-
070_JSP详解
什么是JSP
Java Server Pages Java服务器端页面，和Servlet一样，用于动态Web技术
特点：写JSP，就像写HTML一样
与HTML的区别：
- HTML只能给用户提供静态的数据
-
JSP页面中可以嵌入Java代码，为用户提供动态数据
JSP原理
- Tomcat中有一个work目录
- IDEA中使用Tomcat会在IDEA的Tomcat中产生一个work目录
- jsp文件会转为java程序
- 浏览器向服务器发送请求，不管访问什么资源，其实都是在访问Servlet
/*
* Generated by the Jasper component of Apache Tomcat
* Version: Apache Tomcat/9.0.43
* Generated at: 2021-03-16 15:12:15 UTC
* Note: The last modified time of this file was set to
* the last modified time of the source file after
* generation to assist with modification tracking.
*/
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
public final class index_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent,
org.apache.jasper.runtime.JspSourceImports {
private static final javax.servlet.jsp.JspFactory _jspxFactory =
javax.servlet.jsp.JspFactory.getDefaultFactory();
private static java.util.Map<java.lang.String,java.lang.Long> _jspx_dependants;
private static final java.util.Set<java.lang.String> _jspx_imports_packages;
private static final java.util.Set<java.lang.String> _jspx_imports_classes;
static {
_jspx_imports_packages = new java.util.HashSet<>();
_jspx_imports_packages.add("javax.servlet");
_jspx_imports_packages.add("javax.servlet.http");
_jspx_imports_packages.add("javax.servlet.jsp");
_jspx_imports_classes = null;
}
private volatile javax.el.ExpressionFactory _el_expressionfactory;
private volatile org.apache.tomcat.InstanceManager _jsp_instancemanager;
public java.util.Map<java.lang.String,java.lang.Long> getDependants() {
return _jspx_dependants;
}
public java.util.Set<java.lang.String> getPackageImports() {
return _jspx_imports_packages;
}
public java.util.Set<java.lang.String> getClassImports() {
return _jspx_imports_classes;
}
public javax.el.ExpressionFactory _jsp_getExpressionFactory() {
if (_el_expressionfactory == null) {
synchronized (this) {
if (_el_expressionfactory == null) {
_el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
}
}
}
return _el_expressionfactory;
}
public org.apache.tomcat.InstanceManager _jsp_getInstanceManager() {
if (_jsp_instancemanager == null) {
synchronized (this) {
if (_jsp_instancemanager == null) {
_jsp_instancemanager = org.apache.jasper.runtime.InstanceManagerFactory.getInstanceManager(getServletConfig());
}
}
}
return _jsp_instancemanager;
}
public void _jspInit() {
}
public void _jspDestroy() {
}
public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
throws java.io.IOException, javax.servlet.ServletException {
if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
final java.lang.String _jspx_method = request.getMethod();
if ("OPTIONS".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
return;
}
if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 只允许 GET、POST 或 HEAD。Jasper 还允许 OPTIONS");
return;
}
}
final javax.servlet.jsp.PageContext pageContext;
javax.servlet.http.HttpSession session = null;
final javax.servlet.ServletContext application;
final javax.servlet.ServletConfig config;
javax.servlet.jsp.JspWriter out = null;
final java.lang.Object page = this;
javax.servlet.jsp.JspWriter _jspx_out = null;
javax.servlet.jsp.PageContext _jspx_page_context = null;
try {
response.setContentType("text/html");
pageContext = _jspxFactory.getPageContext(this, request, response,
null, true, 8192, true);
_jspx_page_context = pageContext;
application = pageContext.getServletContext();
