MVC实现登录,增删改查之数据展示:JSP的EL表达式(二)

2022-09-22 13:22:10

这里的数据展示利用jsp的EL表达式，后台放入session,前台EL获取

数据库设计是这样的,一个老师对应有多个学生,在学生表student中建立外键tid与老师表teacher的tid对应,现在老师登录成功以后,实现对老师下面的学生信息进行展示

从后往前写;

1建立与数据库对应的表的实体类student.java

public class Student {

        private int sid;

        private  String  sname;

        private  String sage;

        public int getSid() {

            return sid;

        }

        public void setSid(int sid) {

            this.sid = sid;

        }

        public String getSname() {

            return sname;

        }

        public void setSname(String sname) {

            this.sname = sname;

        }

        public String getSage() {

            return sage;

        }

        public void setSage(String sage) {

            this.sage = sage;

        }

        public Student() {

            super();

        }

        public Student(int sid, String sname, String sage) {

            super();

            this.sid = sid;

            this.sname = sname;

            this.sage = sage;

        }

}

2 StudentDao.java

public interface StudentDao {

    /**

     *

     * @param tid

     * @return 学生对象

     * 根据老师id返回学生对象

     */

    public  List<Student> getStudentBytid(int tid);

}

3 StudentDaoImpl.java

import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;

import java.util.ArrayList;

import java.util.List;

import JDBCUtil.JDBCUtil;

import com.zr.dao.StudentDao;

import com.zr.model.Student;

public class StudentDaoImpl  implements StudentDao{

    /**

     * 根据传入的老师id获取学生

     */

    public List<Student> getStudentBytid(int tid) {

        //定义学生对象集合students接收数据库返回

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

        //获取数据库连接

        Connection con=JDBCUtil.getConnection();

        //编写SQL语句

        StringBuffer sql=new StringBuffer("select * from student where tid=?");

        try {

            PreparedStatement pst=con.prepareStatement(sql.toString());

            pst.setInt(1, tid);

            //返回一个结果集

            ResultSet rs=pst.executeQuery();

            while (rs.next()) {

                //学生对象接收结果集的结果

                Student s=new Student();

                s.setSid(rs.getInt("sid"));

                s.setSname(rs.getString("sname"));

                s.setSage(rs.getString("sage"));

                students.add(s);

            }

        } catch (SQLException e) {

            e.printStackTrace();

        }

        return students;

    }

4 searchService.java

import java.util.List;

import com.zr.model.Student;

public interface searchService {

    /**

     * 查询服务

     * @param tid 通过老师ID

     * @return 学生对象所有信息

     */

public List<Student> getStudents(int  tid);

}

5 searchServiceImpl.java

import java.util.ArrayList;

import java.util.List;

import com.zr.dao.StudentDao;

import com.zr.daoIm.StudentDaoImpl;

import com.zr.model.Student;

import com.zr.service.searchService;

public class searchServiceImpl implements searchService{

    public List<Student> getStudents(int tid) {

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

        StudentDao studentDaoImpl =new StudentDaoImpl();

        students=    studentDaoImpl.getStudentBytid(tid);

        return students;

    }

6 SearchController.java

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;

import javax.servlet.http.HttpSession;

import com.zr.model.Student;

import com.zr.model.Teacher;

import com.zr.service.searchService;

import com.zr.serviceIm.searchServiceImpl;

public class SearchController extends HttpServlet {

    @Override

    protected void service(HttpServletRequest req, HttpServletResponse resp)

            throws ServletException, IOException {

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

        searchService sc=new searchServiceImpl();

        //获取存放在session中的teacher对象

        Teacher teacher=(Teacher) req.getSession().getAttribute("teacher");

        //获取老师ID

        int  td=   teacher.getTid();

        //根据老师id获取学生对象

        students= sc.getStudents(td);

        //将students对象放入session中,前台用EL表达式获取值

        HttpSession session= req.getSession();

        session.setAttribute("students", students);

        req.getRequestDispatcher("main.jsp").forward(req, resp);

    }

    }

7 配置web.xml文件

注意:name要在前

<!-- 查询当前下面的学生信息 -->

          <servlet>

              <servlet-name>selectStus</servlet-name>

              <servlet-class>com.zr.controller.SearchController</servlet-class>

          </servlet>

          <servlet-mapping>

                  <servlet-name>selectStus</servlet-name>

                  <url-pattern>/selectStus</url-pattern>

          </servlet-mapping>

8 mian.jsp前台页面

<body>

    <form action="selectStus">

        <input type="submit" value="查询">

    </form>

    <!-- 展示学生对象信息 -->

    <table class="table table-bordered" style="margin-top: 50px">

        <tr>

            <td>学生编号</td>

            <td>学生名</td>

            <td>学生年龄</td>

        </tr>

        <!-- 利用EL表达式 -->

        <c:forEach items="${students}" var="student" varStatus="studentIndex">

            <tr>

                <td>${student.sid}</td>

                <td>${student.sname}</td>

                <td>${student.sage}</td>

            </tr>

        </c:forEach>

    </table>

</body>

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