Recently, I’m been asked by my colleague (C++ programmer) regarding why java does not contains a constant keyword? Actually java do contains constant function , but it just appear as different keyword – final. A final variable in java is equal to C++ constant. The final keyword is declare before a data type, it make …
Currently my company is using IBATIS and pure SQLs as database persistence mechanism. I like SQL query very much, especially in tuning, but i do not like to write all SQL statement in Java application, it’s easy to hit typo error and what a stupid and tedious job? Finally my company has a new project …
Here is another example to show how to read a file in Java with BufferedInputStream and DataInputStream classes. The readLine() from the type DataInputStream is deprecated. Sun officially announced this method can not convert property from bytes to characters. It’s advised to use BufferedReader. You may interest to read this How to read file from …
In this article, we will show you how to use java.io.BufferedReader to read content from a file Note Read this different ways read a file 1. Files.newBufferedReader (Java 8) In Java 8, there is a new method Files.newBufferedReader(Paths.get(“file”)) to return a BufferedReader filename.txt A B C D E FileExample1.java package com.mkyong; import java.io.BufferedReader; import java.io.IOException; …
HashMap is an object that stores both key=value as a pair. This HashMap permits null values and the null key, unsynchronized and no guarantees to the order of the map. ["key","value"] = ["java","mkyong.com"] 1. HashMap Basic 1.1 Add an Item Map map = new HashMap<String, String>(); map.put("PostgreSQL", "Free Open Source Enterprise Database"); 1.2 Get an …
JQuery is really a powerful and handy JavaScript library. The page or content loading effect is very easy to implement in jQuery. Here’s a example to make your web page content display a fade in page loading effect. It will make your reader a shock impression. 🙂 The idea is simple ~ 1. Create a …
PostgreSQL “Point-in-time Recovery” (PITR) also called as incremental database backup , online backup or may be archive backup. The PostgreSQL server records all users’ data modification transaction like insert, update or delete and write it into a file call write-ahead (WAL) log file. This mechanism use the history records stored in WAL file to do …
Since WordPress version 2.x, jQuery is a build-in Javascript library, explicitly include the jQuery library into WordPress is not necessary. Problem The jQuery is not working in WordPress plug-in writing? When you try to test a simple jQuery effect like following $(document).ready(function(){ alert(‘test’); }); It’s just not working, no alert message box pop up. The …
This article shows how to create a table with zebra stripes effect using jQuery. Table of contents: 1. Include the jQuery script 2. CSS styling the zebra stripes 3. Table Structure 4. jQuery Script 5. Full example 6. References P.S Tested with jQuery 3.7.1 1. Include the jQuery script Include the jQuery script from the …
This article shows different function calling in both JavaScript and jQuery. At the end, we will show an example of how to call a function to create dynamic content after a page is loaded, both in JavaScript and jQuery. Table of contents: 1. JavaScript Function Calling 2. jQuery Function Calling 3. JavaScript – Function calling …
jQuery is a fast, small, and feature-rich JavaScript library. It simplifies HTML document traversal and manipulation, event handling, and animation with an easy-to-use API that works across browsers. This article shows how to load a jQuery script and change the text of a div element to Hello World when the document is ready. P.S Tested …
A few examples to show the use of tar command to create a .tar.gz file on Linux. Table of contents 1. Create, list and extract a .tar.gz file 2. What is tarball or .tar.gz? 3. Create a .tar.gz file 3.1 Tar and compress a file 3.2 Tar and compress multiple files 3.3 Tar and compress …
Today i facing one funny problem, i need to convert a primitive long array (long[]) to an object Long[]. First I thought java JDK should provided this kind of function, however i failed to find it. I have to use a for loop to convert it manually. Below is the covertion source code. long [] …