config = pageContext.getServletConfig();
session = pageContext.getSession();
out = pageContext.getOut();
_jspx_out = out;
out.write("<html>\n");
out.write("<body>\n");
out.write("<h2>Hello World!</h2>\n");
out.write("</body>\n");
out.write("</html>\n");
} catch (java.lang.Throwable t) {
if (!(t instanceof javax.servlet.jsp.SkipPageException)){
out = _jspx_out;
if (out != null && out.getBufferSize() != 0)
try {
if (response.isCommitted()) {
out.flush();
} else {
out.clearBuffer();
}
} catch (java.io.IOException e) {}
if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
else throw new ServletException(t);
}
} finally {
_jspxFactory.releasePageContext(_jspx_page_context);
}
}
}
JSP源码分析
// 初始化
public void _jspInit() {
}
// 销毁
public void _jspDestroy() {
}
//JSPService
public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
throws java.io.IOException, javax.servlet.ServletException {
// 1.判断请求
if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
final java.lang.String _jspx_method = request.getMethod();
if ("OPTIONS".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
return;
}
if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 只允许 GET、POST 或 HEAD。Jasper 还允许 OPTIONS");
return;
}
}
// 2.内置对象
final javax.servlet.jsp.PageContext pageContext;// 页面上下文
javax.servlet.http.HttpSession session = null;// 会话
final javax.servlet.ServletContext application;// Servlet上下文
final javax.servlet.ServletConfig config;// config
javax.servlet.jsp.JspWriter out = null;// out
final java.lang.Object page = this;// page当前页面
javax.servlet.jsp.JspWriter _jspx_out = null;
javax.servlet.jsp.PageContext _jspx_page_context = null;
try {
// 3.输出页面前增加的代码，以下的对象可以在jsp页面中直接使用
response.setContentType("text/html");// 设置响应的页面类型
pageContext = _jspxFactory.getPageContext(this, request, response,
null, true, 8192, true);
_jspx_page_context = pageContext;
application = pageContext.getServletContext();
config = pageContext.getServletConfig();
session = pageContext.getSession();
out = pageContext.getOut();
_jspx_out = out;
// 4.输出页面
out.write("<html>\n");
out.write("<body>\n");
out.write("<h2>Hello World!</h2>\n");
out.write("</body>\n");
out.write("</html>\n");
} catch (java.lang.Throwable t) {
if (!(t instanceof javax.servlet.jsp.SkipPageException)){
out = _jspx_out;
if (out != null && out.getBufferSize() != 0)
try {
if (response.isCommitted()) {
out.flush();
} else {
out.clearBuffer();
}
} catch (java.io.IOException e) {}
if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
else throw new ServletException(t);
}
} finally {
_jspxFactory.releasePageContext(_jspx_page_context);
}
}
JSP流程图
JSP页面转java代码
- 页面中的java代码，会直接应用到java代码中
-
页面中的HTML代码，会转换为
out.write("<html>");，输出到页面
JSP基础语法
示例
创建maven-archetype-webapp项目
替换web.xml为最新版本
<?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"
metadata-complete="true">
</web-app>
查询https://mvnrepository.com，添加依赖到pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.qing</groupId>
<artifactId>javaweb-jsp</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<maven.compiler.source>1.7</maven.compiler.source>
<maven.compiler.target>1.7</maven.compiler.target>
</properties>
<dependencies>
<!--Servlet依赖-->
<!-- https://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
<dependency>
<groupId>javax.servlet</groupId>
<artifactId>javax.servlet-api</artifactId>
<version>4.0.1</version>
</dependency>
<!--JSP依赖-->
