java web 入门实例servlet篇（显示后台数据库列表，删除某一条记录并显示）

时间：2021-02-17 09:24:24

编写过程中需要注意的问题：

1.建立eclipse动态web工程时，需要改写编译后class文件的位置，通常情况下是这个位置：/WebContent/WEB-INF/classes

2.配置的页面链接和servlet类之间有两种方式：

1）通过在web.xml文件中进行配置：示例如下

<?xml version="1.0" encoding="UTF-8"?>

<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">

  <display-name>jspshow1</display-name>

  <servlet>

   <servlet-name>listTheStudent</servlet-name>

   <servlet-class>com.guodiantong.javaweb.ListTheStudent</servlet-class>

  </servlet>

  <servlet-mapping>

  <servlet-name>listTheStudent</servlet-name>

  <url-pattern>/list</url-pattern>

  </servlet-mapping>

  <servlet>

  <servlet-name>deleteTheStudent</servlet-name>

  <servlet-class>com.guodiantong.javaweb.DeleteServlet</servlet-class>

  </servlet>

  <servlet-mapping>

  <servlet-name>deleteTheStudent</servlet-name>

  <url-pattern>/delete</url-pattern>

  </servlet-mapping>

</web-app>

2）通过在eclipse新建servlet时，自动指示设置页面请求和servlet类之间的链接关系：如下图所示

new--->servlet

java web 入门实例servlet篇（显示后台数据库列表，删除某一条记录并显示）

这种也能实现请求和对应的servlet类之间的映射，通过这种方式你会发下，tomcat使用的注解的方式@WebServlet，这种方式在web.xml文件中并没有通过 1）的那种方式显现出来

谈完上述注意的地方，下面开始见工程：先看下项目的目录结构

java web 入门实例servlet篇（显示后台数据库列表，删除某一条记录并显示）

先看下所有的jsp文件：test.jsp文件

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"

    pageEncoding="ISO-8859-1"%>

<!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=ISO-8859-1">

<title>Insert title here</title>

</head>

<body>

<a href="list">list all students</a>

</body>

</html>

　　students.jsp文件：

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

    pageEncoding="UTF-8"%>

    <%@ page import="java.util.List" %>

<%@page import="com.guodiantong.javaweb.*" %>

<!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=ISO-8859-1">

<title>Insert title here</title>

</head>

<body>

<%=request.getAttribute("students") %>

<br>

<%

  List<Student> stus=(List<Student>)request.getAttribute("students");

%>

<table>

<tr>

  <th>flowid</th>

  <th>type</th>

  <th>id_card</th>

  <th>exam_card</th>

  <th>studentname</th>

  <th>location</th>

  <th>grade</th>

  <th>操作</th>

  <%

      for(Student student:stus){

   %>

	<tr>

	   <td><%=student.getFlowid() %></td>

	   <td><%=student.getType() %></td>

	   <td><%=student.getIdcard() %></td>

	   <td><%=student.getExam_card() %></td>

	   <td><%=student.getStudentname() %></td>

	   <td><%=student.getLocation() %></td>

	   <td><%=student.getGrade() %></td>

	   <td><a href="delete?flowid=<%=student.getFlowid() %>">删除</a></td>

	</tr>  

<%

    }

%>

</table>

</body>

</html>

success.jsp文件：

<%@ 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=ISO-8859-1">

<title>Insert title here</title>

</head>

<body>

  操作成功！！

  <a href="list">refresh</a>

</body>

</html>

　　下面是servlet类的代码：List请求对应的servlet类：ListTheStudent.java

package com.guodiantong.javaweb;

import java.io.IOException;

import java.util.ArrayList;

import java.util.List;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ListTheStudent extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        List<Student> students=new ArrayList<Student>();

        StudentDao studentDao=new StudentDao();

        students=studentDao.getAll();

        request.setAttribute("students", students);

        request.getRequestDispatcher("/students.jsp").forward(request, response);

    }

}

delete请求对应的jservlet  java类：DeleteServlet.java

package com.guodiantong.javaweb;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class DeleteServlet extends HttpServlet {

    @Override

    protected void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

    String flowid=request.getParameter("flowid");

    StudentDao studentDao=new StudentDao();

    studentDao.deleteStudent(flowid);

    request.getRequestDispatcher("/success.jsp").forward(request, response);

    }

}

项目中最重要的StudentDao.java

package com.guodiantong.javaweb;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;

public class StudentDao {

public   List<Student>  getAll(){

    Connection connection=null;

