Notes by Dr. Xi
Displaying keyword search results 1 - 10
Created by Dr. Xi on November 11, 2011 10:05:22
Last update: November 11, 2011 10:12:01
This is an HTML image tag filter using Java regex. It takes a string, finds the img tags, replaces the src attribute with one provided by the filter, then adds a class name to the class attribute.
import java.util.regex.*;
import java.io.*;
...
Test file:
<div id="HTML snippet">
<img src="img/big/txt-m...
Created by Dr. Xi on February 12, 2010 22:52:27
Last update: November 08, 2011 19:48:09
For Tomcat 6, there's no default manager username and password. You do have to set it up yourself, though it's pretty straightforward. The Tomcat manager webapp is restricted to users with a role named manager . So you'll need to create a user and assign the manager role to it.
Edit $CATALINA_BASE/conf/tomcat-users.xml to read:
<?xml version='1.0' encoding='utf-8'?>
<!--
...
For tomcat 7:
<tomcat-users>
<role rolename="manager"/>
...
Created by Dr. Xi on July 13, 2011 16:18:05
Last update: July 13, 2011 16:18:05
The goal is to read a file like this:
for (String line: textFileReader) {
// do s...
This is the code:
import java.io.*;
import java.util.Iterator;
...
Created by Dr. Xi on June 21, 2011 15:54:00
Last update: June 22, 2011 11:33:09
Demo code for CSV parsing with SuperCSV parser .
Java code:
import java.io.*;
import java.util.List;
imp...
Test with a simple CSV file:
psmith01,CLASS2B,Peter Smith 1,YEAR2,1,N,ADVANCED,...
The parser worked correctly:
Line 1 has 11 values:
|psmith01|
|CLASS2B|...
Test with a more complicated CSV file:
"psmith01 abc", "CLASS2B " , " Peter...
The parser messed up on all three lines:
Line 1 has 5 values:
|psmith01 abc|
|CLASS...
Using two lines input:
"psmith01 abc", "CLASS2B " , " Peter...
It generates an exception:
Line 1 has 5 values:
|psmith01 abc|
|CLASS...
Add a new line in item two:
"One", "Two
", "Three"
Result:
Line 2 has 3 values:
|One|
|Two
|
|...
Created by Dr. Xi on May 17, 2011 21:14:58
Last update: May 17, 2011 21:17:58
Read certificate one at a time from BufferedInputStream :
// import java.security.cert.*;
public void rea...
Read all certificates from a file as a collection:
public void readCertificates(File f) throws Except...
Created by Dr. Xi on April 27, 2011 08:28:31
Last update: April 27, 2011 08:37:40
JBoss example with hsql:
<persistence>
<persistence-unit name="myapp"...
MySQL example with JDBC :
<persistence
xmlns="http://java.sun.com/xml...
With OpenEJB transaction manager:
<persistence version="1.0"
xmlns="...
With EclipseLink :
<?xml version="1.0" encoding="UTF-8"?>
<persist...
Created by Dr. Xi on January 14, 2010 00:28:27
Last update: March 30, 2011 15:37:44
A task that a Java developer does so frequently is to find out where a certain class can be found - to resolve compilation errors, classpath issues, or version conflicts of the same class introduced by multiple class loaders. A long while back I wrote a simple Perl script to perform the task. Later I was informed that there are Swing based Jar Browser and Jars Browser . Then, there are a couple of shell one-liners:
# one liner 1 find -name "*.jar" -print0 | xarg... But all of them share the same problem: if a class is in a jar nested in another jar, it cannot be found. Such is the case for a class inside a jar under the WEB-INF/lib directory of a...
Created by Dr. Xi on March 30, 2011 13:43:05
Last update: March 30, 2011 13:45:27
Method 1 - use javap with verbose flag:
$ javap HelloWorld -verbose | head
Compiled fro...
Method 2 - use a utility class:
import java.io.*;
import java.nio.ByteBuffer;
...
According to the VM Spec , a Java class file has this structure:
ClassFile {
u4 magic;
...
Created by Dr. Xi on March 28, 2011 11:11:33
Last update: March 28, 2011 11:13:21
grep is a versatile command with many variations (grep, egrep, fgrep, then various implementations). It uses a regula expression (regex) pattern to filter input. But then there are basic and extended flavors of regex - leading to even more confusion. And, beware that there are lots of bad examples of regex in the wild... There are two critical questions to ask when you use grep: which grep implementation are you using? what is the flavor of the regex? Here are some examples for gnu grep v2.7:
# Find all numbers (no decimal point), basic regex... Use the -o flag to show only the matching part instead of the whole matching line: grep -o -E '\b[0-9]{2}\b' The good thing about the gnu grep is that it...
Created by Dr. Xi on March 02, 2011 11:39:18
Last update: March 09, 2011 12:19:30
Some peculiarities about Java PrintWriter: PrintWriter never throws any exceptions. From JavaDoc : Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking checkError(). When error occurs, you'll never know anything more than that it occured, because checkError returns boolean. When a character is out of the range of the character encoding of the PrintWriter, it prints a question mark (?). But this is not an error. Test code:
import java.io.*; public class TestPrintWri... Latin1 test result: java TestPrintWriter iso-8859-1 | od -bc 000000... UTF-8 test result: java TestPrintWriter utf-8 | od -bc 0000000 141... Also, the constructor throws a FileNotFoundException when you try to write to a...
