花了几天的时间,终于实现了这些操作。利用博客来梳理下自己关于javaweb的知识点。
1:test01文件夹(里面有所需的页面资源),我完成的是在里面添加增删改查操作
2:myeclipse(版本没什么要求) eclipse也行
3:数据库 MySQL
4:需要了解到的知识点:
servlet
EL与JSTL表达式
项目的基本框架搭建(javaweb经典三层框架)
5:在myeclipse中建立对应的包结构
所谓三层框架分别为表述层(WEB层)、业务逻辑层()、数据访问层()。
关系:web层依赖业务层 业务层依赖数据层(这个关系很重要)
ps:除了以上三层框架是我们在写一个javaweb项目必须的外,还需要一个实体类(entity)。
需要在MySQL中创建所需数据库,并将表建好。
1、数据库名为db_examsystem。
2、项目信息表名为tb_subject,表结构见表1,其中subjectID为自增长主键,增量为1。
表1 试题信息表(tb_subject)
3、在表tb_subject中插入记录,见表2。
表2试题信息表中的数据
在dao下新建一个DBConn类用来处理对数据进行连接。 这是MySQL的连接方式
package dao;
import java.sql.*;
public class DBConn {
static Connection conn = null;
//连接数据库,返回Connection conn;
public static Connection getConn () {
String driverClassName = "com.mysql.jdbc.Driver";
String url = "jdbc:mysql://localhost:3306/db_examsystem";
String username = "root";
String password = "123";
try {
Class.forName(driverClassName);
conn = DriverManager.getConnection(url, username, password);
} catch (Exception e) {
e.printStackTrace();
}
return conn;
}
}
在entity包下创建Subject实体类(实体类中的对象对应数据库表中的字段数据)
package entity;
public class Subject {
private int subjectID;
private String subjectTitle;
private String subjectOptionA;
private String subjectOptionB;
private String subjectOptionC;
private String subjectOptionD;
private String subjectAnswer;
private String subjectParse;
public int getSubjectID() {
return subjectID;
}
public void setSubjectID(int subjectID) {
this.subjectID = subjectID;
}
public String getSubjectTitle() {
return subjectTitle;
}
public void setSubjectTitle(String subjectTitle) {
this.subjectTitle = subjectTitle;
}
public String getSubjectOptionA() {
return subjectOptionA;
}
public void setSubjectOptionA(String subjectOptionA) {
this.subjectOptionA = subjectOptionA;
}
public String getSubjectOptionB() {
return subjectOptionB;
}
public void setSubjectOptionB(String subjectOptionB) {
this.subjectOptionB = subjectOptionB;
}
public String getSubjectOptionC() {
return subjectOptionC;
}
public void setSubjectOptionC(String subjectOptionC) {
this.subjectOptionC = subjectOptionC;
}
public String getSubjectOptionD() {
return subjectOptionD;
}
public void setSubjectOptionD(String subjectOptionD) {
this.subjectOptionD = subjectOptionD;
}
public String getSubjectAnswer() {
return subjectAnswer;
}
public void setSubjectAnswer(String subjectAnswer) {
this.subjectAnswer = subjectAnswer;
}
public String getSubjectParse() {
return subjectParse;
}
public void setSubjectParse(String subjectParse) {
this.subjectParse = subjectParse;
}
}
创建方法类,这里有两种方法
1:在dao包中创建一个StudentDao接口,里面写增删改查的方法,再在dao中创建StudentDaoImpl类来实现接口,并实现之中的方法。
StudentDao接口:
package dao;
import java.util.List;
import entity.Subject;
public interface SubjectDao {
/*
* 1.添加数据
* 2.查看数据,返回信息
* 3.修改
* 4.删除
*
* */
public boolean add(Subject subject);
public List selectall();
public boolean update(String subjectTitle,String subjectOptionA,String subjectOptionB,
String subjectOptionC,String subjectOptionD,String subjectAnswer,String subjectParse);
public boolean delete(int subjectID);
public List selectByID(String string);
}
StudentDaoImpl类(包含增删改查操作):
package dao;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.mysql.jdbc.Connection;
