• 【JavaWeb】Servlet系列——使用纯Servlet做一个单表的CRUD操作（实际操作实现篇）

    目录

    1、首页信息

    2、查看操作

    3、删除操作

    4、修改操作

    5、增加操作

    6、DBUtil工具类

    7、配置文件

    路径配置文件

    资源配置文件

    8、IDEA整体目录结构

    9、遇到的问题

    已解决

    未解决

    1、首页信息

    使用纯Servlet做一个单表的CRUD操作，这是单表的List页面

     通过查询数据库，通过response.getWriter方法得到一个流将前端页面代码和数据都展示在List页面上（浏览器通过解析能响应出相应的页面），由于只使用了纯Servlet，前端代码写在后端程序当中，非常痛苦。

    1. package com.bjpowernode.oa.web.action;
    2.  
    3. import com.bjpowernode.oa.utils.DBUtil;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9. import java.io.IOException;
    10. import java.io.PrintWriter;
    11. import java.sql.Connection;
    12. import java.sql.PreparedStatement;
    13. import java.sql.ResultSet;
    14. import java.sql.SQLException;
    15.  
    16. public class DeptListServlet extends HttpServlet {
    17.     @Override
    18.     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    19.         doGet(req,resp);
    20.     }
    21.  
    22.     @Override
    23.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    24.         response.setContentType("text/html;charset=UTF-8");
    25.         PrintWriter out = response.getWriter();
    26.  
    27.         String contextPath = request.getContextPath();
    28.  
    29.         out.print("<!DOCTYPE html>");
    30.         out.print("<html>");
    31.         out.print("	<head>");
    32.         out.print("		<meta charset='utf-8'>");
    33.         out.print("		<title>部门列表页面</title>");
    34.         out.print("	</head>");
    35.         out.print("	<body>");
    36.  
    37.         out.print("<script type='text/javascript'>");
    38.         out.print("    function del(dno){");
    39.         out.print("        if(window.confirm('亲，删了不可恢复哦！')){");
    40.         out.print("            document.location.href = '"+contextPath+"/dept/delete?deptno='+dno");
    41.         out.print("        }");
    42.         out.print("    }");
    43.         out.print("</script>");
    44.  
    45.         out.print("");
    46.         out.print("		<h1 align='center'>部门列表</h1>");
    47.         out.print("		<hr >");
    48.         out.print("		<table border='1px' align='center' width='50%'>");
    49.         out.print("			<tr>");
    50.         out.print("				<th>序号</th>");
    51.         out.print("				<th>部门编号</th>");
    52.         out.print("				<th>部门名称</th>");
    53.         out.print("				<th>操作</th>");
    54.         out.print("			</tr>");
    55.         Connection conn = null;
    56.         PreparedStatement ps = null;
    57.         ResultSet rs = null;
    58.         try {
    59.             conn = DBUtil.getConnertion();
    60.             String sql = "select deptno as a,dname,loc from dept";
    61.             ps = conn.prepareStatement(sql);
    62.             rs = ps.executeQuery();
    63.             int i = 0;
    64.             while(rs.next()){
    65.                 String deptno = rs.getString("a");
    66.                 String dname = rs.getString("dname");
    67.                 String loc = rs.getString("loc");
    68.                 out.print("<tr>");
    69.                 out.print("	<td>"+(++i)+"</td>");
    70.                 out.print("	<td>"+deptno+"</td>");
    71.                 out.print("	<td>"+dname+"</td>");
    72.  
    73.                 out.print("	<td>");
    74.                 out.print("		<a href='javascript:void(0)' onclick='del("+deptno+")'>删除</a>");
    75.                 out.print("		<a href='"+contextPath+"/dept/edit?deptno="+deptno+"'>修改</a>");
    76.                 out.print("		<a href='"+contextPath+"/dept/detail?deptno="+deptno+"'>详情</a>");
    77.                 out.print("	</td>");
    78.                 out.print("</tr>");
    79.             }
    80.         } catch (SQLException e) {
    81.             e.printStackTrace();
    82.         }  finally {
    83.             DBUtil.close(conn,ps,rs);
    84.         }
    85.         out.print("		</table>");
    86.         out.print("		<hr >");
    87.         out.print("		<a href='"+contextPath+"/add.html'>新增部门</a>");
    88.         out.print("	</body>");
    89.         out.print("</html>");
    90.     }
    91. }

