Servlet基础及实现增删改查案例

简介: Servlet基础及实现增删改查案例

Servlet基础及实现增删查改案例(JSP--->Servlet--->Java--->数据库)


引言:

      本文主要分享了Servlet的基本概述、如何编写一个Servlet及步骤、Servlet的执行流程、与JSP页面的比较最后分享了一个比较大的增删改查案例(涉及到Servlet、Java、JSP以及数据库);

@[toc]

1. Servlet概述

传统的Java代码无法获取请求参数,只有使用Java程序中的Servlet技术才可以获取,但是需要服务器编译环境的支持;

Servlet就是一个Java程序,一个Java类;可以和浏览器进行交互,是一个动态资源;Servlet的使用需要有服务器编译环境的支持需要导入Servlet的API;

2. 编写Servlet的步骤

  • 首先需要配置好Tomcat
  • 创建一个web项目
  • 创建一个HTML表单
  • 完善包
  • 编写一个继承自HttpServlet的类
  • 重写service方法
  • 完成业务内容
  • 在web.xml中配置Servlet
  • 运行

2.1 服务器编译环境

EClipse

IDEA

2.2 创建一个index.html

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>登录界面</title>
<style >
    body{
    
    
        text-align: center;
    }
</style>
</head>
<body>
    <form action="dealLogin" method = "POST">
        USERNAME:<input type = "text" name = "username"/><br/>
        PASSWORD:<input type = "password" name = "password"/><br/>
        <input type = "submit" value = "LOGIN"/>
    </form>
</body>
</html>

2.3 编写一个继承自HttpServlet的类并重写service方法

package com.kaka.web;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;           
public class UserServlet extends HttpServlet{
   
   
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
   
        //转码
        request.setCharacterEncoding("UTF-8");
        response.setContentType("text/html;charset=UTF-8");

        String username = request.getParameter("username");
        String password = request.getParameter("password");
        System.out.println("username" + username + "password" + password);

        //打印流
        PrintWriter out = response.getWriter();
        out.print("username" + username + "password" + password);
    } 
}

2.4 配置xml

<servlet>
    <servlet-name>myServlet</servlet-name>
    <servlet-class>com.kaka.web.UserServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>myServlet</servlet-name>
    <url-pattern>/dealLogin</url-pattern>
</servlet-mapping>

2.5 运行结果

在这里插入图片描述在这里插入图片描述

3. Servlet的执行流程

以第二板块的Servlet为例:

  1. 根据表单中的action属性dealLogin,与web.xml中的servlet-mapping的url-pattern匹配;
  2. 找到servlet-mapping中的servlet-name指向的对象,如果存在直接调用该对象的service方法;
  3. 如果对象不存在,在servlet节点中查找同名找到servlet-class项的字符串;
  4. 使用Class.forName()方法反射该类对象;
  5. 调用该类的父类的service方法;
  6. 有同类型的请求到来时,重复步骤2;

4. Servlet与JSP的比较

  • 书写方面:jsp由html+java脚本组成;Servlet只能由java语言编写;
  • 执行原理上:jsp转化为java然后编译为.class最后执行执行;Servlet.java直接编译为.class然后执行
  • 内容方面:jsp有9大隐式对象;servlet没有隐式对象;
  • 编写规范上:servlet需要继承HttpServlet,重写父类的方法:service、doGet、doPost.....

