Java web 实现简单的与数据库的交互

Java web 实现简单的与数据库的交互

1. 连接数据库，编写Conn类，该类是固定的对数据库的连接语句，这里使用的是SQL server数据库

package StudentGradeManage;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;

public class Conn {
	public static Connection getConnection()
	{
		Connection con=null;

		try {
			Class.forName("net.sourceforge.jtds.jdbc.Driver");
			String dbURL="jdbc:jtds:sqlserver://127.0.0.1:1433/StudentGrade";
			String db_User="sa";
			String db_pwd="123456";
			con = DriverManager.getConnection(dbURL, db_User, db_pwd);
		} catch (Exception e) {
	
			e.printStackTrace();
		}
		System.out.println(con);
		return con;		
	}
	
	public static void closeConnection(PreparedStatement ps,Connection con,ResultSet rs)
	{
		
			try {
				if(ps!=null)
				ps.close();
				if(con!=null)
					con.close();
				if(rs!=null)
					rs.close();
			} catch (Exception e) {
			
				e.printStackTrace();
			}			
	}
}

2. 编写search.jsp 用于输入查询时的条件，这里可以根据姓名精确查询或模糊查询，也可以根据学号查询

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>









	
	
			
姓名：
			
学号：
			

	
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3. 编写FindServlet

package StudentGradeManage;

import java.io.IOException;
import java.util.ArrayList;
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 FindServlet
 */
@WebServlet("/FindServlet")
public class FindServlet extends HttpServlet {
	private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public FindServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

	/**
	 * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
	 */
	protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		// TODO Auto-generated method stub
		StudentService studentService=new StudentService();
		List list=new ArrayList<>();		
		String sname=request.getParameter("sname");
		String sno=request.getParameter("sno");
		list=studentService.getGrade(sname,sno);
		request.setAttribute("list", list);	
		request.getRequestDispatcher("searchGrade.jsp").forward(request, response);
	}

	/**
	 * @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);
	}

}

4. 编写StudentService类，在该类中编写getGrade方法

/**
	 * 查询
	 * 先判断如果输入的姓名为空就根据学号查询
	 * 如果姓名不为空，那就默认根据姓名查询，可以模糊查询，也可以精确查询			
	 */
	public List getGrade(String sname1,String sno1)
	{					
		List list=new ArrayList<>();										
		Connection con=Conn.getConnection();
		PreparedStatement ps=null;
		String sql="";
		if(sname1=="")
		{
			sql="select * from grade where sno='"+sno1+"'";
		}
		else
		{
			String sname2="%"+sname1+"%";
			sql="select * from grade where sname like '"+sname2+"'";
		}
		try {
			ps = con.prepareStatement(sql);
			System.out.println(sql);
//			ps.setString(1, sno1);
			ResultSet rs = ps.executeQuery();
											
			while(rs.next())
			{
				int id=rs.getInt(1);
				String sno=rs.getString(2);
				String sname=rs.getString(3);
				String cno=rs.getString(4);
				String cname=rs.getString(5);
				int grade=rs.getInt(6);

				Student student=new Student();
				student.setId(id);
				student.setSno(sno);
				student.setSname(sname);
				student.setCno(cno);
				student.setCname(cname);
				student.setGrade(grade);											
				list.add(student);												
			}
		} catch (SQLException e) {
			// TODO 自动生成的 catch 块
			e.printStackTrace();
		}																								
		return list;					
	}

5. 编写searchGrade.jsp，用于显示查询到的数据

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.*"  %>    
<%@ page import="StudentGradeManage.Student"  %>
<%@ page import="StudentGradeManage.ToolsBean" %>







		
		<%
			int sum=0;
			double avg=0;
			List list=(List) request.getAttribute("list");
			if(list==null||list.size()<1)
			{
				out.print("");	
			}
			else
			{
				for(int i=0;i									
		
		<% }
			avg=sum/list.size();
		%>
		<%=sum %>
		<%=avg %>
		
		<%
		}
		%>											
	

		

			
学号
			
姓名
			
课程号
			
课程名
			
成绩
			
操作
		
没有成绩信息

			
<%=ToolsBean.toChinese(list.get(i).getSno()) %>
			
<%=(list.get(i).getSname()) %>
			
<%=ToolsBean.toChinese(list.get(i).getCno()) %>
			
<%=(list.get(i).getCname()) %>
			
<%=list.get(i).getGrade() %>
			

				

					
					
					
				
				
				

					
					
					
				
			
		

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