In this tutorial, we will show you how to use jConsole to remote access a Tomcat instance, for JVM monitoring stuff. Tools and environment used : Ubuntu 13 + Tomcat 7 + 192.168.1.142 Windows 8 + jConsole + 192.168.1.200 1. Tomcat + JMX To connect with jConsole, Tomcat need to enable the JMX options. To …
In Eclipse IDE, run a Java web application with Tomcat server plugin, but the console prompts Exception in thread "x" java.lang.OutOfMemoryError: Java heap space 1. Solution – Increase Heap Size in Tomcat By default, Tomcat allocated a small amount of heap size. To solve it, you need to increase the Tomcat’s heap size manually. 1.1 …
I love grep command on Linux, it helped to search and filter strings easily, always wonder what is the equivalent tool on Windows, and found this findstr recently. In this article, I will share some of my favorite “grep” examples on Linux, and how to “port” it to Windows with “findstr” command. 1. Filter a …
In this article, we will show you how to use the -XX:+PrintFlagsFinal to find out your heap size detail. In Java, the default and maximum heap size are allocated based on this – ergonomics algorithm. Heap sizes Initial heap size of 1/64 of physical memory up to 1Gbyte Maximum heap size of 1/4 of physical …
In this tutorial, we will show you how to generate an auto-incrementing sequence id in MongoDB + Spring Data environment. Tools used in this project : Spring Data MongoDB 1.2.1.RELEASE MongoDB 2.4.5 Eclipse 4.2 Maven 3 At the end of this tutorial, if the collection name “hosting” is saved, a new auto-incrementing sequence id will …
In Spring MVC + JSP view page environment. index.jsp <html> <head> <title>Welcome!</title> <c:url var="assets" value="/resources/abc" /> <link href="${assets}/css/style.min.css" rel="stylesheet"> <script src="<c:url value="/resources/js/jquery.1.10.2.min.js" />"> </script> </head> … </html> In the Spring config file, mapped a resource path, mvc-dispatcher-servlet.xml <beans … <context:component-scan base-package="com.mkyong.test" /> <mvc:resources mapping="/resources/**" location="/resources/" /> </beans> 1. Problem After deployed, Spring MVC can’t get …
In this example, we will show you how to append values in Object[] and int[] array. Object[] obj = new Object[] { "a", "b", "c" }; ArrayList<Object> newObj = new ArrayList<Object>(Arrays.asList(obj)); newObj.add("new value"); newObj.add("new value 2"); 1. Object[] Array Example Example to append values with ArrayList : TestApp.java package com.mkyong.test; import java.util.ArrayList; import java.util.Arrays; public …
Examples show you how to convert between int[] and its’ wrapper class Integer[]. 1. Convert int[] to Integer[] public static Integer[] toObject(int[] intArray) { Integer[] result = new Integer[intArray.length]; for (int i = 0; i < intArray.length; i++) { result[i] = Integer.valueOf(intArray[i]); } return result; } 2. Convert Integer[] to int[] public static int[] toPrimitive(Integer[] …
Below is my website environment : WordPress 3.8.1 CloudFlare Pro Plan 1. Problem I’m unable to login WordPress after changing my custom DNS to CloudFlare, below is the error message : ERROR: Cookies are blocked or not supported by your browser. You must enable cookies to use WordPress P.S The browser’s cookies are enabled. Here’s …
The java.awt libraries are set of classes provided by Java in order to draw shapes on a window. The abbreviation AWT stands for Abstract Windowing Toolkit. Today, the library has been converted into a huge set of classes which allows the user to create an entire GUI based application. The visual appearance of these classes …
In this tutorial, we will show you how to test Spring’s components with TestNG. Tools used : TestNG 6.8.7 Spring 3.2.2.RELEASE Maven 3 Eclipse IDE 1. Project Dependencies To integrate Spring with TestNG, you need spring-test.jar, add the following : pom.xml <properties> <spring.version>3.2.2.RELEASE</spring.version> <testng.version>6.8.7</testng.version> </properties> <dependencies> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency> <dependency> <groupId>org.springframework</groupId> <artifactId>spring-test</artifactId> <version>${spring.version}</version> …
In this tutorial, we will show you how to do the group testing in TestNG. 1. Groups on Methods Review a test group example. runSelenium() and runSelenium1() are belong to group selenium-test. testConnectOracle() and testConnectMsSQL() are belong to group database. runFinal() will be executed if groups selenium-test and database are passed. TestGroup.java package com.mkyong.testng.examples.group; import …
Cobertura is a free Java code coverage tool – calculates the percentage of code accessed by unit tests. In this tutorial, we will show you how to use Maven to generate the Cobertura code coverage report for your project. 1. Cobertura Code Coverage Report Do nothing, just type the following Maven command to download and …
In this tutorial, we will show you how to use MongoDB aggregate function to group documents (data). 1. Test Data Data in JSON format, shows the hosting provider for website. website.json { “_id” : 1, “domainName” : “test1.com”, “hosting” : “hostgator.com” } { “_id” : 2, “domainName” : “test2.com”, “hosting” : “aws.amazon.com”} { “_id” : …
Emma is a free Java code coverage tool. In this tutorial, we will show you how to use Maven to generate the Emma code coverage report for your project, and also how to integrate the Emma report into the Maven project site. 1. Generate Emma Code Coverage Report Do nothing, just type the following Maven …
