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Javawbe的实战案例

發(fā)布時(shí)間：2023/12/20 java 44 豆豆

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提示：文章寫完后，目錄可以自動(dòng)生成，如何生成可參考右邊的幫助文檔

文章目錄

一、maven的一些注意事項(xiàng)?

?二、servlet

1.構(gòu)建一個(gè)空maven項(xiàng)目，刪掉src文件，重新導(dǎo)入依賴，建立一個(gè)新的module

1.1? 子類

?1.2 父類

?二、子類的web.xml配置最新的版本自帶的有點(diǎn)舊

?2.1 定義一個(gè)java類

2.1、編寫servlet映射

2.2 /*IDEA的Tomcat出現(xiàn)亂碼問題解決如下*/?編輯

2.3?

?2.4 Servlet

2.5mapping 問題?

?*.bug問題

Element ‘web-app‘ cannot have character [children], because the type‘s content type is element-only.

2.6? servletcontext對(duì)象

2.7讀取資源類

properties

?2.8HttpServletsponse

?2.9? 實(shí)現(xiàn)重定向

?3.0 HttpServletRequest （重要）

一、maven的一些注意事項(xiàng)?

1.配置問題?

1.Tomcar閃退

2.每次重復(fù)配置maven?

?3.配置好的pom.xml字段含義

?4.maven下main文件下的改變

5. Tomcat官方例子源代碼

?6.導(dǎo)入官方依賴

（1）去官網(wǎng)找到需要的依賴

（2）放到</dependencies> </dependencies>里，再刷新下

?二、servlet

(1).是sun公司開發(fā)的動(dòng)態(tài)web技術(shù)

(2).servlet是sun公司下的一個(gè)API接口，實(shí)現(xiàn)的話只要Java類部署到web中、編寫一個(gè)類，實(shí)現(xiàn)接口

把實(shí)現(xiàn)的servlet的Java程序叫servlet

1.構(gòu)建一個(gè)空maven項(xiàng)目，刪掉src文件，重新導(dǎo)入依賴，建立一個(gè)新的module

1.1? 子類

//子類有的的依賴 <parent><artifactId>untitled2-maven1</artifactId><groupId>org.example</groupId><version>1.0-SNAPSHOT</version></parent>

?1.2 父類

<modules><module>selvert01</module></modules>

?二、子類的web.xml配置最新的版本自帶的有點(diǎn)舊

?2.1 定義一個(gè)java類

package com.bilibili.servlet;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.io.PrintWriter;public class selverts extends HttpServlet {//由于get或者post只是請(qǐng)求實(shí)現(xiàn)的不同的方式，可以互相調(diào)用@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {PrintWriter writer = resp.getWriter();writer.print("hello,,serverr");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);} }

2.1、編寫servlet映射

因?yàn)榫帉懙腏ava程序是要通過瀏覽器訪問的，而瀏覽器是要連接web服務(wù)器，所以需要注冊(cè)servlet

給一個(gè)訪問路徑。

<servlet><servlet-name>hellotya</servlet-name><servlet-class>com.bilibili.servlet.selverts</servlet-class> </servlet> <servlet-mapping><servlet-name>hellotya</servlet-name><url-pattern>hellotya</url-pattern></servlet-mapping>

**2.2 /IDEA的Tomcat出現(xiàn)亂碼問題解決如下/**

2.3? </注冊(cè)名>

?2.4 Servlet

2.5mapping 問題?

1.一個(gè)servlet可以指定一條映射路徑?

<servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/hello</url-pattern></servlet-mapping>

2.一個(gè)servlet可以指定多條映射路徑

<servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/hello1</url-pattern></servlet-mapping><servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/hello2</url-pattern></servlet-mapping>

3.一個(gè)servlet可以指定通用映射路徑??

<servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/hello2/*</url-pattern></servlet-mapping>

4.一個(gè)servlet可以指定默認(rèn)映射路徑(首頁(yè)會(huì)被擠掉)

<servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/*</url-pattern></servlet-mapping>

5.也可以自定義

<servlet-mapping><servlet-name>hello</servlet-name><url-pattern>/*.do</url-pattern></servlet-mapping>

6.優(yōu)先級(jí)

指定好的映射路徑級(jí)別最高，如果沒有舊走默認(rèn)路徑

<servlet><servlet-name>mxx</servlet-name><servlet-class>com.bilibili.servlet.ErrorServlet</servlet-class></servlet><servlet-mapping><servlet-name>mxx</servlet-name><url-pattern>/mxx</url-pattern></servlet-mapping>

?*.bug問題

Element ‘web-app‘ cannot have character [children], because the type‘s content type is element-only.

看代碼注釋有沒有規(guī)定符號(hào)

2.6? servletcontext對(duì)象

我們可以把ServletContext當(dāng)成一個(gè)公用的空間，可以被所有的客戶訪問，如上圖，A、B、C三個(gè)客戶端都可以訪問。WEB容器在啟動(dòng)時(shí)，它會(huì)為每個(gè)Web應(yīng)用程序都創(chuàng)建一個(gè)對(duì)應(yīng)的ServletContext，它代表當(dāng)前Web應(yīng)用，并且它被所有客戶端共享。

2.6.1

servlet1方法

package com.bilibili;import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException;public class mxx extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletContext context = this.getServletContext();String usesrname = "元首";context.setAttribute("usernaem",usesrname);//System.out.println("人事如潮人如水，不甚今朝一場(chǎng)醉");}}

?2.6.2?servlet2方法

package com.bilibili;import javax.servlet.ServletContext; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException;public class getmxx extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {ServletContext context = this.getServletContext();String username = (String)context.getAttribute("username");resp.setContentType("text/html");resp.setCharacterEncoding("utf-8");resp.getWriter().print("名字"+username);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {super.doPost(req, resp);} }

?3.web.xml

<?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/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"metadata-complete="true"><servlet><servlet-name>nazi</servlet-name><servlet-class>com.bilibili.mxx</servlet-class></servlet><servlet-mapping><servlet-name>nazi</servlet-name><url-pattern>/*</url-pattern></servlet-mapping><servlet><servlet-name>getb</servlet-name><servlet-class>com.bilibili.getmxx</servlet-class></servlet><servlet-mapping><servlet-name>getb</servlet-name><url-pattern>/getc</url-pattern></servlet-mapping></web-app>

?用servlet2方法去取servlet1方法里面的名字，用web.xml編程映射路徑，Tomcat啟動(dòng)，就行了，

加了一個(gè)公交車原理，方法都可以去上他。

2.7讀取資源類

properties

在Java目錄、resource下新建的目錄，都被打包到同一路徑下，這一路徑稱為classpath

獲得db.proprites的表內(nèi)的內(nèi)容以及輸出

package com.bilibili;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.io.InputStream; import java.util.Properties;public class Serlvetdemo3 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {InputStream is = this.getServletContext().getResourceAsStream("/target/classes/com/bilibili/mxx");Properties pro = new Properties();pro.load(is);String user =pro.getProperty("username");String pwd =pro.getProperty("password");resp.getWriter().print(user+pwd);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {} }

配置web.xml文件?

<servlet><servlet-name>s5</servlet-name><servlet-class>com.bilibili.ServletDemo2</servlet-class></servlet><servlet-mapping><servlet-name>s5</servlet-name><url-pattern>/s5</url-pattern></servlet-mapping><servlet><servlet-name>s6</servlet-name><servlet-class>com.bilibili.Serlvetdemo3</servlet-class></servlet><servlet-mapping><servlet-name>s6</servlet-name><url-pattern>/s6</url-pattern></servlet-mapping>

