mkyong, Author at Mkyong.com

Tomcat – java.security.AccessControlException: access denied (logging.properties read)

December 28, 2010July 30, 2008 by mkyong

Problem After upgraded to Tomcat version 5.5.25, it starting to hit a lot of errors in security policy : Caused by: java.security.AccessControlException: access denied (java.io.FilePermission /usr/share/tomcat5.5- webapps/jsp-examples/WEB-INF/classes/logging.properties read) Solution Above error is caused by the Tomcat’s policy file, Tomcat 5.5.25 made a lot of modification on policy file. To fix it, you need to make …

What is Tomcat default administrator password ?

February 3, 2016July 30, 2008 by mkyong

Is there or what is the default administrator user and password for Tomcat? Tested : Tomcat 8.0.30 Tomcat 7.0.67 Tomcat 6.0.44 Article update history Updated 03/02/2016 : Add support for Tomcat 7 and 8. Updated 08/04/2011 : Update article. 1. Tomcat 7 and Tomcat 8 Tomcat users are defined in the file – $TOMCAT_HOME/conf/tomcat-users.xml, by …

How to check directory file size on linux (Solution)

August 30, 2012July 24, 2008 by mkyong

hmm… linux whatever also in command line, it really make me uncomfortable, i even need to issue a command to check a directory size. du -lh P.S always issue -h to display file size in human readable format We can check summary of a directory by issuing du -sh

Java – How to remove spaces in between the String

November 8, 2020July 23, 2008 by mkyong

This article shows how to use regex to remove spaces in between a String. A string with spaces in between. String text = "Hello World Java."; We want to remove the spaces and display it as below: Hello World Java. 1. Java regex remove spaces In Java, we can use regex \\s+ to match whitespace …

Javascript call a function after page loaded

March 15, 2024July 22, 2008 by mkyong

This article shows how to call a function after a page is loaded in Javascript. Table of contents: 1. Document: DOMContentLoaded event 2. Window: load event 3. Javascript calls a function after the page loaded 4. References 1. Document: DOMContentLoaded event In modern JavaScript, the most common way to run code after loading the page …

Java decompiler plugin for Eclipse IDE

June 29, 2021July 21, 2008 by mkyong

In Eclipse IDE, we can use Enhanced Class Decompiler plugin to decompile Java class files without source code directly. After installing and configuring the Enhanced Class Decompiler plugin, click on the class or methods, press F3, and the plugin will automatically decompile the Java class. Table of contents 1. What is Enhanced Class Decompiler plugin? …

How to copy Entire Directory in Linux

August 30, 2012July 20, 2008 by mkyong

Command is simple, here i provide two samples to show how to copy entire directory in linux. cp -r sourcedir targetdir for instance, 1) Copy anything from current directory to /usr/local/download cp -r * /usr/local/download 2) Copy whole directory (include content) /usr/local/fromdownload to target /usr/local/download cp -r /usr/local/fromdownload /usr/local/download

How to building PostgreSQL libpq Programs

August 30, 2012July 19, 2008 by mkyong

Create and compile a program with PostgreSQL libpq is not so straightforward. I created a sample program like “testlibpq.c” in PostgreSQL documentation to test it. When i compile it, i hit following error libpq-fe.h: No such file or directory PGconn’ undeclared (first use in this function) mkyong@mkyong-desktop:~/Desktop/index$ gcc -o test.o test.c test.c:8:22: error: libpq-fe.h: No …

Calculate program execute time / time elapsed in C

August 30, 2012July 19, 2008 by mkyong

Here i shared a simple method to calculate program execute time or time elapsed in C /*calculate program execute time */ #include #include int main(int argc, char *argv[]) { time_t start, stop; clock_t ticks; long count; time(&start); // Do stuff int i=0; while(i

Open Browser in Java windows or Linux

August 30, 2012July 18, 2008 by mkyong

A very useful Java code, to open a web browser from Java application in windows or Linux. package com.mkyong; public class StartBrowser { public static void main(String args[]) { String url = "http://www.google.com"; String os = System.getProperty("os.name").toLowerCase(); Runtime rt = Runtime.getRuntime(); try{ if (os.indexOf( "win" ) >= 0) { // this doesn’t support showing urls …

How to handle unknow size user input in C

September 20, 2012July 17, 2008 by mkyong

Here are two examples to handle user input in C. 1. scanf This method is easy get attack by buffer overflow, try input some characters which are more than what you declare to experience about what is buffer overflow. #include #include int main() { char bStr[80]; printf(“\nEnter a very very very long String value:”); scanf(“%s”, …

Backup & Restore Database in PostgreSQL (pg_dump,pg_restore)

August 30, 2012July 16, 2008 by mkyong

Here i demostrate how to backup and restore dabatase in PostgreSQL 1)Backup data with pg_dump pg_dump -i -h localhost -p 5432 -U postgres -F c -b -v -f "/usr/local/backup/10.70.0.61.backup" old_db To list all of the available options of pg_dump , please issue following command. pg_dump -? -p, –port=PORT database server port number -i, –ignore-version proceed …

Fedora Password is Strong !!!

