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Servlet过滤字符串的HTML特殊字符

2014-09-05 09:22 483 查看

（1）在一些情况下我们在用户输入数据的时候我们要判断一下是否合法，就是要过滤一下用户输入的信息是否含有特殊字符；

（2）直接上代码，以供大家参考学习：

ServletUtilities类：

package com.lc.ch04Biaodanshuju;

import javax.servlet.http.HttpServletRequest;

public class ServletUtilities {

public static String filter(String input) {
if (!hasSpecialChars(input)) {
return(input);
}
StringBuffer filtered = new StringBuffer(input.length());
char c;
for(int i=0; i<input.length(); i++) {
c = input.charAt(i);
switch(c) {
case '<': filtered.append("<"); break;
case '>': filtered.append(">"); break;
case '"': filtered.append("""); break;
case '&': filtered.append("&"); break;
default: filtered.append(c);
}
}
return(filtered.toString());
}

private static boolean hasSpecialChars(String input) {
boolean flag = false;
if ((input != null) && (input.length() > 0)) {
char c;
for(int i=0; i<input.length(); i++) {
c = input.charAt(i);
switch(c) {
case '<': flag = true; break;
case '>': flag = true; break;
case '"': flag = true; break;
case '&': flag = true; break;
}
}
}
return(flag);
}
}

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<HTML><HEAD><TITLE>Submit Code Sample</TITLE></HEAD>
<BODY BGCOLOR="#FDF5E6">
<CENTER>
<H1 ALIGN="CENTER">Submit Code Sample</H1>
<FORM ACTION="/servlet/coreservlets.BadCodeServlet">
Code:<BR>
<TEXTAREA ROWS="6" COLS="40" NAME="code"></TEXTAREA><P>
<INPUT TYPE="SUBMIT" VALUE="Submit Code">
</FORM>
</CENTER></BODY></HTML>

package com.lc.ch04Biaodanshuju;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class BadCodeServlet extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
PrintWriter out = response.getWriter();
String title = "Code Sample";
String docType =
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 " +
"Transitional//EN\">\n";
out.println(docType +
"<HTML>\n" +
"<HEAD><TITLE>" + title + "</TITLE></HEAD>\n" +
"<BODY BGCOLOR=\"#FDF5E6\">\n" +
"<H1 ALIGN=\"CENTER\">" + title + "</H1>\n" +
"<PRE>\n" +
getCode(request) +
"</PRE>\n" +
"Now, wasn't that an interesting sample\n" +
"of code?\n" +
"</BODY></HTML>");
}

protected String getCode(HttpServletRequest request) {
return(request.getParameter("code"));
}
}

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