Servlet 中的 CRUD 示例

2025年3月25日 | 阅读 4 分钟

CRUD（创建、读取、更新和删除）应用程序是任何项目开发中最重要的应用程序。在 Servlet 中，我们可以轻松创建 CRUD 应用程序。

Servlet CRUD 示例

在 Oracle 数据库中使用序列创建自动递增的 id 的 "user905" 表。它有 5 个字段：id、name、password、email 和 country。

文件：index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="ISO-8859-1">
<title>Insert title here</title>
</head>
<body>

<h1>Add New Employee</h1>
<form action="SaveServlet" method="post">
<table>
<tr><td>Name:</td><td><input type="text" name="name"/></td></tr>
<tr><td>Password:</td><td><input type="password" name="password"/></td></tr>
<tr><td>Email:</td><td><input type="email" name="email"/></td></tr>
<tr><td>Country:</td><td>
<select name="country" style="width:150px">
<option>India</option>
<option>USA</option>
<option>UK</option>
<option>Other</option>
</select>
</td></tr>
<tr><td colspan="2"><input type="submit" value="Save Employee"/></td></tr>
</table>
</form>

<br/>
<a href="ViewServlet">view employees</a>

</body>
</html>

文件：Emp.java

public class Emp {
private int id;
private String name,password,email,country;
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 getEmail() {
	return email;
}
public void setEmail(String email) {
	this.email = email;
}
public String getCountry() {
	return country;
}
public void setCountry(String country) {
	this.country = country;
}

}

文件：EmpDao.java

import java.util.*;
import java.sql.*;

public class EmpDao {

	public static Connection getConnection(){
		Connection con=null;
		try{
			Class.forName("oracle.jdbc.driver.OracleDriver");
			con=DriverManager.getConnection("jdbc:oracle:thin:@localhost:1521:xe","system","oracle");
		}catch(Exception e){System.out.println(e);}
		return con;
	}
	public static int save(Emp e){
		int status=0;
		try{
			Connection con=EmpDao.getConnection();
			PreparedStatement ps=con.prepareStatement(
                         "insert into user905(name,password,email,country) values (?,?,?,?)");
			ps.setString(1,e.getName());
			ps.setString(2,e.getPassword());
			ps.setString(3,e.getEmail());
			ps.setString(4,e.getCountry());
			
			status=ps.executeUpdate();
			
			con.close();
		}catch(Exception ex){ex.printStackTrace();}
		
		return status;
	}
	public static int update(Emp e){
		int status=0;
		try{
			Connection con=EmpDao.getConnection();
			PreparedStatement ps=con.prepareStatement(
                         "update user905 set name=?,password=?,email=?,country=? where id=?");
			ps.setString(1,e.getName());
			ps.setString(2,e.getPassword());
			ps.setString(3,e.getEmail());
			ps.setString(4,e.getCountry());
			ps.setInt(5,e.getId());
			
			status=ps.executeUpdate();
			
			con.close();
		}catch(Exception ex){ex.printStackTrace();}
		
		return status;
	}
	public static int delete(int id){
		int status=0;
		try{
			Connection con=EmpDao.getConnection();
			PreparedStatement ps=con.prepareStatement("delete from user905 where id=?");
			ps.setInt(1,id);
			status=ps.executeUpdate();
			
			con.close();
		}catch(Exception e){e.printStackTrace();}
		
		return status;
	}
	public static Emp getEmployeeById(int id){
		Emp e=new Emp();
		
		try{
			Connection con=EmpDao.getConnection();
			PreparedStatement ps=con.prepareStatement("select * from user905 where id=?");
			ps.setInt(1,id);
			ResultSet rs=ps.executeQuery();
			if(rs.next()){
				e.setId(rs.getInt(1));
				e.setName(rs.getString(2));
				e.setPassword(rs.getString(3));
				e.setEmail(rs.getString(4));
				e.setCountry(rs.getString(5));
			}
			con.close();
		}catch(Exception ex){ex.printStackTrace();}
		
		return e;
	}
	public static List<Emp> getAllEmployees(){
		List<Emp> list=new ArrayList<Emp>();
		
		try{
			Connection con=EmpDao.getConnection();
			PreparedStatement ps=con.prepareStatement("select * from user905");
			ResultSet rs=ps.executeQuery();
			while(rs.next()){
				Emp e=new Emp();
				e.setId(rs.getInt(1));
				e.setName(rs.getString(2));
				e.setPassword(rs.getString(3));
				e.setEmail(rs.getString(4));
				e.setCountry(rs.getString(5));
				list.add(e);
			}
			con.close();
		}catch(Exception e){e.printStackTrace();}
		
		return list;
	}
}

文件：SaveServlet.java

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("/SaveServlet")
public class SaveServlet extends HttpServlet {
	protected void doPost(HttpServletRequest request, HttpServletResponse response) 
         throws ServletException, IOException {
		response.setContentType("text/html");
		PrintWriter out=response.getWriter();
		
