How to remove a large number of spaces and line breaks generated when JSP outputs HTML

This problem also troubled me for a long time. Because when using EL tags and other tags in jsp, a large number of spaces and newlines will be generated. For example:

------- start ---------- 
<c:choose> 
<c:when test="${fn:length(mainPageList)>1&}"> 
Something 
</c:when> 
<c:otherwise> 
Others 
</c:otherwise> 
</c:choose> 
------- end -----------

This code is output as follows on Tomcat, more A few lines are broken.

------- start ---------- 
Something 
------- end -----------

Of course, generally you won’t find any problems without paying special attention. After all, no matter how many spaces and line breaks are output, the final effect generated by the browser will be the same. This is why most developers ignore this problem; but in fact these spaces and line breaks take up a lot of space. My experience is that about 30% are spaces/line breaks. Some people also say that when the web server outputs HTML in zip, the bandwidth problem caused by spaces can be solved; yes, when zip is used to output HTML, the space for spaces/line breaks will be saved, but this increase The workload of zip is huge, and the biggest problem is that when the browser generates the page, it will still restore all the spaces and line breaks. This is bad news for front-end developers. Faced with a large number of spaces and lengthy HTML source code, it is not easy to find the location of the problematic style.
Let’s talk about the solution below, taking Tomcat as an example:
Option 1, use the trimSpaces function of the web server.
Tomcat5 and above versions can be used, this is the simplest method.

<servlet> 
<servlet-name>jsp</servlet-name> 
<servlet-class>org.apache.jasper.servlet.JspServlet</servlet-class> 
<init-param> 
<param-name>fork</param-name> 
<param-value>false</param-value> 
</init-param> 
<init-param> 
<param-name>trimSpaces </param-name> 
<param-value>true </param-value> 
</init-param> 
<init-param> 
<param-name>xpoweredBy</param-name> 
<param-value>false</param-value> 
</init-param> 
<load-on-startup>3</load-on-startup> 
</servlet>

This solution has a disadvantage. It will remove the newlines of spaces between all jsp EL tags, which may also cause inconvenience in some cases.
For example: Your name is ${firstName} ${lastName}. ==The output is==> Your name is firstNamelastName.
The space between the two ${} variables will also disappear. To solve this problem is quite troublesome, to introduce a variable with only one space.

Your name is ${firstName}${one_space}${lastName}.
This is normal, troublesome. Although you can add a one_space variable to some global variables, the code still looks uncomfortable.
Option 2, I like it better.
This solution can only be used on web servers that support jsp 2.1, such as Tomcat6.
Jsp2.1 has a very useful command;
<%@ page trimDirectiveWhitespaces="true" %>
This command can remove redundant blank lines when the html output by jsp (using EL and tag on jsp will cause A lot of spaces and empty lines), there is no problem with using trimSpaces. Now the jsp output html can be formatted well and looks professional. I used to be envious of Velocity’s templates. The output html is very clean and beautiful, and now jsp can also do it. .
In addition, Tomcat6 has some compatibility issues. For example, you cannot use code like #{} in jsp because it will be executed as a JSF script.
Although this is a small problem, we still have to pay attention to details.

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