Servlet filters special HTML characters of a string

Servlet filters special HTML characters of a string

(1) In some cases, when users enter data, we need to determine whether the data is valid, that is, to filter out whether the user input information contains special characters;

(2) directly add the code for your reference:

ServletUtilities class:

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
 
  ': 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
  
   ': flag = true; break;          case '"': flag = true; break;          case '&': flag = true; break;        }      }    }    return(flag);  }}
  
 

 Submit Code Sample
 
  Submit Code Sample
 

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 =      "\n";    out.println(docType +                "\n" +                "" + title + "\n" +                "\n" +                "" + title + "\n" +                "
\n" +                getCode(request) +                "
\n" +                "Now, wasn't that an interesting sample\n" +                "of code?\n" +                "");  }  protected String getCode(HttpServletRequest request) {    return(request.getParameter("code"));  }}