August 30, 2012July 15, 2008 by mkyong

Fedora you are strong !!! Here i share a bit funny stuff, regarding when i reset my postgres user password in fedora core 8. Please view below picture. Actually i just want to set a easy remember password for user postgres. However i unable to do it. First i enter password as “password” Fedora : …

ClassNotFoundException: org.apache.commons.logging.LogFactory

January 27, 2016July 14, 2008 by mkyong

Starting a web application, but hits the following error messages : … Caused by: java.lang.ClassNotFoundException: org.apache.commons.logging.LogFactory … 1. Normal Case 1.1 Obviously, the Apache Commons logging is missing – commons-logging-xxx.jar. To fix it, get it from Maven central repository. pom.xml <dependency> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId> <version>1.2</version> </dependency> 2. Spring Case 2.1 For Spring application, developers always excluded …

How to set environment variable on Ubuntu

March 4, 2020July 11, 2008 by mkyong

On Ubuntu, there are two system-wide environment variables, both files need admin or sudo to modify it. /etc/environment – It is not a script file, purely assignment expressions, one per line. /etc/environment PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games" JAVA_HOME=/usr/lib/jvm/adoptopenjdk-11-hotspot-amd64 LD_LIBRARY_PATH=/usr/local/lib:/usr/lib/postgresql/8.3/lib /etc/profile.d/*.sh – Files with .sh extension in the /etc/profile.d/ folder. /etc/profile.d/myenv.sh export JAVA_HOME=JAVA_HOME=/usr/lib/jvm/adoptopenjdk-11-hotspot-amd64 export LD_LIBRARY_PATH=/usr/local/lib:/usr/lib/postgresql/8.3/lib export PATH=$PATH:$JAVA_HOME/bin Further Reading: Ubuntu …

PostgreSQL – ERROR: operator does not exist: smallint = character varying (Solution)

May 31, 2010July 11, 2008 by mkyong

Today i hit a weird error, actually my company is plan to migrate existing j2ee web application from PostgreSQL 8.2 to latest PostgreSQL 8.3. But after i set up PostgreSQL 8.3 properly, and start web application, i keep hiting following error org.postgresql.util.PSQLException: ERROR: operator does not exist: smallint = character varying It’s seem like data …

Performance Testing on Partition Table In PostgreSQL – Part 3

May 31, 2010July 8, 2008 by mkyong

I will make a performance test between partition table and non partition table. Here are two tables both contains 200 millions of data. 1) hashvalue_pt (Partiton tables In Month) 2) hashvalue (Non Partiton tables) P.S Please visit Partition Table In PostgreSQL (Create Partition) – Part 1 If you do not know how to do table …

error: C compiler cannot create executables – Ubuntu (Solution)

August 30, 2012July 5, 2008 by mkyong

Default VI for Ubuntu is suck, i have to go install a full package of vi myself. However when i try to compile the vi source code, i hit following error error: C compiler cannot create executables It’s cause all my gcc compiler error, hmm…Ubuntu, why you have so many problem? Compiler also hit error….. …

Install Perl in PostgreSQL, The specified module could not be found.

May 31, 2010July 4, 2008 by mkyong

Here i provide few steps to guide how to install Perl in windows PostgreSQL 1) Install ActivePerl to make your windows support Perl script. 2) Set Perl bin folder to windows environment variable 3) Restart PostgreSQL 4) Issue Createlang command C:\>createlang -U postgres plperl DB_NAME If you hit “The specified module could not be found” …

Partition Table In PostgreSQL (Simulate Millions Data) – Part 2

May 31, 2010July 2, 2008 by mkyong

If you do not know how to do table partition in PostgreSQL, please study Partition Table In PostgreSQL (Create Partition) – Part 1 Here i will provide a simple function to demonstrate how to insert million of data into partition table. –create sequence for testing CREATE SEQUENCE hashvalue_PT_serial START 1; –Generate Dynamic data for testing …

Partition Table In PostgreSQL (Create Partition) – Part 1

May 31, 2010July 2, 2008 by mkyong

Partition table in PostgreSQL is very easy to do, It involve inheritance concept and trigger of PostgreSQL. Here i provide a sample to demonstrate how to partition table in PostgreSQL. Before proceed, please understand some basic concept like,er… better i provide a concept of partition “time” in a table. “Mother” — (Child1, Child2, Child3,Child4, Child5) …

How to install pgAgent on windows (PostgreSQL Job Scheduler)