    2、查看操作

    这一个动态获取部门信息的操作，前端发送请求后，在URL当中向后端传送了name和value信息，后端拿到这些信息后，通过数据库的查询，将其完整的信息响应到页面当中 ，在后退这个按钮当中使用了js代码

    1. package com.bjpowernode.oa.web.action;
    2.  
    3. import com.bjpowernode.oa.utils.DBUtil;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9. import java.io.IOException;
    10. import java.io.PrintWriter;
    11. import java.sql.Connection;
    12. import java.sql.PreparedStatement;
    13. import java.sql.ResultSet;
    14. import java.sql.SQLException;
    15.  
    16. public class DeptDetailServlet extends HttpServlet {
    17.     @Override
    18.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    19.         response.setContentType("text/html;charset=UTF-8");
    20.         PrintWriter out = response.getWriter();
    21.         PreparedStatement ps = null;
    22.         ResultSet rs = null;
    23.         Connection conn = null;
    24.  
    25.         out.print("<!DOCTYPE html>");
    26.         out.print("<html>");
    27.         out.print("    <head>");
    28.         out.print("        <meta charset='utf-8'>");
    29.         out.print("        <title>部门详情</title>");
    30.         out.print("    </head>");
    31.         out.print("    <body>");
    32.         out.print("        <h1>部门详情</h1>");
    33.         out.print("        <hr >");
    34.  
    35.         String deptno = request.getParameter("deptno");
    36.         try {
    37.             conn = DBUtil.getConnertion();
    38.             String sql = "select dname,loc from dept where deptno = ?";
    39.             ps = conn.prepareStatement(sql);
    40.             ps.setString(1,deptno);
    41.             rs = ps.executeQuery();
    42.             while(rs.next()){
    43.                 String dname = rs.getString("dname");
    44.                 String loc = rs.getString("loc");
    45.                 out.print("                部门编号："+deptno+" <br>");
    46.                 out.print("                部门名称："+dname+"<br>");
    47.                 out.print("                部门位置："+loc+"<br>");
    48.             }
    49.         } catch (SQLException e) {
    50.             e.printStackTrace();
    51.         } finally {
    52.             DBUtil.close(conn,ps,rs);
    53.         }
    54.         out.print("<input type='button' value='后退' onclick='window.history.back()'/>");
    55.         out.print("    </body>");
    56.         out.print("</html>");
    57.     }
    58. }

    3、删除操作

     这里使用了js代码，让用户确认是否真正删除，点击删除超链接后同样也会将name和value信息传到后端，当中后端通过sql语句完成数据的删除，删除后立即通过资源的转发跳转到了list页面

    1. package com.bjpowernode.oa.web.action;
    2.  
    3. import com.bjpowernode.oa.utils.DBUtil;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9. import java.io.IOException;
    10. import java.io.PrintWriter;
    11. import java.sql.Connection;
    12. import java.sql.PreparedStatement;
    13. import java.sql.ResultSet;
    14. import java.sql.SQLException;
    15.  
    16. public class DeptDelServlet extends HttpServlet {
    17.     @Override
    18.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    19.         String deptno = request.getParameter("deptno");
    20.  
    21.         Connection conn = null;
    22.         PreparedStatement ps = null;
    23.         int count = 0;
    24.         try {
    25.             conn = DBUtil.getConnertion();
    26.             conn.setAutoCommit(false);
    27.             String sql = "delete from dept where deptno = ?";
    28.             ps = conn.prepareStatement(sql);
    29.             ps.setString(1,deptno);
    30.             count = ps.executeUpdate();
    31.             conn.commit();
    32.         } catch (SQLException e) {
    33.             if (conn != null) {
    34.                 try {
    35.                     conn.rollback();
    36.                 } catch (SQLException e1) {
    37.                     e1.printStackTrace();
    38.                 }
    39.             }
    40.             e.printStackTrace();
    41.         } finally {
    42.             DBUtil.close(conn,ps,null);
    43.         }
    44.         if (count == 1) {
    45.             request.getRequestDispatcher("/dept/list").forward(request,response);
    46.         }else{
    47.             request.getRequestDispatcher("/error.html").forward(request,response);
    48.         }
    49.     }
    50. }

