Java web 简单的增删改查程序

就是简单的对数据进行增删改查。代码如下：

　　1.bean层：用来封装属性及其get set方法 toString方法，有参构造方法，无参构造方法等。

public class Bean {
    private int id;
    private String name;
    private String password;
    private String sex;
    
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    @Override
    public String toString() {
        return "Bean [id=" + id + ", name=" + name + ", password=" + password + ", sex=" + sex + "]";
    }

    public Bean(int id, String name, String password, String sex) {
        super();
        this.id = id;
        this.name = name;
        this.password = password;
        this.sex = sex;
    }

    public Bean() {
        // TODO Auto-generated constructor stub
    }

}

　　2.DBUtil:对数据库连接关闭操作的封装：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;


public class DBUtil {
    private static String url = "jdbc:mysql://localhost:3306/db10?useUnicode=true&characterEncoding=utf8";
    private static String user = "root";
    private static String password = "root";
    private static String jdbcName="com.mysql.jdbc.Driver";
    private Connection con=null;
    public static  Connection getConnection() {
        Connection con=null;
        try {
            Class.forName(jdbcName);
            con=DriverManager.getConnection(url, user, password);
            //System.out.println("数据库连接成功");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            //System.out.println("数据库连接失败");
            e.printStackTrace();
        }
        return con;
        
    }
    public static void close(Connection con) {
        if(con!=null)
            try {
                con.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        
    }
    public static void close(Statement state, Connection conn) {
        if(state!=null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn!=null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
    
    public static void close(ResultSet rs, Statement state, Connection conn) {
        if(rs!=null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(state!=null) {
            try {
                state.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(conn!=null) {
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

}

可以将其定义为一个工具类，每次使用的时候直接复制，然后更改url里数据库的名字，这样可以提高效率。

　　dao层：对数据库的各种增删改查方法的封装：

  1 import java.sql.Connection;
  2 import java.sql.PreparedStatement;
  3 import java.sql.ResultSet;
  4 import java.sql.SQLException;
  5 import java.sql.Statement;
  6 import java.util.ArrayList;
  7 import java.util.List;
  8 
  9 import org.junit.jupiter.api.Test;
 10 
 11 public class Dao {//dao层
 12         private DBUtil dbutil=new DBUtil();
 13         
 14 
 15     public Dao() {
 16         // TODO Auto-generated constructor stub
 17     }
 18     @Test
 19     public boolean insert(Bean bean) {//插入数据的方法
 20         boolean f=false;
 21         String sql="insert into info(id,name,password,sex) values('"+bean.getId()+"','"+bean.getName()+"','"+bean.getPassword()+"','"+bean.getSex()+"')";
 22         Connection conn=DBUtil.getConnection();//数据库连接，加载驱动
 23         Statement state=null; 
 24         try
 25         {
 26             state=conn.createStatement();//实例化Statement对象,方便对sql语句进行操作
 27             System.out.println(conn);
 28             state.executeUpdate(sql);
 29             f=true;
 30             //执行数据库更新操作用于执行INSERT、UPDATE或DELETE语句以及SQLDDL（数据定义语言）语句，
 31             //例如CREATETABLE和DROPTABLE,（创建表和删除表）
 32         }catch(Exception e)//当try语句中s出现异常时，会执行catch中的语句
 33           {
 34             e.printStackTrace();//捕获异常的语句
 35           }
 36          finally //finally作为异常处理的一部分，它只能用在try/catch语句中，并且附带一个语句块，表示这段语句最终一定会被执行（不管有没有抛出异常），经常被用在需要释放资源的情况下。
 37          {
 38              DBUtil.close(conn);
 39          }
 40         return f;
 41     }
 42     
 43     public boolean delete(int id ) {//删除方法
 44         String sql="delete from info where id='"+id+"'";
 45         boolean f=false;
 46         Connection conn =DBUtil.getConnection();
 47         Statement st=null;
 48         try {
 49             st=conn.createStatement();
 50             st.executeUpdate(sql);
 51             f=true;
 52         } catch (SQLException e) {
 53             // TODO Auto-generated catch block
 54             e.printStackTrace();
 55         }
 56         finally{
 57             DBUtil.close(st, conn);
 58         }
 59         return f;
 60     }
 61     public boolean update(Bean bean) {//更新方法
 62         String sql="update info set name='"+bean.getName()+"',password='"+bean.getPassword()+"',sex='"+bean.getSex()+"'where id='"+bean.getId()+"'";
 63         Connection conn=DBUtil.getConnection();
 64         boolean f=false;
 65         Statement st=null;
 66         try {
 67             st=conn.createStatement();
 68             st.executeUpdate(sql);
 69             f=true;
 70         } catch (SQLException e) {
 71             // TODO Auto-generated catch block
 72             e.printStackTrace();
 73         }
 74         return f;
 75     }
 76     
 77     public List<Bean> list(){//查询所有方法
 78         String sql="select * from info order by id ASC";
 79         Connection conn=DBUtil.getConnection();
 80         Statement st=null;
 81         List<Bean> list=new ArrayList<>();
 82         ResultSet rs=null;
 83         Bean bean=null;
 84         try {
 85             st=conn.createStatement();
 86             st.executeQuery(sql);
 87             rs=st.executeQuery(sql);
 88             while(rs.next()) {
 89                 
 90                 int id=rs.getInt("id");
 91                 String name = rs.getString("name");
 92                 String password = rs.getString("password");
 93                 String sex = rs.getString("sex");
 94                 bean=new Bean(id,name,password,sex);
 95                 list.add(bean);
 96             }
 97         } catch (SQLException e) {
 98             // TODO Auto-generated catch block
 99             e.printStackTrace();
100         }
101         finally {
102             DBUtil.close(rs, st, conn);
103         }
104         return list;
105     }
106     
107     
108     
109     
110     
111     }

