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Java基础入门day52

news 来源：原创 2024/7/3 13:10:27

day52

servlet

综合案例

登录功能

  • 设置欢迎页

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"version="4.0"><welcome-file-list><welcome-file>login.html</welcome-file></welcome-file-list>
</web-app>

项目启动直接加载login.html页面

  • login.html，用户输入自己的用户名和密码，提交后交给mylogin请求

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>login</title>
</head>
<body>
​
<form action="mylogin" method="post">username: <input type="text" name="username" placeholder="username"><p />password: <input type="password" name="password" placeholder="password"><p /><input type="submit" value="login"><p />
</form>
</body>
</html>

  • 由mylogin请求对应的servlet来进行处理

package com.saas.servlet;
​
import com.saas.service.IAccountService;
import com.saas.service.impl.AccountServiceImpl;
​
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
​
@WebServlet(urlPatterns = "/mylogin")
public class MyLoginServlet extends HttpServlet {
​private IAccountService ias = new AccountServiceImpl();
​@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doPost(req, resp);}
​@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("text/html");System.out.println("this is my login servlet .");
​String username = req.getParameter("username");String password = req.getParameter("password");
​
​boolean flag = ias.login(username, password);
​if (flag) {System.out.println("login success");req.getRequestDispatcher("main.html").forward(req, resp);} else {System.out.println("login fail");req.getRequestDispatcher("login.html").forward(req, resp);}}
}

  • mylogin所对用的MyLoginServlet会调用IAccountService接口和AccountServiceImpl实现类完成成service中登录方法的校验

package com.saas.service;
​
public interface IAccountService {boolean login(String username, String password);
}

  • AccountServiceImpl是service的实现类，调用dao接口和dao实现类完成dao层的登录方法校验

package com.saas.service.impl;
​
import com.saas.dao.IAccountDao;
import com.saas.dao.impl.AccountDaoImpl;
import com.saas.service.IAccountService;
​
public class AccountServiceImpl implements IAccountService {
​private IAccountDao iAccountDao = new AccountDaoImpl();@Overridepublic boolean login(String username, String password) {return iAccountDao.login(username, password);}
}

  • dao接口

package com.saas.dao;
​
public interface IAccountDao {boolean login(String username, String password);
}

  • dao实现类，使用apache的dbutil工具jar包的queryrunner对象即可完成所有的crud功能

    • 本方法完成登录功能

    • 借助DruidUtil工具类的getDataSource()方法得到一个DataSource对象来创建QueryRunner对象

package com.saas.dao.impl;
​
import com.saas.dao.IAccountDao;
import com.saas.entity.Account;
import com.saas.util.DruidUtil;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
​
import java.sql.SQLException;
​
public class AccountDaoImpl implements IAccountDao {
​private QueryRunner qr = new QueryRunner(DruidUtil.getDataSource());@Overridepublic boolean login(String username, String password) {
​try {String sql = "select * from account where name = ? and pass = ?";Account a = qr.query(sql, new BeanHandler<Account>(Account.class), new Object[]{username, password});
​return a != null;} catch (SQLException e) {throw new RuntimeException(e);}}
}

  • dao借助工具类完成与数据库的交互，得到一个用户名和密码对应的Account对象，通过Account对象是否为空判断用户是否存在

  • dao完成用户账户信息的判断后，返回给service，返回给servlet

  • 在servlet中通过返回值动态决定调转到main.html页面还是继续回到login.html页面，最终完成一个登录功能

查询所有学生

main.html页面中有一个查询所有学生的超链接

<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>main</title>
</head>
<body>
<h1>this is main page</h1>
​
<a href="stus">show all students</a>
</body>
</html>