    4、修改操作

    第一步：用户在list页面点击修改超链接后 ，同样在URL中像后端发送需要修改的部门编号，后端通过getparameter方法拿到这些信息后，查询数据库，连同前端代码，一起响应到网页当中。

    1. package com.bjpowernode.oa.web.action;
    2.  
    3. import com.bjpowernode.oa.utils.DBUtil;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9. import java.io.IOException;
    10. import java.io.PrintWriter;
    11. import java.sql.Connection;
    12. import java.sql.PreparedStatement;
    13. import java.sql.ResultSet;
    14. import java.sql.SQLException;
    15.  
    16. public class DeptEditServlet extends HttpServlet {
    17.     @Override
    18.     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    19.         response.setContentType("text/html;charset=UTF-8");
    20.         PrintWriter out = response.getWriter();
    21.         String contextPath = request.getContextPath();
    22.         Connection conn = null;
    23.         PreparedStatement ps = null;
    24.         ResultSet rs = null;
    25.         out.print("<!DOCTYPE html>");
    26.         out.print("<html>");
    27.         out.print("	<head>");
    28.         out.print("		<meta charset='utf-8'>");
    29.         out.print("		<title>修改部门</title>");
    30.         out.print("	</head>");
    31.         out.print("	<body>");
    32.         out.print("		<h1>修改部门</h1>");
    33.         out.print("		<hr >");
    34.         out.print("		<form action='"+contextPath+"/dept/modify' method='post'>");
    35.  
    36.         String deptno = request.getParameter("deptno");
    37.         try {
    38.             conn = DBUtil.getConnertion();
    39.             String sql = "select dname,loc from dept where deptno = ?";
    40.             ps = conn.prepareStatement(sql);
    41.             ps.setString(1,deptno);
    42.             rs = ps.executeQuery();
    43.             if (rs.next()) {
    44.                 String dname = rs.getString("dname");
    45.                 String loc = rs.getString("loc");
    46.                 out.print("                部门编号<input type='text' name='deptno' value='"+deptno+"' readonly /><br>");
    47.                 out.print("                部门名称<input type='text' name='dname' value='"+dname+"'/><br>");
    48.                 out.print("                部门位置<input type='text' name='loc' value='"+loc+"'/><br>");
    49.             }
    50.         } catch (SQLException e) {
    51.             e.printStackTrace();
    52.         } finally {
    53.             DBUtil.close(conn,ps,rs);
    54.         }
    55.  
    56.         out.print("			<input type='submit' value='修改'/><br>");
    57.         out.print("		</form>");
    58.         out.print("	</body>");
    59.         out.print("</html>");
    60.     }
    61. }

    第二步：点击修改按钮之后，再通过另一个service完成数据的真正修改操作。最后跳转到list页面

    1. package com.bjpowernode.oa.web.action;
    2.  
    3. import com.bjpowernode.oa.utils.DBUtil;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9. import java.io.IOException;
    10. import java.sql.Connection;
    11. import java.sql.PreparedStatement;
    12. import java.sql.SQLException;
    13.  
    14. public class DeptModifyServlet extends HttpServlet {
    15.     @Override
    16.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    17.         response.setContentType("text/html;charset=UTF-8");
    18.         String deptno = request.getParameter("deptno");
    19.         String dname = request.getParameter("dname");
    20.         String loc = request.getParameter("loc");
    21.         Connection conn = null;
    22.         PreparedStatement ps = null;
    23.         int count = 0;
    24.         try {
    25.             conn = DBUtil.getConnertion();
    26.             String sql = "update dept set dname = ?, loc = ? where deptno = ?";
    27.             ps = conn.prepareStatement(sql);
    28.             ps.setString(1, dname);
    29.             ps.setString(2, loc);
    30.             ps.setString(3, deptno);
    31.             count = ps.executeUpdate();
    32.         } catch (SQLException e) {
    33.             e.printStackTrace();
    34.         } finally {
    35.             DBUtil.close(conn, ps, null);
    36.         }
    37.  
    38.         if (count == 1) {
    39.             // 更新成功
    40.             // 跳转到部门列表页面（部门列表页面是通过Java程序动态生成的，所以还需要再次执行另一个Servlet）
    41.             //request.getRequestDispatcher("/dept/list").forward(request, response);
    42.  
    43.             response.sendRedirect(request.getContextPath() + "/dept/list");
    44.         }else{
    45.             // 更新失败
    46.             //request.getRequestDispatcher("/error.html").forward(request, response);
    47.             response.sendRedirect(request.getContextPath() + "/error.html");
    48.         }
    49.     }
    50. }