Often time, Tomcat may hits the following java.lang.OutOfMemoryError: PermGen space error. java.lang.OutOfMemoryError: PermGen space at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:620) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124) It’s usually happened after the Tomcat restarts a few times. 1. Solution By default, Tomcat is assigned a very little PermGen memory for the running process. To fix it, increase the PermGen memory settings …
Here i will show how to set or change default page in Apache. Apache default page is very easy to configure, we just need to configure Apache conf file in following location Apache file path/conf/httpd.conf Make the following changes in httpd.conf file. Change index.html or index.php to whatever default page you want. # # DirectoryIndex: …
Adapter , Adapter , Adapter ~ Actually Adapter design pattern can consider as a simple conversion program / class. It usually used to make two incompatible interfaces or classes to work together. Please review below Adapter design pattern image draw by me, a bit ugly 🙂 Case Study Company A developed a program in Java …
In Unix system like Debian, Ubuntu or Red Hat, It is possible to set a static IP address with ifconfig command. My current Debian system IP address is 10.70.0.61 mkyong:~# ifconfig eth0 Link encap:Ethernet HWaddr 00:15:17:1D:CE:2F inet addr:10.70.0.61 Bcast:10.70.3.255 Mask:255.255.252.0 I want change it to 10.70.0.66, just issue following command to set a static IP …
PostgreSQL comes with an easy to use export tool to export data from PostgreSQL database. In this tutorial, we show you how to export data from PostgreSQL to a file or csv file. 1. Connect PostgreSQL Use psql command to connect to the PostgreSQL database. $ psql -p 5433 -U dba dbname P.S 5433 is …
Today, i found out that one of the SQL query is hanging in PostgreSQL, and never release itself. “Cancel query” command won’t help, and the query just hanging there and show an “idle in transaction” status. It left me no choice but go Debian terminal to issue “kill” command to terminate it manually. Query hanging …
According to World Wide Web Consortium (W3C), the tag in HTML is deprecated. It is removed in a from its recommendations.W3C encourage to use style sheets (CSS) to define the layout and display properties of HTML elements. However there still a lot of people using it, it still worth to mention a while here. Font …
Life is full of colors, so does HTML ~ Color formula as below RED + GREEN + BLUE = COLOR Colors are displayed combining RED, GREEN, and BLUE. Usually we can change html font color in two ways 1) Use Color Name Red Color Red Color 2) Use Hex code (#) Red Color Red Color …
As we all know PostgreSQL 8.3 make very strong checking on data type, it make a lot application hit many data type error after migration from PostgreSQL8.x to PostgreSQL8.3. Mostly is cause by data type checking. One of the common error is to_date() function. It accept two text as parameters. to_date(text,text) Ok now i create …
Here i show a simple java example to demonstrate how to let user download a file from website. No matter you are using struts , JSP, Spring or whatever other java framework, the logic is same. 1) First we have to set HttpServletResponse response to tell browser about system going to return an application file …
This article shows how to write data to a comma-separated values (CSV) file. Topics: OpenCSV – Write data to a CSV file Single class CSV writer – Write data to a CSV file Single class CSV writer – Unit Tests Note The RFC 4180 defines the format or definitions of a CSV file or text/csv …
Problem The Spring AOP transaction is not working in following interceptors? <bean id="testAutoProxyCreator" class="org.springframework.aop.framework.autoproxy.BeanNameAutoProxyCreator"> <property name="interceptorNames"> <list> <idref bean="urlInterceptorInsert" /> <idref bean="urlInterceptorCommit" /> <idref bean="urlInterceptorRelease" /> <idref bean="matchGenericTxInterceptor" /> </list> </property> <property name="beanNames"> <list> <idref local="urlBo" /> </list> </property> </bean> The “matchGenericTxInterceptor” transaction interceptor, suppose to intercept urlInterceptorInsert, urlInterceptorCommit,urlInterceptorRelease, but it’s not work as expected? …
