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1.JSP入门

时间：2017-01-12 09:37:18      阅读：270      评论：0      收藏：0      [点我收藏+]

标签：转换   错误信息   extend   nat   web   err   exti   jsp内置对象   全局变量   

一.JSP基础

1.JSP概述

　　JSP（Java Server Pages）是JavaWeb服务器端的动态资源。它与html页面的作用是相同的，显示数据和获取数据。

　　JSP = html + Jsp脚本（代码片段） + JSP动态标签

技术分享

2.JSP语法　

  •  <%=…%>：输出！打到这里内容等同与打到response.getWriter().print(…)中了。

<%=”hello”%>，可以

<%=System.out.println(“hello”);%>，不可以！

<%= Math.min(10,20)%>，可以

  • <%...%>：代码片段！打到这里内容等同与打到方法中。注：每次访问不会在原值上加加，因为是局部变量。并且多个代码片段之间是互通的！

<%int i = 10;i = 100;%>，可以。

<%System.out.print(“hello”);%>，可以

<%private int a = 10;%>，不可以

<%public volid fun1() {}%>，不可以

  • <%!...%>：定义（声明）！打到这里的内容等同与打到类体中。class A {…} 注：每次访问时会在原值上加加，因为是全局变量。

<%! int a;%>：可以；

<%! public void fun2() {..}%>：可以

<%!private class A {}%>：可以

 　　　　注：在声明中，不能使用9大内置对象，因为查看JSP真身发现9大内置对象都在_jspservice下方，而声明实在_jspservice上方的，所以不能使用九大内置对象，只有java代码段和表达式可以使用这九大内置对象。

JSP内置对象：不用创建即可直接使用！

l  application：SevletContext

l  request：HttpServletRequest

l  response：HttpServletResponse

l  session：HttpSession

l  out：JspWriter，等同与response.getWriter()

l  config：ServletConfig

l  exception：异常对象，它是Throwable

l  page：Object，它表示this。例如：Object page = this;

l  pageContext：页面上下文！PageContext

　　　　

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>JSP演示</title>
  </head>
  
  <body>
    <h1>JSP演示</h1>
    <%
        // Java语句
        String s1 = "hello jsp";
        // 不会输出到客户端，而是在服务器端的控制台打印
        System.out.println(s1);
    %>
  <!-- 输出到客户端浏览器上 -->
    输出变量：<%=s1 %><br/>
    输出int类型常量：<%=100 %><br/>
    输出String类型常量：<%="你好" %><br/>
    <br/>
    使用表达式输出常量是很傻的一件事，因为可以直接使用html即可，下面是输出上面的常量：<br/>
    100<br/>
    你好   
  </body>
</html>

输出三种形式：
　　1.直接打字
　　2.out.print("你好")
　　3.response.getwriter(),print("你好")

3.JSP原理

  1. jsp就是servlet!
  2. tomcat会把jsp转换成html，其实是把jsp变成.java
  3. 然后把.java编译成.class，其实这个类就是一个servlet!
  4. 而这个servlet中存在大量out.write(“<html>”)，这就是最终的输出结果，即html

4.jsp注释　

  我们现在已经知道JSP是需要先编译成.java，再编译成.class的。其中<%-- ... --%>中的内容在JSP编译成.java时会被忽略的，即JSP注释。

  也可以在JSP页面中使用html注释：<!-- … -->，但这个注释在JSP编译成的.java中是存在的，它不会被忽略，而且会被发送到客户端浏览器。但是在浏览器显示服务器发送过来的html时，因为<!-- … -->是html的注释，所以浏览器是不会显示它的。

附:jsp真身代码

　　

package org.apache.jsp;

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

public final class regist_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;

  static {
    _jspx_dependants = new java.util.HashMap<java.lang.String,java.lang.Long>(2);
    _jspx_dependants.put("jar:file:/F:/tomcat/webapps/day11_30/WEB-INF/lib/jstl-1.2.jar!/META-INF/c.tld", Long.valueOf(1153356282000L));
    _jspx_dependants.put("/WEB-INF/lib/jstl-1.2.jar", Long.valueOf(1480475931708L));
  }

  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("java.util");
    _jspx_imports_packages.add("javax.servlet.jsp");
    _jspx_imports_packages.add("javax.servlet.http");
    _jspx_imports_classes = null;
  }

  private org.apache.jasper.runtime.TagHandlerPool _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody;

  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() {
    _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody = org.apache.jasper.runtime.TagHandlerPool.getTagHandlerPool(getServletConfig());
  }

  public void _jspDestroy() {
    _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.release();
  }