<!-- https://mvnrepository.com/artifact/javax.servlet.jsp/javax.servlet.jsp-api -->
<dependency>
<groupId>javax.servlet.jsp</groupId>
<artifactId>javax.servlet.jsp-api</artifactId>
<version>2.3.3</version>
</dependency>
<!--JSTL表达式依赖-->
<!-- https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl-api -->
<dependency>
<groupId>javax.servlet.jsp.jstl</groupId>
<artifactId>jstl-api</artifactId>
<version>1.2</version>
</dependency>
<!--standard标签库-->
<!-- https://mvnrepository.com/artifact/taglibs/standard -->
<dependency>
<groupId>taglibs</groupId>
<artifactId>standard</artifactId>
<version>1.1.2</version>
</dependency>
</dependencies>
</project>
配置Tomcat
JSP基础语法
JSP作为java技术的一种应用，它拥有一些自己扩充的语法，java所有语法都支持。
JSP表达式
<%--JSP表达式
作用：用来将程序的输出，输出到客户端
语法：<%= 变量或者表达式 %>
--%>
<%=new java.util.Date()%>
<hr>
<%=2*3%>
JSP脚本
<%--JSP脚本
作用：用来写java方法内代码
语法：<% java方法类代码 %>
--%>
<%
int sum = 0;
for (int i = 1; i <= 100; i++) {
sum += i;
}
out.println("<h1>sum=" + sum + "</h1>");
%>
<%--在代码中嵌入HTML--%>
<%
for (int i = 0; i < 5; i++) {
%>
<h1>hello,world <%=i%></h1>
<%
}
%>
JSP文件生成的java文件
public void _jspService(final javax.servlet.http.HttpServletRequest request, final javax.servlet.http.HttpServletResponse response)
throws java.io.IOException, javax.servlet.ServletException {
if (!javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
final java.lang.String _jspx_method = request.getMethod();
if ("OPTIONS".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
return;
}
if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method)) {
response.setHeader("Allow","GET, HEAD, POST, OPTIONS");
response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSP 只允许 GET、POST 或 HEAD。Jasper 还允许 OPTIONS");
return;
}
}
final javax.servlet.jsp.PageContext pageContext;
javax.servlet.http.HttpSession session = null;
final javax.servlet.ServletContext application;
final javax.servlet.ServletConfig config;
javax.servlet.jsp.JspWriter out = null;
final java.lang.Object page = this;
javax.servlet.jsp.JspWriter _jspx_out = null;
javax.servlet.jsp.PageContext _jspx_page_context = null;
try {
response.setContentType("text/html");
pageContext = _jspxFactory.getPageContext(this, request, response,
null, true, 8192, true);
_jspx_page_context = pageContext;
application = pageContext.getServletContext();
config = pageContext.getServletConfig();
session = pageContext.getSession();
out = pageContext.getOut();
_jspx_out = out;
out.write("<html>\n");
out.write("<body>\n");
out.write('\n');
out.print(new java.util.Date());
out.write("\n");
out.write("<hr>\n");
out.print(2*3);
out.write("\n");
out.write("<hr>\n");
out.write('\n');
int sum = 0;
for (int i = 1; i <= 100; i++) {
sum += i;
}
out.println("<h1>sum=" + sum + "</h1>");
out.write('\n');
out.write('\n');
for (int i = 0; i < 5; i++) {
out.write("\n");
out.write("<h1>hello,world ");
out.print(i);
out.write("</h1>\n");
}
out.write("\n");
out.write("</body>\n");
out.write("</html>\n");
} catch (java.lang.Throwable t) {
if (!(t instanceof javax.servlet.jsp.SkipPageException)){
out = _jspx_out;
if (out != null && out.getBufferSize() != 0)
try {
if (response.isCommitted()) {
out.flush();
} else {
out.clearBuffer();
}
} catch (java.io.IOException e) {}
if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
else throw new ServletException(t);
}
} finally {
_jspxFactory.releasePageContext(_jspx_page_context);
}
}
JSP声明
<%--JSP声明
作用：用来写java类内代码
语法：<%! java类内代码 %>
--%>
<%!