5. 基于Servlt完成CRUD

步骤:

  • 编写数据库
  • 创建web工程、建包
  • 配置xml文件
  • 创建index.jsp 含有查询部门信息链接,作为主界面;
  • 创建StudentList.jsp 全查展示页
  • 创建StuServlet 完成list查询的逻辑

    • 含有action=list的传参 根据action的字符串取值做不同的操作
    • 编写StuDao
    • 编写Student实体
  • 在列表页添加链接: < a href="addStudent.jsp" >添加学生信息
  • 编写addStudent.jsp页面

  • 在service方法中添加逻辑分支

5.1 创建数据库STUDENT表

CREATE TABLE student(
    id INT PRIMARY KEY AUTO_INCREMENT,
    NAME VARCHAR(50) NOT NULL,
    sex VARCHAR(10) DEFAULT 'man',
    age VARCHAR(5)
) CHARSET = utf8;

5.2 xml文件的配置

<servlet>
      <servlet-name>stuServlet</servlet-name>
      <servlet-class>com.kaka.controller.StuServlet</servlet-class>
      <!-- 设置servlet的初始化参数 -->
    <init-param>
        <param-name>encoding</param-name>
        <param-value>UTF-8</param-value>
    </init-param>
  </servlet>
  <servlet-mapping>
      <servlet-name>stuServlet</servlet-name>
      <url-pattern>/stu</url-pattern>
  </servlet-mapping>

5.3 创建index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title>主页面</title>
</head>
<body>
    <a href="stu?action=list">查询学生信息</a>
</body>
</html>

5.4 创建StudentList.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import = "java.util.*,com.kaka.entity.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title>显示学生信息清单</title>
</head>
<body>
    <h2>显示学生信息清单</h2>
    <div>
        <a href = "addStudent.jsp">添加学生信息</a>
        <table>
            <tr><td>ID</td><td>NAME</td><td>SEX</td><td>AGE</td>
            <%
                if(request.getAttribute("stus")!=null){
                    List<Student> li = (List<Student>)request.getAttribute("stus");
                for(int i = 0; i < li.size(); i++){
                    Student student = li.get(i);
            %>
            <tr>
                <td><%=student.getId() %></td>
                <td><%=student.getName() %>
                <td><%=student.getSex() %></td>
                <td><%=student.getAge() %></td>
                <td>
                    <a href = "stu?action=findOne&id=<%=student.getId()%>">修改</a>&nbsp;
                    <a href = "stu?action=delete&id=<%=student.getId()%>">删除</a>
                </td>
            </tr>
            <%
                }
            }
            %>
        </table>
    </div>
</body>
</html>

5.5 创建addStudent.jsp

  • 在添加表单中需要含有action的隐藏域
  • < input type="hidden" name="action" value="add" / >
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title>添加学生信息</title>
</head>
<body>
    <h1>添加学生信息</h1>
    <form action="stu" method = "POST">
    <input type = "hidden" name = "action" value = "add"/>
    ID:<input type="text" name="id"/><br/>
    NAME:<input type = "text" name = "name"/><br/>
    SEX:<input type = "text" name = "sex"/><br/>
    AGE:<input type = "text" name = "age"/><br/>
        <input type = "submit" value = "add"/><br/>    
    </form>
</body>
</html>

5.6 创建updateStudent.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import = "com.kaka.entity.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gbk">
<title>修改信息界面</title>
</head>
<body>
    <h1>修改界面</h1>
    <%
        Student s = (Student)request.getAttribute("student");
        if(s!=null){
    %>
    <form action="stu" method="POST">
    <input type = "hidden" name = "action" value = "update"/>
    ID:<input type="text" name="id" value="<%=s.getId()%>" readonly="true"/><br/>
    NAME:<input type = "text" name = "name" value="<%=s.getName()%>"/><br/>
    SEX:<input type = "text" name = "sex" value="<%=s.getSex()%>"/><br/>
    AGE:<input type = "text" name = "age" value="<%=s.getAge()%>"/><br/>
        <input type = "submit" value = "update"/><br/>    
    </form>
    <%}else{
        out.print("修改的对象不存在!!!");
    }
    %>
</body>
</html>

5.7 创建JDBCUtil.java

package com.kaka.util;

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

public class JDBCUtil {
   
   
    //定义常量
    final static String driver = "com.mysql.jdbc.Driver";
    final static String url = "jdbc:mysql://localhost:3306/db0711?useUnicode=true&characterEncoding=utf8";
    final static String username = "root";
    final static String password = "root";

