学习前，请先搞定数据库的驱动和连接，具体看黑马课程《java web》。
idea
先配置好Tomcat才可以进行，具体可以在CSDN上找教程
差旅费的简单单表增删改查
以下是数据库
以下是控制台代码。
其中部分代码看不懂的话，可以在B站中《JAVA JDBC》中搞定
其中数据库的操作因人而异，根据自己的用户名和密码进行操作
import javax.servlet.; // 导入Servlet包，用于创建Servlet
import javax.servlet.http.; // 导入HTTP Servlet包，用于处理HTTP请求和响应
import java.io.IOException; // 导入IOException，用于处理输入输出异常
import java.io.PrintWriter; // 导入PrintWriter，用于向客户端发送字符文本
import java.sql.*; // 导入SQL包，用于数据库操作
import java.util.ArrayList;
import java.util.List;
public class CourseServlet extends HttpServlet { // 定义CourseServlet类，继承自HttpServlet
private Connection connect = null; // 声明一个Connection对象，用于数据库连接
public void init() { // Servlet初始化方法try {// 数据库连接信息String url = "jdbc:mysql://localhost:3306/data"; // 数据库URLString user = "root"; // 数据库用户名String password = "167183"; // 数据库密码// 加载MySQL JDBC驱动程序Class.forName("com.mysql.cj.jdbc.Driver"); // 加载MySQL JDBC驱动System.out.println("驱动加载成功"); // 打印驱动加载成功的消息// 建立与数据库的连接connect = DriverManager.getConnection(url, user, password); // 连接到数据库System.out.println("数据库连接成功"); // 打印数据库连接成功的消息} catch (SQLException e) { // 捕获SQL异常System.out.printf("数据库连接失败"); // 打印连接失败的错误消息e.printStackTrace(); // 打印堆栈跟踪，用于调试} catch (ClassNotFoundException e) { // 捕获ClassNotFound异常System.out.println("驱动加载失败"); // 打印驱动加载失败的错误消息e.printStackTrace(); // 打印堆栈跟踪，用于调试}
}public void destroy() { // Servlet销毁方法try {if (connect != null) { // 检查连接是否不为nullconnect.close(); // 关闭数据库连接}} catch (SQLException e) { // 捕获SQL异常e.printStackTrace(); // 打印堆栈跟踪，用于调试}
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("UTF-8"); // 设置请求字符编码为UTF-8response.setCharacterEncoding("UTF-8"); // 设置响应字符编码为UTF-8response.setContentType("text/html; charset=UTF-8"); // 设置响应内容类型为HTML，并指定UTF-8字符集String action = request.getParameter("action"); // 从请求中获取action参数if ("add".equals(action)) { // 如果action为"add"addCourse(request, response); // 调用addCourse方法} else if ("update".equals(action)) { // 如果action为"update"updateCourse(request, response); // 调用updateCourse方法} else if ("delete".equals(action)) { // 如果action为"delete"deleteCourse(request, response); // 调用deleteCourse方法}
}
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {request.setCharacterEncoding("UTF-8"); // 设置请求字符编码为UTF-8response.setCharacterEncoding("UTF-8"); // 设置响应字符编码为UTF-8response.setContentType("text/html; charset=UTF-8"); // 设置响应内容类型为HTML，并指定UTF-8字符集String action = request.getParameter("action"); // 从请求中获取action参数if ("view".equals(action)) { // 如果action为"view"viewCourses(request, response); // 调用viewCourses方法} else if ("search".equals(action)) { // 如果action为"search"searchCourses(request, response); // 调用searchCourses方法}
}
private void addCourse(HttpServletRequest request, HttpServletResponse response) throws IOException {int id = Integer.parseInt(request.getParameter("id"));String name= request.getParameter("name");String department = request.getParameter("department");String destination = request.getParameter("destination");String departuredate = request.getParameter("departuredate");String returndate = request.getParameter("returndate");String type = request.getParameter("type");String reason = request.getParameter("reason");try {String sql = "INSERT INTO courses (id, name,department ,destination, departuredate,returndate,type,reason) VALUES (?, ?, ?, ?, ?,?,?,?)";PreparedStatement stmt = connect.prepareStatement(sql);stmt.setInt(1, id);stmt.setString(2, name);stmt.setString(3, department);stmt.setString(4,destination);stmt.setString(5, departuredate);stmt.setString(6, returndate);stmt.setString(7, type);stmt.setString(8, reason);int rowsAffected = stmt.executeUpdate();response.getWriter().write("ID为: " + id);} catch (SQLException e) {e.printStackTrace();response.getWriter().write("出错");}
}
private void updateCourse(HttpServletRequest request, HttpServletResponse response) throws IOException {// 从请求参数中获取详情String id = request.getParameter("id");String name = request.getParameter("name");String department = request.getParameter("department");String destination = request.getParameter("destination");String departuredate = request.getParameter("departuredate");String returndate = request.getParameter("returndate");String Type = request.getParameter("Type");String Reason = request.getParameter("Reason");try {// SQL查询用于更新数据库中现有String sql = "UPDATE courses SET destination = ?, departuredate = ?, returndate = ?, Type = ?, Reason = ? WHERE id = ?"; // SQL更新语句// 使用 try-with-resources 自动管理资源try (PreparedStatement stmt = connect.prepareStatement(sql)) {stmt.setString(1, destination);stmt.setString(2, departuredate);stmt.setString(3, returndate);stmt.setString(4, Type);stmt.setString(5, Reason);stmt.setString(6, id); // 设置IDint rowsAffected = stmt.executeUpdate(); // 执行更新，并获取受影响的行数if (rowsAffected > 0) { // 如果有行被更新response.getWriter().write("更新成功，ID为 " + id); // 响应成功消息} else {response.getWriter().write("未找到ID为 " + id); // 响应未找到课程的消息}}} catch (SQLException e) { // 捕获SQL异常e.printStackTrace(); // 打印堆栈跟踪，用于调试response.getWriter().write("出错: " + e.getMessage()); // 响应错误消息，包含异常信息}