?2.8HttpServletsponse

HttpServletsponse應(yīng)用

2.8.1下載文件

設(shè)置參數(shù)

package Demo;import javax.servlet.ServletException; import javax.servlet.ServletOutputStream; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.FileInputStream; import java.io.IOException; import java.net.URLEncoder;public class demo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // 1.獲取下載路徑String resultpath = "E:\\ecn_bews_project\\untitled2-maven1\\response\\src\\main\\resources\\醫(yī)智諾.png";System.out.println("下載文件路徑"+resultpath); // 2.下載文件名resultpath.substring(resultpath.lastIndexOf("\\")+1); // 3. 設(shè)置瀏覽器支持下載resp.setHeader("Content-disposition","attachment;filename"+ URLEncoder.encode("GBK")); // 4.下載文件的輸入流FileInputStream in = new FileInputStream(resultpath); // 5.創(chuàng)建緩沖區(qū)int len = 0;byte[] buffer = new byte[1024]; // 7.獲取OutputStream對(duì)象ServletOutputStream out = resp.getOutputStream(); // 8.把FileOutputStream流寫入buffer緩沖區(qū)9.使用OutputStream將緩沖區(qū)中的數(shù)據(jù)輸出到客戶端while ((len =in.read(buffer))>0){out.write(buffer,0,len);}in.close();out.close();}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

配置文件

<?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/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"metadata-complete="true"><servlet><servlet-name>file</servlet-name><servlet-class>Demo.demo1</servlet-class></servlet><servlet-mapping><servlet-name>file</servlet-name><url-pattern>/down</url-pattern></servlet-mapping></web-app>

2.8.2 瀏覽器刷新驗(yàn)證

package Demo;import javax.imageio.ImageIO; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.awt.*; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random;public class demo2 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//如何讓瀏覽器刷新五秒鐘每次resp.setHeader("refresh","3");//在內(nèi)存中創(chuàng)建圖片BufferedImage image = new BufferedImage(80, 80, BufferedImage.TYPE_INT_RGB);//得到圖片Graphics2D p = (Graphics2D) image.getGraphics();//Java的2d畫筆//設(shè)置圖片背景顏色p.setColor(Color.blue);p.fillRect(0,0,80,20);//給圖片寫數(shù)據(jù)p.setColor(Color.pink);p.setFont(new Font(null,Font.BOLD,20));p.drawString(makenum(),0,20);//告訴瀏覽器，這個(gè)請(qǐng)求用圖片打開resp.setContentType("image/jpeg");//網(wǎng)站存在緩存，不讓瀏覽器緩存resp.setDateHeader("exprise",-1);resp.setHeader("Cache-Control","no-cache");resp.setHeader("Prama","no-cache");//把圖片寫給瀏覽器ImageIO.write(image,"jpg",resp.getOutputStream());}//生成隨機(jī)數(shù)private String makenum(){Random num = new Random();String i = num.nextInt(999999)+"";StringBuffer sg = new StringBuffer();for (int j = 0; j <6-i.length() ; j++) {sg.append("0");}String s = sg.toString() + i;return i;}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} } <?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/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"metadata-complete="true"><servlet><servlet-name>image</servlet-name><servlet-class>Demo.demo2</servlet-class></servlet><servlet-mapping><servlet-name>image</servlet-name><url-pattern>/images</url-pattern></servlet-mapping></web-app>

?2.9? 實(shí)現(xiàn)重定向

@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.sendRedirect("/re/img"); //重定向}

重定向和轉(zhuǎn)發(fā)的區(qū)別

相同：都會(huì)跳轉(zhuǎn)web網(wǎng)頁(yè)

不同：重定向的url地址會(huì)變，轉(zhuǎn)發(fā)不會(huì)?

重定向案例代碼實(shí)現(xiàn)輸入賬號(hào)密碼就跳轉(zhuǎn)到"成功"頁(yè)面

web.xml

<servlet><servlet-name>Request</servlet-name><servlet-class>Demo.demo4</servlet-class></servlet><servlet-mapping><servlet-name>Request</servlet-name><url-pattern>/login</url-pattern></servlet-mapping>

?success.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>Title</title> </head> <body><h1>haihaihiaa</h1></body> </html>

index.jsp

<html> <body> <h2>Hello World!</h2><%--這里提交的路徑，在尋找項(xiàng)目的路徑--%> <%--${pageContext.request.contextPath}代表當(dāng)前的項(xiàng)目--%> <form action="${pageContext.request.contextPath}/login" method="get">用戶名:<input type="text" name="username"><br>密碼：<input type="password" name="password"><br><input type="submit"> </form></body> </html>

demo4.java?

