1.JSP入门

Posted stubborn

tags:

篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了1.JSP入门相关的知识,希望对你有一定的参考价值。

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

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;
  }
}

 

以上是关于1.JSP入门的主要内容,如果未能解决你的问题,请参考以下文章

day06-jsp

JSP # JSP入门及简单概述

推荐net开发cad入门阅读代码片段

jsp入门

快速掌握JSP入门---(Java服务器端页面)

Java Web学习总结JSP