}private void deleteCourse(HttpServletRequest request, HttpServletResponse response) throws IOException {String name= request.getParameter("name");try {// SQL查询用于删除数据库中的课程String sql = "DELETE FROM courses WHERE name = ?"; // SQL删除语句PreparedStatement stmt = connect.prepareStatement(sql); // 准备SQL语句stmt.setString(1, name);int rowsAffected = stmt.executeUpdate(); // 执行更新，并获取受影响的行数if (rowsAffected > 0) { // 如果有行被删除response.getWriter().write("删除成功，名字为 " + name); // 响应成功消息} else {response.getWriter().write("未找到名字为 " + name); // 响应未找到的消息}} catch (SQLException e) { // 捕获SQL异常e.printStackTrace(); // 打印堆栈跟踪，用于调试response.getWriter().write("出错"); // 响应错误消息}
}private void viewCourses(HttpServletRequest request, HttpServletResponse response) throws IOException {response.setContentType("text/html"); // 设置响应内容类型为HTMLPrintWriter out = response.getWriter(); // 获取用于输出的PrintWriter对象out.println("<html><body>"); // 输出HTML开头out.println("<h2>差旅费报销列表</h2>"); // 输出标题out.println("<ul>"); // 开始无序列表try {// SQL查询用于从数据库中获取课程列表String sql = "SELECT * FROM courses"; // SQL查询语句PreparedStatement stmt = connect.prepareStatement(sql); // 准备SQL语句ResultSet rs = stmt.executeQuery(); // 执行查询，并获取结果集while (rs.next()) { // 遍历结果集// 输出每一门课程的详细信息out.println("<li>ID: " + rs.getString("id") + ", 姓名: " + rs.getString("name") + ", 部门: " + rs.getInt("department") +", 目的地: " + rs.getString("destination") +", 出差日期: " + rs.getString("departuredate") +", 返回日期: " + rs.getString("returndate") +",出差类别: " + rs.getString("Type")+", 出差事由: " + rs.getString("Reason") + "</li>");}} catch (SQLException e) { // 捕获SQL异常e.printStackTrace(); // 打印堆栈跟踪，用于调试}out.println("</ul>"); // 结束无序列表out.println("</body></html>"); // 输出HTML结束
}private void searchCourses(HttpServletRequest request, HttpServletResponse response) throws IOException {String departuredate = request.getParameter("departuredate"); // Get departure date from requestString reason = request.getParameter("Reason"); // Get reason from requestresponse.setContentType("text/html"); // Set response content type to HTMLPrintWriter out = response.getWriter(); // Get PrintWriter object for outputout.println("<html><body>"); // Output HTML starttry {// Start building SQL queryStringBuilder sql = new StringBuilder("SELECT * FROM courses WHERE 1=1"); // Use 1=1 for easier appendingList<String> parameters = new ArrayList<>();// Add Reason parameter if providedif (reason != null && !reason.isEmpty()) {sql.append(" AND Reason LIKE ?");parameters.add("%" + reason + "%");}// Add departuredate parameter if providedif (departuredate != null && !departuredate.isEmpty()) {sql.append(" AND departuredate LIKE ?");parameters.add("%" + departuredate + "%");}// Prepare SQL statementtry (PreparedStatement stmt = connect.prepareStatement(sql.toString())) {// Set parametersfor (int i = 0; i < parameters.size(); i++) {stmt.setString(i + 1, parameters.get(i));}try (ResultSet rs = stmt.executeQuery()) { // Execute query and get result setif (rs.next()) { // Process records if anyout.println("<h2>查询结果</h2>"); // Output results headerout.println("<ul>"); // Start unordered listdo {out.println("<li>ID: " + rs.getString("id") + ", 姓名: " + rs.getString("name") + ", 部门: " + rs.getInt("department") +", 目的地: " + rs.getString("destination") +", 出差日期: " + rs.getString("departuredate") +", 返回日期: " + rs.getString("returndate") +", 出差类别: " + rs.getString("Type") +", 出差事由: " + rs.getString("reason") + "</li>");} while (rs.next()); // Loop through all resultsout.println("</ul>"); // End unordered list} else {out.println("<h2>未找到符合条件的出差申请</h2>"); // No results found message}}}} catch (SQLException e) { // Catch SQL exceptionse.printStackTrace(); // Print stack trace for debuggingout.println("<li>查询出错: " + e.getMessage() + "</li>"); // Output error message}out.println("</body></html>"); // Output HTML end
}
}
以下是页面
（1）
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
