Java基础入门day57

day57

JSP、Servlet，Java bean和JDBC整合项目

index.jsp页面

<%@ page contentType="text/html; charset=UTF-8" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head><title>JSP - Hello World</title>
</head>
<body>
<h1><%= "student page!" %>
</h1>
<br/>
<a href="Stu">all student</a>
<a href="stu.jsp">save student</a>
</body>
</html>

用户点击all student超链接会请求Stu这个url所对应Servlet叫做StudentServlet

StudentServlet.java

package com.saas.servlet;

import com.saas.service.IStudentService;
import com.saas.service.impl.StudentServiceImpl;
import com.saas.entity.Student;

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.util.List;

@WebServlet(urlPatterns = "/Stu")
public class StudentServlet 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 {System.out.println("Student Servlet");
List<Student> students =iss.getAllStudents();

//        resp.getWriter().write(students.toString());
req.setAttribute("students",students);
req.getRequestDispatcher("stus.jsp").forward(req,resp);}
}

该servlet结束StudentService以及StudentDao完成数据的查询，得到Student的List数据，并将该list存放在key值为students所对应的request范围内

最后跳转到stus.jsp页面

stus.jsp

<%@ page import="com.saas.entity.Student" %>
<%@ page import="java.util.List" %><%--
Created by IntelliJ IDEA.
User: Administrator
Date: 2024/5/23
Time: 9:24
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head><title>students</title>
</head>
<body>
<h1>all students</h1>

<table border="1" width="80%" align="center"><tr><td>sid</td><td>name</td><td>sex</td><td>age</td><td>score</td><td>cid</td><td>operation</td></tr><%List<Student> students = (List<Student>) request.getAttribute("students");for (Student student : students) {%><tr><td><%=student.getSid()%></td><td><%=student.getName()%></td><td><%=student.getSex()%></td><td><%=student.getAge()%></td><td><%=student.getScore()%></td><td><%=student.getCid()%></td><td><a href="Stu?action=getStudentBySid&sid=<%=student.getSid()%>">update</a></td></tr><%}%>
</table>
</body>
</html>
在该JSP页面中通过JSP的内置对象request获取到key值为students的value所对应的Student的list数据

在该页面中使用循环对于Student类所对应的list students进行遍历

先画表格的头部

再去循环list

list中嵌套html标签，通过表格里面的tr循环所有的数据到表格中

最终将Student的所有对象的list在浏览器页面中以表格的方式呈现给用户

升级StudentServlet.java

package com.saas.servlet;

import com.saas.service.IStudentService;
import com.saas.service.impl.StudentServiceImpl;
import com.saas.entity.Student;

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.util.List;

@WebServlet(urlPatterns = "/Stu")
public class StudentServlet extends BaseServlet {
private IStudentService iss = new StudentServiceImpl();

protected void getAllStudents(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {System.out.println("Student Servlet");
List<Student> students =iss.getAllStudents();

//        resp.getWriter().write(students.toString());
req.setAttribute("students",students);
req.getRequestDispatcher("stus.jsp").forward(req,resp);}

protected void getStudentBySid(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        super.doGet(req, resp);String ssid = req.getParameter("sid");
int sid = ssid == null ? 0 : Integer.parseInt(ssid);
Student student = iss.getStudentBySid(sid);

//        resp.getWriter().write(student.toString());
req.setAttribute("student", student);
req.getRequestDispatcher("stu.jsp").forward(req, resp);}
protected void saveStudent(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {String name = req.getParameter("name");String sex = req.getParameter("sex");String sage = req.getParameter("age");int age = sage == null ? 0 : Integer.parseInt(sage);String sscore = req.getParameter("score");double score = sscore == null ? 0 : Double.parseDouble(sscore);String scid = req.getParameter("cid");int cid = scid == null ? 0 : Integer.parseInt(scid);String ssid = req.getParameter("sid");int sid = ssid == null ? 0 : Integer.parseInt(ssid);
Student s = new Student();s.setSid(sid);s.setName(name);s.setSex(sex);s.setAge(age);s.setScore(score);s.setCid(cid);boolean flag = iss.updateStudent(s);
if(flag){resp.sendRedirect("Stu?action=getAllStudents");}}
}

这个Servlet里面完成了三个功能，查询所有学生，查询单个学生和修改学生

这个类继承了我们之前反射完成的BaseServlet，可以保证整个项目中，只需要一个方法完成对于不同操作的分支处理

BaseServlet.java

package com.saas.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

public class BaseServlet extends HttpServlet {
@Overrideprotected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

//        req.setCharacterEncoding("UTF-8");
//        resp.setCharacterEncoding("UTF-8");
//        resp.setContentType("text/html;charset=UTF-8");

Class<? extends BaseServlet> clazz = getClass();
String action = req.getParameter("action");
try {Method method = clazz.getDeclaredMethod(action, HttpServletRequest.class, HttpServletResponse.class);
method.setAccessible(true);
method.invoke(this, req, resp);} catch (NoSuchMethodException e) {throw new RuntimeException(e);} catch (IllegalAccessException e) {throw new RuntimeException(e);} catch (InvocationTargetException e) {throw new RuntimeException(e);}}
}

