JSP: custom tag to modify its body

This is a skeleton of what is needed to build a custom jsp tag which does something to its body. For example a tag could change the urls of all the links found in its body.

<br />package com.mycompany.package.of.the.tag;<br /><br />import javax.servlet.jsp.JspException;<br />import javax.servlet.jsp.JspWriter;<br />import javax.servlet.jsp.tagext.BodyContent;<br />import javax.servlet.jsp.tagext.BodyTagSupport;<br /><br />public class CustomTag extends BodyTagSupport {<br />private static final long serialVersionUID = 1L;<br /><br />public int doAfterBody() throws JspException {<br /> try {<br /> BodyContent bc = getBodyContent();<br /> String body = bc.getString();<br /> // do something to the body here.<br /> JspWriter out = bc.getEnclosingWriter();<br /> if(body != null) {<br /> out.print(buff.toString());<br /> }<br /> } catch(IOException ioe) {<br /> throw new JspException("Error: "+ioe.getMessage());<br /> }<br /> return EVAL_BODY_INCLUDE;<br /> }<br />}<br />

make a file called CustomTag.tld and put it into WEB-INF:
<br /><?xml version = "1.0" encoding = "ISO-8859-1" ?><br /><!DOCTYPE taglib<br />PUBLIC "-//Sun Microsystems, Inc.//DTD JSP Tag Library 1.1//EN"<br />"http://java.sun.com/j2ee/dtds/web-jsptaglibrary_1_1,dtd"><br /><taglib><br /><tlibversion>1.0</tlibversion><br /><jspversion>1.1</jspversion><br /><uri>com.mycompany.CustomTag</uri><br /><shortname>Custom Tag</shortname><br /><tag><br /><name>ct</name><br /><tagclass>com.mycompany.package.of.the.tag.CustomTag</tagclass><br /><bodycontent>JSP</bodycontent><br /></tag><br /></taglib><br /><br />

use it like this on your JSP:
<%@ taglib uri="com.mycompany.CustomTag" prefix="x"%>

<x:ct>
here is some stuff inside the tag!
<c:out value="${someparam}"/>
</x:ct>

How to make a redirect servlet

make a servlet which calls the following method on doPost() and on doGet()

<br />private void doRedirect(HttpServletRequest request, HttpServletResponse response) throws ServletException {<br /> String servletPath = request.getServletPath();<br /> //do something with the path<br /> String newServletPath = servletPath.toLowerCase();<br /> try {<br /> getServletContext().getRequestDispatcher(newServletPath).forward(request, response);<br /> } catch(IOException ioE) {<br /> throw new ServletException("Unable to forward request: " + servletPath + " to path: " + newServletPath, ioE);<br /> }<br />}<br />

improve eclipse performance in windows

this eclipse plugin forces windows keep eclipse in memory / reduces thrashing

http://suif.stanford.edu/pub/keepresident/

UNIX: list what sudo permissions you have

> sudo -l
Password:
You may run the following commands on this host:
(root) /usr/local/apache/bin/
(root) NOPASSWD: /app/teamsite/iw-home/opendeploy/bin/iwsyncdb.ipl
(root) NOPASSWD: /etc/init.d/smb
(root) NOPASSWD: /usr/local/samba/bin
(root) NOPASSWD: /bin/vi /etc/group
(root) NOPASSWD: /usr/local/bin/top
(root) NOPASSWD: /bin/vi /etc/group
(root) NOPASSWD: /usr/bin/ls
(root) NOPASSWD: /usr/ucb/vipw
(root) NOPASSWD: /usr/local/bin/top
(root) /bin/tail

Javascript: matching with regex

There seem to be 3 ways to use regular expressions in javascript:
1.
var val = document.getElementById("some_id").value;
val.replace(/^\s+|\s+$/g, ""); //trim using regex
2.
var alpha = /^[A-Za-z]+$/ ;
var val = document.getElementById("some_id").value;
if(alpha.test(val)){
//val matches alpha
}
3.

var val = document.getElementById("some_id").value;
var alpha ='((?:[a-z][a-z]+))'; // Word 1
var p = new RegExp(alpha,["i"]);
var m = p.exec(val);
if (m.length>0)
{
   var word=m[1];
   //word is the capture group 1
}

if anyone knows a better way, feel free to share.

NoClassDefFoundError: com/sun/mail/util/SharedByteArrayInputStream

problem:
when trying to send mail i get error: NoClassDefFoundError: com/sun/mail/util/SharedByteArrayInputStream

solution:
get mail.jar and put it on your classpath

http://java.sun.com/products/javamail/downloads/index.html

Java: find nested balanced tags

Problem:
I needed to parse out some divs from a html page, and java's regex cant do it. atleast when you have arbitrary number of nested balanced elements.