对数据库进行操作的方法都封装在里面。

　　servlet：简单说servlet就是跳转的类，当什么情况下干什么跳转到哪里。

import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class servlet
 */
@WebServlet("/servlet")
public class servlet extends HttpServlet {
    Dao dao=new Dao();
    private static final long serialVersionUID = 1L;
    /**
     * @see HttpServlet#HttpServlet()
     */
    public servlet() {
        super();
        // TODO Auto-generated constructor stub
    }


    private void update(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("utf-8");
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        String password = request.getParameter("password");
        String sex = request.getParameter("sex");
        Bean bean=new Bean(id,name,password,sex);
        dao.update(bean);
        request.setAttribute("message", "修改成功");
        request.getRequestDispatcher("servlet?method=list").forward(request, response);
    }

    private void list(HttpServletRequest request, HttpServletResponse response) throws Exception {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("utf-8");
        List<Bean> list = dao.list();
        request.setAttribute("list", list);
        request.getRequestDispatcher("list.jsp").forward(request,response);
    }

    private void delete(HttpServletRequest request, HttpServletResponse response) throws Exception, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("UTF-8");
        int id=Integer.parseInt(request.getParameter("id"));
        dao.delete(id); //进行数据库的删除操作
        request.setAttribute("message", "删除成功");
        request.getRequestDispatcher("servlet?method=list").forward(request, response);
    }

    private void insert(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("utf-8");
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        String password = request.getParameter("password");
        String sex = request.getParameter("sex");
        Bean bean=new Bean(id,name,password,sex);
        if(dao.insert(bean)) {
            request.setAttribute("message", "添加成功");
            request.getRequestDispatcher("index.jsp").forward(request, response);
        }
    }
    
    

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("utf-8");
        String method=request.getParameter("method");
        if("insert".equals(method)) {
            insert(request,response);
            
        }
        else if("delete".equals(method)) {
            try {
                delete(request,response);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            
        }
        else if("update".equals(method)) {
            update(request,response);
        }
        else if("list".equals(method)) {
            try {
                list(request,response);
            } catch (Exception e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

注意：在创建的时候一定要选择创建servlet而不是类如图：

　　

 输入完名字以后点击next选择自己要写的方法：

jsp页面：

　　index.jsp：主页面：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>首页</title>

</head>
<body><% 
Object message =request.getAttribute("message");
if(message!=null&&!"".equals(message)){
%>
    <script type="text/javascript">
    alert("<%=request.getAttribute("message")%>");
    </script>
<%}%>



    <div align="center">
        <h1>简单的增删改查</h1>
        <div>
            <a href="insert.jsp">添加</a>
        </div>
        <div>
            <a href="servlet?method=list">删除</a>
        </div>
        <div>
            <a href="servlet?method=list">修改</a>
        </div>
        <div>
            <a href="servlet?method=list">查询</a>
        </div>


    </div>
</body>
</html>

主页面就是一个菜单，至于为什么删除修改查询的链接都是servlet?method=list，那是因为他们都去调用servlet里面的list方法：

    private void list(HttpServletRequest request, HttpServletResponse response) throws Exception {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("utf-8");
        List<Bean> list = dao.list();
        request.setAttribute("list", list);
        request.getRequestDispatcher("list.jsp").forward(request,response);
    }