package Demo;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException;public class demo4 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//處理請(qǐng)求String username = req.getParameter("username");String password = req.getParameter("password");System.out.println(username+";"+password);resp.sendRedirect("/re/success.jsp");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

?3.0 HttpServletRequest （重要）

?HttpServletRequest代表客戶端的請(qǐng)求，用戶通過http協(xié)議訪問服務(wù)器，http請(qǐng)求中的所有信息會(huì)被封裝到HttpServletRequest，通過HttpServletRequest方法，獲得客戶端所有的響應(yīng)

?web.xml

<?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/javaeehttp://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"metadata-complete="true"><servlet><servlet-name>loginselvert</servlet-name><servlet-class>ppackage.demo1</servlet-class></servlet><servlet-mapping><servlet-name>loginselvert</servlet-name><url-pattern>/loginsel</url-pattern></servlet-mapping> </web-app>

?demo1.java

package ppackage;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; import java.util.Arrays;public class demo1 extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {//后臺(tái)接收到亂碼問題req接收設(shè)置成GBKreq.setCharacterEncoding("UTF-8");resp.setCharacterEncoding("UTF-8");String username = req.getParameter("username");String password = req.getParameter("password");String[] hobbies = req.getParameterValues("hobbies");System.out.println(username);System.out.println(password);System.out.println(Arrays.toString(hobbies));//通過請(qǐng)求轉(zhuǎn)發(fā)System.out.println(req.getContextPath());req.getRequestDispatcher(req.getContextPath()+"/succ.jsp").forward(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

succ.jsp?

<%--Created by IntelliJ IDEA.User: ecnDate: 2022/8/12Time: 16:31To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>Title</title> </head> <body><h1>success</h1></body> </html>

index.jsp?

<%--Created by IntelliJ IDEA.User: ecnDate: 2022/8/12Time: 16:06To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>登錄</title> </head> <body> <h1>登錄</h1> <div style="text-align: center"><%--以post表單提交到loginsel請(qǐng)求--%><form action="${pageContext.request.contextPath}/loginsel" method="post">username:<input type="text"name="username"><br>passoword:<input type="password"name="p"><br>hobby:<input type="checkbox"name="hobbies" value="唱">唱<input type="checkbox"name="hobbies" value="跳">跳<input type="checkbox"name="hobbies" value="rap">rap<input type="checkbox"name="hobbies" value="籃球">籃球<input type="checkbox"name="hobbies" value="說(shuō)唱">說(shuō)唱<br><input type="submit"></form> </div></body> </html>

3.1、cookie 和session

3.1.1、會(huì)話：用戶打開一個(gè)瀏覽器，點(diǎn)擊很多超鏈接，訪問很多web資源，關(guān)閉瀏覽器，這個(gè)過程稱為會(huì)話

cookie：服務(wù)端給客戶一個(gè)信件，客戶端下次訪問服務(wù)端帶上信件就可以，客戶端技術(shù)

session：服務(wù)器已經(jīng)登記你的來(lái)到，下次來(lái)時(shí)直接匹配，服務(wù)器技術(shù)，可以保存信息

3.12 cookie?

//cookie，服務(wù)器端從客戶端獲取Cookie[] cookies = req.getCookies();//這里返回?cái)?shù)組。說(shuō)明Cookie有多個(gè)存在cookie.getValue()//獲得cookie的valuecookie.getName()//獲得cookie的keynew Cookie("lastloginTime", System.currentTimeMillis()+"");//新建一個(gè)cookiecookie.setMaxAge(24*60*60);//設(shè)置cookie的有效期resp.addCookie(cookie);//響應(yīng)給客戶端一個(gè)cookieURLEncode.encode("嘻嘻嘻","UTF-8");//編碼URLDecoder.decode(cookie.getValue(),"UTF-8") //解碼兩個(gè)都用于中文亂碼

3.13、session

//得到sessionHttpSession session = req.getSession();demo1s name = (demo1s) session.getAttribute("name");System.out.println(demo1s.toString());}//手動(dòng)注銷session.invalidate();

web.xml 會(huì)話自動(dòng)配置

<session-config><session-timeout>1</session-timeout></session-config>

3.14、JSP?