static {
System.out.println("静态代码块");
}
private int globalVal = 0;
public void test() {
System.out.println(globalVal);
}
%>
生成的java代码
static {
System.out.println("静态代码块");
}
private int globalVal = 0;
public void test() {
System.out.println(globalVal);
}
区别：JSP声明会被编译到JSP生成的java类中，JSP表达式和JSP声明则会被编译到JSP生成的_jspService方法中
JSP指令
page 定义网页属性
<%--导包--%>
<%@ page import="java.util.Date" %>
<%--定制错误页面，错误时跳转到自定义错误页面--%>
<%@ page errorPage="error/500.jsp" %>
<%--显式声明这是一个错误页面--%>
<%@ page isErrorPage="true" %>
<%--定义页面编码--%>
<%@ page pageEncoding="utf-8" %>
include 包含其他页面
<%--jsp指令--%>
<%--引入公用头部--%>
<%@ include file="common/header.jsp"%>
<h1>网页主体</h1>
<%--引入公用底部--%>
<%@ include file="common/footer.jsp"%>
<%--两者的区别：
jsp指令，会将两个页面合并到本页面
jsp标签，拼接页面，本质还是三个页面
jsp标签比较常用，注：jsp标签路径加/，代表web根目录
--%>
<%--jsp标签--%>
<%--引入公用头部--%>
<jsp:include page="/common/header.jsp"/>
<h1>网页主体</h1>
<%--引入公用底部--%>
<jsp:include page="/common/footer.jsp"/>
taglib 引入标签库
9大内置对象
- javax.servlet.http.HttpServletRequest request
- javax.servlet.http.HttpServletResponse response
- javax.servlet.ServletException exception
- javax.servlet.jsp.PageContext pageContext
- javax.servlet.http.HttpSession session
- javax.servlet.ServletContext application
- javax.servlet.ServletConfig config
- javax.servlet.jsp.JspWriter out
- java.lang.Object page = this
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>Title</title>
</head>
<body>
<%--内置对象--%>
<%
pageContext.setAttribute("name1", "1号");// 保存的数据在一个页面有效
request.setAttribute("name2", "2号");// 保存的数据在一个请求有效，请求转发会携带这个数据
session.setAttribute("name3", "3号");// 保存的数据在一个回话有效，从打开浏览器到关闭浏览器
application.setAttribute("name4", "4号");// 保存的数据在服务器中有效，从启动服务器到关闭服务器
%>
<%--脚本片段中的代码会原封不动的生成到jsp.java，所以jsp脚本中的代码遵守java语法，注释也用java注释--%>
<%
// 从pageContext中取值，通过寻找的方式来，从底层到高层（作用域）：pageContext<request<session<application
String name1 = (String) pageContext.findAttribute("name1");
String name2 = (String) pageContext.findAttribute("name2");
String name3 = (String) pageContext.findAttribute("name3");
String name4 = (String) pageContext.findAttribute("name4");
String name5 = (String) pageContext.findAttribute("name5");
%>
<%--使用JSP表达式和EL表达式输出的区别：针对没有的数据，JSP表达式会输出null，EL表达式不会输出--%>
<h1>JSP表达式输出值</h1>
<h3><%=name1%></h3>
<h3><%=name2%></h3>
<h3><%=name3%></h3>
<h3><%=name4%></h3>
<h3><%=name5%></h3>
<hr>
<h1>EL表达式输出值</h1>
<h3>${name1}</h3>
<h3>${name2}</h3>
<h3>${name3}</h3>
<h3>${name4}</h3>
<h3>${name5}</h3>
</body>
</html>
JSP标签、JSTL标签、EL表达式
需要依赖的包
<!--JSTL表达式依赖-->
<!-- https://mvnrepository.com/artifact/javax.servlet.jsp.jstl/jstl-api -->
<dependency>
<groupId>javax.servlet.jsp.jstl</groupId>
<artifactId>jstl-api</artifactId>
<version>1.2</version>
</dependency>
<!--standard标签库-->
<!-- https://mvnrepository.com/artifact/taglibs/standard -->
