有效沟通问答-【官方】百战程序员_IT在线教育培训机构

@WebServlet("/attr.do")
public class ServletContextAttrListenerServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext servletContext = this.getServletContext();
        servletContext.setAttribute("key","itBz");
        servletContext.setAttribute("key","SxtIt");
        servletContext.removeAttribute("key");
    }
}

public class ServletContextAttrListener implements ServletContextAttributeListener {
    /**
     * 向ServletContext对象中添加属性时会触发该监听方法，并将
     * ServletContext对象传递到该方法中。触发事件的方法
     * servletContext.setAttribute("key","value")。
     * @param scae
     */
    @Override
    public void attributeAdded(ServletContextAttributeEvent scae) {
        System.out.println("------------------Start Added----------------------");
        System.out.println("name: "+scae.getName()+"value: "+scae.getValue());
        System.out.println(scae.getServletContext());
        System.out.println("------------------End Added----------------------");
    }

com.itbaizhan.listener.ServletContextAttrListener

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解 1216楼

这里面css语法包括子元素选取，兄弟元素选取，父节点选取都可以用吗？

JAVA 全系列/第六阶段：JavaWeb开发/XML技术 1217楼

请求URL为“/abc/a.do”,Servlet能映射到 /abc 吗？

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解（旧） 1218楼

老师，我学的比较晚，下载的版本比较新，想问一下这几个目录是干嘛的呢，点开后都是这样的

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解（旧） 1219楼

使用xml文件配置网页报500错误是咋回事，老师能帮忙看看嘛

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0"
         metadata-complete="false">
    <context-param>
        <param-name>key1</param-name>
        <param-value>BJSXT</param-value>
    </context-param>
    <context-param>
        <param-name>key2</param-name>
        <param-value>BJSXT</param-value>
    </context-param>
    <servlet>
        <servlet-name>demoServlet</servlet-name>
        <servlet-class>com.example.demo.DemoServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>demoServlet</servlet-name>
        <url-pattern>/demo.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>getRequestDataServlet</servlet-name>
        <servlet-class>com.example.demo.GetRequestDataServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getRequestDataServlet</servlet-name>
        <url-pattern>/getinfo.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>getRequestHeaderServlet</servlet-name>
        <servlet-class>com.example.demo.GetRequestHeaderServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>getRequestHeaderServlet</servlet-name>
        <url-pattern>/getHeader.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>LanguageServlet</servlet-name>
        <servlet-class>com.example.demo.LanguageServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LanguageServlet</servlet-name>
        <url-pattern>/Languages.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>RespByteServlet</servlet-name>
        <servlet-class>com.example.demo.RespByteServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>RespByteServlet</servlet-name>
        <url-pattern>/RespByte.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>RedirectServlet</servlet-name>
        <servlet-class>com.example.demo.RedirectServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>RedirectServlet</servlet-name>
        <url-pattern>/Redirect.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>DownFileServlet</servlet-name>
        <servlet-class>com.example.demo.DownFileServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>DownFileServlet</servlet-name>
        <url-pattern>/Down.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>GetBaseInfoServlet</servlet-name>
        <servlet-class>com.example.demo.GetBaseInfoServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>GetBaseInfoServlet</servlet-name>
        <url-pattern>/getBaseInfo.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>ContextReadInfoServlet</servlet-name>
        <servlet-class>com.example.demo.ContextReadInfoServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ContextReadInfoServlet</servlet-name>
        <url-pattern>/Context.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>GlobalContainerServlet</servlet-name>
        <servlet-class>com.example.demo.GlobalContainerServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>GlobalContainerServlet</servlet-name>
        <url-pattern>/Global.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>GetConfigInfoServlet</servlet-name>
        <servlet-class>com.example.demo.GetConfigInfoServlet</servlet-class>
        <init-param>
            <param-name>key1</param-name>
            <param-value>BJSXT</param-value>