java Server pages ：java服務(wù)器端頁(yè)面，用于開發(fā)動(dòng)態(tài)技術(shù)

與HTML的區(qū)別：

? ?1.HTML只給用戶通過靜態(tài)的數(shù)據(jù)? 2.jsp可以嵌入Java代碼，為用戶提供動(dòng)態(tài)數(shù)據(jù)

JSP本質(zhì)就是一個(gè)Selvert類 ,用戶通過網(wǎng)絡(luò)上的web容器將jsp頁(yè)面轉(zhuǎn)換為xxx.class文件，所以用戶最后訪問到的是class文件還是一個(gè)selvert類。

<%--jsp表達(dá)式作用用來(lái)將程序輸出到客戶端<%=表達(dá)式或變量%>--%><%=new java.util.Date()%><hr><%--jsp腳本片段--%><%int sum =0;for (int i = 0; i < 100; i++) {sum=+i;}out.println(sum);%><%--在代碼中嵌入HTML元素--%><%for (int i = 0; i < 5; i++) {%><h1>大叔大嬸市場(chǎng)撒 <%=i%></h1><%}%>

3.14.1 jsp聲明?

<%!static {System.out.println("localstatcia selvert");}private int gdsa =0;public void kkk(){System.out.println("進(jìn)入了方法");} %>

?/***/bug

<%--如果圖片不顯示出來(lái)就取這樣寫--%> <img src="./img/11.png"alt="500">

3.14.2jsp指令將兩個(gè)頁(yè)面合二為一?

<%@include file="common/head.jsp"%> <h1>網(wǎng)頁(yè)主體</h1> <%@include file="common/foot.jsp"%>

?4.九大內(nèi)置對(duì)象

<%pageContext.setAttribute("name1","大廈1"); //保存的數(shù)據(jù)只在一個(gè)頁(yè)面有效request.setAttribute("name2","大廈2");//保存的數(shù)據(jù)只在一次請(qǐng)求有效，請(qǐng)求轉(zhuǎn)發(fā)會(huì)攜帶session.setAttribute("name3","大廈3"); //保存的數(shù)據(jù)在一次會(huì)話中有效application.setAttribute("name4","大廈4");//保存的數(shù)據(jù)只會(huì)在服務(wù)器有效，從打開服務(wù)器到關(guān)閉服務(wù)器 %><%String name1 = (String) pageContext.findAttribute("name1");String name2 = (String) pageContext.findAttribute("name2");String name3 = (String) pageContext.findAttribute("name3");String name4 = (String) pageContext.findAttribute("name4");%><h1>取出的值：</h1> <h1>${name1}</h1> <h1>${name2}</h1> <h1>${name3}</h1> <h1>${name4}</h1>

?4.1 EL 標(biāo)簽、jsp標(biāo)簽、JSTL標(biāo)簽

4.1.1 EL標(biāo)簽：獲取數(shù)據(jù)、執(zhí)行運(yùn)算、獲取web開發(fā)的常用對(duì)象

依賴的包

<dependency><groupId>javax.servlet.jsp.jstl</groupId><artifactId>jstl-api</artifactId><version>1.2</version></dependency><dependency><groupId>taglibs</groupId><artifactId>standard</artifactId><version>1.1.2</version></dependency>

jsp標(biāo)簽?

<jsp:forward page="/jsptag-EL.jsp"> <jsp:param name="name" value="value11"></jsp:param>> <jsp:param name="age" value="vlaue222"></jsp:param> </jsp:forward>

?4.1.2 jstl表達(dá)式

就是用來(lái)彌補(bǔ)HTML標(biāo)簽的不足，可以自定義標(biāo)簽，并且與java語(yǔ)言相同

核心標(biāo)簽：

使用前要導(dǎo)入taglib。

在TOmcat中也要導(dǎo)入jstl包，standard的包才能使用，如果沒有導(dǎo)入就會(huì)跳轉(zhuǎn)不到那個(gè)頁(yè)面

?/** Ctrl + alt +L 對(duì)齊代碼

<%@ page contentType="text/html;charset=UTF-8" language="java" %> <%--c = core 核心--%> <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> <html> <head><title>Title</title> </head> <body> <h4>if測(cè)試</h4><hr> <form action="coreif.jsp" method="get"><input type="text" name="username" value="${param.username}"><input type="submit" value="登錄"> </form> <%--判斷提交管理員是否，是的話輸出歡迎--%> <c:if test="${param.username=='adimin'}" var="isAdmin"><c:out value="管理員welcome"/> </c:if> <c:out value="${isAdmin}"/></body> </html>

<c:when>?

