JSP笔记01——尝试

JSP ————> servlet

我的第1个Java Web应用程序——index.jsp

我的第2个Java Web应用程序——welcome-file

我的第3个Java Web应用程序——conf/server.xml

我的第4个Java Web应用程序——jsp page

我的第5个Java Web应用程序——jsp 脚本

我的第6个Java Web应用程序——jsp 声明

我的第7个Java Web应用程序——JSP 表达式

我的第8个Java Web应用程序——JSP页面生命周期

我的第9个Java Web应用程序——我的乘法口诀表！

1

<!doctype html>
<html lang="en">
 <head>
  <meta charset="UTF-8">
  <meta name="Generator" content="EditPlus®">
  <meta name="Author" content="">
  <meta name="Keywords" content="">
  <meta name="Description" content="">
  <title>Document</title>
 </head>
 <body>
  <h1>???????</h1>
 </body>
</html>

<?xml version="1.0" encoding="ISO-8859-1" ?>

<web-app 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"
         version="2.4">
</web-app>

2

<?xml version="1.0" encoding="ISO-8859-1" ?>

<web-app 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"
         version="2.4">
         <welcome-file-list>
             <welcome-file>/index.jsp</welcome-file>
         </welcome-file-list>
</web-app>

3

4

jsp=java server page

<%@ page language="java" import="java.util.*" contentType="text/html;charset=utf-8" %>

<html>
    <body>
        <h1 align="center">啤酒推荐</h1>
        <p>
        <%
            List styles = (List)request.getAttribute("styles");
            Iterator it = styles.iterator();
            while (it.hasNext()) {
                out.print("<br>try: " + it.next());
            }
        %>
    </body>
</html>

5

<%@ page language="java" import="java.util.*" contentType="text/html;charset=utf-8" %>

<html>
    <body>
        <h1 align="center">啤酒推荐</h1>
        <p>
        <%
            List styles = (List)request.getAttribute("styles");
            Iterator it = styles.iterator();
            while (it.hasNext()) {
                out.print("<br>try: " + it.next());
            }
        %>
        <%
            out.print("<br /><br />今天天气貌似不错！");
            // out是一个内置的对象！
        %>
    </body>
</html>

6

两种声明方式的差异。参考：http://www.cnblogs.com/zengmiaogen/archive/2012/04/15/2450414.html

我们既可以在<%%>中声明变量，也可以在<%!%>中声明变量，

那么，这两种声明方式有什么区别呢？事实上，<%!%>相当于类的实例域，而<%%>相当于方法体。

// TO-DO

7

<%@ page language="java" import="java.util.*" contentType="text/html;charset=utf-8" %>

<html>
    <body>
        <p>this is a simple test</p>
        <%!
            String words = "this is a simple test.";
            int sum(int x, int y) {
                return x + y;
            }
        %>
        <p>words=<%=words%></p>
        <p>3+4=<%=sum(3,4)%></p>
    </body>
</html>

8

当我们访问jsp页面的时候，jsp引擎（web容器）首先判断是否是第一次请求...

这个时候我就想，要是可以直接看到它编译出来的字节码就好了，那么到哪里查看呢？——答案是在tomcat的work目录下，不仅有字节码，还有源代码，我们查看一下上一节的代码。

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/7.0.77
 * Generated at: 2017-06-09 10:07:20 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.*;
import java.util.*;

public final class test_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent {

            String words = "this is a simple test.";
            int sum(int x, int y) {
                return x + y;
            }

  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 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 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 {

    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;charset=utf-8");
      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("\r\n");
      out.write("\r\n");
      out.write("<html>\r\n");
      out.write("    <body>\r\n");
      out.write("    \t<p>this is a simple test</p>\r\n");
      out.write("    \t");
      out.write("\r\n");
      out.write("    \t<p>words=");
      out.print(words);
      out.write("</p>\r\n");
      out.write("    \t<p>3+4=");
      out.print(sum(3,4));
      out.write("</p>\r\n");
      out.write("    </body>\r\n");
      out.write("</html>");
    } 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);
    }
  }
}

9

<%@ page language="java" import="java.util.*" contentType="text/html;charset=utf-8" %>

<html>
    <body>
        <p>这是我的乘法口诀表！</p>

        <%
            for (int i = 1; i <= 9; ++i) {
                for (int j = 1; j <= i; ++j) {
                    out.print(i + " * " + j + " = " + i*j + "   ");
                }
                out.print("<br />");
            }
        %>

    </body>
</html>

看完视频后修改了一下，&nbsp;是空格占位符

<%@ page language="java" import="java.util.*" contentType="text/html;charset=utf-8" %>

<html>
    <body>
        <p>这是我的乘法口诀表！</p>

        <%!
            void printTable() {
                for (int i = 1; i <= 9; ++i) {
                    for (int j = 1; j <= i; ++j) {
                        out.print(i + " * " + j + " = " + i*j + "&nbsp;&nbsp;&nbsp;&nbsp;");
                    }
                    out.print("<br />");
                }
            }
        %>

        <%
            printTable();
        %>

    </body>
</html>

10什么是内置对象

11 jsp有哪些内置对象

12 jsp内置对象的官方文档