  • 该超链接发送一个地址为stus的请求，该请求交给一个servlet: AllStudentServlet.java

package com.saas.servlet;import com.saas.entity.Student;
import com.saas.service.IStudentService;
import com.saas.service.impl.StudentServiceImpl;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;@WebServlet(urlPatterns = "/stus")
public class AllStudentServlet extends HttpServlet {private IStudentService iss = new StudentServiceImpl();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("text/html");resp.setCharacterEncoding("UTF-8");req.setCharacterEncoding("UTF-8");List<Student> list = iss.getAllStudents();System.out.println(list);PrintWriter out = resp.getWriter();out.print("<table border='1' align='center' width='80%'>");out.print("<tr>");out.print("<td>编号</td>");out.print("<td>姓名</td>");out.print("<td>性别</td>");out.print("<td>年龄</td>");out.print("<td>成绩</td>");out.print("<td>管理</td>");out.print("</tr>");for (Student s : list) {out.print("<tr>");out.print("<td>" + s.getSid() + "</td>");out.print("<td>" + s.getName() + "</td>");out.print("<td>" + s.getSex() + "</td>");out.print("<td>" + s.getAge() + "</td>");out.print("<td>" + s.getScore() + "</td>");out.print("<td><a href='GetStudentBySidServlet?sid=" + s.getSid() + "'>update</a> <a href='#'>delete</a> </td>");out.print("</tr>");}out.print("</table>");}
}

  • 该servlet借助IStudentService的service接口和StudentServiceImpl的service接口的实现类，完成全部学生信息的查询

  • service接口IStudentService.java

package com.saas.service;import com.saas.entity.Student;import java.util.List;public interface IStudentService {List<Student> getAllStudents();Student getStudentBySid(int sid);boolean updateStudent(Student student);
}

  • service接口的实现类StudentServiceImpl.java

package com.saas.service.impl;import com.saas.dao.IStudentDao;
import com.saas.dao.impl.StudentDaoImpl;
import com.saas.entity.Student;
import com.saas.service.IStudentService;import java.util.List;public class StudentServiceImpl implements IStudentService {private IStudentDao isd = new StudentDaoImpl();@Overridepublic List<Student> getAllStudents() {return isd.getAllStudents();}@Overridepublic Student getStudentBySid(int sid) {return isd.getStudentBySid(sid);}@Overridepublic boolean updateStudent(Student student) {return isd.updateStudent(student) > 0;}
}

Student的service接口调用Student的dao完成与数据库的交互，并将数据返回

package com.saas.dao;import com.saas.entity.Student;import java.util.List;public interface IStudentDao {List<Student> getAllStudents();Student getStudentBySid(int sid);int updateStudent(Student student);
}
package com.saas.dao.impl;import com.saas.dao.IStudentDao;
import com.saas.entity.Student;
import com.saas.util.DruidUtil;
import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;import java.sql.SQLException;
import java.util.List;public class StudentDaoImpl implements IStudentDao{private QueryRunner qr = new QueryRunner(DruidUtil.getDataSource());@Overridepublic List<Student> getAllStudents() {try {return qr.query("select * from student", new BeanListHandler<Student>(Student.class));} catch (SQLException e) {throw new RuntimeException(e);}}@Overridepublic Student getStudentBySid(int sid) {try {return qr.query("select * from student where sid = ?", new BeanHandler<Student>(Student.class), sid);} catch (SQLException e) {throw new RuntimeException(e);}}@Overridepublic int updateStudent(Student student) {try {return qr.update("update student set name = ?, sex = ?, score = ?, cid = ?, age = ? where sid = ? ",student.getName(), student.getSex(), student.getScore(), student.getCid(), student.getAge(), student.getSid());} catch (SQLException e) {throw new RuntimeException(e);}}
}

  • 完成所有学生信息的查询，返回给service，返回给servlet

  • 在servlet中将学生的list借助servlet在页面中以表格方式呈现

查询单个学生对象

  • 在AllStudentServlet这个servlet的表格中，每一个数据的最后放置了一个修改的超链接

  • <a href='GetStudentBySidServlet?sid=" + s.getSid() + "'>update</a>

  • 在这个超链接中，href为GetStudentBySidServlet，那么请求将交给GetStudentBySidServlet地址所对应的sevlet，该请求的最后还有一个问号传参