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>Title</title> </head> <body> <c:set var="score" value="95"/><c:choose><c:when test="${score>=90}">優(yōu)秀</c:when><c:when test="${score>=85}">良好</c:when><c:when test="${score>=80}">一般</c:when></c:choose></body> </html>

?<c:foreach>?

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%@ page import="java.util.ArrayList" %><%--Created by IntelliJ IDEA.User: ecnDate: 2022/8/16Time: 11:17To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>Title</title> </head> <body> <%ArrayList<String> objects = new ArrayList<>();objects.add(0, "22成都市");objects.add(1, "23額溫槍所");objects.add(2, "24委屈");objects.add(3, "25大廈");objects.add(4, "22額溫槍");request.setAttribute("list", objects); %> <%-- var：遍歷出來(lái)的變量 items，遍歷的對(duì)象 begin 哪里開始 end 哪里結(jié)束 step 結(jié)束 --%> <c:forEach var="objects" items="${list}"><c:out value="${objects}"/><br></c:forEach><hr><c:forEach var="objects" items="${list}" begin="1" end="3" step="2"><c:out value="${objects}"/><br> </c:forEach></body> </html>

?<c:when>

?5、Javabean

用法都和之前的表達(dá)式有異曲同工之處所以直接上代碼

?javabean.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head><title>Javabean</title> </head> <body><jsp:useBean id="people" class="pojo.people" scope="page"/><jsp:setProperty name="people" property="id" value="18"/> <jsp:setProperty name="people" property="plane" value="腓特烈"/> <jsp:setProperty name="people" property="tanks" value="Z23"/>坦克：<jsp:getProperty name="people" property="tanks"/> 飛機(jī)：<jsp:getProperty name="people" property="plane"/> id：<jsp:getProperty name="people" property="id"/></body> </html>

?people。java

package pojo;public class people {//實(shí)體類一般與數(shù)據(jù)庫(kù)表一一對(duì)應(yīng)public people(int id, String tanks, String plane) {this.id = id;this.tanks=tanks;this.plane = plane;}private int id;private String tanks;private String plane;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getTanks() {return tanks;}public void setTanks(String tanks) {this.tanks = tanks;}public String getPlane() {return plane;}public void setPlane(String plane) {this.plane = plane;}@Overridepublic String toString() {return "people{" +"id=" + id +", tanks='" + tanks + '\'' +", plane='" + plane + '\'' +'}';} }

?6.MVC

?7.Filter

?和Selvert一樣，只是接口不同，多了chain

filter.java

package com.filter;import javax.servlet.*; import java.io.IOException; //初始化 public class filters implements Filter {//執(zhí)行前@Overridepublic void init(FilterConfig filterConfig) throws ServletException {System.out.println("filter執(zhí)行前");}//chain/** 1.過濾器中的所有代碼，在過濾特定請(qǐng)求時(shí)會(huì)執(zhí)行* 2. 必須讓過濾器繼續(xù)同行*/@Overridepublic void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {servletRequest.setCharacterEncoding("gbk");servletResponse.setCharacterEncoding("gbk");servletResponse.setContentType("text/html;charset=GBK");System.out.println("filter執(zhí)行前");filterChain.doFilter(servletRequest,servletResponse);System.out.println("filter執(zhí)行后");}//銷毀@Overridepublic void destroy() {System.out.println("filter銷毀！");} }

web.xml配置filter

<filter><filter-name>filters</filter-name><filter-class>com.filter.filters</filter-class></filter><filter-mapping><filter-name>filters</filter-name><url-pattern>/filteres/*</url-pattern></filter-mapping> </web-app>

showselvert.java

package servlet;import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException;public class showselvert extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {// resp.setCharacterEncoding("gbk");resp.getWriter().write("你你好");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doGet(req, resp);} }