    //声明常用的对象
    protected Connection conn = null;
    protected PreparedStatement pstmt = null;
    protected ResultSet rs = null;

    //静态代码块
    static{
   
   
        try {
   
   
            Class.forName(driver);
        } catch (ClassNotFoundException e) {
   
   
            e.printStackTrace();
        }
    }

    //获取连接
    public void getConnection(){
   
   
        try {
   
   
            conn = DriverManager.getConnection(url, username, password);
        } catch (SQLException e) {
   
   
            e.printStackTrace();
        }
    }

    //关闭资源
    public void closeAll(){
   
   
        if(rs != null){
   
   
            try {
   
   
                rs.close();
            } catch (SQLException e) {
   
   
                e.printStackTrace();
            }
        }
        if(pstmt != null){
   
   
            try {
   
   
                pstmt.close();
            } catch (SQLException e) {
   
   
                e.printStackTrace();
            }
        }
        if(conn != null){
   
   
            try {
   
   
                conn.close();
            } catch (SQLException e) {
   
   
                e.printStackTrace();
            }
        }
    }
}

5.8 创建Student.java实现类

package com.kaka.entity;

public class Student {
   
   
    private int id;
    private String name;
    private String sex;
    private String age;
    public Student() {
   
   
        super();
        // TODO Auto-generated constructor stub
    }
    public Student(int id, String name, String sex, String age) {
   
   
        super();
        this.id = id;
        this.name = name;
        this.sex = sex;
        this.age = age;
    }
    @Override
    public String toString() {
   
   
        return "Student [id=" + id + ", name=" + name + ", sex=" + sex + ", age=" + age + "]";
    }
    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 getSex() {
   
   
        return sex;
    }
    public void setSex(String sex) {
   
   
        this.sex = sex;
    }
    public String getAge() {
   
   
        return age;
    }
    public void setAge(String age) {
   
   
        this.age = age;
    }
}

5.9 创建StuDao.java接口

package com.kaka.dao;
import java.util.List;
import com.kaka.entity.Student;
public interface StuDao {
   
   
    public List<Student> findAll();

    public boolean addStudent(Student student);

    public Student findOne(int id);

    public boolean updateStudent(Student student);

    public boolean deleteDeptById(int id);
}

5.10 创建StuDaoImpl.java接口实现类

package com.kaka.dao;

import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.kaka.entity.Student;
import com.kaka.util.JDBCUtil;

public class StuDaoImpl  extends JDBCUtil implements StuDao{
   
   

    @Override
    public List<Student> findAll() {
   
   
        List<Student> li = new ArrayList<Student>();
        try {
   
   
            String sql = "SELECT * FROM STUDENT";
            super.getConnection();
            super.pstmt = super.conn.prepareStatement(sql);
            rs = pstmt.executeQuery();
            while(rs.next()){
   
   
                Student stu = new Student();
                stu.setId(rs.getInt("id"));
                stu.setName(rs.getString("name"));
                stu.setSex(rs.getString("sex"));
                stu.setAge(rs.getString("age"));
                li.add(stu);
            }
            return li;
        } catch (SQLException e) {
   
   
            e.printStackTrace();
        }finally{
   
   
            super.closeAll();
        }
        return null;
    }

    @Override
    public boolean addStudent(Student student) {
   
   
        try {
   
   
            String sql = "INSERT INTO STUDENT(id,name,sex,age) VALUES(?,?,?,?)";
            super.getConnection();
            super.pstmt = super.conn.prepareStatement(sql);
            pstmt.setInt(1, student.getId());
            pstmt.setString(2, student.getName());
            pstmt.setString(3, student.getSex());
            pstmt.setString(4, student.getAge());
            int i = pstmt.executeUpdate();
            if(i > -1){
   