    PreparedStatement preparedStatement=null;

    ResultSet resultSet=null;

    List<Student> students=new ArrayList<Student>();

   try {

       String driverClass="com.mysql.jdbc.Driver";

       String url="jdbc:mysql:///dsm";

       String user="root";

       String password="12345678";

       Class.forName(driverClass);

    connection=DriverManager.getConnection(url, user, password);

    String sql="SELECT flow_id,Type,id_card,exam_card,student_name,location,grade "

            +"FROM examstudent";

    preparedStatement=connection.prepareStatement(sql);

    resultSet=preparedStatement.executeQuery();

    while(resultSet.next()){

        String flowid=resultSet.getString(1);

        System.out.println(flowid);

        String type=resultSet.getString(2);

        String idcard=resultSet.getString(3);

        String exam_card=resultSet.getString(4);

        String studentname=resultSet.getString(5);

        String location=resultSet.getString(6);

        String grade=resultSet.getString(7);

        Student student=new Student(flowid, type, idcard, exam_card,

                studentname, location, grade);

        students.add(student);

    }

} catch (Exception e) {

    e.printStackTrace();

}finally{

    try {

        if(resultSet !=null){

            resultSet.close();

        }

    } catch (SQLException e) {

        // TODO Auto-generated catch block

        e.printStackTrace();

    }

    try {

        if(preparedStatement !=null){

            preparedStatement.close();

        }

    } catch (SQLException e) {

        // TODO Auto-generated catch block

        e.printStackTrace();

    }

    try {

        if(connection !=null){

            connection.close();

        }

    } catch (SQLException e) {

        // TODO Auto-generated catch block

        e.printStackTrace();

    }

}

    return students;

}

public   void  deleteStudent(String flowid){

    Connection connection=null;

    PreparedStatement preparedStatement=null;

   try {

       String driverClass="com.mysql.jdbc.Driver";

       String url="jdbc:mysql:///dsm";

       String user="root";

       String password="12345678";

       Class.forName(driverClass);

    connection=DriverManager.getConnection(url, user, password);

    String sql="DELETE FROM examstudent where flow_id=?";

    preparedStatement=connection.prepareStatement(sql);

    preparedStatement.setString(1, flowid);

    preparedStatement.execute();

} catch (Exception e) {

    e.printStackTrace();

}finally{

    try {

        if(preparedStatement !=null){

            preparedStatement.close();

        }

    } catch (SQLException e) {

        // TODO Auto-generated catch block

        e.printStackTrace();

    }

    try {

        if(connection !=null){

            connection.close();

        }

    } catch (SQLException e) {

        // TODO Auto-generated catch block

        e.printStackTrace();

    }

}

}

}

项目中的javabean  ：Student.java

package com.guodiantong.javaweb;

public class Student {

private String flowid;

private String type;

private String idcard;

private String exam_card;

private String studentname;

private String location;

private String grade;

public String getFlowid() {

    return flowid;

}

public void setFlowid(String flowid) {

    this.flowid = flowid;

}

public String getType() {

    return type;

}

public void setType(String type) {

    this.type = type;

}

public String getIdcard() {

    return idcard;

}

public void setIdcard(String idcard) {

    this.idcard = idcard;

}

public String getExam_card() {

    return exam_card;

}

public void setExam_card(String exam_card) {

    this.exam_card = exam_card;

}

public String getStudentname() {

    return studentname;

}

public void setStudentname(String studentname) {

    this.studentname = studentname;

}

public String getLocation() {

    return location;

}

public void setLocation(String location) {

    this.location = location;

}

public String getGrade() {

    return grade;

}

public void setGrade(String grade) {

    this.grade = grade;

}

public Student() {

    super();

}

public Student(String flowid, String type, String idcard, String exam_card,

        String studentname, String location, String grade) {

    super();

    this.flowid = flowid;

    this.type = type;

    this.idcard = idcard;

    this.exam_card = exam_card;

    this.studentname = studentname;

    this.location = location;

    this.grade = grade;

}

@Override

public String toString() {

    return "Student [flowid=" + flowid + ", type=" + type + ", idcard="

            + idcard + ", exam_card=" + exam_card + ", studentname="

            + studentname + ", location=" + location + ", grade=" + grade + "]";

}

}

提到javabean就需要看一下后台数据表格的结构：

java web 入门实例servlet篇（显示后台数据库列表，删除某一条记录并显示）

就是这些！！

　　

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