浅谈如何删除JSP编译后的空行

当你在客户端用view source看JSP生成的代码时，会发现有很多空行，他们是由< %...% >后的回车换行而生成的，也就是说每一行由< %...% >包含的JSP代码到客户端都变成一个空行，虽然不影响浏览，但还是希望能把他们删掉。这里将为大家介绍如何删除JSP编译后的空行。
Tomcat删除JSP编译后的空行办法如下：

1. 支持JSP 2.1+ ，在每个要去空行的页面里包含下面代码：

<%@ page trimDirectiveWhitespaces="true" %> 在 Tomcat 6.0.14下测试JSP编译成功

2. 支持servlet 2.5+, 即 web.xml的 XSD版本为2.5，在web.xml中加入如下代码

<jsp-config>
<jsp-property-group>
<url-pattern>*.jsp</url-pattern>
<trim-directive-whitespaces>true</trim-directive-whitespaces>
</jsp-property-group>
</jsp-config> 在tomcat 6.0.14下测试JSP编译成功

3. Tomcat 5.5.x+，在Tomcat安装目录/conf/web.xml中找到名叫"jsp"的servlet，添加下面一段代码：
<init-param>
<param-name>trimSpaces</param-name>
<param-value>true</param-value>
</init-param>
本人没测过，不过tomcat中web.xml文件的帮助这么说的

trimSpaces          Should white spaces in template text between  actions or directives be trimmed?  [false]

在实际操作中我加入了5.5的配置到页面中并反复启动了几次tomcat但是还是没有成功，后来才想到JSP已经编译成servlet了所以没有能改变，进入到tomcat中的work目录把已经进行JSP编译的class全部删除，哇哈哈，整个世界清净了，成功删除空行

resin删除JSP编译后的空行办法如下：

I'm getting a lot of whitespace in my JSP that I don't intend to be there. Why is it appearing and how can I get rid of it?

The extra whitespace is coming from newlines, often at the end of declaration lines at the beginning of the JSP. For example, the following jsp:

 <%@ page import='java.util.*' %>
<%@ page import='java.io.*' %>
Hello world
 

Has newlines in these locations:

<%@ page import='java.util.*' %>NL
<%@ page import='java.io.*' %>NL
Hello worldNL
The result contains the newlines, which may be surprising:

Hello world
One solution is to let the JSP tag extend across the newline:

<%@     page import='java.util.*'
%><%@ page import='java.io.*'
%>Hello world
Another solution is to use JSP comments to remove the newlines:

<%@ page import='java.util.*' %><%--
--%><%@ page import='java.io.*' %><%--
--%>Hello world
Another solution is to use the XML syntax of JSP. Parsing of XML causes removal of extra whitespace.

<jsp:root>
<jsp:directive.page import="java.util.*"/>
<jsp:directive.page import="java.io.*"/>

<jsp:text>Hello world</jsp:text>
</jsp:root>
Resin also supports the use of the '/' character to eat whitespace (this is a Resin specific feature):

<%@ page import='java.util.*' %>/
<%@ page import='java.io.*' %>/
Hello world