This article analyzes the usage of base tags in JSP page files. Share it for your reference, as follows:
When we use IDE tools to generate JSP pages, we usually include the following two pieces of code.
<% String path = (); String basePath = ()+"://"+()+":"+()+path+"/"; %> <head> <base href="<%=basePath%>"> </head>
They are definitely not useless code, as follows:
The base tag is a base link tag, a single tag. Used to change the parameter set value of all link marks in the file. It can only be applied between the marker <head> and </head>. All relative paths on your web page will be preceded by the address pointed to by the base link.
Important attributes:
href---Set the link address of the prefix
target---Set the window for the file display, the same as the target in the a tag
Simple example:
<html> <head> <base href=http://localhost target="_blank"> <meta http-equiv="Content-Type" content="text/html; charset=gb2312"> <title>basemark</title> <link rel="Shortcut Icon" href=""> </head> <body> <a href="" target="_self"></a> <a href=""></a> </body> </html>
When the link is clicked, the file that jumps out is http://localhost/ or http://localhost/, which adds the address pointed to by the base link before these files with relative paths. If the link in the target file does not specify the target attribute, use the target attribute in the base tag.
It is often used in frame structures, such as the left and right frames, and displays the connections in the file in the left frame in the right frame. Just use base to mark it and write its target attribute value as the right frame name, so you no longer need to specify the target attribute for every connection in the file in the left frame.
When used, the BASE element must appear in the document's HEAD before any reference to an external source.
In addition, if the page turns to a servlet, and the servlet is a jsp page forwarded, if you write the relative path at this time, you should first find the path of the servlet, that is, the path in the url-pattern configured in the configuration. For example, suppose there is a place in the root directory of the webapplication, and the home page is submitted to the servlet, and the Serlet will distribute forward to the servlet. The url configuration of the servlet is as follows:
Then after the Servlet completes forward turn, if there is no <base href="<%=basePath%>"> <script type="text/javascript" src="script/"></script> in <base href="<%=basePath%>"> , it will be invalid because the access path of the Servlet is http://localhost/webapp/servlet/TestServlet, then the web server will go to http://localhost/webapp/servlet/ to find this file, so if you encounter such a situation, it is recommended to use the absolute path, and there will be no error.
I hope this article will be helpful to everyone's JSP programming.