JavaWeb 项目 --- 表白墙和在线相册

文章目录

一. 案例: 表白墙 (使用模板引擎)
- 1. 首先创建 maven 项目
- 2. 创建好模板文件
- 3. 使用数据库存储数据.创建一个类用于数据库连接
- 4. 使用监视器来初始化 Thymeleaf
- 5. 编写 Servlet 代码
- - ① 重写 doGet 方法
  - ② 重写 doPost 方法
  - ③ 实现 load 方法
  - ④ 实现 save 方法
- 6. 注意事项
- 7. 部署之后运行截图
二. 案例: 在线相册 (使用模板引擎)
- 1. 首先创建 maven 项目
- 2. 创建好模板文件
- 3. 这是通过访问文件夹里的图片的
- 4. 使用监视器来初始化 Thymeleaf
- 5. 编写加载页面的 Servlet代码
- - 创建一个类,重写 doGet 方法
  - 实现 loadImage 方法
- 6. 编写提交图片的 Servlet 代码
- - ① 创建一个类,重写 doPost 方法
- 7. 注意事项
- 8. 部署之后运行截图

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




    
    
    
    表白墙


    
        
            表白墙
            输入后点击提交,会将信息显示在表格中
            class="two">谁:
            class="two">对谁:
            class="two">说什么:
            
            
                th:text="${message.from}">wz对th:text="${message.to}">zw说: th:text="${message.message}">wzz

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;

@WebListener
public 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 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 load() {
        List 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

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 h2,
.sample h4 {
    margin: 0;
    text-transform: uppercase;
}
.sample h2 {
    font-weight: 400;
}
.sample h4 {
    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;

@WebListener
public 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 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 loadImage() {
        List 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

8. 部署之后运行截图

文件中已经存了两个图片,一运行就可以看到这些图片

点击图片还能放大

上传图片,上传两个图片

JavaWeb 项目 --- 表白墙 和 在线相册

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JavaWeb 项目 --- 表白墙和在线相册