintWriter;

import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

/**
 * Wraps the response object to capture the text written to it.
 */
public class CharResponseWrapper extends HttpServletResponseWrapper {
    private CharArrayWriter output;

    public CharResponseWrapper(HttpServletResponse response) {
        super(response);
        this.output = new CharArrayWriter();
    }

    public String toString() {
        return output.toString();
    }

    public PrintWriter getWriter() {
        return new PrintWriter(output);
    }
}

Example web.xml

<web-app>
    <filter>
      <filter-name>RegexFilter</filter-name>
      <filter-class>com.example.RegexFilter</filter-class>
      <init-param><param-name>search1</param-name><param-value><![CDATA[(<\s*a\s[^>]*)(?<=\s)target\s*=\s*(?:'_parent'|"_parent"|_parent|'_top'|"_top"|_top)]]></param-value></init-param>
      <init-param><param-name>replace1</param-name><param-value>$1</param-value></init-param>
    </filter>
    <filter-mapping>
      <filter-name>RegexFilter</filter-name>
      <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>


I am not sure if this is what looking for, but there is a URL rewrite filter. It supports regex. Please see here http://www.tuckey.org/urlrewrite/

Hope this helps.


SiteMesh is popular for this type of work.


SiteMesh has moved into a standalone Project: http://www.sitemesh.org/

0

上一篇:

下一篇:

精彩评论

暂无评论...
验证码 换一张
取 消

最新问答

问答排行榜