		String name=request.getParameter("name");
		String password=request.getParameter("password");
		String email=request.getParameter("email");
		String country=request.getParameter("country");
		
		Emp e=new Emp();
		e.setName(name);
		e.setPassword(password);
		e.setEmail(email);
		e.setCountry(country);
		
		int status=EmpDao.save(e);
		if(status>0){
			out.print("<p>Record saved successfully!</p>");
			request.getRequestDispatcher("index.html").include(request, response);
		}else{
			out.println("Sorry! unable to save record");
		}
		
		out.close();
	}

}

文件：EditServlet.java

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("/EditServlet")
public class EditServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) 
           throws ServletException, IOException {
		response.setContentType("text/html");
		PrintWriter out=response.getWriter();
		out.println("<h1>Update Employee</h1>");
		String sid=request.getParameter("id");
		int id=Integer.parseInt(sid);
		
		Emp e=EmpDao.getEmployeeById(id);
		
		out.print("<form action='EditServlet2' method='post'>");
		out.print("<table>");
		out.print("<tr><td></td><td><input type='hidden' name='id' value='"+e.getId()+"'/></td></tr>");
		out.print("<tr><td>Name:</td><td><input type='text' name='name' value='"+e.getName()+"'/></td></tr>");
		out.print("<tr><td>Password:</td><td><input type='password' name='password' value='"+e.getPassword()+"'/>
                </td></tr>");
		out.print("<tr><td>Email:</td><td><input type='email' name='email' value='"+e.getEmail()+"'/></td></tr>");
		out.print("<tr><td>Country:</td><td>");
		out.print("<select name='country' style='width:150px'>");
		out.print("<option>India</option>");
		out.print("<option>USA</option>");
		out.print("<option>UK</option>");
		out.print("<option>Other</option>");
		out.print("</select>");
		out.print("</td></tr>");
		out.print("<tr><td colspan='2'><input type='submit' value='Edit & Save '/></td></tr>");
		out.print("</table>");
		out.print("</form>");
		
		out.close();
	}
}

文件：EditServlet2.java

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("/EditServlet2")
public class EditServlet2 extends HttpServlet {
	protected void doPost(HttpServletRequest request, HttpServletResponse response) 
          throws ServletException, IOException {
		response.setContentType("text/html");
		PrintWriter out=response.getWriter();
		
		String sid=request.getParameter("id");
		int id=Integer.parseInt(sid);
		String name=request.getParameter("name");
		String password=request.getParameter("password");
		String email=request.getParameter("email");
		String country=request.getParameter("country");
		
		Emp e=new Emp();
		e.setId(id);
		e.setName(name);
		e.setPassword(password);
		e.setEmail(email);
		e.setCountry(country);
		
		int status=EmpDao.update(e);
		if(status>0){
			response.sendRedirect("ViewServlet");
		}else{
			out.println("Sorry! unable to update record");
		}
		
		out.close();
	}

}

文件：DeleteServlet.java

import java.io.IOException;
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("/DeleteServlet")
public class DeleteServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) 
             throws ServletException, IOException {
		String sid=request.getParameter("id");
		int id=Integer.parseInt(sid);
		EmpDao.delete(id);
		response.sendRedirect("ViewServlet");
	}
}

文件：ViewServlet.java

import java.io.IOException;
import java.io.PrintWriter;
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;
@WebServlet("/ViewServlet")
public class ViewServlet extends HttpServlet {
	protected void doGet(HttpServletRequest request, HttpServletResponse response) 
               throws ServletException, IOException {
		response.setContentType("text/html");
		PrintWriter out=response.getWriter();
		out.println("<a href='index.html'>Add New Employee</a>");
		out.println("<h1>Employees List</h1>");
		
		List<Emp> list=EmpDao.getAllEmployees();
		
		out.print("<table border='1' width='100%'");
		out.print("<tr><th>Id</th><th>Name</th><th>Password</th><th>Email</th><th>Country</th>
                 <th>Edit</th><th>Delete</th></tr>");
		for(Emp e:list){
		 out.print("<tr><td>"+e.getId()+"</td><td>"+e.getName()+"</td><td>"+e.getPassword()+"</td>
                 <td>"+e.getEmail()+"</td><td>"+e.getCountry()+"</td><td><a href='EditServlet?id="+e.getId()+"'>edit</a></td>
                 <td><a href='DeleteServlet?id="+e.getId()+"'>delete</a></td></tr>");
		}
		out.print("</table>");
		
		out.close();
	}
}