“public” is PostgreSQL default scheme, i have to change it because i had migrated a new database data into another new schema call “new_public”. Before start to change, i have to check what is current PostgreSQL default schema? 1) Command SHOW search_path 2) Check postgresql.conf #————————————————————————— # CLIENT CONNECTION DEFAULTS #————————————————————————— # – Statement Behavior …
This tutorial shows you how to install OpenJDK 8, 11, 16, and other JDK builds on Ubuntu 20. 1. APT Install JDK (OpenJDK 8 and 11) 2. Install JDK manually (OpenJDK 16) 3. Install Oracle JDK on Ubuntu 4. Switch between different JDK versions 5. Add JAVA_HOME to Ubuntu environment variable 6. References 1. APT …
Today my boss ask me install a tomcat in linux machine. After i ssh into that machine, i wonder what is the Linux distribution version? Red Hat? Ubuntu? Fedora? Debian? However with a simple command, i can check what is linux distribution version mymachine:~# cat /proc/version Linux version 2.6.18-5-686-bigmem (Debian 2.6.18.dfsg.1-13etch3) ([email protected]) (gcc version 4.1.2 …
How can i get a random row from a query result in PostgreSQL? The answer is easy, just using RANDOM() built-in function in PostgreSQL SELECT scoreid FROM n_score ORDER BY RANDOM() limit 1; Above example will get a random score id from table n_score. Everytime execute it will get a random score id. Done.
Problem Ubuntu…beside Default VI is suck, here is another issue for me. My mouse wheel scrolling is not working in Ubuntu8.04. However i installed Ubuntu in vmware, but i do not think it is vmware cause of this issue. Solution Here i find some useful information regarding Mouse Wheel Scrolling malfunction issuse, please check Ubuntu …
I want my subquery results (multi rows) return as a singale row in my query. For example. select u.url, (select c.categoryid from category c where c.categoryid = u.categoryid) from url u If url contains multiple categories, subquery will return multiple rows as following P.S Subquery return multiple rows is not supported in most of the …
Many webmasters like to disable the right click button to protect their own content. Here is the JavaScript to disable right click button on a website : <script> <!– //edit this message to say what you want var message = "Function Disabled"; function clickIE() { if (document.all) { alert(message); return false; } } function clickNS(e) …
Here is a brief explanation about Java Web Start from SUN “Java Web Start is a mechanism for program delivery through a standard Web server. Typically initiated through the browser, these programs are deployed to the client and executed outside the scope of the browser. Once deployed, the programs do not need to be downloaded …
This tutorial shows you how to install Tomcat on Ubuntu, with help of the buith-in apt-get command. 1. apt-get install 1.1 Find an available Tomcat package to install $ sudo apt-cache search tomcat //… tomcat7 – Servlet and JSP engine tomcat7-admin – Servlet and JSP engine — admin web applications tomcat7-common – Servlet and JSP …
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Problem As i said in previously post, Tomcat 5.5.25 made a lot of modification in policy file, which may enhance security on web application but it also causing a lot of problem, see another error message : SEVERE: Context initialization failed java.security.AccessControlException: access denied (java.lang.RuntimePermission accessDeclaredMembers) at java.security.AccessControlContext.checkPermission(AccessControlContext.java:323) Solution Policy file issue, vi 04webapps.policy, this …
To find out the Tomcat version, find this file – version.sh for *nix or version.bat for Windows. This version.sh file is normally located in the Tomcat bin folder. For example : mkyong@hcompass:/usr/share/tomcat7/bin$ ./version.sh Using CATALINA_BASE: /usr/share/tomcat7 Using CATALINA_HOME: /usr/share/tomcat7 Using CATALINA_TMPDIR: /usr/share/tomcat7/temp Using JRE_HOME: /usr Using CLASSPATH: /usr/share/tomcat7/bin/bootstrap.jar:/usr/share/tomcat7/bin/tomcat-juli.jar Server version: Apache Tomcat/7.0.28 Server built: Apr …
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 …
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 …
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