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

3. Servlet的执行流程

以第二板块的Servlet为例：

根据表单中的action属性dealLogin，与web.xml中的servlet-mapping的url-pattern匹配；
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；
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；
使用Class.forName()方法反射该类对象；
调用该类的父类的service方法；
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=UTF-8">
<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=UTF-8">
<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=UTF-8">
<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=UTF-8">
<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

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)

1. Servlet概述

2. 编写Servlet的步骤

2.1 服务器编译环境

2.2 创建一个index.html

2.3 编写一个继承自HttpServlet的类并重写service方法

2.4 配置xml

2.5 运行结果

3. Servlet的执行流程

4. Servlet与JSP的比较

5. 基于Servlt完成CRUD

5.1 创建数据库STUDENT表

5.2 xml文件的配置

5.3 创建index.jsp

5.4 创建StudentList.jsp

5.5 创建addStudent.jsp

5.6 创建updateStudent.jsp

5.7 创建JDBCUtil.java

5.8 创建Student.java实现类

5.9 创建StuDao.java接口

5.10 创建StuDaoImpl.java接口实现类

5.11 创建StuServlet.java

5.12 运行结果

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插件

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)

1. Servlet概述

2. 编写Servlet的步骤

2.1 服务器编译环境

2.2 创建一个index.html

2.3 编写一个继承自HttpServlet的类并重写service方法

2.4 配置xml

2.5 运行结果

3. Servlet的执行流程

4. Servlet与JSP的比较

5. 基于Servlt完成CRUD

5.1 创建数据库STUDENT表

5.2 xml文件的配置

5.3 创建index.jsp

5.4 创建StudentList.jsp

5.5 创建addStudent.jsp

5.6 创建updateStudent.jsp

5.7 创建JDBCUtil.java

5.8 创建Student.java实现类

5.9 创建StuDao.java接口

5.10 创建StuDaoImpl.java接口实现类

5.11 创建StuServlet.java

5.12 运行结果

热门文章

最新文章

相关课程

相关电子书