import entity.Subject;
public class SubjectDaoImpl implements SubjectDao {
Connection conn = (Connection) DBConn.getConn();
@Override
public boolean add(Subject subject) {
boolean flag = false;
try {
String sql="insert tb_subject values('"+subject.getSubjectID()+"','"
+subject.getSubjectTitle()+"','"
+subject.getSubjectOptionA()+"','"
+subject.getSubjectOptionB()+"','"
+subject.getSubjectOptionC()+"','"
+subject.getSubjectOptionD()+"','"
+subject.getSubjectAnswer()+"','"
+subject.getSubjectParse()+"')";
PreparedStatement pstmt = conn.prepareStatement(sql);
int i = pstmt.executeUpdate();
pstmt.close();
conn.close();
if(i>0) {
flag = true;
}
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}
@Override
public List selectall() {
List list = new ArrayList();
try {
String sql = "select * from tb_subject";
PreparedStatement pstmt = conn.prepareStatement(sql);
ResultSet rs = pstmt.executeQuery();
while(rs.next()) {
Subject subject = new Subject();
subject.setSubjectID(rs.getInt("subjectID"));
subject.setSubjectTitle(rs.getString("subjectTitle"));
subject.setSubjectOptionA(rs.getString("subjectOptionA"));
subject.setSubjectOptionB(rs.getString("subjectOptionB"));
subject.setSubjectOptionC(rs.getString("subjectOptionC"));
subject.setSubjectOptionD(rs.getString("subjectOptionD"));
subject.setSubjectAnswer(rs.getString("subjectAnswer"));
subject.setSubjectParse(rs.getString("subjectParse"));
list.add(subject);
}
rs.close();
pstmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
return list;
}
@Override
public List selectByID(String subjectID) {
List list = new ArrayList();
try {
String sql = "select * from tb_subject where subjectID=?";
PreparedStatement pstmt = conn.prepareStatement(sql);
pstmt.setString(1,subjectID );
ResultSet rs = pstmt.executeQuery();
while(rs.next()) {
Subject subject = new Subject();
subject.setSubjectID(rs.getInt("subjectID"));
subject.setSubjectTitle(rs.getString("subjectTitle"));
subject.setSubjectOptionA(rs.getString("subjectOptionA"));
subject.setSubjectOptionB(rs.getString("subjectOptionB"));
subject.setSubjectOptionC(rs.getString("subjectOptionC"));
subject.setSubjectOptionD(rs.getString("subjectOptionD"));
subject.setSubjectAnswer(rs.getString("subjectAnswer"));
subject.setSubjectParse(rs.getString("subjectParse"));
list.add(subject);
}
rs.close();
pstmt.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
return list;
}
@Override
public boolean update( String subjectTitle,
String subjectOptionA, String subjectOptionB,
String subjectOptionC, String subjectOptionD, String subjectAnswer,
String subjectParse) {
boolean flag = false;
try {
String sql = "update tb_subject set subjectOptionA = '"+subjectOptionA+"',subjectOptionB = '"+subjectOptionB+"',subjectOptionC = '"+subjectOptionC+
"',subjectOptionD = '"+subjectOptionD+"',subjectAnswer = '"+subjectAnswer+"',subjectParse = '"+subjectParse+"' where subjectTitle = '"+subjectTitle+"'";
PreparedStatement pstmt = conn.prepareStatement(sql);
int i = pstmt.executeUpdate();
pstmt.close();
conn.close();
if(i>0)flag = true;
} catch (SQLException e) {
e.printStackTrace();
}
return flag;
}
@Override