        </init-param>
        <init-param>
            <param-name>key2</param-name>
            <param-value>ITBZ</param-value>
        </init-param>
    </servlet>
    <servlet-mapping>
        <servlet-name>GetConfigInfoServlet</servlet-name>
        <url-pattern>/Config.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>CreatCookieSrvlet</servlet-name>
        <servlet-class>com.example.demo.CreatCookieSrvlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CreatCookieSrvlet</servlet-name>
        <url-pattern>/Cookie.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>GetCookieDataServlet</servlet-name>
        <servlet-class>com.example.demo.GetCookieDataServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>GetCookieDataServlet</servlet-name>
        <url-pattern>/GetCookie.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>WelcomeServlet</servlet-name>
        <servlet-class>com.example.demo.WelcomeServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>WelcomeServlet</servlet-name>
        <url-pattern>/Welcome.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>CreateHttpSessionServlet</servlet-name>
        <servlet-class>com.example.demo.CreateHttpSessionServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>CreateHttpSessionServlet</servlet-name>
        <url-pattern>/CreatSession.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>GetHttpSessionDataServlet</servlet-name>
        <servlet-class>com.example.demo.GetHttpSessionDataServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>GetHttpSessionDataServlet</servlet-name>
        <url-pattern>/GetSessionData.do</url-pattern>
    </servlet-mapping>
    <session-config>
        <session-timeout>1</session-timeout>
    </session-config>
    <servlet>
        <servlet-name>WelcomeSessionServlet</servlet-name>
        <servlet-class>com.example.demo.WelcomeSessionServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>WelcomeSessionServlet</servlet-name>
        <url-pattern>/WelcomeSession.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>AutoStartServlet</servlet-name>
        <servlet-class>com.example.demo.AutoStartServlet</servlet-class>
        <init-param>
            <param-name>path</param-name>
            <param-value>image</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>
    <servlet-mapping>
        <servlet-name>AutoStartServlet</servlet-name>
        <url-pattern>/auto.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>ThreadSafeServlet</servlet-name>
        <servlet-class>com.example.demo.ThreadSafeServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>ThreadSafeServlet</servlet-name>
        <url-pattern>/Safe.do</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>FileUploadServlet</servlet-name>
        <servlet-class>com.example.demo.FileUploadServlet</servlet-class>
        <multipart-config>
            <file-size-threshold>2000</file-size-threshold>
        </multipart-config>
    </servlet>
    <servlet-mapping>
        <servlet-name>FileUploadServlet</servlet-name>
        <url-pattern>/fileupload.do</url-pattern>
    </servlet-mapping>
</web-app>

package com.example.demo;

import javax.servlet.ServletContext;
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 javax.servlet.http.Part;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.UUID;

public class FileUploadServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        req.setCharacterEncoding("utf-8");
        String desc = req.getParameter("desc");
        Part part=req.getPart("file");
//        InputStream inputStream = part.getInputStream();
        String filename= UUID.randomUUID().toString()+part.getSubmittedFileName().substring(part.getSubmittedFileName().lastIndexOf("."));
        ServletContext servletContext = this.getServletContext();
        String realPath = servletContext.getRealPath("image"+filename);
        part.write(realPath);
        PrintWriter out=resp.getWriter();
        out .println("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">");
        out.println("<HTML>");
        out.println(" <HEAD><TITLE>A Servlet</TITLE></HEAD>");
        out.println(" <BODY>");
        out.println("上传成功");
        out.println("</BODY>");
        out.println("</HTML>");
        out.flush();
        out.close();
    }
}

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解（旧） 1220楼

老师，请你帮我看一下我的项目，始终都是出现错误，走的一直是error.jsp页面

OneSelfProject_Test.zip

数据库内容及代码；

数据库备份，文件格式不支持，就不上传文件了，

/*
SQLyog 企业版 - MySQL GUI v8.14 
MySQL - 5.7.19 : Database - oneselfproject
*********************************************************************
*/