August 30, 2012June 29, 2008 by mkyong

This is a surprise for me that PostgreSQL do not have any build-in job scheduler. However It did pack into pgAdmin source but i wonder why it didnt intsall it by default? Here i provide some steps to show how to install pgAgent(Job Scheduler) on windows as services 1) Go to your PgAdim file path …

How to check hard disk size on linux (Solution)

November 2, 2012June 27, 2008 by mkyong

So, how much is my hard disk size left? To check file sizes in *nix system, use the command df -h df -h

How to find large file size on linux

August 30, 2012June 25, 2008 by mkyong

Often time, you may need to know which file contains large file size, and delete it to save space. Here’s a code pattern to show you how to find large file size on Linux : find {directory} -type f -size +100000k -exec ls -lh {} \; | awk ‘{ print $9 ": " $5 }’ …

How to check ip address in linux

August 30, 2012June 24, 2008 by mkyong

Just issue following command to check your ip address in linux /sbin/ifconfig ya, my ip address now is 10.0.0.6

PostgreSQL Network Access – (Solution)

December 18, 2012June 22, 2008 by mkyong

After we installed and configure PostgreSQL properly, it is no problem to access locally, however when we access through the network , we hit following error message. could not connect to server: Connection refused (0x0000274D/10061) Is the server running on host “10.0.0.6” and accepting TCP/IP connections on port 5432? It is because PostgreSQL disable network …

How to compile PostgreSQL database source code in linux

May 31, 2010June 22, 2008 by mkyong

It’s been a long time i didnt update my blog, recently i’m busy research on Hyper Estraier , it is a powerful full text search engine written in c, i will write some information about it future. Ok i provide following steps to show how to compile PostgreSQL database source code in linux. 1) Please …

How to install postgresql in fedora core

August 30, 2012June 21, 2008 by mkyong

Here i share how i install postgresql in fedora core. I spent full day to find out a solution. Hope this help 1) First please get a PostgeSQL source code n compile it for installation or using yum command in fedora core. a) Regarding PostgeSQL source code Compilation, please visit here https://mkyong.com/database/how-to-compile-postgresql-database-source-code-in-linux/ b) Regarding Yum …

How to install java jdk on fedora core (linux)

June 20, 2017June 11, 2008 by mkyong

How to install java jdk on fedora core? here i provide few steps to demonstrate how it’s work. Installation Setup 1 ) Please visit sun java website to download any java jdk version you like. http://java.sun.com/javase/downloads/index.jsp 2 ) Click download, select Linux platform, language and accept license and continue. 3 ) Select “Linux RPM in …

List all ports opened in windows (netstat -nb)

August 30, 2012June 6, 2008 by mkyong

Recently some of my ports always conflict with the port i want to open in window. I try to find out how can i know what programs or ports currently using in my computer? With a simple command, it will show exactly what i want to know. Please issue following command in windows command prompt. …

How to uninstall postgresql from fedora core

August 30, 2012June 5, 2008 by mkyong

Here i show how to uninstall Postgresql from fedora core. change to root user or process owner and issue following command. yum remove postgresql Hope this help.

PostgreSQL – Create table from existing table

May 31, 2010June 2, 2008 by mkyong

PostgreSQL support function like create a new table(with data) from an existing table. It can be achieved with following two syntax. 1) CREATE TABLE ‘NEW_TABLE_NAME’ AS SELECT * FROM ‘TABLE_NAME_YOU_WANT_COPY’; 2) SELECT * INTO ‘NEW_TABLE_NAME’ FROM ‘TABLE_NAME_YOU_WANT_COPY’ ; Sometime i also use this method to temporary backup table :), according to PostgresSQL ‘CREATE TABLE AS’ …

Java – Check if array contains duplicated value

November 15, 2020May 31, 2008 by mkyong

This article shows a few ways to detect if an array contains a duplicated value. Java 8 Stream, compare the array size. TreeSet, compare the array size. Two for loops, classic algorithm, 0(n^2). Set, 0(n). Bitmap, boolean[] 0(n). All the above solutions are tested with the below program and generate the same output. (except 5. …

How to clear browsing history in Firefox

August 30, 2012May 19, 2008 by mkyong

Firefox keeps browsing history of every web pages you visited. Sometime you need to clear browsing history in order to hide the web pages you visited before. Browser History To view your web page history in Firefox, do this Hold down the CTRL key and press H. Click History tab, and click Show in Sidebar. …

Html Tutorial Hello World

August 30, 2012May 19, 2008 by mkyong

In this tutorial, you will learn how to create a simple hello world page with HTML. Firstly, let explains some of the HTML basics. HTML is stands for Hyper Text Markup Language HTML is a text file which consists a set of markup tags like (<html><body></html></body>). Almost all of the markup tag has start tag …