字符替换过滤器,允许用户一些代码做简单样式

<<jsp&sevlet 学习笔记>> 课后题P178 3

题目:你的应用程序不允许用户输入 html 标签但可以允许用户输入一些代码做简单样式,例如:

• [b]粗体[/b]

• [i]斜体[/i]

• [big]放大字体[/big]

• [small]缩小字体[/small]

一:运行效果:

(1).用户自定义HTML标签

(2)过滤HTML标签:

提交前:

提交后:

前后结果表面上看是一样的,实际提交后的HTML字符已经做了过滤,断点调试超链接处理过的结果:

 二:HTML标签过滤器:

package cc.openhome.controler;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter("/*")
public class HtmlFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest sreq, ServletResponse sresp, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) sreq;
        HttpServletResponse resp = (HttpServletResponse) sresp;
        MyHtmlRequest mreq = new MyHtmlRequest(req);
        chain.doFilter(mreq,resp);
    }
    @Override
    public void destroy() {

    }
}

过滤HTML标签方法:

package cc.openhome.controler;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class MyHtmlRequest extends HttpServletRequestWrapper {
    private HttpServletRequest req;
    public MyHtmlRequest(HttpServletRequest req){
        super(req);
        this.req = req;
    }

    public String getParameter(String name){
        String value = getRequest().getParameter(name);
        if(value == null){
            return null;
        }
        return filter(value);
    }

    public String filter(String message){
        if(message == null){
            return null;
        }
        char content[] = new char[message.length()];
        message.getChars(0,message.length(),content,0);
        StringBuilder result = new StringBuilder(content.length + 50);
        for(int i = 0;i < content.length;i++){
            switch (content[i]){
                case '<':
                    result.append("&lt;");
                    break;
                case '>':
                    result.append("&gt;");
                    break;
                case '&':
                    result.append("&amp;");
                    break;
                case '"':
                    result.append("&quot");
                    break;
                default:
                    result.append(content[i]);
            }
        }
        return result.toString();
    }
}

三:用户自定义标签过滤器

package cc.openhome.controler;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter("/*")
public class CustomizeStyleFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest sreq, ServletResponse sresp, FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) sreq;
        HttpServletResponse resp = (HttpServletResponse) sresp;

        CustomizeStyle custyle = new CustomizeStyle(req);
        chain.doFilter(custyle,resp);
    }

    @Override
    public void destroy() {

    }
}

过滤特殊字符方法:

package cc.openhome.controler;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

public class CustomizeStyle extends HttpServletRequestWrapper {

    private HttpServletRequest req;
    public CustomizeStyle(HttpServletRequest req){
        super(req);
        this.req = req;
    }

    public String getParameter(String name){
        String value = this.req.getParameter(name);
        if(value == null){
            return null;
        }
        return filter(value);
    }

    public String filter(String message){
        if (message == null){
            return null;
        }
        char content[] = new char[message.length()];
        message.getChars(0,message.length(),content,0);
        StringBuffer res = new StringBuffer(content.length+50);
        for(int i = 0;i < content.length;i++){
            switch (content[i]){
                case '[' :
                res.append('<');
                break;
                case ']':
                res.append('>');
                break;
                default:
                res.append(content[i]);
                break;
            }

        }
        return res.toString();
    }
}

四:展示过滤结果的代码

package cc.openhome.view;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet("/htmltext.view")
public class HtmlFilterText extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("UTF-8");
        resp.setContentType("text/html;charset=UTF-8");
        String name = req.getParameter("username");
        String content = req.getParameter("comment");
        PrintWriter out = resp.getWriter();
        out.println("<!DOCTYPE HTML PUBLIC '-//W3C//DTD HTML 4.01'" +
                "Transitional//EN");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>文本显示</title>");
        out.println("<meta http-equiv='Content-Type' content='text/html;charset=UTF-8'>");
        out.println("</head>");
        out.println("<body>");
        out.println("<form action='' method='post'>");
        out.println("用户名: <input type='text' name='user' value="+name+"><br>");
        //out.println("文本:  <textarea rows='4' cols='50' name=''>");
        //out.println(content);
        //out.println("</textarea>");
        //out.println("提交: <input type= 'submit'>");
        out.println(content);
        out.println("</form>");
        out.println("</body>");
        out.println("</html>");
        out.close();
    }
}

说明: 笨菜原想在输入文本textarea中,展示字体样式,发现前端功力不够,没有过多研究,就直接显示在body里面了.

五:首页请求页面:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>html字符过滤</title>
</head>
<body>
<form action="htmltext.view" id="uform" method="post">
name: <input type="text" name="username"><br>
文本:  <textarea rows="4" cols="50" name="comment" form="uform"></textarea><br>
提交:    <input type="submit">
</form>
</body>
</html>

六:运行动态效果:

七:总结:

(1).曾经在导入  commons-text-1.6.jar 包时,使用 StringEscapeUtils.escapeHtml(),来完成将取得的请求参数值进行字符替换时出现一下错误未能解决:

在stacOverflow上提问,有国外大佬说是可能引入包的编译路径和运行路径不一致导致的,笨菜未能找到运行路径和编译路径,暂时搁置,若有大神看到此贴请指点笨菜一波.

所以重新写了HTML标签过滤器

(2),web Filter的使用过程.

(3),未设置过滤器顺序,本程序先运行的HTML过滤器,后运行的自定义过滤器.

八.参考文档:

https://cloud.tencent.com/developer/article/1129462

感谢文档作者.