JSP的基础使用及应用案例

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本文深入讲解JSP基础知识，涵盖页面格式、隐式对象、数据交互、注释与输出语法，以及通过案例演示JSP处理表单数据、调用Java类、遍历集合和实现数据库查询的过程。

JSP的基础使用及应用案例

引言：

本文主要分享了有关JSP的相关知识，包括：JSP页面的格式、九个隐式对象、JSP三个页面的交互、JSP注释、输出语法、编译指令（导包、include）、JSP中调用类对象、遍历集合、使用JSP实现从数据库中拿到数据然后输出；

1. JSP开发_引入

文件后缀.jsp
文件首行编译指令
<%@ page language=“java” contentType=“text/html; charset=UTF-8”
pageEncoding=“UTF-8”%>
jsp： java server page 服务器端页面

2. JSP的九个隐式对象

JSP中编译执行时默认会产生9个隐式对象：

2.1 Request ：请求对象

javax.servlet.http.HttpServletRequest 类的实例，获取客户端请求信息，主要用于接受http协议传送到服务器的数据,当页面请求到web容器时，JSP引擎对请求数据信息封装成request

常用方法：

request.getParameter(“表单属性名称”)：获取表单参数，返回值String；
request.setAttribute(“key”,“value”)：设定请求转发对象；
Object obj = request.getAttribute(“key”)：获取请求转发对象;
request.getRequestDispatcher(“去往页面”).forward(request,response)：页面请求转发;

2.2 Response：响应对象

javax.servlet.http.HttpServletResponse类的实例，代表客户端的响应，当服务器创建request对象时会同时创建用于响应这个客户端的response对象，主要用于将jsp容器处理过的对象传送到客户端；

服务器响应客户端时对外发出的信息统一封装成reponse对象，随request同时创建；

2.3 out对象

响应输出为输出对象，可以把字符型打印到浏览器，打印流（PrintWriter），用来在response对象中写入内容；

2.4 session对象

javax.servlet.http.HttpSession 类的实例，代表浏览器的一次回话，用来跟踪在各个客户端请求间的会话；

有多次请求组成，有生命周期在tomcat的server.xml中设定默认25‘或30’

同一设备同一浏览器发出多次请求，属于同一session；
同一设备，不同浏览器发出多次请求，为不同session；
不同设备发出请求属于不同session
session超时就终止
服务关闭，session清空

2.5 application对象

application对象直接包装了servlet的ServletContext类的对象，是javax.servlet.ServletContext 类的实例，代表当前的web应用类似于一个全局变量；

全局作用域，随服务器启动创建，随服务器关闭消亡；

2.6 config对象

javax.servlet.ServletConfig 类的实例，包装了servlet的ServletConfig类的对象，可以获取服务器的配置信息；

2.7 pageContext对象

javax.servlet.jsp.PageContext 类的实例，页面的上下文对象，可以从中获取到当前页面的其他信息，可以从中获取到其他8个隐含对象；

2.8 Page对象

指的是当前jsp对应的servlet对象的引用

2.9 exception对象

用来处理jsp文件在执行时所产生的错误和异常

3. GET和POST传输方式

get请求地址或链接请求参数会坠在请求url中，有大小限制2k大小；

post：邮寄无大小限制；

4. JSP案例（输入界面—>JSP处理—>展示界面）

4.1 输入界面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

<title>提交页面</title> 
<style type="text/css">
html{
	heigth: 100%;
}
body{
	heigth:100%;
	margin:0px;
	background-image : url("img/back.jpg");
	background-size : cover;
}
#center{
	width: 100%;
	padding-top: 40px;
	display: flex;
	align-items: center;
	justify-content: center;
	color: red;
}
#center input{
	margin-top: 5px;
	width: 300px;
	height: 35px;
	border: 1px solid gray;
	border-radius: 3px;
}
#submit input{
	align-items: center;
	justify-content: center;
	margin-top: 5px;
	width: 150px;
	height: 35px;
	margin-left:900px;
}
</style>
</head>
<body>
	<div>
	<form action="dispose.jsp" method = "POST">
		<font size="7" color="black" face="华文行楷" ><h1><center>提交信息</center></h1></font>
	<div id = "center">
		<table >
			<tr>
				<td >成员姓名</td>
				<td>
					<input type = "text" name = "stuname" placeholder="输入姓名！！！"/>
				</td>
			</tr>
			<tr>
				<td>年&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;龄</td>
				<td>
					<input type = "text" name = "age" placeholder="输入年龄！！！"/>
				</td>
			</tr>
			<tr>
				<td>毕业院校</td>
				<td>
					<input type = "text" name = "school" placeholder="输入院校！！！"/>
				</td>
			</tr>
			<tr>
				<td>所学专业</td>
				<td>
					<input type = "text" name = "specialty" placeholder="输入专业！！！"/>
				</td>
			</tr>
			<tr>
				<td>目前住址</td>
				<td>
					<input type = "text" name = "address" placeholder="输入地址！！！"/>
				</td>
			</tr>
			<tr>
				<td>联系电话</td>
				<td>
					<input type = "text" name = "phone" placeholder="输入电话！！！"/>
				</td>
			</tr>
		</table>
	</div>
	
