MVC-結合Servlet和JSP實現查詢功能
阿新 • • 發佈：2019-01-02
使用MVC的思想，結合Servlet和JSP進行做查詢操作
- 實體類Hero
package bean; public class Hero { public int id; public String name; public float hp; public int damage; 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 float getHp() { return hp; } public void setHp(float hp) { this.hp = hp; } public int getDamage() { return damage; } public void setDamage(int damage) { this.damage = damage; } } - HeroDAO
使用在前面教程中用到的HeroDAO用於從資料庫查詢資料package dao; import java.sql.Connection; import java.sql.DriverManager; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.ArrayList; import java.util.List; import bean.Hero; public class HeroDAO { public HeroDAO() { try { Class.forName("com.mysql.jdbc.Driver"); } catch (ClassNotFoundException e) { e.printStackTrace(); } } public Connection getConnection() throws SQLException { return DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/how2java?characterEncoding=UTF-8", "root", "admin"); } public int getTotal() { int total = 0; try (Connection c = getConnection(); Statement s = c.createStatement();) { String sql = "select count(*) from hero"; ResultSet rs = s.executeQuery(sql); while (rs.next()) { total = rs.getInt(1); } System.out.println("total:" + total); } catch (SQLException e) { e.printStackTrace(); } return total; } public void add(Hero hero) { String sql = "insert into hero values(null,?,?,?)"; try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) { ps.setString(1, hero.name); ps.setFloat(2, hero.hp); ps.setInt(3, hero.damage); ps.execute(); ResultSet rs = ps.getGeneratedKeys(); if (rs.next()) { int id = rs.getInt(1); hero.id = id; } } catch (SQLException e) { e.printStackTrace(); } } public void update(Hero hero) { String sql = "update hero set name= ?, hp = ? , damage = ? where id = ?"; try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) { ps.setString(1, hero.name); ps.setFloat(2, hero.hp); ps.setInt(3, hero.damage); ps.setInt(4, hero.id); ps.execute(); } catch (SQLException e) { e.printStackTrace(); } } public void delete(int id) { try (Connection c = getConnection(); Statement s = c.createStatement();) { String sql = "delete from hero where id = " + id; s.execute(sql); } catch (SQLException e) { e.printStackTrace(); } } public Hero get(int id) { Hero hero = null; try (Connection c = getConnection(); Statement s = c.createStatement();) { String sql = "select * from hero where id = " + id; ResultSet rs = s.executeQuery(sql); if (rs.next()) { hero = new Hero(); String name = rs.getString(2); float hp = rs.getFloat("hp"); int damage = rs.getInt(4); hero.name = name; hero.hp = hp; hero.damage = damage; hero.id = id; } } catch (SQLException e) { e.printStackTrace(); } return hero; } public List<Hero> list() { return list(0, Short.MAX_VALUE); } public List<Hero> list(int start, int count) { List<Hero> heros = new ArrayList<Hero>(); String sql = "select * from hero order by id desc limit ?,? "; try (Connection c = getConnection(); PreparedStatement ps = c.prepareStatement(sql);) { ps.setInt(1, start); ps.setInt(2, count); ResultSet rs = ps.executeQuery(); while (rs.next()) { Hero hero = new Hero(); int id = rs.getInt(1); String name = rs.getString(2); float hp = rs.getFloat("hp"); int damage = rs.getInt(4); hero.id = id; hero.name = name; hero.hp = hp; hero.damage = damage; heros.add(hero); } } catch (SQLException e) { e.printStackTrace(); } return heros; } } - HeroListServlet
作為控制器的HeroListServlet，其作用就是通過dao獲取所有的heros物件，然後放在request中，跳轉到listHero.jsppackage servlet; import java.io.IOException; import java.util.List; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import bean.Hero; import dao.HeroDAO; public class HeroListServlet extends HttpServlet { protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { List<Hero> heros = new HeroDAO().list(); request.setAttribute("heros", heros); request.getRequestDispatcher("listHero.jsp").forward(request, response); } } - web.xml
<web-app> <servlet> <servlet-name>HeroListServlet</servlet-name> <servlet-class>servlet.HeroListServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>HeroListServlet</servlet-name> <url-pattern>/listHero</url-pattern> </servlet-mapping> </web-app> - listHero.jsp
作為檢視的listHero.jsp，其作用就是把控制器傳過來的資料顯示出來
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" import="java.util.*"%> <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%> <table align='center' border='1' cellspacing='0'> <tr> <td>id</td> <td>name</td> <td>hp</td> <td>damage</td> <td>edit</td> <td>delete</td> </tr> <c:forEach items="${heros}" var="hero" varStatus="st"> <tr> <td>${hero.id}</td> <td>${hero.name}</td> <td>${hero.hp}</td> <td>${hero.damage}</td> <td><a href="editHero?id=${hero.id}">edit</a></td> <td><a href="deleteHero?id=${hero.id}">delete</a></td> </tr> </c:forEach> </table>