这篇文章主要介绍了JavaWeb增删改查的基本操作是什么的相关知识，内容详细易懂，操作简单快捷，具有一定借鉴价值，相信大家阅读完这篇JavaWeb增删改查的基本操作是什么文章都会有所收获，下面我们一起来看看吧。
大致流程是：
首先访问到servlet层，在servlet层里调用StudentRepository的各个方法，然后展示到jsp页面中。所以浏览器访问路径是servlet层里StudentServlet中@WebServlet("/student")的路径(http://localhost:8080/student)
工具：idea，mysql数据库
数据库：
Student.java
public class Student { private Integer id; private String name; private Integer numsex; private Integer age; private String password;
public Integer getId() { return id;
} public void setId(Integer id) { this.id = id;
} public String getName() { return name;
} public void setName(String name) { this.name = name;
} public Integer getNumsex() { return numsex;
} public void setNumsex(Integer numsex) { this.numsex = numsex;
} public Integer getAge() { return age;
} public void setAge(Integer age) { this.age = age;
} public String getPassword() { return password;
} public void setPassword(String password) { this.password = password;
} public Student(Integer id, String name, Integer numsex, Integer age, String password) { this.id = id; this.name = name; this.numsex = numsex; this.age = age; this.password = password;
} @Override
public String toString() { return "Student{" + "id=" + id + ", name='" + name + '\'' + ", numsex=" + numsex + ", age=" + age + ", password='" + password + '\'' + '}';
}StudentRepository：
import com.javaweb.entity.Student;import com.javaweb.util.JDBCTools;import java.sql.*;import java.util.ArrayList;import java.util.List;
public class StudentRepository {
public List<Student> findAll(){
List<Student> list=new ArrayList<>();
Connection connection=null;
PreparedStatement preparedStatement=null;
ResultSet resultSet=null; try { //调用JDBCTools连接mysql数据库
connection= JDBCTools.getConnection(); String sql="select * from student";//查询语句
preparedStatement=connection.prepareStatement(sql);
resultSet = preparedStatement.executeQuery(); while (resultSet.next()){ //从resultSet拿出每个属性数据
Integer id=resultSet.getInt(1); String name=resultSet.getString(2);
Integer numsex=resultSet.getInt(3);
Integer age=resultSet.getInt(4); String password=resultSet.getString(5); //这里可以理解为，resultSet拿出每个属性数据赋予student对象，形成一个有数据的student对象
Student student = new Student(id, name, numsex, age, password);
list.add(student);//可能多条数据，放到集合中
}
} catch (SQLException e) {
e.printStackTrace();
} finally { //调用JDBCTools，关闭connection，preparedStatement，resultSet
JDBCTools.release(connection,preparedStatement,resultSet);
} return list;
} //添加操作
public void add(Integer id,String name,Integer numsex,
Integer age,String password){
Connection connection=null;
PreparedStatement preparedStatement=null; try {
connection= JDBCTools.getConnection(); String sql="insert into student(id,name,numsex,age,password) values (?,?,?,?,?)";
preparedStatement=connection.prepareStatement(sql); //这里注意第一个参数对应sql语句问号的序号，
preparedStatement.setInt(1,id);//就是把id替代sql的第一个问号，id由前端传过来
preparedStatement.setString(2,name);
preparedStatement.setInt(3,numsex);
preparedStatement.setInt(4,age);
preparedStatement.setString(5,password);
preparedStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
JDBCTools.release(connection,preparedStatement,null);
}
} //删除操作
public void deleteById(Integer id){
Connection connection=null;
PreparedStatement preparedStatement=null; try {
connection= JDBCTools.getConnection(); String sql="delete from student where id=?";
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setInt(1,id);
preparedStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
}finally {
JDBCTools.release(connection,preparedStatement,null);
}
} //根据id查询
public Student findById(Integer id){
Connection connection=null;
PreparedStatement preparedStatement=null;
ResultSet resultSet=null;
Student student=null; try {
connection= JDBCTools.getConnection(); String sql="select * from student where id=?";
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setInt(1,id);
resultSet = preparedStatement.executeQuery(); while (resultSet.next()){
Integer id2=resultSet.getInt(1); String name=resultSet.getString(2);
Integer numsex=resultSet.getInt(3);
Integer age=resultSet.getInt(4); String password=resultSet.getString(5);
student = new Student(id2, name, numsex, age, password);
}
} catch (SQLException e) {
e.printStackTrace();
}finally {
JDBCTools.release(connection,preparedStatement,resultSet);
} return student;
} //更新操作
public void update(Integer id,String name,Integer numsex,
Integer age,String password){
Connection connection=null;
PreparedStatement preparedStatement=null; try {
connection= JDBCTools.getConnection(); String sql="update student set name=?,numsex=?,age=?,password=? where id=?";
preparedStatement=connection.prepareStatement(sql);
preparedStatement.setString(1,name);
preparedStatement.setInt(2,numsex);
preparedStatement.setInt(3,age);
preparedStatement.setString(4,password);
preparedStatement.setInt(5,id);
preparedStatement.executeUpdate();
} catch (SQLException e) {
e.printStackTrace();
} finally {
JDBCTools.release(connection,preparedStatement,null);
}
}
}StudentServlet：
