一篇彻底搞懂jsp

一篇彻底搞懂jsp 770 阅读 0 评论 0 点赞

一篇彻底搞懂jsp

jsp

page指令

使用此属性，可以定义一个jsp页面的相关属性

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

设置该页面的类型为text/html类型，其中编码为Unicode 类型的UTF-8 语言为java

从Tomcat安装目录中可以找到可以使用的MIME类型

<mime-mapping>
 <extension>ait</extension>
 <mime-type>application/vnd.dvb.ait</mime-type>
</mime-mapping>

错误页设置

设置page指令的errorPage属性，设置错误页

<%--
 Created by IntelliJ IDEA.
 User: ming
 Date: 19-3-6
 Time: 下午9:29
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="application/vnd.dvb.ait;charset=UTF-8" language="java" %>
<%@ page errorPage="error.jsp" %>
<html>
 <head>
 <title>$Title$</title>
 </head>
 <body>
 <%
 // 运行错误
 int result = 10 / 0;
 %>
 </body>
</html>

设置如果出现错误，跳转到error.jsp文件

> 错误页的跳转属于服务器端跳转

数据库连接操作

maven安装驱动

访问网址

https://search.maven.org/artifact/mysql/mysql-connector-java/8.0.15/jar

输入依赖

<dependency>
 <groupId>mysql</groupId>
 <artifactId>mysql-connector-java</artifactId>
 <version>8.0.15</version>
</dependency>

jsp书写代码，并网页展示

<%@ page import="java.sql.*" %>
<html>
<body>
<h2>Hello World!</h2>
<%!
 // 数据库驱动程序
 public static final String DBDRIVER = "com.mysql.cj.jdbc.Driver";
 // 数据库连接地址
 public static final String DBURL = "jdbc:mysql://47.94.95.84:32786/test";
 // 用户名
 public static final String DBUSER = "root";
 // 密码
 public static final String DBPASS = "ABCcba20170607";
%>
<%
 // 声明数据库连接对象
 Connection connection = null;
 // 连接
 PreparedStatement preparedStatement = null;
 // 结果集
 ResultSet resultSet = null;
 String sql = "SELECT * from emp";
%>
<%
 try{
 Class.forName(DBDRIVER);
 // 数据库连接
 connection = DriverManager.getConnection(DBURL, DBUSER, DBPASS);
 // 实例化sql
 preparedStatement = connection.prepareStatement(sql);
 // 查询
 resultSet = preparedStatement.executeQuery();
 while(resultSet.next()){
 int empon = resultSet.getInt(1);
 String ename = resultSet.getString(2);
 String job = resultSet.getString(3);
 %>
 <%=empon%>
 <%=ename%>
 <%=job%>
 <%
 }
 }catch (Exception e){
 System.out.println(e);
 }finally {
 resultSet.close();
 preparedStatement.close();
 connection.close();
 }
%>
</body>
</html>

包含指令

网页分为头尾中

静态包含

在jsp编译的时候插入一个包含文本或代码的文件。包含过程为静态的,代码文件包含，生成一个完整的jsp文件，再次包含生成class文件，加载进入容器。

<html>
<body>
 <%@include file="info.html"%>
 <%@include file="info.inc"%>
</body>
</html>

动态包含

<%--
 Created by IntelliJ IDEA.
 User: ming
 Date: 19-3-9
 Time: 下午3:43
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
参数1<%=request.getParameter("name")%>
参数2<%=request.getParameter("info")%>

<%--
 Created by IntelliJ IDEA.
 User: ming
 Date: 19-3-9
 Time: 下午4:51
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
 <title>Title</title>
</head>
<body>
 <%
 String username = "LiHua";
 %>
 <h1>动态传递参数</h1>
 <jsp:include page="./receive_param.jsp">
 <jsp:param name="name" value="<%=username%>"/>
 <jsp:param name="info" value="ming"/>
 </jsp:include>
</body>
</html>

运行以后可以发现显示出结果

> 两种包含，静态包含是先包含，后处理，动态包含为先处理后包含

跳转指令

此跳转为服务端跳转

即一个request传递到另外一个page

<%--
 Created by IntelliJ IDEA.
 User: ming
 Date: 19-3-9
 Time: 下午5:14
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<h1>这是跳转后的页面</h1>
<h2><%=request.getParameter("name")%></h2>
<h2><%=request.getParameter("info")%></h2>

