html注释和jsp注释

一、HTML注释

二、JSP注释
　　<%--注释内容--%>
三、HTML注释和JSP注释的区别：
　　3.1 HTML注释会被JSP翻译引擎翻译到Servlet的out.write()中，而JSP注释则会被JSP翻译引擎忽略，在Servlet中是看不到的。
　　3.2 在客户端浏览器查看源码时，HTML注释是可以查看到的，但JSP注释在客户端是查看不到的。

四、示例　

　　4.1 jsp源码　

<%@ 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">
<title>first_jsp</title>
</head>
<body>
<!-- HTML注释 -->
<%--JSP注释 --%>
My First jsp!
</body>
</html>

　　4.2 经Tomcat遵循JSP规范将该JSP页面翻译的.java源文件如下：　　

/*
 * Generated by the Jasper component of Apache Tomcat
 * Version: Apache Tomcat/7.0.85
 * Generated at: 2019-01-22 17:21:18 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 index_jsp extends org.apache.jasper.runtime.HttpJspBase
    implements org.apache.jasper.runtime.JspSourceDependent {

  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("
");
      out.write("<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
");
      out.write("<html>
");
      out.write("<head>
");
      out.write("<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
");
      out.write("<title>first_jsp</title>
");
      out.write("</head>
");
      out.write("<body>
");
      out.write("<!-- HTML注释 -->
");
      out.write("
");
      out.write("My First jsp!
");
      out.write("</body>
");
      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);
    }
  }
}

　　我们可以看到只有HTML注释被out.write()到客户端了。所以我们到客户端浏览器查看源码，其截图如下：

　　 html注释和jsp注释

　　经过上面我们总结出，如果注释内容相对的安全保密则我们用JSP注释，否则的话用HTML注释。但一般遵循安不安全都使用JSP注释为最佳原则。服务端源码能看到就行，不让你客户端看到本程序代码的注释内容。

html注释和jsp注释

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