jsp+servlet+bean+mysql例子

青旅半醒 2021-09-26 11:00 192阅读 0赞

mysql数据库是demo，表是stu，只有id和name字段。

本例子中jsp有添加和查询功能。命名有点乱，只是为了实现功能，回忆下基础内容。

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
    
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
    <html>
      <head>
    	<script src="http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js"></script>
    	<script src="http://cdn.bootcss.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
    	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>My JSP 'index.jsp' starting page</title>
      </head>
      
    	<body>
    	  <form id="fm">
    	  	学号：<input type="text" id="id" name="id"><br>
    	  	姓名：<input type="text" id="name" name="name"><br>
    	  	<input type="button" id="btn" value="添加学生">
    	  </form>
    	  <br>
    	 
    	  <form>
    	  	 学生id：<input type="text" id="idd" name="idd">
    	  	 <input type="button" id="btnn" value="查询姓名">
    	  </form>
    	  <p id="p"></p>
        
      
    		<script type="text/javascript">
    		$(function(){
    			$("#btn").click(function(){
    				$.ajax({
    					type:"post",
    					datatype:"text",
    					data:{
    						id:$("#id").val(),
    						name:$("#name").val(),
    						i:"add"
    					},
    					url:"MyServlet",
    					success:function(data){
    						if(data==1){
    							alert("添加成功");
    						}
    						else
    							alert("添加失败");
    					}
    				});
    			});
    			
    			
    			$("#btnn").click(function(){
    				$.ajax({
    					type:"post",
    					datatype:"text",
    					data:{
    						idd:$("#idd").val(),
    						i:"query"
    					},
    					url:"MyServlet",
    					success:function(data){
    						if(data=="zero"){
    							$("#p").html("无此学生");
    						}
    						else
    							alert(data);
    							$("#p").html(""+data);
    					}
    				});
    			});
    			
    		});
    		</script>
    	</body>
    </html>

下面是servlet

package demo;
    
    import java.io.IOException;
    import java.io.PrintWriter;
    
    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    
    @WebServlet("/MyServlet")
    public class MyServlet extends HttpServlet {
    	private static final long serialVersionUID = 1L;
    
        public MyServlet() {
            super();
        }
    
    	protected void doGet(HttpServletRequest request, HttpServletResponse response) 
    			throws ServletException, IOException {
    		response.setCharacterEncoding("utf-8");
    		response.setContentType("text/html");
    		PrintWriter out=response.getWriter();
    		String ii=request.getParameter("i");
    		if(ii.equals("add"))
    		{
    			int id=Integer.parseInt(request.getParameter("id"));
    			String name=request.getParameter("name");
    			
    			int i=UserDao.add(new User(id,name));
    			if(i==1){
    				out.print(1);
    			}
    			else{
    				out.print(0);
    			}
    		}
    		else if(ii.equals("query"))
    		{
    			int idd=Integer.parseInt(request.getParameter("idd"));
    			User u=UserDao.find(idd);
    			if(u==null)
    			{
    				out.print("zero");
    			}
    			else
    			{
    				String name=u.getname();
    				out.print(name);
    			}
    		}
    		return;
    	}
    
    	protected void doPost(HttpServletRequest request, HttpServletResponse response)
    			throws ServletException, IOException {
    
    		doGet(request, response);
    	}
    
    }

然后是业务层的bean

package demo;
    
    public class User {
    	private int id;
    	private String name;
    	User()
    	{
    		
    	}
    	User(int id,String name)
    	{
    		this.id=id;
    		this.name=name;
    	}
    	public int getid()
    	{
    		return this.id;
    	}
    	public void setid(int id)
    	{
    		this.id=id;
    	}
    	public String getname()
    	{
    		return this.name;
    	}
    	public void setname(String name)
    	{
    		this.name=name;
    	}
    }

再是数据访问接口dao

package demo;
    
    import java.sql.*;
    
    public class UserDao {
    	public static int add(User user)
    	{
    		int flag=0;
    		Connection conn=null;
    		PreparedStatement ps=null;
    		try{
    			conn=JdbcUtil.getConn();
    			String sql="insert into stu(id,name) values(?,?)";
    			ps=conn.prepareStatement(sql);
    			ps.setInt(1, user.getid());
    			System.out.println(user.getid());
    			System.out.println(user.getname());
    			ps.setString(2, user.getname());
    			flag=ps.executeUpdate();
    		}
    		catch(Exception e)
    		{
    			e.printStackTrace();
    		}
    		finally
    		{
    			JdbcUtil.free(null,ps,conn);
    		}
    		return flag;
    	}
    	
    	public static User find(int id)
    	{
    		Connection conn=null;
    		PreparedStatement ps=null;
    		ResultSet rs=null;
    		User user=null;
    		try{
    			conn=JdbcUtil.getConn();
    			String sql="select * from stu where id=?";
    			ps=conn.prepareStatement(sql);
    			ps.setInt(1, id);
    			rs=ps.executeQuery();
    			if(rs.next())
    			{
    				user=new User();
    				user.setid(rs.getInt("id"));
    				user.setname(rs.getString("name"));;
    			}
    			
    		}catch(Exception e){
    			e.printStackTrace();
    		}
    		
    		finally
    		{
    			JdbcUtil.free(rs,ps,conn);
    		}		
    		return user;
    	}
    	
    }

最后是连接数据库的类

package demo;
    
    import java.sql.*;
    
    public class JdbcUtil {
    	static String driverName=null;
    	static String url=null;
    	private JdbcUtil(){}
    	static{	
    		try{
    			driverName="com.mysql.jdbc.Driver";
    	    	 String url1="jdbc:mysql://localhost:3306/demo";
    	    	 String url2="?user=root&password=rootroot";
    	    	 String url3="&useUnicode=true&characterEncoding=UTF-8";
    	    	 url=url1+url2+url3;
    	    	 Class.forName(driverName);
    
    		}catch(Exception e)
    		{
    			throw new ExceptionInInitializerError(e);
    		}
    	}
    	public static Connection getConn() throws SQLException
    	{
    		return DriverManager.getConnection(url);
    	}
    	public static void free(ResultSet rs,Statement st,Connection conn)
    	{
    		try
    		{
    			if(rs!=null) rs.close();
    		}
    		catch(SQLException e)
    		{
    			e.printStackTrace();
    		}
    		finally
    		{
    			try
    			{
    				if(st!=null) st.close();
    			}
    			catch(SQLException e)
    			{
    				e.printStackTrace();
    			}
    			finally
    			{				
    				if(conn!=null)
    				{
    					try
    					{
    						conn.close();
    					}
    					catch(SQLException e)
    					{
    						e.printStackTrace();
    					}
    				}
    			}
    		}
    	}
    }

最后的结果  
![SouthEast][]

[SouthEast]: /images/20210923/a30e6fc493f84f1ebb5a5a984cf852d7.png