?8.監(jiān)聽器

package listener;import javax.servlet.ServletContext; import javax.servlet.http.HttpSessionEvent; import javax.servlet.http.HttpSessionListener;//在線人數(shù)監(jiān)聽 public class online implements HttpSessionListener {//創(chuàng)建session監(jiān)聽//一旦創(chuàng)建session就會(huì)觸發(fā)這個(gè)事件@Overridepublic void sessionCreated(HttpSessionEvent httpSessionEvent) {ServletContext session = httpSessionEvent.getSession().getServletContext();Integer sessionline = (Integer) session.getAttribute("sessionline");if (sessionline==null){sessionline= new Integer(1);}else {int count = sessionline.intValue();sessionline = new Integer(count+1);}session.setAttribute("sessionline",sessionline);}//銷毀session監(jiān)聽//一旦銷毀session就會(huì)觸發(fā)這個(gè)事件public void sessionDestroyed(HttpSessionEvent httpSessionEvent) {ServletContext session = httpSessionEvent.getSession().getServletContext();Integer sessionline = (Integer) session.getAttribute("sessionline");if (sessionline==null){sessionline= new Integer(0);}else {int count = sessionline.intValue();sessionline = new Integer(count-1);}session.setAttribute("sessionline",sessionline);}} <listener><listener-class>listener.online</listener-class></listener> </web-app>

8.1、GUI?

嵌套兩種顏色Java窗口

package listener;import java.awt.*; import java.awt.event.WindowEvent; import java.awt.event.WindowListener;public class TestCanel {public static void main(String[] args) {Frame frame = new Frame("放假啊啊啊啊啊1");//新建一個(gè)窗體Panel panel = new Panel(null);//面板frame.setLayout(null);//設(shè)置窗體布局frame.setBounds(300,400,500,500);frame.setBackground(new Color(0,0,225));//設(shè)置背景顏色panel.setBounds(50,50,300,300);panel.setBackground(new Color(0,255,0));frame.add(panel);frame.setVisible(true);//監(jiān)聽事件（關(guān)閉）frame.addWindowListener(new WindowListener() {@Overridepublic void windowOpened(WindowEvent e) {System.out.println("打開");}@Overridepublic void windowClosing(WindowEvent e) {System.out.println("關(guān)掉");System.exit(0);}@Overridepublic void windowClosed(WindowEvent e) {}@Overridepublic void windowIconified(WindowEvent e) {System.out.println("激活");}@Overridepublic void windowDeiconified(WindowEvent e) {System.out.println("未激活");}@Overridepublic void windowActivated(WindowEvent e) {}@Overridepublic void windowDeactivated(WindowEvent e) {}});} }

?8.2 JDBC?

package bilibili;import java.sql.*;public class TestJdbc {public static void main(String[] args) throws ClassNotFoundException, SQLException {String url ="jdbc:mysql://43.142.160.32:3306/jdbc?useUnicode=true&characterEncoding=GBK";String username = "mxx";//這里設(shè)置自己密碼 Class.forName("com.mysql.jdbc.Driver");Connection connection = DriverManager.getConnection(url, username, password);Statement statement = connection.createStatement();String sql ="select * from user";ResultSet rs = statement.executeQuery(sql);while (rs.next()){System.out.println("id"+rs.getObject("id"));System.out.println("name"+rs.getObject("name"));System.out.println("password"+rs.getObject("password"));System.out.println("email"+rs.getObject("email"));System.out.println("birthday"+rs.getObject("birthday"));}rs.close();statement.close();connection.close();} }

?8.2.1 @Test

一種特有的Java包，要導(dǎo)包進(jìn)來(lái)，可以到系統(tǒng)自帶的包 alt +enter?

9.總結(jié)

整體來(lái)說(shuō)還是比較知識(shí)點(diǎn)分散，在投入項(xiàng)目時(shí)也遇到許多問題，繼續(xù)前進(jìn)吧！

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