/*!40101 SET NAMES utf8 */;

/*!40101 SET SQL_MODE=''*/;

/*!40014 SET @OLD_UNIQUE_CHECKS=@@UNIQUE_CHECKS, UNIQUE_CHECKS=0 */;
/*!40014 SET @OLD_FOREIGN_KEY_CHECKS=@@FOREIGN_KEY_CHECKS, FOREIGN_KEY_CHECKS=0 */;
/*!40101 SET @OLD_SQL_MODE=@@SQL_MODE, SQL_MODE='NO_AUTO_VALUE_ON_ZERO' */;
/*!40111 SET @OLD_SQL_NOTES=@@SQL_NOTES, SQL_NOTES=0 */;
CREATE DATABASE /*!32312 IF NOT EXISTS*/`oneselfproject` /*!40100 DEFAULT CHARACTER SET utf8 */;

USE `oneselfproject`;

/*Table structure for table `user` */

DROP TABLE IF EXISTS `user`;

CREATE TABLE `user` (
  `UserID` varchar(20) NOT NULL,
  `UserName` varchar(20) NOT NULL,
  `UserEmial` varchar(20) NOT NULL,
  PRIMARY KEY (`UserID`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

/*Data for the table `user` */

insert  into `user`(`UserID`,`UserName`,`UserEmial`) values ('191340065','HUIDOU','2195592699@QQ.COM'),('191340128','LIZIYING','4537535634@QQ.COM');

/*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
/*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
/*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
/*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;

JAVA 全系列/第六阶段：JavaWeb开发/Web实战案例 1221楼

没有解决

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解 1222楼

在login.jsp页面输入正确的用户名和密码之后，跳到了错误页面error.jsp

用debug找了一下显示空指针异常，但是没看出有什么问题。。

webdemo.rar

JAVA 全系列/第六阶段：JavaWeb开发/Web实战案例 1223楼

我这个不知道什么情况，数字格式能输出，但是日期格式不能输出。
文件：FormatServlet    和     format.jsp

还有上一节的也这样，遍历Map集合的时候，取不出结果。
文件：FindUsers2Servlet   和   showUsers2.jsp

jspdemo.zip

JAVA 全系列/第六阶段：JavaWeb开发/JSP技术详解 1224楼

我找不到这个目录呀，用户里找了好久也没找到tomcat这个，这怎么回事

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解 1225楼

1.问题：输入正确的账号密码但还是登录不进，如下图

2.控制台报错，如下图

3.源代码压缩包

源代码 (1).rar

JAVA 全系列/第六阶段：JavaWeb开发/Web实战案例 1226楼

老师，持久层是的接口实现是用JDBC技术，①驱动程序②建立连接③执行sql语句的ps对象④执行sql语句⑤while循环获取查到的结果集

然后我理解的是，应该执行完sql语句，判断是否查到数据库的用户名和密码，再用while循环获取查到的结果集的数据库对应某一列的结果集。

然后这里把判断放到业务层了，其他的步骤都放到持久层了。第一个问题：可以把⑤也放到业务层吗

第二个问题：如果判断为否，持久层的⑤会执行吗

$R)SQ)N_{F@ROF@TG{M(ST38.png$

JAVA 全系列/第六阶段：JavaWeb开发/Web实战案例 1227楼

老师，这里Filter被实例化一次，然后会被放在缓存吗？

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解 1228楼

知乎作者的html：

<span class="ZhihuDaily-Author">作者 / ChemX</span>

利用Jsoup：

Elements author = document.getElementsByClass("ZhihuDaily-Author");
Elements author2= document.select(".ZhihuDaily-Author");
System.out.println(author);

两种都无法获取作者信息

JAVA 全系列/第六阶段：JavaWeb开发/XML技术（旧） 1229楼

这里是我的配置本机ip登录时无法连接

JAVA 全系列/第六阶段：JavaWeb开发/Servlet技术详解 1230楼

同学您好