先把数据库里所有的信息显示出来，然后在通过request.getRequestDispatcher("list.jsp").forward(request,response);进行跳转，跳转到list.jsp界面，并将之前的所有数据(request,response)一并转发过去

insert.jsp:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>添加</title>
</head>
<body>
    <%
        Object message = request.getAttribute("message");
        if (message != null && !"".equals(message)) {
    %>
    <script type="text/javascript">
              alert("<%=request.getAttribute("message")%>"); //弹出对话框
    </script>
    <%
        }
    %>
    <div align="center">
        <h1>添加信息</h1>
        <a href="index.jsp">返回主页</a>
        <form action="servlet?method=insert" method="post">
        <div>
            id<input type="text" id="id" name="id" />
        </div>
        <div>
            name<input type="text" id="name" name="name" />
        </div>
        <div>
            password<input type="text" id="password" name="password" />
        </div>
        <div>
            sex<input type="radio" id="sex" name="sex" value="男"/>男 <input type="radio"
                id="sex" name="sex" value="女" />女
        </div>
        <div>
            <button type="submit">添&nbsp;&nbsp;&nbsp;加</button>
        </div>
        </form>
    </div>
</body>
</html>

正常的添加页面。

　　list.jsp界面：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
   <%@taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
         Object message = request.getAttribute("message");
         Object grade_list = request.getAttribute("grade_list");
         if(message!=null && !"".equals(message)){
     
    %>
         <script type="text/javascript">
              alert("<%=request.getAttribute("message")%>");
         </script>
    <%} %>
    <div align="center">
        <h1 >信息列表</h1>
        <a href="index.jsp">返回主页</a>
        <table >
            <tr>
                <td>id</td>
                <td>姓名</td>
                <td>密码</td>
                <td>性别</td>
                <td align="center" colspan="2">操作</td>
            </tr>
            <c:forEach items="${list}" var="item">
                <tr>
                    <td>${item.id}</td>
                    <td>${item.name}</td>
                    <td>${item.password}</td>
                    <td>${item.sex}</td>
                    <td><a href="update.jsp?id=${item.id}&name=${item.name}&password=${item.password}&sex=${item.sex}">修改</a></td>
                    <td><a href="servlet?method=delete&id=${item.id}">删除</a></td>
                </tr>
            </c:forEach>
        </table>
    </div>
    
</body>
</html>

其中用到了标签库(<c:forEach>)，需要导入jstl的包，并且加入其核心依赖，为固定值，如果不了解请点击：https://www.cnblogs.com/tkg1314/p/12008284.html查看jstl标签库。用<c:forEach>来遍历信息，然后每行信息都有删除和修改操作。修改的话跳转到update.jsp并且将id,name,password,sex的值传过去。删除是跳转到servlet的delete方法：

private void delete(HttpServletRequest request, HttpServletResponse response) throws Exception, IOException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("UTF-8");
        int id=Integer.parseInt(request.getParameter("id"));
        dao.delete(id); //进行数据库的删除操作
        request.setAttribute("message", "删除成功");
        request.getRequestDispatcher("servlet?method=list").forward(request, response);
    }

因为delete只需要id所以只需要将id传过去。

至于每个jsp里面的：

<%
         Object message = request.getAttribute("message");
         Object grade_list = request.getAttribute("grade_list");
         if(message!=null && !"".equals(message)){
     
    %>
         <script type="text/javascript">
              alert("<%=request.getAttribute("message")%>");
         </script>
    <%} %>

是用来获取servlet里面你通过setAttribute方法添加的信息(红色加粗)：并且提示出来

    private void insert(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException {
        // TODO Auto-generated method stub
        request.setCharacterEncoding("utf-8");
        int id = Integer.parseInt(request.getParameter("id"));
        String name = request.getParameter("name");
        String password = request.getParameter("password");
        String sex = request.getParameter("sex");
        Bean bean=new Bean(id,name,password,sex);
        if(dao.insert(bean)) {
            request.setAttribute("message", "添加成功");
            request.getRequestDispatcher("index.jsp").forward(request, response);
        }
    }

这样便完成了一个简单的java web 数据库的简单增删改查，没有做页面，那个password不是密码，只是一个名字，因此<input>标签没用password类型。

运行结果：

主页面：

 添加操作：

 

 添加之前的表数据：

添加之后

修改操作：

 

 删除操作：

 

体会：做了一个简单的增删改查明白了每个类的作用以及联系。bean是用将属性的get，set等方法进行封装。dao层，是对数据库表操作的封装，里面有sql语句的执行等。而DBUtil是对数据库连接和关闭等操作的封装。servlet是跳转，通过调用dao层的方法实现跳转操作。然后jsp页面，有一个主页面 写超链接链接到其他页面。当然你对数据的删改都是在查询的基础上操作的，如果没有显示出信息就不能去删除和修改。当然我把id设为了主键自增，但我没有写验证主键的条件。另外还有什么不对的地方希望大家和老师多多指点！

转自：https://www.cnblogs.com/tkg1314/p/12014713.html