   
                return true;
            }
        } catch (SQLException e) {
   
   
            e.printStackTrace();
        }finally{
   
   
            super.closeAll();
        }
        return false;
    }

    @Override
    public Student findOne(int id) {
   
   
        try {
   
   
            String sql = "SELECT * FROM STUDENT WHERE ID=?";
            super.getConnection();
            pstmt = conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            rs = pstmt.executeQuery();
            Student student = new Student();
            if(rs.next()){
   
   
                student.setId(rs.getInt("id"));
                student.setName(rs.getString("name"));
                student.setSex(rs.getString("sex"));
                student.setAge(rs.getString("age"));
            }
            return student;
        } catch (SQLException e) {
   
   
            e.printStackTrace();
        }finally{
   
   
            super.closeAll();
        }
        return null;
    }

    @Override
    public boolean updateStudent(Student student) {
   
   
        try {
   
   
            String sql = "UPDATE STUDENT SET name=?,sex=?,age=? WHERE id=?";
            super.getConnection();
            super.pstmt = super.conn.prepareStatement(sql);
            pstmt.setString(1, student.getName());
            pstmt.setString(2, student.getSex());
            pstmt.setString(3, student.getAge());
            pstmt.setInt(4, student.getId());
            int i = pstmt.executeUpdate();
            if(i > -1){
   
   
                return true;
            }
        } catch (SQLException e) {
   
   
            e.printStackTrace();
        }finally{
   
   
            super.closeAll();
        }
        return false;
    }

    @Override
    public boolean deleteDeptById(int id) {
   
   
        try {
   
   
            String sql = "DELETE FROM STUDENT WHERE ID=?";
            super.getConnection();
            super.pstmt = super.conn.prepareStatement(sql);
            pstmt.setInt(1, id);
            int i = pstmt.executeUpdate();
            if(i > -1){
   
   
                return true;
            }
        } catch (SQLException e) {
   
   
            e.printStackTrace();
        }finally{
   
   
            super.closeAll();
        }
        return false;
    }
}

5.11 创建StuServlet.java

package com.kaka.controller;

import java.io.IOException;
import java.util.List;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.kaka.dao.StuDao;
import com.kaka.dao.StuDaoImpl;
import com.kaka.entity.Student;

public class StuServlet extends HttpServlet{
   
   
    private final static String oldEncoding = "ISO-8859-1";
    private  static String newEncoding = null;
    public StuServlet() {
   
   
        super();

    }

    @Override
    public void destroy() {
   
   
        super.destroy();
    }

    @Override
    public void init(ServletConfig config) throws ServletException {
   
   
        newEncoding = config.getInitParameter("encoding");
    }

    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
   
   
        //获取操作类型
        String action = request.getParameter("action");

        //根据操作类型执行特定操作
        if("list".equals(action)){
   
   
            //获取StuDao对象
            StuDao studao = new StuDaoImpl();

            //调用dao中的findAll方法
            List<Student> all = studao.findAll();

            //将查询结果放入request作用域中
            request.setAttribute("stus", all);

            //请求转向到列表显示页面
            request.getRequestDispatcher("studentList.jsp").forward(request, response);
        }else if("add".equals(action)){
   
   
            //获取表单数据
            int id = Integer.parseInt(request.getParameter("id")==null?"0":request.getParameter("id"));
            String name = request.getParameter("name");
            //转码
            String newName = new String(name.getBytes(oldEncoding),newEncoding);
            String sex = request.getParameter("sex");
            String newSex = new String(sex.getBytes(oldEncoding),newEncoding);
            String age = request.getParameter("age");
            String newAge = new String(age.getBytes(oldEncoding),newEncoding);

            //封装实体对象
            Student student = new Student(id,newName,newSex,newAge);
            //创建dao对象
            StuDao studao = new StuDaoImpl();
            boolean b = studao.addStudent(student);
            if(b){
   
