Jsp基础语法

page指令介绍

Language : 用来定义要使用的脚本语言；
contentType：定义 JSP 字符的编码和页面响应的 MIME 类型；
pageEncoding：Jsp 页面的字符编码

<%@ page language="java" contentType="text/html; charset=utf-8" pageEncoding="utf-8"%>

scriptlet标签

通过 scriptlet 标签我们可以在 Jsp 里嵌入 Java 代码；
第一种：<%! %> 我们可以在里面定义全局变量、方法、类；
第二种：<% %> 我们可以在里面定义局部变量、编写语句；
第三种：<%= %> 我们可以在里面输出一个变量或一个具体内容；

<%@ page language="java" contentType="text/html; charset=utf-8"
    pageEncoding="utf-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<%!
    String str="全局变量";
%>
<%!
    public void fun1(){
        System.out.println("全局方法");
    }
%>
<%!
    class C{
        private int a;
        public void f(){
            System.out.println("全局类");
        }
    }
%>
<%
    int a=1234;
    String b="java";
    out.println(a+b+"局部变量");
%>
<title>Insert title here</title>
</head>
<body>
<%=b %>
</body>
</html>

scriptlet.jsp

当你通过http请求一个JSP页面是，首先Tomcat会将JSP编译成为Servlet,然后执行Servlet.在其java文件中可以看出哪些是全局变量，哪些是局部变量。

JSP编译后的路径： apache-tomcat-7.0.65\work\Catalina\localhost\XX

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/7.0.65
 * Generated at: 2017-03-04 08:10:55 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.*;

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


    String str="全局变量";


    public void fun1(){
        System.out.println("全局方法");
    }


    class C{
        private int a;
        public void f(){
            System.out.println("全局类");
        }
    }

  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("<!DOCTYPE html PUBLIC \"-//W3C//DTD HTML 4.01 Transitional//EN\" \"http://www.w3.org/TR/html4/loose.dtd\">\r\n");
      out.write("<html>\r\n");
      out.write("<head>\r\n");
      out.write("<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\">\r\n");
      out.write('\r');
      out.write('\n');
      out.write('\r');
      out.write('\n');
      out.write('\r');
      out.write('\n');

    int a=1234;
    String b="java";
    out.println(a+b+"局部变量");

      out.write("\r\n");
      out.write("<title>Insert title here</title>\r\n");
      out.write("</head>\r\n");
      out.write("<body>\r\n");
      out.print(b );
      out.write("\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);
    }
  }
}

scriptlet_jsp.java

Jsp注释

Html 注释客户端可见
<%-- --%> Jsp注释客户端不可见
// java 单行注释
/* */ java 多行注释

Jsp包含指令

<%@ include file=”要包含的文件”%> 静态包含先包含，后编译处理 (合并后编译可能会有变量冲突)；
<jsp:include page=”要包含的文件”> 动态包含先编译处理，后包含；以后开发用动态包含；

<body>
<%-- <h1>静态包含</h1>
<%@ include file="common/head.html" %>
<p>content</p>
<%@ include file="common/footer.jsp" %> --%>
<h1>动态包含</h1>
<jsp:include page="common/head.html"/>
<p>content</p>
<jsp:include page="common/footer.jsp"/>
</body>

View Code

Jsp跳转指令，服务器内部跳转，可带参数；

<body>
<jsp:forward page="target.jsp">
    <jsp:param value="java1234" name="userName"/>
    <jsp:param value="123456" name="password"/>
</jsp:forward>
</body>
----------------------------target.jsp------------------------------------------
<body>
服务器内部跳转后的页面<br/>
userName:<%=request.getParameter("userName") %><br/>
password:<%=request.getParameter("password") %><br/>
</body>

View Code

关于EL表达式中requestScope和param区别

http://blog.csdn.net/lioncode/article/details/8155374

posted @ 2017-03-04 16:35 SKYisLimit 阅读(148) 评论(0) 收藏举报

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SKYisLimit

Jsp基础语法

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