import com.javaweb.entity.Student;import com.javaweb.repository.StudentRepository;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.util.List;@WebServlet("/student")public class StudentServlet extends HttpServlet { //调用StudentRepository中的增删改查方法
private StudentRepository studentRepository=new StudentRepository(); @Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //判断前端传来的标记，以此执行相对应的增删改查操作
String method=req.getParameter("method"); if (method==null){
method="findAll";
} switch (method){ case "findAll"://查询所有数据
List<Student> list = studentRepository.findAll();//调用StudentRepository中的findAll()方法
req.setAttribute("list",list);//存入request中
req.getRequestDispatcher("index.jsp").forward(req,resp);//转发到index.jsp中
case "delete"://删除操作
String idStr=req.getParameter("id");
Integer id=Integer.parseInt(idStr);
studentRepository.deleteById(id);//根据id删除
resp.sendRedirect("/student"); break; case "findById":
idStr=req.getParameter("id");
id=Integer.parseInt(idStr);
req.setAttribute("student",studentRepository.findById(id));
req.getRequestDispatcher("update.jsp").forward(req,resp); break; case "add":
req.getRequestDispatcher("add.jsp").forward(req,resp);
}
} @Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
req.setCharacterEncoding("UTF-8");//防止中文乱码
String method=req.getParameter("method"); switch (method){ case "add"://添加操作
//获取前端传来的数据
String idStr=req.getParameter("id");
String name=req.getParameter("name");
String numsexStr=req.getParameter("numsex");
String ageStr=req.getParameter("age");
String password=req.getParameter("password");
Integer id=Integer.parseInt(idStr);//转化为整型
Integer numsex=Integer.parseInt(numsexStr);
Integer age=Integer.parseInt(ageStr);
studentRepository.add(id,name,numsex,age,password);//调用add方法
break; case "update"://更新操作
idStr=req.getParameter("id");
name=req.getParameter("name");
numsexStr=req.getParameter("numsex");
ageStr=req.getParameter("age");
password=req.getParameter("password");
id=Integer.parseInt(idStr);
numsex=Integer.parseInt(numsexStr);
age=Integer.parseInt(ageStr);
studentRepository.update(id, name, numsex, age, password); break;
}
resp.sendRedirect("/student");//重定向到index.jsp页面
}
}JDBCTools：
import java.sql.*;public class JDBCTools { private static Connection connection; private static String url="jdbc:mysql://localhost:3306/he?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone = GMT"; private static String user="root";//用户名
private static String pass="123z";//密码
static { try {
Class.forName("com.mysql.cj.jdbc.Driver");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
} public static Connection getConnection(){ try {
connection= DriverManager.getConnection(url,user,pass);
} catch (SQLException e) {
e.printStackTrace();
} return connection;
} public static void release(Connection connection, Statement statement, ResultSet resultSet){ try { if (connection!=null) {
connection.close();
} if (statement!=null){
statement.close();
} if (resultSet!=null){
resultSet.close();
}
} catch (SQLException e) {
e.printStackTrace();
}
}
}其中，web.xml创建之后不曾配置过，所以不贴代码了
add.jsp：
<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>Title</title></head><body><form action="/student" method="post"> 编号: <input type="text" name="id"/><br/> 姓名：<input type="text" name="name"/><br/> 性别：<input type="text" name="numsex"/><br/> 年龄：<input type="text" name="age"/><br/> 密码：<input type="password" name="password"/><br/> <input type="hidden" name="method" value="add"/> <input type="submit" value="提交"/></form></body></html>
index.jsp：
<%@ page contentType="text/html;charset=UTF-8" language="java" %><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><html>
<head>
<title>$Title$</title>
</head>
<body>
<h1>学生管理系统</h1>
<div ><a href="/student?method=add">添加</a></div>
<table>
<tr>
<th>编号</th>
<th>姓名</th>
<th>性别</th>
<th>年龄</th>
<th>密码</th>
<th>操作</th>
</tr>
<c:forEach items="${list}" var="student">
<tr>
<td>${student.id}</td>
<td>${student.name}</td>
<td>${student.numsex}</td>
<td>${student.age}</td>
<td>${student.password}</td>
<td>
<a href="/student?method=delete&id=${student.id}">删除</a>
<a href="/student?method=findById&id=${student.id}">修改</a>
</td>
</tr>
</c:forEach>
</table>
</body></html>update.jsp：
<%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head>
<title>Title</title></head><body><form action="/student" method="post">
编号: <input type="text" name="id" value="${student.id}" readonly/><br/>
姓名：<input type="text" name="name" value="${student.name}"/><br/>
性别：<input type="text" name="numsex" value="${student.numsex}"/><br/>
年龄：<input type="text" name="age" value="${student.age}"/><br/>
密码：<input type="password" name="password" value="${student.password}"/><br/>
<input type="hidden" name="method" value="update"/>
<input type="submit" value="修改"/></form></body></html>注意访问的路径，我的是http://localhost:8080/student，student这个名字对应servlet层里@WebServlet("/student")的路径名
访问的首页：
这里就可以进行对应的增删改操作了
点击添加：会跳转到添加页面：
提交成功后自动跳转到首页并展示
点击删除：数据直接删掉，数据库也同步删掉了
点击修改：跳转到修改页面，其中id设置不能修改：
提交后自动返回首页：
修改成功，同时数据库也修改成功!
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