深究<%@include%>和<jsp:include>
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<%@include%>和<jsp:include>的区别.本人在研究这里的内容的时候碰到了一些疑惑的地方,故找了一篇文章参考了一下!
文章中有一些出入,所以自己又修改了一番!
<%@include%>:我们知道JSP文件本身就是servlet,然而JSP文件需要预先编译成servlet,也就是class文件,而<%@include%>页面jsp在请求之前就已经进行了预编译,所有代码包含进来之后,一起进行处理,把所有代码合在一起,编译成一个servlet!
<jsp:include>:所有JSP文件代码分别处理,是在页面被请求的时候才进行编译,将多个jsp文件编译成多个servlet,页面语法相对独立,处理完成之后再将代码的显示结果(处理结果)组合进来。
显而易见,两者的区别就区别开了!
随后我们来看一下JSP中的两种包含页面的用法!
第一种:include指令:当JSP转换成Servlet时引入指定文件
<%@ pagecontentType="text/html;charset=GB2312" language="java"errorPage=""%><%@ include file="head.jsp"%><%@ include file="body.jsp"%><%@ include file="tail.jsp"%>第二种:<jsp:include>动作元素:当JSP页面被请求时引入指定文件
<%@ page contentType="text/html; charset=GB2312"language="java" errorPage=""%><jsp:include page="head.jsp"/><jsp:include page="body.jsp"/><jsp:include page="tail.jsp"/>
<%@ page contentType="text/html; charset=GB2312"language="java" errorPage=""%><jsp:include page="head.jsp"/><jsp:includepage="body.jsp"><jsp:param name="uid"value="username"/><jsp:param name="pwd"value="password"/></jsp:include><jsp:includepage="tail.jsp"/>
<jsp:include> :动态包含html文件和JSP文件的区别
第一种情况(<jsp:include>包含的是html文件):
DynamicInclude.jsp:
<%@pagecontentType="text/html;charset=gb2312"%><html> <head> <title>动态包含</title> </head> <body style="background-color:lightblue"> <jsp:include page="header.html"flush="true"/><!--动态包含--> <tableborder="1" align="center"> <tr> <td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td> </tr> <tr> <td>a</td><td>b</td><td>c</td><td>d</td> </tr> </table> </body></html>
Header.html :
(注意,JSP本身就是servlet,而html却不是,也就是此处最大的却别了!)
<h2style="font-family:arial;color:red;font-size:25px;text-align:center"> 动态包含的标题(HTML)</h2>
运行之后,只生成一个servlet,和上面的代码对应如下:
out.write("\r\n"); out.write("<html>\r\n"); out.write("\t<head>\r\n"); out.write("\t\t<title>动态包含</title>\r\n"); out.write("\t</head>\r\n"); out.write("\t<bodystyle=\"background-color:lightblue\">\r\n"); out.write("\r\n"); out.write("\t\t"); org.apache.jasper.runtime.JspRuntimeLibrary.include(request,response, "header.html", out, true); out.write("<!--动态包含-->\r\n"); out.write("\r\n"); out.write("\t\t<table border=\"1\"align=\"center\">\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>a</td><td>b</td><td>c</td><td>d</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t</table>\r\n"); out.write("\t</body>\r\n"); out.write("</html>");
第二种情况(<jsp:include>包含的是jsp文件):
DynamicInclude.jsp:
<%@pagecontentType="text/html;charset=gb2312"%><html> <head> <title>动态包含</title> </head> <bodystyle="background-color:lightblue"> <jsp:include page="header.jsp"flush="true"/><!--动态包含--> <tableborder="1" align="center"> <tr> <td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td> </tr> <tr> <td>a</td><td>b</td><td>c</td><td>d</td> </tr> </table> </body></html>
Header.jsp :
<%@pagecontentType="text/html;charset=gb2312"%><html> <body> <h2style="font-family:arial;color:red;font-size:25px;text-align:center"> 动态包含的标题(JSP) </h2> </body></html>
运行之后,生成了两个servlet,DynamicInclude_jsp.java和header_jsp.java
这也是为什么 Header.jsp中要写上<%@page contentType="text/html;charset=gb2312"%>和完整的<html></html>和<body></body>
而Header.html不用写的原因。因为后者两个.jsp文件是两个相互独立的整体,它们之间的关系是通过request和reponse来发生的,而前者只是简单的嵌套。后者的两个servlet对应的代码如下:
DynamicInclude_jsp.java:
out.write("\r\n"); out.write("<html>\r\n"); out.write("\t<head>\r\n"); out.write("\t\t<title>动态包含</title>\r\n"); out.write("\t</head>\r\n"); out.write("\t<bodystyle=\"background-color:lightblue\">\r\n"); out.write("\r\n"); out.write("\t\t"); org.apache.jasper.runtime.JspRuntimeLibrary.include(request,response, "header.jsp", out, true); out.write("<!--动态包含-->\r\n"); out.write("\r\n"); out.write("\t\t<table border=\"1\"align=\"center\">\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>a</td><td>b</td><td>c</td><td>d</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t</table>\r\n"); out.write("\t</body>\r\n"); out.write("</html>");
header_jsp.java:
out.write("\r\n"); out.write("<html>\r\n"); out.write("\t<body>\r\n"); out.write("\t\t<h2 style=\"font-family:arial;color:red;font-size:25px;text-align:center\">\r\n"); out.write("\t\t\t动态包含的标题(JSP)\r\n"); out.write("\t\t</h2>\r\n"); out.write("\t</body>\r\n"); out.write("</html>");
从而我们可以清楚的明白了,<jsp:include file=""> 引入html和jsp的区别了!