<dependency>
<groupId>taglibs</groupId>
<artifactId>standard</artifactId>
<version>1.1.2</version>
</dependency>
JSP标签
<%--包含页面--%>
<jsp:include page="header.jsp"></jsp:include>
<%--请求转发--%>
<jsp:forward page="500.jsp">
<jsp:param name="id" value="1"></jsp:param>
<jsp:param name="name" value="张三丰"></jsp:param>
</jsp:forward>
JSTL标签
https://www.runoob.com/jsp/jsp-jstl.html
JSTL标签库的使用是为了弥补HTML标签的不足，它自定义了许多标签，可以供我们使用，标签的功能和java代码一样。
安装使用步骤
- Tomcat安装JSTL标签库
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.4"
xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<jsp-config>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/fmt</taglib-uri>
<taglib-location>/WEB-INF/fmt.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/fmt-rt</taglib-uri>
<taglib-location>/WEB-INF/fmt-rt.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/core</taglib-uri>
<taglib-location>/WEB-INF/c.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/core-rt</taglib-uri>
<taglib-location>/WEB-INF/c-rt.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/sql</taglib-uri>
<taglib-location>/WEB-INF/sql.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/sql-rt</taglib-uri>
<taglib-location>/WEB-INF/sql-rt.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/x</taglib-uri>
<taglib-location>/WEB-INF/x.tld</taglib-location>
</taglib>
<taglib>
<taglib-uri>http://java.sun.com/jsp/jstl/x-rt</taglib-uri>
<taglib-location>/WEB-INF/x-rt.tld</taglib-location>
</taglib>
</jsp-config>
</web-app>
-
使用任何库，必须在每个 JSP 文件中的头部包含
标签。
核心标签
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
格式化标签
<%@ taglib prefix="fmt" uri="http://java.sun.com/jsp/jstl/fmt" %>
SQL 标签
<%@ taglib prefix="sql" uri="http://java.sun.com/jsp/jstl/sql" %>
XML 标签
<%@ taglib prefix="x" uri="http://java.sun.com/jsp/jstl/xml" %>
JSTL 函数
<%@ taglib prefix="fn" uri="http://java.sun.com/jsp/jstl/functions" %>
EL表达式
获取数据
执行运算
获取web开发的常用对象
JavaBean-实体类
JavaBean有特定的写法
- 必须有一个无参构造，如果没有有参构造，无参构造隐式默认有
- 属性必须私有化private
- 必须有对应的get/set方法
一般用来和数据库的字段做映射
ORM-对象关系映射
- 表-->类
- 字段-->属性
- 行记录-->对象
原文：https://www.cnblogs.com/wl3pb/p/14646758.html
最新更新
nodejs爬虫
Python正则表达式完全指南
爬取豆瓣Top250图书数据
shp 地图文件批量添加字段
爬虫小试牛刀（爬取学校通知公告）
【python基础】函数-初识函数
【python基础】函数-返回值
HTTP请求：requests模块基础使用必知必会
Python初学者友好丨详解参数传递类型
如何有效管理爬虫流量？
2个场景实例讲解GaussDB(DWS)基表统计信息估
常用的 SQL Server 关键字及其含义
动手分析SQL Server中的事务中使用的锁
openGauss内核分析：SQL by pass & 经典执行
一招教你如何高效批量导入与更新数据
天天写SQL，这些神奇的特性你知道吗？
openGauss内核分析：执行计划生成
[IM002]Navicat ODBC驱动器管理器 未发现数据
初入Sql Server 之 存储过程的简单使用
SQL Server -- 解决存储过程传入参数作为s
JavaScript判断两个数组相等的四类方法
js如何操作video标签
React实战--利用甘特图和看板，强化Paas平
【记录】正则替换的偏方
前端下载 Blob 类型整理
抽象语法树AST必知必会
关于JS定时器的整理
JS中使用Promise.all控制所有的异步请求都完
js中字符串的方法
import-local执行流程与node模块路径解析流程