public boolean delete(int subjectID) {
boolean flag = false;
try {
String sql = "delete from tb_subject where subjectID = '"+subjectID+"'";
PreparedStatement pstmt = conn.prepareStatement(sql);
int i = pstmt.executeUpdate();
pstmt.close();
conn.close();
if(i>0) flag = true;
} catch (SQLException e) {
System.out.println("删除失败!");
e.printStackTrace();
}
return flag;
}
}
2:在service包中创建StudentService类,在dao包中创建StudentDao类来实现StudentService类中的方法。(具体操作以后更新)
六:实现servlet和对应jsp(html)页面
Servlet有两种方式创建,一种手工创建。另一种程序自动生成。前者自己创建java类,实现Servlet具体内容,然后需要去WEB_INF下的web.xml去配置servlet . 而后者则直接由程序替我们配置好了Servlet
1:增
创建SubjectAddServlet
package action;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.SQLException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.SubjectDao;
import dao.SubjectDaoImpl;
import entity.Subject;
public class SubjectServlet extends HttpServlet {
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String subjectTitle=request.getParameter("subjectTitle");
String subjectOptionA=request.getParameter("subjectOptionA");
String subjectOptionB=request.getParameter("subjectOptionB");
String subjectOptionC=request.getParameter("subjectOptionC");
String subjectOptionD=request.getParameter("subjectOptionD");
String subjectAnswer=request.getParameter("subjectAnswer");
String subjectParse=request.getParameter("subjectParse");
Subject Subject =new Subject();
Subject.setSubjectTitle(subjectTitle);
Subject.setSubjectOptionA(subjectOptionA);
Subject.setSubjectOptionB(subjectOptionB);
Subject.setSubjectOptionC(subjectOptionC);
Subject.setSubjectOptionD(subjectOptionD);
Subject.setSubjectAnswer(subjectAnswer);
Subject.setSubjectParse(subjectParse);
SubjectDao sd = new SubjectDaoImpl();
try{
sd.add(Subject);
}catch(Exception e){
System.out.println("添加失败");
e.printStackTrace();
}
}
}
注意:
ps:因为在设计数据库中我们设置的subjectID为自增长,所以这里添加数据的时候不用添加subjectID这一字段。
request.getParameterr("xxx"):getParameter表示接收参数,参数为页面提交的参数,包括:表单提交的参数、URL重写(就是xxx?id=1中的id)传的参数等,因此这个并没有设置参数的方法(没有setParameter),而且接收参数返回的不是Object,而是String类型
试题题目:
选项A:
选项B:
选项C:
选项D:
答案:
A
B
C
D
试题解析:
注意:
action=“SubjectAddServlet”为SubjectAddServlet在web.xml中的URL目录
当在servlet中完成的操作需要获取页面表单等的数据时,需要在页面中指向对应的servlet。
2:删
- 创建SubjectDeleteServlet
package action;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.SubjectDao;
import dao.SubjectDaoImpl;
import entity.Subject;
public class SubjectDeleteServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String subjejctID = (String) request.getParameter("subjectID");
int userSubjectID = Integer.parseInt(subjejctID);
SubjectDao sd = new SubjectDaoImpl();
sd.delete(userSubjectID);
}
}
注意:doGet(),doPost()
当需要获取页面中的数据时,用doPost。
当用到URL重写(就是xxx?id=1中的id)传的参数时,用doGet()。
或者是把具体方法写到doPost中,在doGet()方法中调用doPost方法。
- subjectDelete.jsp部分页面
注意:
删除页面和查询页面是公用一个页面
${list }:EL表达式 获取request域中名为list的值
页面使用的到JSTL表达式 即c标签。使用c标签需要引入头文件<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"%> 。
需要注意的的是El标签配合JSTl标签的使用, 例子forEach标签的遍历内容即为EL表达式获取的${list }
而且当指定别名后var="s" ,别名可以随便起,为了方便一般是小写类名命名。
C标签内遍历的属性也是需要用${ }获取。此时别名s即为当前集合中的Subject对象,想得到属性只需要用 ${ s.属性名 } 即可
3:改
- 创建SubjectUpdateServlet
package action;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.SubjectDao;
