This article shows how to set the $JAVA_HOME environment variable on older Mac OS X and the latest macOS 11. Topics macOS release history What is /usr/libexec/java_home $JAVA_HOME and macOS 11 Big Sur $JAVA_HOME and Mac OS X 10.5 Leopard $JAVA_HOME and older Mac OS X Switch between different JDK versions Solution Steps to set […]
In Java, you can use HttpServletRequest.getRemoteAddr() to get the client’s IP address that’s accessing your Java web application. import javax.servlet.http.HttpServletRequest; String ipAddress = request.getRemoteAddr(); 1. Proxy Server or Cloudflare For web application which is behind a proxy server, load balancer or the popular Cloudflare solution, you should get the client IP address via the HTTP […]
Problem Downloaded a Java sample from Alexa API on Amazon service, imports it into Eclipse, but unable to compile and hits following “Access restriction” errors : Access restriction: The type BASE64Encoder is not accessible due to restriction on required library /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Classes/classes.jar P.S Using JDK 1.6 and Eclipse IDE 4.2 import sun.misc.BASE64Encoder; // Access restriction error […]
In this tutorial, we show you 2 examples to calculate date / time difference in Java : Manual time calculation. Joda time library. 1. Manual time calculation Converts Date in milliseconds (ms) and calculate the differences between two dates, with following rules : 1000 milliseconds = 1 second 60 seconds = 1 minute 60 minutes […]
Problem See following Spring REST example, if a request such as “http://localhost:8080/site/google.com” is submitted, Spring returns “google“. Look like Spring treats “.” as file extension, and extract half of the parameter value. SiteController.java package com.mkyong.web.controller; import org.springframework.stereotype.Controller; import org.springframework.ui.ModelMap; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; @Controller @RequestMapping("/site") public class SiteController { @RequestMapping(value = "/{domain}", method […]
In this example, we show you how to use Java and DOM XML parser to get the Alexa ranking from below the undocumented API : http://data.alexa.com/data?cli=10&url=domainName 1. Alexa API For example, type following URL in your browser : http://data.alexa.com/data?cli=10&url=mkyong.com Alexa will return back following XML result : <ALEXA VER="0.9" URL="mkyong.com/" HOME="0" AID="="> <DMOZ> <SITE BASE="mkyong.com/" […]
In this example, we will show you how to get Google PageRank (PR) in Java. To request a PageRank for “mkyong.com”, you just need to send following HTTP request : http://toolbarqueries.google.com/tbr?client=navclient-auto&hl=en&ch=6236440745 &ie=UTF-8&oe=UTF-8&features=Rank&q=info:mkyong.com P.S Above URL is used by Google toolbar plugin. The tricky part is following hashing value : ch=6236440745 Google is using Bob Jenkins […]
Jsoup, a HTML parser, its “jquery-like” and “regex” selector syntax is very easy to use and flexible enough to get whatever you want. Below are three examples to show you how to use Jsoup to get links, images, page title and “div” element content from a HTML page. Download jsoup The jsoup is available in […]
Guide to create a web application with Maven, and add Spring MVC as web framework.
The web.xml is a configuration file to describe how a web application should be deployed. Here’re 5 web.xml examples, just for self-reference. 1. Servlet 3.1 deployment descriptor Java EE 7 XML schema, namespace is http://xmlns.jcp.org/xml/ns/javaee/ web.xml <web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" version="3.1"> </web-app> 2. Servlet 3.0 deployment descriptor Java EE 6 XML schema, namespace is […]
This tutorial shows you how to convert a Java project to Java web application project in Eclipse 4.2, it should work in older version as well. 1. Java Project A simple Java project. 2. Project Facets Right click on the project properties. Select “Project Facets“, and click “convert to faceted form…” Check “Dynamic Web Module” […]
Create a simple Java project from Maven template, and also showing how to compile, run unit test, and package the project into a jar file.