Solution:
<br /><br />private String removeDivContents(String id, String clazz,<br /> String text){<br />String div = "<div class="\"><br /> +clazz.toLowerCase()+"\" id=\""+id.toLowerCase()+"\">";<br />String textl = text.toLowerCase();<br />int index = textl.indexOf(div);<br />if(index == -1){<br /> return text;<br />}<br />int loc = index + div.length();<br />int end = findBalancedClosingTag(loc, textl,<br /> "<div","</div>", 1);<br />return text.substring(0,index) + text.substring(end);<br />}<br /><br />private int findBalancedClosingTag(int start,<br />String textl, String startTag, String endTag, int unClosedStarts){<br />int index = textl.indexOf(endTag,start);<br />if(index == -1){<br /> return start;<br />}<br />Pattern p = Pattern.compile(startTag);<br />Matcher m = p.matcher(textl.substring(start, index));<br />unClosedStarts --; // we are in this function so we closed ONE start tag<br />while(m.find()){<br /> unClosedStarts ++;<br />}<br />if(unClosedStarts == 0){<br /> return index + endTag.length();<br />} else {<br /> return findBalancedClosingTag(index + endTag.length(), textl, startTag, endTag, unClosedStarts);<br />}<br />}<br />
Use at your own risk.

UNIX: dd trick to speed up disk access times

This was stolen from the Lucene mailing list as a strategy to warm up an IndexSearcher:
Something like dd if=/path/to/index/foo.cfs of=/dev/null
Basically, force the data through the kernel preemptively, so FS caches it.
Run vmstat while doing it, and if the index hasn't been cached by the FS, you should see a spike in IO activity while dd is running.

source: (something in the middle of the thread)
http://www.gossamer-threads.com/lists/lucene/java-user/43418

java.lang.NoSuchFieldError:prohibited Lucene Highligher

Problem:

java.lang.NoSuchFieldError: prohibited
    at
org.apache.lucene.search.highlight.QueryTermExtractor
.getTermsFromBooleanQuery(QueryTermExtractor.java:91)

Solution:

You are using an old (pre 1.9) highlighter lib on a
1.9+ lucene. You need to pull the latest highlighter
sources from the svn repos, make a jar out of them and
use that inst

also, 'prohibited' referes to actual method param inside
of highlighter. 

nice regex util class, replaceAll

elliotth.blogspot.com/java-implementation-of-rubys-gsub.html

Here is an example of what this does:

String result = new Rewriter("([0-9]+) US cents") {
public String replacement() {
  long dollars = Long.parseLong(group(1))/100;
     return "$" + dollars;
  }
}.rewrite("5000 US cents");
System.out.println(result);

prints>> $50

nice!

java.io.IOException: read past EOF on Lucene

Problem:
This is the error:
java.io.IOException: read past EOF

Lucene throws that error when you try to read an index.

Solution:
The lucene index was most likely corrupted at some point. In my case, it broke during the ant's copy in the deployment.

Other pages say that it may be because the index uses a weird char set where chars may be bigger or smaller then what you think they are, so if you think they are 8 bits, and they are actually 7, you will read past EOF.

using cron on solaris

crontab -l

figure out whats in your cron, copy to a file called myCron
modify the file and add the crap you want
50 13 * * * /usr/local/subversion/svnbackup.sh
this runs the script at 1:50pm every day
then copy the file into the cron:

crontab < myCron

yey!

UNIX: delete files older then X days old

This can be useful when making a rolling backup script

find /directory -type f -mtime +12 | xargs rm

/directory: your directory name that the files are under (rename appropriately)
-type f: only delete files (not subdirectories)
+12: older than 12 days old

quick mod by 11

1==1 (mod 11)
10==-1 (mod 11)
100==1 (mod 11)
1000==-1 (mod 11)

Therefore 123456 == 6 - 5 + 4 - 3 + 2 - 1 (mod 11) == 3 (mod 11)
Obviously you may need to do a further % operation after adding and subtracting digits, but it should be reasonably fast.

change eclipse max memory

in the shortcut:
eclipse.exe -vmargs -Xmx256m -Xms128m

handy eclipse template: class quick init

public ${enclosing_type}() {
${cursor}
}
public static void main(String[] args){
new ${enclosing_type}();
}

how to update ports on freebsd (better way)

first get cvsup_fastest

then make a script

#!/bin/sh
cvsup -gL2 -h`cvsup_fastest -Q -c us` /usr/share/examples/cvsup/ports-supfile



cron this or whatever

unix shell scripting: args check

usage()
{
echo "Usage: program [args] [bleee]"
}
if [ $# -eq 0 ] ; then
echo "ERROR Insufficient arguments"
usage
exit 1
fi

send email on solaris 8 with xmail

/bin/mailx -s "subject" email@address.com < /path/to/message/body.txt

the message body has to be a file.

Set env variables with tcsh

setenv VARIABLE /some/path/:/some/other/path