<%--
 Created by IntelliJ IDEA.
 User: ming
 Date: 19-3-9
 Time: 下午5:11
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%
 String username = "LiHua";
%>
<jsp:forward page="forward_demo02.jsp">
 <jsp:param name="name" value="<%=username%>"/>
 <jsp:param name="info" value="ming"/>
</jsp:forward>

jsp 实栗 jsp + jdbc 实现登录

实现思路

一个表单页，输入用户登录和密码，然后信息提交到jsp页面进行验证，如果可以服务器跳转到登录成功页，失败，跳转到错误页

> 跳转的时候窗口的URL地址会发生变化

代码如下

编写登录代码

<!DOCTYPE html>
<html lang="zh_CN">
<head>
 <meta charset="UTF-8">
 <title>登录</title>
</head>
<body>
 <h1>登录操作</h1>
 <form action="login_check.jsp" method="post">
 <h1>用户登录</h1>
 <p>
 登录id
 <input type="text" name="id"/>
 </p>
 <p>
 登录密码
 <input type="password" name="password"/>
 </p>
 <input type="submit" value="登录"/>
 <input type="reset" value="重置"/>
 </form>
</body>
</html>

登录处理

<%@ page import="java.sql.*" %>
<%--
 Created by IntelliJ IDEA.
 User: ming
 Date: 19-3-9
 Time: 下午5:50
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
 <title>Title</title>
</head>
<body>
<%!
 // 数据库驱动程序
 public static final String DBDRIVER = "com.mysql.cj.jdbc.Driver";
 // 数据库连接地址
 public static final String DBURL = "jdbc:mysql://47.94.95.84:32786/test";
 // 用户名
 public static final String DBUSER = "root";
 // 密码
 public static final String DBPASS = "ABCcba20170607";
%>
<%
 // 连接对象
 Connection connection = null;
 // 操作
 PreparedStatement preparedStatement = null;
 // 结果
 ResultSet resultSet = null;
 // 标志位
 boolean falge = false;
 // 用户真实姓名
 String name = null;
%>
<%
 try{
 Class.forName(DBDRIVER);
 // 获得连接
 connection = DriverManager.getConnection(DBURL, DBUSER, DBPASS);
 // 编写sql验证ID 密码
 String sql = "SELECT name FROM user WHERE userid = ? AND password = ?";
 // 实例化操作对象
 preparedStatement = connection.prepareStatement(sql);
 // 设置查询内容
 preparedStatement.setString(1, request.getParameter("id"));
 preparedStatement.setString(2, request.getParameter("password"));
 // 执行查询
 resultSet = preparedStatement.executeQuery();
 // 如果可以查询到，表示合法用户
 if(resultSet.next()){
 name = resultSet.getString(1);
 // 修改标志位
 falge = true;
 }
 }catch (Exception e){
 e.printStackTrace();
 }finally {
 try{
 resultSet.close();
 preparedStatement.close();
 connection.close();
 }catch (Exception e){
 e.printStackTrace();
 }
 }
%>
<%
 // 登录成功
 if(falge){
 // 进行服务器端跳转
%>
 <jsp:forward page="./login_sucess.jsp">
 <jsp:param name="uname" value="<%=name%>"/>
 </jsp:forward>
<%
 }else{
%>
 <jsp:forward page="./login_failure.html"/>
<% 
 }
%>
</body>
</html>

登录完成

<%--
 Created by IntelliJ IDEA.
 User: ming
 Date: 19-3-9
 Time: 下午10:22
 To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
 <title>Title</title>
</head>
<body>
<h1>登录成功</h1>
<%=request.getParameter("uname")%>
</body>
</html>

登录失败

<%-- Created by IntelliJ IDEA. User: ming Date: 19-3-9 Time: 下午10:22 To change this template use File | Settings | File Templates.--%><%@ page contentType="text/html;charset=UTF-8" language="java" %><html><head> <title>Title</title></head><body><h1>登录成功</h1><%=request.getParameter("uname")%></body></html>

效果演示