The Java 7 Concurrency Cookbook, containing over 60 examples show you how to do multithreaded programming in Java. It shows varies threading topics from beginner level to advanced level, including thread management like create, interrupt and monitor thread, using Java 5 Executor frameworks to run or schedule threads, and the latest Java 7 fork/Join Frameworks […]
Here’s an example to show you how to search a file named “post.php” from directory “/Users/mkyong/websites” and all its subdirectories recursively. FileSearch.java package com.mkyong; import java.io.File; import java.util.ArrayList; import java.util.List; public class FileSearch { private String fileNameToSearch; private List<String> result = new ArrayList<String>(); public String getFileNameToSearch() { return fileNameToSearch; } public void setFileNameToSearch(String fileNameToSearch) { […]
Here are 3 examples to show you how to do “threading” in Spring. See the code for self-explanatory. 1. Spring + Java Threads example Create a simple Java thread by extending Thread, and managed by Spring’s container via @Component. The bean scope must be “prototype“, so that each request will return a new instance, to […]
In Java, we can use ProcessBuilder or Runtime.getRuntime().exec to execute external shell command : 1. ProcessBuilder ProcessBuilder processBuilder = new ProcessBuilder(); // — Linux — // Run a shell command processBuilder.command("bash", "-c", "ls /home/mkyong/"); // Run a shell script //processBuilder.command("path/to/hello.sh"); // — Windows — // Run a command //processBuilder.command("cmd.exe", "/c", "dir C:\\Users\\mkyong"); // Run a […]
By default, the bash terminal in Mac OSX looks plain. bash terminal, profile = Homebrew 1. Add Color To Bash To make the bash terminal console more colorful, you need to create or edit a ~/.bash_profile file, and configure the LSCOLORS value. See following example to show you how to create a new .bash_profile and […]
A Java example to show you how to count the total number of duplicated entries in a List, using Collections.frequency and Map. CountDuplicatedList.java package com.mkyong; import java.util.ArrayList; import java.util.Collections; import java.util.HashMap; import java.util.HashSet; import java.util.List; import java.util.Map; import java.util.Set; import java.util.TreeMap; public class CountDuplicatedList { public static void main(String[] args) { List<String> list = new […]
To call getResourceAsStream in a static method, we use ClassName.class instead of getClass() 1. In non static method getClass().getClassLoader().getResourceAsStream("config.properties")) 2. In static method ClassName.class.class.getClassLoader().getResourceAsStream("config.properties")) 1. Non Static Method A .properties file in project classpath. src/main/resources/config.properties #config file json.filepath = /Users/mkyong/Documents/workspace/SnakeCrawler/data/ FileHelper.java package com.mkyong; import java.io.IOException; import java.io.InputStream; import java.util.Properties; public class FileHelper { public static […]
This tutorial will show you how to use the maven-jar-plugin to create a manifest file, and package / add it into the final jar file. The manifest file is normally used to define following tasks : Define the entry point of the Application, make the Jar executable. Add project dependency classpath. When you run the […]
When editing post or page in WordPress, sometime the server’s firewall will block my IP address, and the log showed the following error: Terminal lfd: (mod_security) mod_security triggered by xx.xx.xx.xx : 5 in the last 300 secs The quick fix is to restart the modem or uses a VPN to get a new IP to […]
In this tutorial, we will show you how to use Maven build tool, to create a single executable Jar, and how to deal with the project’s dependencies. Tools used : Maven 3.1.1 JDK 1.7 log4j 1.2.17 Joda-time 2.5 Eclipse 4.3 1. Create a simple Java project Create a Java project from the Maven quick start […]
Some of the Java enum examples, and how to use it, nothing special, just for self-reference. Note Consider the Enum type if your program consists of a fixed set of constants, like seasons of the year, operations calculator, user status and etc. 1. Basic Enum UserStatus.java public enum UserStatus { PENDING, ACTIVE, INACTIVE, DELETED; } […]
Here’s the scenario, create a custom JSF validator, injects a bean via Spring’s @Autowired. UsernameValidator.java – Custom JSF validator package com.mkyong.user; import javax.faces.application.FacesMessage; import javax.faces.component.UIComponent; import javax.faces.context.FacesContext; import javax.faces.validator.FacesValidator; import javax.faces.validator.Validator; import javax.faces.validator.ValidatorException; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Scope; import org.springframework.stereotype.Component; import com.mkyong.user.bo.UserService; @Component @Scope("request") @FacesValidator("UsernameValidator") public class UsernameValidator implements Validator { @Autowired UserService userService; @Override public […]
See a simple JSF example : <h:form id="signup-form"> <h:inputText id="email" value="#{beanBean.email}" /> </h:form> It will generates following HTML code : <input id="signup-form:email" type="text" /> Uses jQuery selector to get the email id, but failed. <script> jQuery(document).ready(function($) { $(‘#signup-form:email’).checkEmailFormat(); }); </script> Solution This is a well-known problem to integrate JSF and jQuery – the colon “:” […]