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

final java.lang.String _jspx_method = request.getMethod();
if (!"GET".equals(_jspx_method) && !"POST".equals(_jspx_method) && !"HEAD".equals(_jspx_method) && !javax.servlet.DispatcherType.ERROR.equals(request.getDispatcherType())) {
response.sendError(HttpServletResponse.SC_METHOD_NOT_ALLOWED, "JSPs only permit GET POST or HEAD");
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;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");

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 ‘regist.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("\t<link rel=\"stylesheet\" type=\"text/css\" href=\"styles.css\">\r\n");
      out.write("\t-->\r\n");
      out.write("<script type=\"text/javascript\">\r\n");
      out.write("\tfunction _change(){\r\n");
      out.write("\t\tvar imgEle = document.getElementById(\"imgEle\");\r\n");
      out.write("\t\timgEle.src = \"");
      if (_jspx_meth_c_005furl_005f0(_jspx_page_context))
        return;
      out.write("?\"+ new Date().getTime(); \r\n");
      out.write("\t}\r\n");
      out.write("</script>\r\n");
      out.write("  </head>\r\n");
      out.write("  \r\n");
      out.write("  <body>\r\n");
      out.write("<h1>注册页面</h1>\r\n");
      out.write("<!--\r\n");
      out.write("1.显示表单页面\r\n");
      out.write("2.显示服务器端的输入校验错误信息\r\n");
      out.write("3.显示后台校验错误信息\r\n");
      out.write("4.校验失败时回显数据\r\n");
      out.write("-->\r\n");
      out.write("<p style=\"color:red;font-size:10pt;font-weight:900\">");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${msg}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("</p>\r\n");
      out.write("<form action=\"");
      if (_jspx_meth_c_005furl_005f1(_jspx_page_context))
        return;
      out.write("\" method=\"post\">\r\n");
      out.write("用户名：<input type=\"text\" name=\"username\" value=\"");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${form.username}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("\"/>\r\n");
      out.write("\t\t<span style=\"color:red;font-size:10pt;font-weight:900\">");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${errors.username}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("</span>\r\n");
      out.write("\t\t<br/>\t\t\r\n");
      out.write("性　别：<input type=\"text\" name=\"gender\" value=\"");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${form.gender}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("\"/>\r\n");
      out.write("\t\t<span style=\"color:red;font-size:10pt;font-weight:900\">");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${errors.gender}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("</span>\r\n");
      out.write("\t\t<br/>\r\n");
      out.write("年　龄：<input type=\"text\" name=\"age\" value=\"");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${form.age}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("\"/>\r\n");
      out.write("\t\t<span style=\"color:red;font-size:10pt;font-weight:900\">");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${errors.age}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("</span>\r\n");
      out.write("\t\t<br/>\r\n");
      out.write("密　码：<input type=\"password\" name=\"password\"/>\r\n");
      out.write("\t\t<span style=\"color:red;font-size:10pt;font-weight:900\">");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${errors.password}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("</span>\r\n");
      out.write("\t\t<br/>\r\n");
      out.write("确认密码：<input type=\"password\" name=\"repassword\"/>\r\n");
      out.write("\t\t<span style=\"color:red;font-size:10pt;font-weight:900\">");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${errors.repassword}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("</span>\r\n");
      out.write("\t\t<br/>\r\n");
      out.write("验证码：<input type=\"text\" name=\"verifyCode\" size=\"3\" value=\"");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${form.verifyCode}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("\"/>\r\n");
      out.write("\t\t<img  src=\"");
      if (_jspx_meth_c_005furl_005f2(_jspx_page_context))
        return;
      out.write("\" id=\"imgEle\"/>\r\n");
      out.write("\t\t<a href=\"javascript:_change()\">换一张</a>\r\n");
      out.write("\t\t<span style=\"color:red;font-size:10pt;font-weight:900\">");
      out.write((java.lang.String) org.apache.jasper.runtime.PageContextImpl.proprietaryEvaluate("${errors.verifyCode}", java.lang.String.class, (javax.servlet.jsp.PageContext)_jspx_page_context, null));
      out.write("</span>\r\n");
      out.write("\t\t<br/>\r\n");
      out.write("\t<input type=\"submit\" value=\"注册\"/>\r\n");
      out.write("</form>\r\n");
      out.write("  </body>\r\n");
      out.write("</html>\r\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);
    }
  }

