功能描述

將請(qǐng)求響應(yīng)中所有的禁用關(guān)鍵字替換掉之后再輸出。

使用方法

在 java web 項(xiàng)目的 web.xml 文件中添加如下代碼。

StopWordsFilter

com.hmw.filter.StopWordsFilter

需要禁用的關(guān)鍵字，一個(gè)關(guān)鍵字占一行

keys

QQ

百度

七一五

StopWordsFilter

*.jsp

過濾器源碼

ReplaceKeyWordFilter.java

package?com.hmw.filter;

import?java.io.IOException;

import?java.io.PrintWriter;

import?java.util.HashSet;

import?java.util.Iterator;

import?java.util.Set;

import?java.util.StringTokenizer;

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;

/**

*?替換關(guān)鍵字的濾器

*

*?@author

*/

public?class?StopWordsFilter?implements?Filter?{

private?Set?keyWords?=?new?HashSet();

/**

*?將需要進(jìn)行替換的關(guān)鍵字添加到一個(gè)定義好的?Set?中

*/

@Override

public?void?init(FilterConfig?config)?throws?ServletException?{

String?keys?=??config.getInitParameter("keys");

StringTokenizer?tokenizer?=?new?StringTokenizer(keys);

String?token?=?null;

while?(tokenizer.hasMoreTokens())?{

token?=?tokenizer.nextToken();

if(token?!=?null?&&?token.length()?>?0){

keyWords.add(tokenizer.nextToken());

}

}

}

@Override

public?void?doFilter(ServletRequest?request,?ServletResponse?response,

FilterChain?chain)?throws?ServletException,?IOException?{

CharArrayWrapper?responseWrapper?=?new?CharArrayWrapper(

(HttpServletResponse)?response);

//?調(diào)用請(qǐng)求資源(使用自己包裝的?responseWrapper)

chain.doFilter(request,?responseWrapper);

//?取得響應(yīng)字符串

String?responseString?=?responseWrapper.toString();

//?將需要替換的關(guān)鍵字用“**”替換掉

Iterator?iter?=?keyWords.iterator();

while?(iter.hasNext())?{

responseString?=?replace(responseString,?iter.next(),?"**");

}

//?修改響應(yīng)頭信息中的?Content-Length

response.setContentLength(responseString.length());

PrintWriter?out?=?response.getWriter();

out.write(responseString);

}

@Override

public?void?destroy()?{

}

/**

*?將字符串中的所有的指定子字符串替換掉

*?@param?mainString?需要進(jìn)行替換的字符串

*?@param?orig?需要被替換的子串

*?@param?replacement?替換后的新串

*?@return?返回替換后的字符串

*/

public?static?String?replace(String?mainString,?String?orig,?String?replacement)?{

String?result?=?"";

int?oldIndex?=?0;

int?index?=?0;

int?origLength?=?orig.length();

while?((index?=?mainString.indexOf(orig,?oldIndex))?!=?-1)?{

result?=?result?+?mainString.substring(oldIndex,?index)?+?replacement;

oldIndex?=?index?+?origLength;

}

result?=?result?+?mainString.substring(oldIndex);

return?result;

}

}

CharArrayWrapper.java

package?com.hmw.filter;

import?java.io.CharArrayWriter;

import?java.io.PrintWriter;

import?javax.servlet.http.HttpServletResponse;

import?javax.servlet.http.HttpServletResponseWrapper;

/**

*?A?response?wrapper?that?takes?everything?the?client?would?normally?output?and

*?saves?it?in?one?big?character?array.

*/

public?class?CharArrayWrapper?extends?HttpServletResponseWrapper?{

private?CharArrayWriter?charWriter;

/**

*?Initializes?wrapper.

*?

*?First,?this?constructor?calls?the?parent?constructor.?That?call?is

*?crucial?so?that?the?response?is?stored?and?thus?setHeader,?*setStatus,

*?addCookie,?and?so?forth?work?normally.

*?

*?Second,?this?constructor?creates?a?CharArrayWriter?that?will?be?used?to

*?accumulate?the?response.

*/

public?CharArrayWrapper(HttpServletResponse?response)?{

super(response);

charWriter?=?new?CharArrayWriter();

}

/**

*?When?servlets?or?JSP?pages?ask?for?the?Writer,?don't?give?them?the?real

*?one.?Instead,?give?them?a?version?that?writes?into?the?character?array.

*?The?filter?needs?to?send?the?contents?of?the?array?to?the?client?(perhaps

*?after?modifying?it).

*/

@Override

public?PrintWriter?getWriter()?{

return?new?PrintWriter(charWriter);

}

/**

*?Get?a?String?representation?of?the?entire?buffer.

*?

*?Be?sure?not?to?call?this?method?multiple?times?on?the?same

*?wrapper.?The?API?for?CharArrayWriter?does?not?guarantee?that?it

*?"remembers"?the?previous?value,?so?the?call?is?likely?to?make?a?new

*?String?every?time.

*/

@Override

public?String?toString()?{

return?charWriter.toString();

}

/**?Get?the?underlying?character?array.?*/

public?char[]?toCharArray()?{

return?charWriter.toCharArray();

}

}

總結(jié)

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