JavaWeb表白墙和在线相册怎么实现
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一. 案例: 表白墙 (使用模板引擎)
1. 首先创建 maven 项目
引入需要的依赖,创建必要的目录
2. 创建好模板文件
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <meta http-equiv="X-UA-Compatible" content="IE=edge"> <meta name="viewport" content="width=device-width, initial-scale=1.0"> <title>表白墙</title></head><body> <form action="confession" method="post"> <div class="parent"> <div id="wall">表白墙</div> <div id="remind">输入后点击提交,会将信息显示在表格中</div> <div class="one"><span class="two">谁:</span><input type="text" class="text" name="from"></div> <div class="one"><span class="two">对谁:</span><input type="text" class="text" name="to"></div> <div class="one"><span class="two">说什么:</span><input type="text" class="text" name="message"></div> <div class="one"><input type="submit" value="提 交" class="press"></div> <div class="elem" th:each="message : ${messages}"> <span th:text="${message.from}">wz</span>对<span th:text="${message.to}">zw</span>说: <span th:text="${message.message}">wzz</span> </div> </div> </form> <style> * { margin: 0; padding: 0; } .parent { width: 400px; margin: 0 auto; } #wall { font-size: 30px; font-weight: 700; text-align: center; margin: 5px; } #remind{ font-size:13px; text-align: center; color:gray; margin: 5px; } .one { display: flex; justify-content: center; align-items: center; height: 40px; } .two { width: 100px; line-height: 40px; } .one .text{ width: 200px; height: 20px; padding-left: 3px; } .one .press{ width: 304px; height: 40px; color:white; background-color: orange; border-radius: 5px; border: none; } .one .press:active{ background-color: red; } .elem { text-align: center; margin: 15px; } </style></body></html>3. 使用数据库存储数据.创建一个类用于数据库连接
ConnectionDB 类
import com.mysql.cj.jdbc.MysqlDataSource;import javax.sql.DataSource;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class ConnectionDB { private static final String URL = "jdbc:mysql://127.0.0.1:3306/confessionWall2?characterEncoding=utf-8&useSSL=true&serverTimezone=UTC"; private static final String USERNAME = "root"; private static final String PASSWORD = "0000"; private static volatile DataSource dataSource = null; public static DataSource getDataSource() { if(dataSource == null){ synchronized (ConnectionDB.class){ if(dataSource == null) { dataSource = new MysqlDataSource(); ((MysqlDataSource) dataSource).setURL(URL); ((MysqlDataSource) dataSource).setUser(USERNAME); ((MysqlDataSource) dataSource).setPassword(PASSWORD); } } } return dataSource; } public static Connection getConnection() throws SQLException { return getDataSource().getConnection(); } public static void close(Connection connection, PreparedStatement statement, ResultSet resultSet){ if(resultSet != null){ try { resultSet.close(); } catch (SQLException e) { e.printStackTrace(); } } if(statement != null){ try { statement.close(); } catch (SQLException e) { e.printStackTrace(); } } if(connection != null){ try { connection.close(); } catch (SQLException e) { e.printStackTrace(); } } }}4. 使用 监视器 来初始化 Thymeleaf
ThymeleafConfig 类
注意加上注解
import org.thymeleaf.TemplateEngine;import org.thymeleaf.templateresolver.ServletContextTemplateResolver;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import javax.servlet.annotation.WebListener;@WebListenerpublic class ThymeleafConfig implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent servletContextEvent) { System.out.println("ServletContext 初始化完毕!"); ServletContext context = servletContextEvent.getServletContext(); TemplateEngine engine = new TemplateEngine(); ServletContextTemplateResolver resolver = new ServletContextTemplateResolver(context); resolver.setPrefix("/WEB-INF/template/"); resolver.setSuffix(".html"); resolver.setCharacterEncoding("utf-8"); engine.setTemplateResolver(resolver); context.setAttribute("engine",engine); } @Override public void contextDestroyed(ServletContextEvent servletContextEvent) { }}5. 编写 Servlet 代码
首先创建一个 Confession 类
class Confession{ public String from; public String to; public String message;}① 重写 doGet 方法
@Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setContentType("text/html;charset=utf-8"); List<Confession> list = load(); TemplateEngine engine = (TemplateEngine) getServletContext().getAttribute("engine"); WebContext webContext = new WebContext(req,resp,getServletContext()); webContext.setVariable("messages",list); engine.process("confessionwall",webContext, resp.getWriter()); }② 重写 doPost 方法
resp.setContentType("text/html;charset=utf-8"); Confession confession = new Confession(); confession.from = req.getParameter("from"); confession.to = req.getParameter("to"); confession.message = req.getParameter("message"); save(confession); resp.sendRedirect("confession");③ 实现 load 方法
private List<Confession> load() { List<Confession> list = new ArrayList<>(); Connection connection = null; PreparedStatement statement = null; ResultSet resultSet = null; try { connection = ConnectionDB.getConnection(); String sql = "select * from confession"; statement = connection.prepareStatement(sql); resultSet = statement.executeQuery(); while(resultSet.next()){ Confession confession = new Confession(); confession.from =resultSet.getString("from"); confession.to = resultSet.getString("to"); confession.message = resultSet.getString("message"); list.add(confession); } } catch (SQLException throwables) { throwables.printStackTrace(); } finally { ConnectionDB.close(connection,statement,resultSet); } return list; }④ 实现 save 方法
private void save(Confession confession) { Connection connection = null; PreparedStatement statement = null; try{ connection = ConnectionDB.getConnection(); String sql = "insert into confession values (?,?,?)"; statement = connection.prepareStatement(sql); statement.setString(1,confession.from); statement.setString(2, confession.to); statement.setString(3,confession.message); int ret = statement.executeUpdate(); if(ret == 1){ System.out.println("插入成功"); }else{ System.out.println("插入失败"); } } catch (SQLException throwables) { throwables.printStackTrace(); } finally { ConnectionDB.close(connection,statement,null); } }6. 注意事项
注意模板引擎
注意 乱码的情况,要添加utf-8
用数据库的方法存数据,要先创建好数据库
create database confessionWall2;use confessionWall2;create table confession( `from` varchar(1024), `to` varchar(1024), `message` varchar(1024));还有一些必要的注解也要加上.
7. 部署之后 运行截图
浏览器输入对应的URL
在数据库为空的时候界面如下
在输入几个数据之后 如下
此时的数据库中表的内容
重新部署再进入URL发现数据还是存在.
二. 案例: 在线相册 (使用模板引擎)
1. 首先创建 maven 项目
引入必要的依赖,已经必要的目录
2. 创建好模板文件
image.html
<!DOCTYPE html><html lang="en"><head> <meta charset="UTF-8"> <title>相册</title> <link rel="stylesheet" href="./style.css"></head><body> <div class="nav"> <form action="upload" method="POST" enctype="multipart/form-data" > <input type="file" name="myImage"> <input type="submit" value="上传图片"> </form> </div> <div class="parent"> <!-- 第一组图片 --> <figure class="sample" th:each="image : ${images}"> <img th:class="lazy" data-src="${image.url}" alt="sample1" /> <figcaption> <div> <h3 th:text="${image.name}">Deconovo</h3> </div> </figcaption> <a th:href="${image.url}"></a> </figure> </div> </body></html>style.css
@import url(https://fonts.googleapis.com/css?family=Raleway:400,700);*{ margin: 0 auto; padding: 0 auto; box-sizing: border-box;}html,body{ width: 100%; height: calc(100% - 50px); background-color: #212121;}.parent{ display: flex; justify-content: center; align-items: center; flex-flow: wrap; margin: 0; height: 100%;}.nav{ background-color: rgba(255,255,255,0.3); height: 50px; width: 100%; display: flex; justify-content: left; align-items: center;}.sample { font-family: 'Raleway', Arial, sans-serif; position: relative; overflow: hidden; margin: 10px; min-width: 230px; max-width: 315px; width: 100%; color: #ffffff; text-align: center; font-size: 16px; background-color: #000000;}.sample *,.sample *:before,.sample *:after { -webkit-box-sizing: border-box; box-sizing: border-box; -webkit-transition: all 0.55s ease; transition: all 0.55s ease;}.sample img { max-width: 100%; backface-visibility: hidden; vertical-align: top;}.sample figcaption { position: absolute; bottom: 25px; right: 25px; padding: 5px 10px 10px;}.sample figcaption:before,.sample figcaption:after { height: 2px; width: 400px; position: absolute; content: ''; background-color: #ffffff;}.sample figcaption:before { top: 0; left: 0; -webkit-transform: translateX(100%); transform: translateX(100%);}.sample figcaption:after { bottom: 0; right: 0; -webkit-transform: translateX(-100%); transform: