9大JSP隐式对象与Servlet之间的暧昧

来源：互联网发布：ubuntu 主分区扩容编辑：程序博客网时间：2024/04/29 22:26

作者：绝版青春来源

JSP隐私对象是Web容器加载的一组类的实例,恩,也就是直接在jsp页面当中使用的对象!
在这里我就简单的、浅薄的小结一下了...(0^_^0)

                   JSP隐私对象
          |
       -----------------------------------------------------------
       |                   |                  |                  |
输入输出对象       作用域通信对象        Servlet对象        错误对象
       |                   |        |                  |
      out               session              page             exception
       |                   |                  |                  |
     request          application          config
       |                   |
    response        pageContext

实验环境搭配:
1.Tomcat/webapps/建立Web站点目录Test
2.Test/创建WEB-INF文件夹,即可以搭建起Web站点服务
3.tomcat/work/Catalina/localhost/Test/org/apache/jsp中找到对应的jsp生成的.java文件

===JSP页面中的使用:===
...
<body>
  <%
   out.print("使用out隐式对象输入页面内容");
   %>
</body>
...

===Servlet中生成的代码:===

...
JspFactory _jspxFactory = null;
PageContext pageContext = null;
JspWriter out = null;

pageContext = _jspxFactory.getPageContext(this, request, response,
null, true, 8192, true);
out = pageContext.getOut();
out.print("使用out隐式对象输入页面内容");
...

**************************index.jsp文件*************************

<%@page contentType="text/html;charset=gbk"%>
<html>
<head>
  <title>Test</title>
</head>
<body>
  <%
   out.print("使用out隐式对象输入页面内容");
   %>
</body>
</html>

********************************end*****************************

********************生成的index_jsp.java文件********************

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 {

private static java.util.Vector _jspx_dependants;

public java.util.List getDependants() {
return _jspx_dependants;
}

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

    JspFactory _jspxFactory = null;

    // _jspx_page_context = pageContext;
    PageContext pageContext = null;
    PageContext _jspx_page_context = null;
    HttpSession session = null;
    ServletContext application = null;

    Object page = this;
    ServletConfig config = null;

    // _jspx_out = out;
    JspWriter out = null;
    JspWriter _jspx_out = null;

    try {
      _jspxFactory = JspFactory.getDefaultFactory();

      response.setContentType("text/html;charset=gbk");

      //创建pageContext对象
      pageContext = _jspxFactory.getPageContext(this, request, response,
         null, true, 8192, true);
      _jspx_page_context = pageContext;

      //创建application对象
      application = pageContext.getServletContext();

      //创建session对象
      session = pageContext.getSession();


      //创建config对象
      config = pageContext.getServletConfig();


      //创建out对象
      out = pageContext.getOut();
      _jspx_out = out;

      out.write("/r/n");
      out.write("<html>/r/n");
      out.write("/t<head>/r/n");
      out.write("/t/t<title>Test</title>/r/n");
      out.write("/t</head>/r/n");
      out.write("/t<body>/r/n");
      out.write("/r/n");
      out.write("/t/t");

   out.print("使用out隐式对象输入页面内容");

      out.write("/r/n");
      out.write("/t</body>/r/n");
      out.write("</html>");
    } catch (Throwable t) {
      if (!(t instanceof SkipPageException)){
        out = _jspx_out;
        if (out != null && out.getBufferSize() != 0)
          out.clearBuffer();
        if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
      }
    } finally {
      if (_jspxFactory != null) _jspxFactory.releasePageContext(_jspx_page_context);
    }
}
}
********************************end********************************

===JSP页面中的使用:===
...
<body>
  <%
   request.setAttribute("name","value");
   request.getAttribute("name");
   注意:getAttribute()只能取到setAttribute()存入的Value

   String temp = request.getParameter("name");
   String[] temp = request.getParameterValues("name");
  %>
</body>
...

===Servlet中生成的代码:===

...
public void _jspService(HttpServletRequest request, HttpServletResponse response)
        throws java.io.IOException, ServletException {
           request.setAttribute("name","value");
        }
...

===JSP页面中的使用:===
...
<body>
  <%
   response.setContentType("text/html;charset=gbk");
   response.sendRedirect("another.jsp");
  %>
</body>
...

===Servlet中生成的代码:===
...
public void _jspService(HttpServletRequest request, HttpServletResponse response)
        throws java.io.IOException, ServletException {
            response.setContentType("text/html;charset=gbk");
        response.sendRedirect("second.jsp");
        }
...

===JSP页面中的使用:===
...
<body>
  <%
   session.setAttribute("name","value");
   String temp = (String)session.getAttribute("name");
  %>
</body>
...

===Servlet中生成的代码:===

...
JspFactory _jspxFactory = null;
PageContext pageContext = null;
HttpSession session = null;

pageContext = _jspxFactory.getPageContext(this, request, response,
null, true, 8192, true);
session = pageContext.getSession();
session.setAttribute("name","value");
String temp = (String)session.getAttribute("name");
...

===JSP页面中的使用:===
...
<body>
  <%
   application.setAttribute("name","value");
   String tempApp = (String)application.getAttribute("name");
  %>
</body>
...

===Servlet中生成的代码:===

...
JspFactory _jspxFactory = null;
PageContext pageContext = null;
ServletContext application = null;

pageContext = _jspxFactory.getPageContext(this, request, response,
null, true, 8192, true);
application = pageContext.getServletContext();
application.setAttribute("name","value");
String tempApp = (String)application.getAttribute("name");
...

===JSP页面中的使用:===
...
<body>
  <%
   pageContext.setAttribute("name","value");
   String tempPage = (String)pageContext.getAttribute("name");
  %>
</body>
...

===Servlet中生成的代码:===

...
JspFactory _jspxFactory = null;
PageContext pageContext = null;

pageContext = _jspxFactory.getPageContext(this, request, response,
                      null, true, 8192, true);

pageContext.setAttribute("name","value");
String tempPage = (String)pageContext.getAttribute("name");
...

===JSP页面中的使用:===
...
<body>
<%=((javax.servlet.jsp.HttpJspPage)page).getServletInfo()%>
</body>
...

===Servlet中生成的代码:===

...
page对象表示页面本身,她是java.lang.Objec类的一个实例.为jsp页面创建Servlet类定义变量和方法.
这些变量和方法包含页面的信息.使用page对象可以访问所有这些变量和方法.
page对象很少使用?一般使用page指令即可?(为什么?)
...

===JSP页面中的使用:===
...
<%
String tempConfig = (String)config.getInitParameter("test");
out.println(tempConfig);
%>
...

===Servlet中生成的代码:===
...
JspFactory _jspxFactory = null;
PageContext pageContext = null;

pageContext = _jspxFactory.getPageContext(this, request, response,
                      null, true, 8192, true);
config = pageContext.getServletConfig();
String tempConfig = (String)config.getInitParameter("test");
out.println(tempConfig);
...

<--------------------------exception.jsp----------------------------------->
<%@ page contentType="text/html; charset=gb2312" errorPage="/error.jsp" %>
<html>
<head>
<title>出错演示</title>
</head>
<body>
<%
String t="test";
int i=Integer.parseInt(t);
%>
</body>
</html>

<--------------------------error.jsp----------------------------------->
<%@ page contentType="text/html; charset=gb2312" language="java" isErrorPage="true" %>
<html>
<head>
<title>出错了！</title>
</head>
<body>
出错了！
<br>
发生了以下的错误：
<br>
<%=exception.getMessage()%>
<%
exception.printStackTrace(out);
%>
</body>
</html>