   
                //使用重定向
                response.sendRedirect("stu?action=list");
                //request.getRequestDispatcher("stu?action=list").forward(request, response);
            }
        }else if("findOne".equals(action)){
   
   
                int id = Integer.parseInt(request.getParameter("id")==null?"0":request.getParameter("id"));
                //创建dao对象
                StuDao studao = new StuDaoImpl();
                //根据ID查找
                Student student = studao.findOne(id);
                //将需要修改的对象放入request作用域中
                request.setAttribute("student", student);
                //请求转向到编辑页面
                request.getRequestDispatcher("updateStudent.jsp").forward(request, response);
        }else if("update".equals(action)){
   
   
            //获取表单数据
            int id = Integer.parseInt(request.getParameter("id")==null?"0":request.getParameter("id"));
            String name = request.getParameter("name");
            String sex = request.getParameter("sex");
            String age = request.getParameter("age");
            //转码
            String newName = new String(name.getBytes(oldEncoding),newEncoding);
            String newSex = new String(sex.getBytes(oldEncoding),newEncoding);
            String newAge = new String(age.getBytes(oldEncoding),newEncoding);
            //封装实体对象
            Student student = new Student(id,newName,newSex,newAge);
            //创建dao对象
            StuDao studao = new StuDaoImpl();
            boolean b = studao.updateStudent(student);
            if(b){
   
   
                //使用重定向
                response.sendRedirect("stu?action=list");
                //request.getRequestDispatcher("stu?action=list").forward(request, response);
            }
        }else if("delete".equals(action)){
   
   
            //获取需要删除的对象id
             int id = Integer.parseInt(request.getParameter("id")==null?"0":request.getParameter("id"));
            //创建dao对象
            StuDao studao = new StuDaoImpl();
            boolean  b = studao.deleteDeptById(id);
             if(b){
   
   
                 //使用重定向
                 response.sendRedirect("stu?action=list");
             }
        }
    }
}

5.12 运行结果

显示清单页面----->全查
图片.png

图片.png

目录
相关文章
|
1月前
Servlet使用适配器模式进行增删改查案例(IDeptService.java)
Servlet使用适配器模式进行增删改查案例(IDeptService.java)
17 0
|
1月前
Servlet使用适配器模式进行增删改查案例(EmpDaoImpl.java)
Servlet使用适配器模式进行增删改查案例(EmpDaoImpl.java)
15 0
|
1月前
Servlet使用适配器模式进行增删改查案例(IEmpService.java)
Servlet使用适配器模式进行增删改查案例(IEmpService.java)
18 0
|
2天前
|
Java 关系型数据库 MySQL
servlet+jsp+jdbc 实现增删改查 的同学录
servlet+jsp+jdbc 实现增删改查 的同学录
|
1月前
使用ueditor实现多图片上传案例——Servlet层(UploadServlet)
使用ueditor实现多图片上传案例——Servlet层(UploadServlet)
19 0
|
1月前
Servlet使用适配器模式进行增删改查案例(BaseServiceImplTest.java)
Servlet使用适配器模式进行增删改查案例(BaseServiceImplTest.java)
12 0
|
1月前
Servlet使用适配器模式进行增删改查案例(EmpServiceImpl.java)
Servlet使用适配器模式进行增删改查案例(EmpServiceImpl.java)
12 0
|
1月前
Servlet使用适配器模式进行增删改查案例(DeptServiceImpl.java)
Servlet使用适配器模式进行增删改查案例(DeptServiceImpl.java)
12 0
|
1月前
|
Java
学院管理系统【JSP+Servlet+JavaBean】(Java课设)
学院管理系统【JSP+Servlet+JavaBean】(Java课设)
44 3
学院管理系统【JSP+Servlet+JavaBean】(Java课设)
|
1月前
|
Java
排课系统【JSP+Servlet+JavaBean】(Java课设)
排课系统【JSP+Servlet+JavaBean】(Java课设)
36 5


http://www.vxiaotou.com