JDBC+Servlet+JSP整合开发之22.JSP简介

2021-12-14 09:16:25

–对JSP的需求
–JSP的结构
–JSP的好处
–JSP实例
?创建一个简单的JSP页面

###########################################

? JSP
–JSP 全称Java Server Page
?对JSP的需求
–使用servlet可以容易地完成下述任务：
? 读取表单数据
? 读取HTTP请求报头
? 设置HTTP状态代码和响应报头
? 使用cookie以及进行会话跟踪
?跨servlet共享数据
? 跨请求记录数据
? 获得有趣且报酬丰厚的工作
? 但使用servlet也有不尽如人意的地方：
–使用println语句生成HTML
–维护上述的HTML

? JSP的结构
–思想:
?大部分的页面使用常规的HTML
?用特殊的标签将servlet代码标记出来
?整个JSP页面最终转换成servlet（仅执行一次），实际
被调用的是servlet（每个请求）
–示例

使用Servlet输出0~9的页面

LoopServlet

测试

使用JSP输出0~9的页面

MyFirstJsp.jsp

测试

看一下JSP页面转换的Servlet文件存放在哪里哈~

MyFirstJsp_jsp.java

package org.apache.jsp;

import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.util.*;

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

    private static final JspFactory _jspxFactory = JspFactory.getDefaultFactory();

    private static java.util.List _jspx_dependants;

    private javax.el.ExpressionFactory _el_expressionfactory;
    private org.apache.AnnotationProcessor _jsp_annotationprocessor;

    public Object getDependants() {
        return _jspx_dependants;
    }

    public void _jspInit() {
        _el_expressionfactory = _jspxFactory.getJspApplicationContext(getServletConfig().getServletContext()).getExpressionFactory();
        _jsp_annotationprocessor = (org.apache.AnnotationProcessor) getServletConfig().getServletContext().getAttribute(org.apache.AnnotationProcessor.class.getName());
    }

    public void _jspDestroy() {
    }

    public void _jspService(HttpServletRequest request, HttpServletResponse response)
                throws java.io.IOException, ServletException {

        PageContext pageContext = null;
        HttpSession session = null;
        ServletContext application = null;
        ServletConfig config = null;
        JspWriter out = null;
        Object page = this;
        JspWriter _jspx_out = null;
        PageContext _jspx_page_context = null;

        try {
            response.setContentType("text/html;charset=ISO-8859-1");
            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');
            out.write('\n');

String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

            out.write("\r\n");
            out.write("\r\n");
            out.write("<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\">\r\n");
            out.write("<html>\r\n");
            out.write("    <head>\r\n");
            out.write("        <base href=\"");
            out.print(basePath);
            out.write("\">\r\n");
            out.write("        \r\n");
            out.write("        <title>My JSP 'MyFirstJsp.jsp' starting page</title>\r\n");
            out.write("        \r\n");
            out.write("\t<meta http-equiv=\"pragma\" content=\"no-cache\">\r\n");
            out.write("\t<meta http-equiv=\"cache-control\" content=\"no-cache\">\r\n");
            out.write("\t<meta http-equiv=\"expires\" content=\"0\">        \r\n");
            out.write("\t<meta http-equiv=\"keywords\" content=\"keyword1,keyword2,keyword3\">\r\n");
            out.write("\t<meta http-equiv=\"description\" content=\"This is my page\">\r\n");
            out.write("\t\r\n");
            out.write("\r\n");
            out.write("    </head>\r\n");
            out.write("    \r\n");
            out.write("    <body>\r\n");
            out.write("    \t<h1>My First JSP!</h1>\r\n");
            out.write("        ");

                for(int i=0;i<10;i++){
                        out.println(i);
                        out.print("<br/>");
                }
            out.write("\r\n");
            out.write("    </body>\r\n");
            out.write("</html>\r\n");
        } catch (Throwable t) {
            if (!(t instanceof SkipPageException)){
                out = _jspx_out;
                if (out != null && out.getBufferSize() != 0)
                    try { out.clearBuffer(); } catch (java.io.IOException e) {}
                if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
            }
        } finally {
            _jspxFactory.releasePageContext(_jspx_page_context);
        }
    }
}

? JSP的好处
–尽管JSP技术能够做的事情并不比servlet多，但JSP可以使下述任务更为容易：
? 输出HTML
? 阅读和维护这些HTML
–JSP使得下面的做法成为可能：
? 使用标准的HTML工具，比如Macromedia DreamWeaver或FrontPage
? 由小组的另外一些成员完成HTML布局，不关注Java编程
–JSP鼓励我们：
? 将创建内容（Java）代码同表示内容的（HTML）代码分离开来

? JSP实例
–创建一个简单的JSP页面

###########################################

附件：http://down.51cto.com/data/2355476

本文转自redking51CTO博客，原文链接：http://blog.51cto.com/redking/291153，如需转载请自行联系原作者

码农公寓

相关文章