In PrimeFaces, if focus component <p:focus> is enabled : When page is loaded, it will focus on first visible input field; If validation failed, it will focus on first error field automatically. It works very nice, and a must use component in form handling. Just wonder why don’t make it enable by default? In this […]
To validate email, uses JSF <f:validateRegex>, and puts following regular expression. This regex should be able to validates most of the email format, and I’m using it for few projects. Email Regular Expression ^[_A-Za-z0-9-\+]+(\.[_A-Za-z0-9-]+)*@[A-Za-z0-9-]+(\.[A-Za-z0-9]+)*(\.[A-Za-z]{2,})$ P.S For detail explanation, refer to this how to validate email address with regular expression. In this tutorial, we will show […]
In PrimeFaces, your can use <p:watermark> to display watermark effect on input field. This watermark component is using HTML5 placeholder attribute in supported browsers like Safari, Chrome and Firefox, and fall back to JavaScript solution for non-support browser like IE. Display watermark text in input field <p:inputText id="username" required="true" label="username" size="40" value="#{userBean.username}" /> <p:watermark for="username" […]
Mac OS x 10.8.3, running a Java’s web application on Tomcat, port 8080. Users from same network are able to access my web server via port 80, but failed on port 8080. Is there a firewall setting blocked the incoming connection via port 8080. Solution 1 The simplest solution is turn off your Firewall. Mac […]
Often times, you may need to override default PrimeFaces CSS with your pretty customize values. In this example, we will show you how to override PrimeFaces error message style. Debug with FireBug, the PF’s error messages style are from primefaces.css primefaces.css .ui-message-info, .ui-message-error, .ui-message-warn, .ui-message-fatal { border: 1px solid; margin: 0px 5px; padding: 2px 5px; […]
Since PrimeFaces 3.0, it provides a very customizable resource ordering. See following order : 1. “first” facet if defined. <f:facet name="first"> <!– load css, js or others –> </f:facet> 2. PrimeFaces – JSF registered CSS. 3. PrimeFaces – Theme CSS. 4. “middle” facet if defined. <f:facet name="middle"> <!– load css, js or others –> </f:facet> […]
Since Spring 3.0, Spring supports for the standard JSR 330: Dependency Injection for Java. In Spring 3 application, you can uses standard @Inject instead of Spring’s @Autowired to inject a bean. @Named instead of Spring’s @Component to declare a bean. Those JSR-330 standard annotations are scanned and retrieved the same way as Spring annotations, the […]
In Spring, you can uses this special <null /> tag to pass a “null” value into constructor argument or property. 1. Constructor Argument The wrong way to inject a null into constructor argument, a really common mistake, and nice try 🙂 <bean id="defaultMongoTypeMapper1" class="org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper"> <constructor-arg name="typeKey" value="null" /> </bean> Correct way. <bean id="defaultMongoTypeMapper" class="org.springframework.data.mongodb.core.convert.DefaultMongoTypeMapper"> <constructor-arg […]
By default, SpringData’s MappingMongoConverter add an extra “_class” column for every object saved in MongoDB. For example, public class User { String username; String password; //…getters and setters } Save it MongoOperations mongoOperation = (MongoOperations)ctx.getBean("mongoTemplate"); User user = new User("mkyong", "password123"); mongoOperation.save(user, "users"); Result > db.users.find() { "_class" : "com.mkyong.user.User", "_id" : ObjectId("5050aef830041f24ff2bd16e"), "password" : […]
A quick guide to show you how to do basic operations like create, update, find, delete record and indexing in MongoDB. This example is using MongoDB 2.0.7, running on Mac OS X 10.8, both MongoDB client and server console are run on localhost, same machine. 1. Install MongoDB Install MongoDB on Windows, Ubuntu or Mac […]
This article is described how I find out the Denial of Service (DoS) IP and null route it, to solve the high load issue on my server. 1. High Load Recently, the server has hit an abnormally high load, CPU usage hits, average 15-20%. #top load average: 15.08, 18.30, 20.63 2. Who is Connected? Not […]
Below is an Unix command to list all the IP addresses connected to your server on port 80. netstat -tn 2>/dev/null | grep :80 | awk ‘{print $5}’ | cut -d: -f1 | sort | uniq -c | sort -nr | head Output – Total connections by IP, from highest to lowest. 97 114.198.236.100 56 […]
After migrated to a new server, the W3 Total Cache plugin is not working, no cache page or min file redirect, and display following error messages at the W3tc admin page: It appears Page Cache URL rewriting is not working. If using apache, verify that the server configuration allows .htaccess or if using nginx verify […]
SCP uses Secure Shell (SSH) to transfer data between client and remote server, it’s fast and secure. In this article, we will show you two common SCP copying examples : Copying data from your computer to remote server. Copying data from remote server to your computer. 1. Copying data to Remote Server Example 1.1 – […]
This bug is annoying me a very long time. In WordPress, after updating or saving a new post or existing post, sometime, it will redirect to a 404 page, and this is happening randomly, no idea to identify what is the root caused. After read few similar posts – this and this, I find out […]