  private boolean _jspx_meth_c_005furl_005f0(javax.servlet.jsp.PageContext _jspx_page_context)
          throws java.lang.Throwable {
    javax.servlet.jsp.PageContext pageContext = _jspx_page_context;
    javax.servlet.jsp.JspWriter out = _jspx_page_context.getOut();
    //  c:url
    org.apache.taglibs.standard.tag.rt.core.UrlTag _jspx_th_c_005furl_005f0 = (org.apache.taglibs.standard.tag.rt.core.UrlTag) _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.get(org.apache.taglibs.standard.tag.rt.core.UrlTag.class);
    _jspx_th_c_005furl_005f0.setPageContext(_jspx_page_context);
    _jspx_th_c_005furl_005f0.setParent(null);
    // /regist.jsp(26,16) name = value type = null reqTime = true required = false fragment = false deferredValue = false expectedTypeName = null deferredMethod = false methodSignature = null
    _jspx_th_c_005furl_005f0.setValue("/VerifyCodeServlet");
    int _jspx_eval_c_005furl_005f0 = _jspx_th_c_005furl_005f0.doStartTag();
    if (_jspx_th_c_005furl_005f0.doEndTag() == javax.servlet.jsp.tagext.Tag.SKIP_PAGE) {
      _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.reuse(_jspx_th_c_005furl_005f0);
      return true;
    }
    _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.reuse(_jspx_th_c_005furl_005f0);
    return false;
  }

  private boolean _jspx_meth_c_005furl_005f1(javax.servlet.jsp.PageContext _jspx_page_context)
          throws java.lang.Throwable {
    javax.servlet.jsp.PageContext pageContext = _jspx_page_context;
    javax.servlet.jsp.JspWriter out = _jspx_page_context.getOut();
    //  c:url
    org.apache.taglibs.standard.tag.rt.core.UrlTag _jspx_th_c_005furl_005f1 = (org.apache.taglibs.standard.tag.rt.core.UrlTag) _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.get(org.apache.taglibs.standard.tag.rt.core.UrlTag.class);
    _jspx_th_c_005furl_005f1.setPageContext(_jspx_page_context);
    _jspx_th_c_005furl_005f1.setParent(null);
    // /regist.jsp(40,14) name = value type = null reqTime = true required = false fragment = false deferredValue = false expectedTypeName = null deferredMethod = false methodSignature = null
    _jspx_th_c_005furl_005f1.setValue("RegistServlet");
    int _jspx_eval_c_005furl_005f1 = _jspx_th_c_005furl_005f1.doStartTag();
    if (_jspx_th_c_005furl_005f1.doEndTag() == javax.servlet.jsp.tagext.Tag.SKIP_PAGE) {
      _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.reuse(_jspx_th_c_005furl_005f1);
      return true;
    }
    _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.reuse(_jspx_th_c_005furl_005f1);
    return false;
  }

  private boolean _jspx_meth_c_005furl_005f2(javax.servlet.jsp.PageContext _jspx_page_context)
          throws java.lang.Throwable {
    javax.servlet.jsp.PageContext pageContext = _jspx_page_context;
    javax.servlet.jsp.JspWriter out = _jspx_page_context.getOut();
    //  c:url
    org.apache.taglibs.standard.tag.rt.core.UrlTag _jspx_th_c_005furl_005f2 = (org.apache.taglibs.standard.tag.rt.core.UrlTag) _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.get(org.apache.taglibs.standard.tag.rt.core.UrlTag.class);
    _jspx_th_c_005furl_005f2.setPageContext(_jspx_page_context);
    _jspx_th_c_005furl_005f2.setParent(null);
    // /regist.jsp(57,13) name = value type = null reqTime = true required = false fragment = false deferredValue = false expectedTypeName = null deferredMethod = false methodSignature = null
    _jspx_th_c_005furl_005f2.setValue("/VerifyCodeServlet");
    int _jspx_eval_c_005furl_005f2 = _jspx_th_c_005furl_005f2.doStartTag();
    if (_jspx_th_c_005furl_005f2.doEndTag() == javax.servlet.jsp.tagext.Tag.SKIP_PAGE) {
      _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.reuse(_jspx_th_c_005furl_005f2);
      return true;
    }
    _005fjspx_005ftagPool_005fc_005furl_0026_005fvalue_005fnobody.reuse(_jspx_th_c_005furl_005f2);
    return false;
  }
}

 

1.JSP入门

标签：转换   错误信息   extend   nat   web   err   exti   jsp内置对象   全局变量   

原文地址：http://www.cnblogs.com/insistence/p/6274988.html
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