	<div id = "submit">		
		<table >
			<tr>
				<td colspan="2">
					<input type = "submit" value = "提交"/>
				</td>
			</tr>
		</table>
	</div>
	</form>
</div>
</body>
</html>

4.2 JSP处理操作

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%
	//请求转化
	request.setCharacterEncoding("UTF-8");
	response.setContentType("text/html;charset=utf-8");
	//接收表单请求参数
	String stuname = request.getParameter("stuname");
	int age = Integer.parseInt(request.getParameter("age"));
	String school = request.getParameter("school");
	String specialty = request.getParameter("specialty");
	String address = request.getParameter("address");
	String phone = request.getParameter("phone");
	
	//业务处理
	System.out.println("stuname:" + stuname +"age:" + age + "school:" + school + "specialty:" + specialty + "address:" + address + "phone:" + phone);
	
	//显示成功页面
	RequestDispatcher rd = request.getRequestDispatcher("show.jsp");
	
	//请求转发
	rd.forward(request, response);
%>

4.3 展示界面

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>展示页面</title>
<style type="text/css">
html{
	heigth: 100%;
}
body{
	heigth:100%;
	margin:0px;
	background-image : url("img/1.jpg");
	background-size : cover;
}
#center{
	width: 100%;
	padding-top: 40px;
	display: flex;
	align-items: center;
	justify-content: center;
	color: black;
	font-fimaly:"楷体";
	font-size: 50px;
	font-style: oblique;
	font-weight: bolder;
}
</style>
</head>
<body>
	<div>
		<font size="7" color="black" face="华文行楷" ><h1><center>展示页面</center></h1></font>
		<div id = "center">
		<table >
			<tr>
				<td>
					<%
						out.write("学员姓名："+request.getParameter("stuname") + "</br>");
						out.write("学员年龄："+request.getParameter("age") + "</br>");
						out.write("毕业院校："+request.getParameter("school") + "</br>");
						out.write("所学专业："+request.getParameter("specialty") + "</br>");
						out.write("现住地址："+request.getParameter("address") + "</br>");
						out.write("电话号码："+request.getParameter("phone") + "</br>");
					%> 
				</td>
			</tr>
		</table>
	</div>
	</div>
</body>
</html>

4.4 运行结果

在这里插入图片描述

5. JSP相关语法及知识

5.1 JSP注释

HTML注释：

< !-- xxxx-- > ：可以发送到浏览器中；

JSP注释：

<%–xxxxxx–%>：只能存在于jsp中，不会随网页发往浏览器；

    <!-- HTML注释，浏览器可见 -->
    <%--Java注释,浏览器不可见 --%>

5.2 JSP中的输出语法

输出到java控制台 System.out.XXX() 原生的java语法
out输出：输出到响应流中
- <% out.print(“xxxx”)%>
表达式输出
- <%=java表达式%>

5.2.1 home.html页面传入数据

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Person info...</title>
<style>
body{
	text-align: center;
}
</style>
</head>
<script>
function fasong(){
	alert("fasong....");
	var form1 = window.document.getElementById("form1");
	form1.submit();
}
</script>
<body>
	<h2>欢迎你!!!</h2>
	<form action="dealPerson.jsp" method="GET" id = "form1">
	<table align = "center">
		<tr><td align =  "right">personName:</td><td><input type = "text" name = "name"/></td></tr>
		<tr><td align =  "right">age:</td><td><input type = "text" name = "age"/></td></tr>
		<tr><td align =  "right">sex:</td>
		<td>
		<input type = "radio" name = "sex" value = "man"/>男
		<input type = "radio" name = "sex" value = "woman"/>女
		</td></tr>
		<tr><td colspan =  "2"><input type = "button" value = "发送" onclick = "fasong()"/></td></tr>
	</table>
	</form>
</body>
</html>