  • 该请求将交由GetStudentBySidServlet.java的servlet来处理

package com.saas.servlet;import com.saas.entity.Student;
import com.saas.service.IStudentService;
import com.saas.service.impl.StudentServiceImpl;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.PrintWriter;@WebServlet("/GetStudentBySidServlet")
public class GetStudentBySidServlet extends HttpServlet {private IStudentService studentService = new StudentServiceImpl();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {resp.setContentType("text/html");resp.setCharacterEncoding("UTF-8");req.setCharacterEncoding("UTF-8");System.out.println("this is update student page.");String ssid = req.getParameter("sid");int sid = ssid == null ? 0 : Integer.parseInt(ssid);Student s = studentService.getStudentBySid(sid);PrintWriter out = resp.getWriter();out.print("<h1>this is update student page.</h1>");out.print("<form action='UpdateStudentServlet' method='post'>");out.print("<input type=\"hidden\" name=\"sid\" value=\"" + s.getSid() + "\"><p />");out.print("name:<input type=\"text\" name=\"name\" value=\"" + s.getName() + "\"><p />");out.print("sex:<input type=\"text\" name=\"sex\" value=\"" + s.getSex() + "\"><p />");out.print("age:<input type=\"text\" name=\"age\" value=\"" + s.getAge() + "\"><p />");out.print("score:<input type=\"text\" name=\"score\" value=\"" + s.getScore() + "\"><p />");out.print("cid:<input type=\"text\" name=\"cid\" value=\"" + s.getCid() + "\"><p />");out.print("<input type=\"submit\" value=\"update\"><p />");out.print("</form>");}
}

  • 该servlet借助IStudentService对象的getStudentBySid方法，进行用户编号查询用户的操作

  • 该servlet同样调用service以及dao完成数据的查询，得到sid对应的学生对象

  • 得到问号传参传递过来的sid的值，将该sid对应的学生对象以表单方式呈现给用户

修改学生对象

  • 在GetStudentBySidServlet的servlet里面，由form表单将数据库中指定sid对应的学生对象呈现在页面表单中

  • 用户在该表单中修改该学生信息

  • 点击提交按钮，将发送一个新的请求，该请求是form表单中action所对应的UpdateStudentServlet的servlet

  • 所以该表单提交后交给UpdateStudentServlet这个sevlet

package com.saas.servlet;import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;import com.saas.entity.Student;
import com.saas.service.IStudentService;
import com.saas.service.impl.StudentServiceImpl;@WebServlet(urlPatterns = "/UpdateStudentServlet")
public class UpdateStudentServlet extends HttpServlet {private IStudentService istudentService = new StudentServiceImpl();@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {doPost(req, resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {req.setCharacterEncoding("utf-8");resp.setCharacterEncoding("utf-8");resp.setContentType("text/html;charset=utf-8");int sid = Integer.parseInt(req.getParameter("sid"));String name = req.getParameter("name");String sex = req.getParameter("sex");double score = Double.parseDouble(req.getParameter("score"));int cid = Integer.parseInt(req.getParameter("cid"));int age = Integer.parseInt(req.getParameter("age"));Student student = new Student(sid, name, sex, score, cid, age);boolean flag = istudentService.updateStudent(student);if (flag) {resp.getWriter().write("<script>alert('修改成功');location.href='/day51/stus'</script>");} else {resp.getWriter().write("<script>alert('修改失败');location.href='/day51/stus'</script>");}}
}

该servlet收集用户输入的所有信息，将这些所有信息封装为一个Student对象

再将Student对象借助Student的service和dao完成一个修改功能

修改成功后给用户一个修改成功的弹框并跳转到stus所对应的servlet展示最新的学生列表信息

修改失败给用户一个提示，也跳转到stus请求对应的serlvet

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