import dao.SubjectDaoImpl;
import entity.Subject;
public class SubjectUpdateServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
String subjectID = request.getParameter("subjectID");
String subjectTitle=request.getParameter("subjectTitle");
String subjectOptionA=request.getParameter("subjectOptionA");
String subjectOptionB=request.getParameter("subjectOptionB");
String subjectOptionC=request.getParameter("subjectOptionC");
String subjectOptionD=request.getParameter("subjectOptionD");
String subjectAnswer=request.getParameter("subjectAnswer");
String subjectParse=request.getParameter("subjectParse");
SubjectDao sd = new SubjectDaoImpl();
try{
sd.update( subjectTitle, subjectOptionA, subjectOptionB, subjectOptionC,
subjectOptionD, subjectAnswer, subjectParse);
}catch(Exception e) {
System.out.println("修改失败!");
e.printStackTrace();
}
}
}
注意:
request.getParameter("")获取页面参数
试题题目:
选项A:
选项B:
选项C:
选项D:
答案:
答案解析:
注意:
action=“SubjectUpdateServlet”为SubjectUpdateServlet在web.xml中的URL目录
当在servlet中完成的操作需要获取页面表单等的数据时,需要在页面中指向对应的servlet。
4:查
这里需要完成两个查询(查询返回列表;查询返回列表详细)
- 查询返回列表
创建SubjectListServlet:
package action;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.SubjectDao;
import dao.SubjectDaoImpl;
import entity.Subject;
public class SubjectListServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
SubjectDao sd = new SubjectDaoImpl();
List list = sd.selectall();
request.setAttribute("list", list);
request.getRequestDispatcher("/subjectList.jsp").forward(request, response);//转发到指定页面
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
注意:当不需要页面的参数时,页面由servlet引出
转发(request.getRequestDispatcher().forward();)和重定向(response.sendRedirect();)区别:
(1).重定向的执行过程:Web服务器向浏览器发送一个http响应--》浏览器接受此响应后再发送一个新的http请求到服务器--》服务器根据此请求寻找资源并发送给浏览器。它可以重定向到任意URL,不能共享request范围内的数据。
(2).重定向是在客户端发挥作用,通过新的地址实现页面转向。
(3).重定向是通过浏览器重新请求地址,在地址栏中可以显示转向后的地址。
(4).转发过程:Web服务器调用内部方法在容器内部完成请求和转发动作--》将目标资源发送给浏览器,它只能在同一个Web应用中使用,可以共享request范围内的数据。
(5).转发是在服务器端发挥作用,通过forward()方法将提交信息在多个页面间进行传递。
(6).转发是在服务器内部控制权的转移,客户端浏览器的地址栏不会显示出转向后的地址。
subjectList.jsp部分页面:
注意:
这里的顺序是,先访问的是SubjectListServlet,在转发到此页面,此页面的查看和删除又通过对应的servlet来实现对应的功能。
- 查询返回列表详细
创建SubjectShowServlet:
package action;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import dao.SubjectDao;
import dao.SubjectDaoImpl;
import entity.Subject;
public class SubjectShowServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
request.setCharacterEncoding("utf-8");
response.setContentType("text/html;charset=utf-8");
SubjectDao sd = new SubjectDaoImpl();
List list = sd.selectByID(request.getParameter("subjectID"));
request.setAttribute("list", list);
request.getRequestDispatcher("/subjectShow.jsp").forward(request, response);
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}
注意:
这个查询方法需要通过限制条件subjectID来查询,不然显示出来的是所有的数据
subjectShow.jsp部分页面
试题编号:
${u.subjectID }
试题题目:
${u.subjectTitle }
选项A:
${u.subjectOptionA }
选项B:
${u.subjectOptionB }
选项C:
${u.subjectOptionC }
选项D:
${u.subjectOptionD }
答案:
${u.subjectAnswer }
答案解析:
${u.subjectParse }
注意:
页面同样运用的是EL和jstl表达式
七:总结
在学习的道路上,一昧的看视频是没有用的,当看完一个阶段的视频后,要对该阶段写一个小项目,这样才能将视频中的知识点融会贯通。
项目源码(页面):点击打开链接
建议保留页面相关代码,servlet及jsp相关代码自己敲。