5.2.2 Java输出以及Out输出

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%
	//获取表单提交的内容
	String name = request.getParameter("name");
	String ageStr = request.getParameter("age");
	String sex = request.getParameter("sex");
	int age = Integer.parseInt(ageStr);
	//Java输出
	System.out.println(name + "\t" + age +"\t" +sex);
	out.print("<html><head><title>使用Java书写HTML</title></head>");
	out.print("<body>");
    out.print("<h2>");
    out.print(name+" "+age+" "+sex);
    out.print("</h2>");
    out.print("</body></html>");
%>

5.2.3 表达式输出

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>使用Java书写HTML</title>
</head>
<body>
	<h2>
	<% 
		//获取表单提交的属性数据
		String name = request.getParameter("name");
		String ageStr = request.getParameter("age");
		String sex = request.getParameter("sex");
		int age = Integer.parseInt(ageStr);
	%>
	<%--JSP表达式：必须等号开始，不能带有分号 --%>
	name:<%=request.getParameter("name") %><br/>
	age:<%=request.getParameter("age") %><br/>
	sex:<%=request.getParameter("sex") %><br/>
	</h2>
</body>
</html>

5.3 JSP常见的编译指令

5.3.1 page

import属性（导包）：

方法1： <%@ page language=“java” contentType=“text/html; charset=UTF-8”
import=“java.util.,java.text.” pageEncoding=“UTF-8”%>
方法2：<%@page import =“java.text.*” %>

<!-- 打印当前系统时间-->
<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import="java.util.*"%>
 <%@page import = "java.text.*" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<%
	Date date = new Date();
	SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
	String dateStr = sdf.format(date);
	%>
	<%=dateStr %>
</body>
</html>

5.3.2 include

语法：<%@include file=“xxx.jsp”%>

作用：将页面通用部分单独作为一个页，可以重复利用便于修改；

5.3.2.1 页头

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<h2>页头</h2>
	<span align = "right"></span>
</body>
</html>

5.3.2.2页脚

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<h2>页脚</h2>
</body>
</html>

5.3.2.3 main.jsp_添加页头页脚

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<%@include file = "header.jsp" %>
	<h2>main content......</h2>
	<%@include file = "footer.jsp" %>
</body>
</html>

5.3.2.4 list.jsp_复用页头页脚

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	 <%@include file="header.jsp" %>
  	<h2>我是商品列表清单</h2>
  	 <%@include file="footer.jsp" %>
</body>
</html>

5.4 JSP中调用Java类对象

步骤：

导包
创建对象
调用方法

5.4.1 编写Person类

package com.kaka.entity;

public class Person {
	private int pid;
	private String pname;
	private int age;
	private String address;
	public Person() {
		super();
	}
	public Person(int pid, String pname, int age, String address) {
		super();
		this.pid = pid;
		this.pname = pname;
		this.age = age;
		this.address = address;
	}
	@Override
	public String toString() {
		return "Person [pid=" + pid + ", pname=" + pname + ", age=" + age + ", address=" + address + "]";
	}
	public int getPid() {
		return pid;
	}
	public void setPid(int pid) {
		this.pid = pid;
	}
	public String getPname() {
		return pname;
	}
	public void setPname(String pname) {
		this.pname = pname;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getAddress() {
		return address;
	}
	public void setAddress(String address) {
		this.address = address;
	}
}

5.4.2 编写entityUse,jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import="com.kaka.entity.Person"%>
<%
//jsp中使用java对象-实体应用
	Person person = new Person();
	person.setPid(1001);
	person.setPname("kaka");
	person.setAge(23);
	person.setAddress("陕西省西安市");
	
	//将person对象放入request作用域中
	request.setAttribute("person", person);
	request.getRequestDispatcher("success.jsp").forward(request, response);
%>

5.4.3 编写success,jsp

<%@ page language="java" import="com.kaka.entity.Person" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
  if( request.getAttribute("person")!=null){
	  Person per = (Person) request.getAttribute("person");  
	  out.write(per.toString());
  }
%>
</body>
</html>