    5、增加操作

    不知何种问题，无法打开新增部门超链接跳转的页面，404报错

    主要实现思想：与修改类似，不再赘述。 

    1. <!DOCTYPE html>
    2. <html>
    3. 	<head>
    4. 		<meta charset="utf-8">
    5. 		<title>新增部门</title>
    6. 	</head>
    7. 	<body>
    8. 		<h1>新增部门</h1>
    9. 		<hr >
    10. 		<form action="/oa/dept/save" method="post">
    11. 			部门编号<input type="text" name="deptno"/><br>
    12. 			部门名称<input type="text" name="dname"/><br>
    13. 			部门位置<input type="text" name="loc"/><br>
    14. 			<input type="submit" value="保存"/><br>
    15. 		</form>
    16. 	</body>
    17. </html>
    1. package com.bjpowernode.oa.web.action;
    2.  
    3. import com.bjpowernode.oa.utils.DBUtil;
    4.  
    5. import javax.servlet.ServletException;
    6. import javax.servlet.http.HttpServlet;
    7. import javax.servlet.http.HttpServletRequest;
    8. import javax.servlet.http.HttpServletResponse;
    9. import java.io.IOException;
    10. import java.io.PrintWriter;
    11. import java.sql.Connection;
    12. import java.sql.PreparedStatement;
    13. import java.sql.SQLException;
    14.  
    15. public class DeptSaveServlet extends HttpServlet {
    16.     @Override
    17.     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    18.         response.setContentType("text/html;charset=UTF-8");
    19.         PrintWriter out = response.getWriter();
    20.         Connection conn =null;
    21.         PreparedStatement ps = null;
    22.         String deptno = request.getParameter("deptno");
    23.         String dename = request.getParameter("dename");
    24.         String loc = request.getParameter("loc");
    25.         int count = 0;
    26.         try {
    27.             conn = DBUtil.getConnertion();
    28.             String sql ="insert into dept(deptname,dename,loc) value(?,?,?)";
    29.             conn.prepareStatement(sql);
    30.             ps.setString(1,deptno);
    31.             ps.setString(2,dename);
    32.             ps.setString(3,loc);
    33.             count = ps.executeUpdate();
    34.         } catch (SQLException e) {
    35.             e.printStackTrace();
    36.         } finally {
    37.             DBUtil.close(conn,ps,null);
    38.         }
    39.         if (count ==1) {
    40.             request.getRequestDispatcher("/dept/list").forward(request,response);
    41.         }else{
    42.             request.getRequestDispatcher("/error.html").forward(request,response);
    43.         }
    44.     }
    45. }

    6、DBUtil工具类

    手写了DBUtil工具类，封装了一部分的jdbc连接数据库操作，大大减少了代码量

    1. package com.bjpowernode.oa.utils;
    2.  
    3. import java.sql.*;
    4. import java.util.ResourceBundle;
    5.  
    6. public class DBUtil {
    7.     private static ResourceBundle bundle = ResourceBundle.getBundle("resources.jdbc");
    8.     private static String driver = bundle.getString("driver");
    9.     private static String url = bundle.getString("url");
    10.     private static String user = bundle.getString("user");
    11.     private static String password = bundle.getString("password");
    12.     static {
    13.         //注册驱动
    14.         try {
    15.             Class.forName(driver);
    16.         } catch (ClassNotFoundException e) {
    17.             e.printStackTrace();
    18.         }
    19.     }
    20.     //获取连接
    21.     public static Connection getConnertion() throws SQLException {
    22.         Connection conn = DriverManager.getConnection(url, user, password);
    23.         return conn;
    24.     }
    25.     //释放资源
    26.     public static void close(Connection conn, Statement ps, ResultSet rs){
    27.         if (rs != null) {
    28.             try {
    29.                 rs.close();
    30.             } catch (SQLException e) {
    31.                 e.printStackTrace();
    32.             }
    33.         }
    34.         if (ps != null) {
    35.             try {
    36.                 ps.close();
    37.             } catch (SQLException e) {
    38.                 e.printStackTrace();
    39.             }
    40.         }
    41.         if (conn != null) {
    42.             try {
    43.                 conn.close();
    44.             } catch (SQLException e) {
    45.                 e.printStackTrace();
    46.             }
    47.         }
    48.     }
    49.  
    50. }