translateX(-100%);}.sample figcaption div:before,.sample figcaption div:after { width: 2px; height: 300px; position: absolute; content: ''; background-color: #ffffff;}.sample figcaption div:before { top: 0; left: 0; -webkit-transform: translateY(100%); transform: translateY(100%);}.sample figcaption div:after { bottom: 0; right: 0; -webkit-transform: translateY(-100%); transform: translateY(-100%);}.sample h3,.sample h5 { margin: 0; text-transform: uppercase;}.sample h3 { font-weight: 400;}.sample h5 { display: block; font-weight: 700; background-color: #ffffff; padding: 5px 10px; color: #000000;}.sample a { position: absolute; top: 0; bottom: 0; left: 0; right: 0;}.sample:hover img,.sample.hover img { zoom: 1; filter: alpha(opacity=50); -webkit-opacity: 0.5; opacity: 0.5;}.sample:hover figcaption:before,.sample.hover figcaption:before,.sample:hover figcaption:after,.sample.hover figcaption:after,.sample:hover figcaption div:before,.sample.hover figcaption div:before,.sample:hover figcaption div:after,.sample.hover figcaption div:after { -webkit-transform: translate(0, 0); transform: translate(0, 0);}.sample:hover figcaption:before,.sample.hover figcaption:before,.sample:hover figcaption:after,.sample.hover figcaption:after { -webkit-transition-delay: 0.15s; transition-delay: 0.15s;}3. 这是通过访问文件夹里的图片的
在webapp下创建一个文件夹 image,里面存放图片.
通过 getServletContext().getRealPath("/image") 来获取绝对路径
4. 使用 监视器 来初始化 Thymeleaf
这里的代码不变
import org.thymeleaf.TemplateEngine;import org.thymeleaf.templateresolver.ServletContextTemplateResolver;import javax.servlet.ServletContext;import javax.servlet.ServletContextEvent;import javax.servlet.ServletContextListener;import javax.servlet.annotation.WebListener;@WebListenerpublic class ThymeleafConfig implements ServletContextListener { @Override public void contextInitialized(ServletContextEvent servletContextEvent) { System.out.println("ServletContext 初始化完毕"); ServletContext context = servletContextEvent.getServletContext(); TemplateEngine engine = new TemplateEngine(); ServletContextTemplateResolver resolver = new ServletContextTemplateResolver(context); resolver.setPrefix("/WEB-INF/template/"); resolver.setSuffix(".html"); resolver.setCharacterEncoding("utf-8"); engine.setTemplateResolver(resolver); context.setAttribute("engine",engine); } @Override public void contextDestroyed(ServletContextEvent servletContextEvent) { }}5. 编写加载页面的 Servlet代码
创建一个 Image 类
class Image { public String name; public String url;}创建一个类,重写 doGet 方法
@WebServlet("/Image")public class OnlineImageServlet extends HttpServlet { @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { resp.setContentType("text/html;charset=utf-8"); // 1. 扫描指定路径 /webapp/image 路径 List<Image> images = loadImage(); // 2. 构造到模板页面 TemplateEngine engine = (TemplateEngine) getServletContext().getAttribute("engine"); WebContext webContext = new WebContext(req,resp,getServletContext()); webContext.setVariable("images",images); String html = engine.process("image",webContext); resp.getWriter().write(html); }}实现 loadImage 方法
注意使用 getRealPath 方法
以及注意使用 file.listFiles()方法
private List<Image> loadImage() { List<Image> images = new ArrayList<>(); // 首先得到 /webapp/image 的绝对路径 ServletContext context = this.getServletContext(); // 这里是将 webapp下的目录转换成一个绝对路径 String path = context.getRealPath("/image"); // 根据路径 看里面有哪些图片. File file = new File(path); File[] files = file.listFiles(); for(File f:files){ Image image = new Image(); image.name = f.getName(); image.url = "image/"+f.getName(); images.add(image); } return images; }6. 编写提交图片的 Servlet 代码
① 创建一个类,重写 doPost 方法
注意一定要加上注解@MultipartConfig
import javax.servlet.ServletException;import javax.servlet.annotation.MultipartConfig;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;// 这个注解在上传文件的功能中是必要的@MultipartConfig@WebServlet("/upload")public class UploadServlet extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String path = getServletContext().getRealPath("/image"); Part part = req.getPart("myImage"); part.write(path + "/" + part.getSubmittedFileName()); resp.sendRedirect("Image"); }}7. 注意事项
主要是得到文件夹,找到路径的步骤复杂点.重点掌握这几种方法的使用
前后端约定好的名称要对应.
传文件需要加上注解,否则会报500的错误.@MultipartConfig
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