这个Servlet中，让所有的Servlet都继承自该类，该类的service方法中动态获取传递过来的action用来交给各自Servlet中的业务方法

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 s);
}
这个业务类中只是实现了查询所有，根据id查询单个对象以及修改功能，我们可以根据自己的需要进行方法的增减

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 studentDao = new StudentDaoImpl();
@Overridepublic List<Student> getAllStudents() {return studentDao.getAllStudents();}
@Overridepublic Student getStudentBySid(int sid) {return studentDao.getStudentBySid(sid);}
@Overridepublic boolean updateStudent(Student s) {return studentDao.updateStudent(s) > 0;}
}

service接口的实现类，通过调用dao来完成自己的业务方法

IStudentDao.java

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 s);
}
dao接口中用来完成dao层的查询所有，查询单个对象，以及修改功能，我们也可以后期做增减

StudentDaoImpl.java

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 s) {try {return qr.update("update student set name = ?, age =? , sex = ?, score = ?, cid = ? where sid = ?",s.getName(), s.getAge(), s.getSex(), s.getScore(), s.getCid(), s.getSid());} catch (SQLException e) {throw new RuntimeException(e);}}
}

dao层的实现类，借助apache的dbutil工具jar包的api query runner完成dao的具体功能

Student.java

package com.saas.entity;public class Student {private int  sid;private String  name;private String  sex;private double  score;private int  cid;private int  age;@Overridepublic String toString() {return "Student{" +"sid=" + sid +", name='" + name + '\'' +", sex='" + sex + '\'' +", score=" + score +", cid=" + cid +", age=" + age +'}';}public int getSid() {return sid;}public void setSid(int sid) {this.sid = sid;}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 double getScore() {return score;}public void setScore(double score) {this.score = score;}public int getCid() {return cid;}public void setCid(int cid) {this.cid = cid;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}
}

学生的实体类

MySQL

mysql> desc student;
+-------+-------------+------+-----+---------+-------+
| Field | Type        | Null | Key | Default | Extra |
+-------+-------------+------+-----+---------+-------+
| sid   | int(11)     | YES  |     | NULL    |       |
| name  | varchar(20) | YES  |     | NULL    |       |
| sex   | char(6)     | YES  |     | NULL    |       |
| score | double      | YES  |     | NULL    |       |
| cid   | int(11)     | YES  |     | NULL    |       |
| age   | int(11)     | YES  |     | NULL    |       |
+-------+-------------+------+-----+---------+-------+
6 rows in set (0.00 sec)

数据库中student的表结构

DruidUtil.java

package com.saas.util;import com.alibaba.druid.pool.DruidDataSource;
import com.alibaba.druid.pool.DruidDataSourceFactory;import javax.sql.DataSource;public class DruidUtil {private static Env env = Env.getInstance();public static DataSource getDataSource(){try {DruidDataSource dataSource = (DruidDataSource) DruidDataSourceFactory.createDataSource(env);dataSource.setUrl(env.getProperty("url"));dataSource.setUsername(env.getProperty("user"));dataSource.setPassword(env.getProperty("pass"));dataSource.setDriverClassName(env.getProperty("driver"));return dataSource;} catch (Exception e) {throw new RuntimeException(e);}}
}

连接池工具类

Env.java

package com.saas.util;import java.io.IOException;
import java.util.Properties;public class Env extends Properties {private static final long serialVersionUID = 1L;private static Env env = new Env();private Env() {super();try {load(getClass().getResourceAsStream("/db.properties"));} catch (IOException e) {throw new RuntimeException(e);}}public static Env getInstance() {return env;}public static String get(String key) {return env.getProperty(key);}
}

单例模式动态加载db.properties文件是为了更好地实现跨平台操作

db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/saas?characterEncoding=utf-8
user=root
pass=Abc@1234

CharacterFilter.java

package com.saas.filter;import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.annotation.WebServlet;
import java.io.IOException;//@WebServlet("/*")
public class CharacterFilter implements Filter {@Overridepublic void init(FilterConfig filterConfig) throws ServletException {}@Overridepublic void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {request.setCharacterEncoding("UTF-8");response.setCharacterEncoding("UTF-8");response.setContentType("text/html;charset=UTF-8");chain.doFilter(request, response);}}

关于中文乱码的处理交给当前的过滤器来完成

web.xml

<?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"><filter><filter-name>CharacterFilter</filter-name><filter-class>com.saas.filter.CharacterFilter</filter-class></filter><filter-mapping><filter-name>CharacterFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping>
</web-app>

三个jar包支持

commons-dbutils-1.6.jar druid-1.0.28.jar mysql-connector-java-5.1.37.jar

小结：

以上功能写了三个功能，查询所有学生对象，根据sid查询单个学生对象以及修改功能

之前我们也写过，只不过今天关于serlet中编写的html代码完全交给了jsp页面，杜绝了在Servlet的java代码中编写了大量的Java代码

只要是页面标签性的东西都交给jsp去完成

只要是逻辑控制的东西都交给servlet的逻辑控制去完成