<%@include%>:静态包含
第一种情况:<%@include%>包含的是jsp文件。
StaticInclude.jsp:
<%@pagecontentType="text/html;charset=gb2312"%><html> <head> <title>静态包含</title> </head> <bodystyle="background-color:lightblue"> <%@include file="header.jsp"%><!--静态包含--> <tableborder="1" align="center"> <tr> <td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td> </tr> <tr> <td>a</td><td>b</td><td>c</td><td>d</td> </tr> </table> </body></html>
header.jsp:
<%@pagecontentType="text/html;charset=gb2312"%><h2style="font-family:arial;color:red;font-size:25px;text-align:center"> 静态包含的标题(JSP)</h2>
运行之后,只生成一个servlet,和上面的代码对应如下:
out.write("\r\n"); out.write("<html>\r\n"); out.write("\t<head>\r\n"); out.write("\t\t<title>静态包含</title>\r\n"); out.write("\t</head>\r\n"); out.write("\t<body style=\"background-color:lightblue\">\r\n"); out.write("\r\n"); out.write("\t\t"); out.write("\r\n"); out.write("<h2style=\"font-family:arial;color:red;font-size:25px;text-align:center\">\r\n"); out.write("\t静态包含的标题(JSP)\r\n"); out.write("</h2>"); out.write("<!--静态包含-->\r\n"); out.write("\t\t<table border=\"1\"align=\"center\">\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>a</td><td>b</td><td>c</td><td>d</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t</table>\r\n"); out.write("\t</body>\r\n"); out.write("</html>");
第二种情况:当<%@include%>包含的是html文件。
StaticInclude.jsp:
<%@pagecontentType="text/html;charset=gb2312"%><html> <head> <title>静态包含</title> </head> <bodystyle="background-color:lightblue"> <%@include file="header.html"%><!--静态包含--> <tableborder="1" align="center"> <tr> <td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td> </tr> <tr> <td>a</td><td>b</td><td>c</td><td>d</td> </tr> </table> </body></html>
header.html:
<%@pagecontentType="text/html;charset=gb2312"%><h2style="font-family:arial;color:red;font-size:25px;text-align:center"> 静态包含的标题(HTML)</h2>
运行之后,也是只生成一个servlet,和上面的代码对应如下:
out.write("\r\n"); out.write("<html>\r\n"); out.write("\t<head>\r\n"); out.write("\t\t<title>静态包含</title>\r\n"); out.write("\t</head>\r\n"); out.write("\t<bodystyle=\"background-color:lightblue\">\r\n"); out.write("\r\n"); out.write("\t\t"); out.write("\r\n"); out.write("<h2style=\"font-family:arial;color:red;font-size:25px;text-align:center\">\r\n"); out.write("\t静态包含的标题(HTML)\r\n"); out.write("</h2>"); out.write("<!--静态包含-->\r\n"); out.write("\t\t<table border=\"1\"align=\"center\">\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>姓名</td><td>性别</td><td>年龄</td><td>爱好</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t\t<tr>\r\n"); out.write("\t\t\t\t<td>a</td><td>b</td><td>c</td><td>d</td>\r\n"); out.write("\t\t\t</tr>\r\n"); out.write("\t\t</table>\r\n"); out.write("\t</body>\r\n"); out.write("</html>");
由上可以总结出:
对于静态包含,<%@include%>,中包含的文件,只是简单的嵌入到主文件中,就是在jsp页面转化成Servlet时才嵌入到主文件中,因为运行的结果是只生成了一个Servlet。
而对于动态包含<jsp:incude>,如果被包含文件是动态的,那么就会生成两个Servlet,也就是被包含文件也要经过jsp引擎编译执行生成一个Servlet,两个Servlet通过request和reponse进行通信。如果被包含的文件是静态的,那么这种情况和<%@include>就很相似,只生成了一个Servlet,但是他们之间没有进行简单的嵌入,而依然是通过request和reponse进行的通信。
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