    7、配置文件

    路径配置文件

    1. <?xml version="1.0" encoding="UTF-8"?>
    2. <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    3.          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    4.          xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
    5.          version="4.0">
    6.     <!--修改部门-->
    7.     <servlet>
    8.         <servlet-name>modify</servlet-name>
    9.         <servlet-class>com.bjpowernode.oa.web.action.DeptModifyServlet</servlet-class>
    10.     </servlet>
    11.     <servlet-mapping>
    12.         <servlet-name>modify</servlet-name>
    13.         <url-pattern>/dept/modify</url-pattern>
    14.     </servlet-mapping>
    15.  
    16.     <!--查看部门列表-->
    17.     <servlet>
    18.         <servlet-name>List</servlet-name>
    19.         <servlet-class>com.bjpowernode.oa.web.action.DeptListServlet</servlet-class>
    20.     </servlet>
    21.     <servlet-mapping>
    22.         <servlet-name>List</servlet-name>
    23.         <url-pattern>/dept/list</url-pattern>
    24.     </servlet-mapping>
    25.  
    26.     <!--查看部门详细信息-->
    27.     <servlet>
    28.         <servlet-name>Detail</servlet-name>
    29.         <servlet-class>com.bjpowernode.oa.web.action.DeptDetailServlet</servlet-class>
    30.     </servlet>
    31.     <servlet-mapping>
    32.         <servlet-name>Detail</servlet-name>
    33.         <url-pattern>/dept/detail</url-pattern>
    34.     </servlet-mapping>
    35.  
    36.     <!--删除部门-->
    37.     <servlet>
    38.         <servlet-name>Del</servlet-name>
    39.         <servlet-class>com.bjpowernode.oa.web.action.DeptDelServlet</servlet-class>
    40.     </servlet>
    41.     <servlet-mapping>
    42.         <servlet-name>Del</servlet-name>
    43.         <url-pattern>/dept/delete</url-pattern>
    44.     </servlet-mapping>
    45.  
    46.     <!--跳转到修改页面-->
    47.     <servlet>
    48.         <servlet-name>Edit</servlet-name>
    49.         <servlet-class>com.bjpowernode.oa.web.action.DeptEditServlet</servlet-class>
    50.     </servlet>
    51.     <servlet-mapping>
    52.         <servlet-name>Edit</servlet-name>
    53.         <url-pattern>/dept/edit</url-pattern>
    54.     </servlet-mapping>
    55.  
    56.     <!--保存部门-->
    57.     <servlet>
    58.         <servlet-name>save</servlet-name>
    59.         <servlet-class>com.bjpowernode.oa.web.action.DeptSaveServlet</servlet-class>
    60.     </servlet>
    61.     <servlet-mapping>
    62.         <servlet-name>save</servlet-name>
    63.         <url-pattern>/dept/save</url-pattern>
    64.     </servlet-mapping>
    65. </web-app>

    资源配置文件

    1. driver=com.mysql.cj.jdbc.Driver
    2. url=jdbc:mysql://localhost:3306/bjpowernode
    3. user=root
    4. password=123456

    8、IDEA整体目录结构

    9、遇到的问题

    已解决

    配置文件绑定错误

    配置文件class类路径错误

    配置文件忘记写路径

    js当中路径中，变量在字符串中的格式错误

    sql语句错误，忘记加条件，导致数据显示错误

    post用doPost接收，不要用doGet

    未解决

    WEB-INF下的lib添加mysql 驱动jar包之后，一定还需要在TomCat的lib下也添加mysql驱动jar包吗，为什么有的不在TomCat的lib下添加mysql驱动jar包也能访问到数据库的数据，有的必须添加jar包才能访问到数据。

    404错误，未找出，导致增加操作的页面无法打开

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  • 原文地址：https://blog.csdn.net/m0_61163395/article/details/125528099