5.4.4 运行结果

在这里插入图片描述

5.5 JSP中如何遍历Java集合对象

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import = "com.kaka.entity.Person,java.util.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<%
	//jsp中遍历对象对象应用
	List<Person> li = new ArrayList<Person>();
	li.add(new Person(1001,"kaka",23,"西安"));
	li.add(new Person(1002,"zhangsan",23,"武汉"));
	li.add(new Person(1003,"lisi",23,"北京"));
	li.add(new Person(1004,"wangwu",23,"西安"));
%>

	<table>
	   <tr>
	  	 <th>id</th>
	  	 <th>name</th>
	  	 <th>age</th>
	  	 <th>address</th>
	   </tr>
	   <%for(int i=0;i<li.size();i++) {
	      Person p = (Person) li.get(i);
	   %>
	   <tr>
	     <td><%=p.getPid() %></td> 
	     <td><%=p.getPname() %></td>
	     <td><%=p.getAge() %></td>
	     <td><%=p.getAddress() %></td>
	   </tr>
	   <%} %>
	</table>
</body>
</html>

遍历结果

在这里插入图片描述

5.6 JSP实现数据库查找功能

利用JDBC从数据库中拿到数据，在通过JSP页面显示出来

5.6.1 编写Dept.java类

package com.kaka.entity;

public class Dept {
	private int id;
	private String name;
	private String sex;
	private String age;
	public Dept() {
		super();
	}
	public Dept(int id, String name, String sex, String age) {
		super();
		this.id = id;
		this.name = name;
		this.sex = sex;
		this.age = age;
	}
	@Override
	public String toString() {
		return "Dept [id=" + id + ", name=" + name + ", sex=" + sex + ", age=" + age + "]";
	}
	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 String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public String getAge() {
		return age;
	}
	public void setAge(String age) {
		this.age = age;
	}
}

5.6.2 编写BaseDao.javaJDBC工具类

package com.kaka.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class BaseDao {
	//定义常量
	final static String driver = "com.mysql.jdbc.Driver";
	final static String url = "jdbc:mysql://localhost:3306/db0711?useUnicode=true&characterEncoding=utf8";
	final static String username = "root";
	final static String password = "root";
	//声明常用的对象
	protected Connection conn = null;
	protected PreparedStatement pstmt = null;
	protected ResultSet rs = null;
	//静态块
	static{
		try {
			Class.forName(driver);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
	}
	
	//获取连接
	public void getConnection(){
		try {
			conn = DriverManager.getConnection(url,username,password);
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
	}
	//关闭资源
	public void closeAll(){
		if(rs != null){
			try {
				rs.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if(pstmt != null){
			try {
				pstmt.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
		if(conn != null){
			try {
				conn.close();
			} catch (SQLException e) {
				e.printStackTrace();
			}
		}
	}
}

5.6.3 编写接口类DeptDao.java

package com.kaka.dao;
import java.util.List;
import com.kaka.entity.Dept;
public interface DeptDao {
	public List<Dept> findAll();
}

5.6.4 编写接口实现类DeptDaoImpl.java

package com.kaka.dao.impl;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import com.kaka.dao.DeptDao;
import com.kaka.entity.Dept;
import com.kaka.util.BaseDao;

public class DeptDaoImpl extends BaseDao implements DeptDao{

	@Override
	public List<Dept> findAll() {
		String sql = "select * from student";
		List<Dept> li = new ArrayList<Dept>();
		try {
			super.getConnection();
			pstmt = conn.prepareStatement(sql);
			rs = pstmt.executeQuery();
			while(rs.next()){
				Dept d = new Dept();
				d.setId(rs.getInt("id"));
				d.setName(rs.getString("name"));
				d.setSex(rs.getString("sex"));
				d.setAge(rs.getString("age"));
				li.add(d);
			}
			return li;
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			super.closeAll();
		}
		return null;
	}
}

5.6.5 编写showDept.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8" import="java.util.*,com.kaka.entity.*,com.kaka.dao.*,com.kaka.dao.impl.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
	<table>
		<tr>
			<td>ID</td><td>NAME</td><td>SEX</td><td>AGE</td>
		</tr>
		<%
			DeptDao deptDao = new DeptDaoImpl();
			List<Dept> depts = deptDao.findAll();
			for(int i = 0; i < depts.size(); i++){
				Dept d = depts.get(i);
		%>
		<tr>
		<td><%=d.getId() %></td>
		<td><%=d.getName() %></td>
		<td><%=d.getAge() %></td>
		<td><%=d.getSex() %></td>
		<td><a href = "#">编辑</a><a href = "#">删除</a></td>
		</tr>
		<%}%>
	</table>
</body>
</html>