Creating a Maven site, but the build is very slow to generate the dependency report. C:\mkyong_projects\>mvn site [INFO] Scanning for projects… [INFO] [INFO] ————————————– [INFO] Building Maven Webapp 1.0-SNAPSHOT [INFO] ————————————– [INFO] //… [INFO] Generating "Project License" report [INFO] Generating "Project Team" report [INFO] Generating "Project Summary" report [INFO] Generating "Dependencies" report //…… Hanging here… …
Review the “maven-emma-plugin” in pom.xml : pom.xml <project> //… <build> <plugins> <plugin> <groupId>org.codehaus.mojo</groupId> <artifactId>emma-maven-plugin</artifactId> <version>1.0-alpha-3</version> <inherited>true</inherited> <executions> <execution> <phase>process-classes</phase> <goals> <goal>instrument</goal> </goals> </execution> </executions> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-surefire-plugin</artifactId> <inherited>true</inherited> <configuration> <forkMode>once</forkMode> <reportFormat>xml</reportFormat> <classesDirectory> ${project.build.directory}/generated-classes/emma/classes </classesDirectory> </configuration> </plugin> </plugins> </build> </project> 1. Problem When I run the command mvn emma:emma to generate the code coverage report, …
Eclipse IDE prompts warning on new DefaultHttpClient, mark this class as deprecated. package com.mkyong.web.controller; import org.apache.http.Header; import org.apache.http.HttpResponse; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; public class WebCrawler { public static void main(String[] args) throws Exception { HttpClient client = new DefaultHttpClient(); HttpGet request = new HttpGet("https://mkyong.com"); HttpResponse response = client.execute(request); //… } } Solution Dive …
If a web request is coming from Google crawler or Google bot, the requested “user agent” should look similar like this : Mozilla/5.0 (compatible; Googlebot/2.1; +http://www.google.com/bot.html) or (rarely used): Googlebot/2.1 (+http://www.google.com/bot.html) Source : Google crawlers 1. Java Example In Java, you can get the “user agent” from HttpServletRequest. Example : Service hosted at abcdefg.com @Autowired …
This example shows you how to get the HTTP request headers in Java. To get the HTTP request headers, you need this class HttpServletRequest : 1. HttpServletRequest Examples 1.1 Loop over the request header’s name and print out its value. WebUtils.java package com.mkyong.web.utils; import javax.servlet.http.HttpServletRequest; import java.util.Enumeration; import java.util.HashMap; import java.util.Map; public class WebUtils { …
You have been told a lot that you can’t manage memory in Java. Well, it has changed since HotSpot release of the Java VM. There is a way to directly allocate and deallocate memory as well as write and read it… Of course we are talking about the JVM memory where the Java program runs. …
If you like my works and tutorials on “mkyong.com”, please consider making a donation of $10 or whatever you can to protect and sustain the following charities : Thanks. 1. Doctors Without Borders The Doctors Without Borders works in nearly 70 countries providing medical aid to those most in need regardless of their race, religion, …
In this tutorial, we will show you how to use @Test attributes invocationCount and threadPoolSize to perform a load test or stress test on a website. Tools used : TestNG 6.8.7 Selenium 2.39.0 Maven 3 P.S We are using the Selenium library to automate browsers to access a website. 1. Project Dependency Get TestNG and …
In this tutorial, we will show you how to create two custom annotations – @Test and @TestInfo, to simulate a simple unit test framework. P.S This unit test example is inspired by this official Java annotation article. 1. @Test Annotation This @interface tells Java this is a custom annotation. Later, you can annotate it on …
A classic example, show you how to get started with TestNG unit test framework. Tools used : TestNG 6.8.7 Maven 3 Eclipse IDE 1. TestNG Dependency Add TestNG library in the pom.xml. pom.xml <dependency> <groupId>org.testng</groupId> <artifactId>testng</artifactId> <version>6.8.7</version> <scope>test</scope> </dependency> 2. TestNG Example Review a simple class, has a method to return a fixed email “[email protected]”. …
This article shows the difference in time taken for similar operations on a String object and StringBuffer object. String being an immutable class, it instantiates a new object each time an operation is performed on it StringBuffer being a mutable class, the overhead of object instantiation during operations is removed. Hence, the time taken for …
In this tutorial, we show you how to convert an IP address to its decimal equivalent in Java, and vice versa. For examples : 255.255.255.255 <-> 4294967295 192.168.1.2 <-> 3232235778 1. IP Address to Decimal We show you two ways to convert an IP address to a decimal number Normal power of 256 Bit shifting …
Before you understand what is & 0xFF, make sure you know following stuffs : Bitwise AND operator, link. Converts hex to/from binary, and decimal to/from binary. In short, & 0xFF is used to make sure you always get the last 8 bits. Let’s see an example to convert an IP address to/from decimal number. 1. …
In this tutorial, we will show you how to include static resources like JavaScript or CSS in a JSP page. Summary steps : Put static resources like cs, js or images into this folder webapp\resources Create a Spring mvc:resources mapping Include in JSP page via JSTL tag c:url or Spring tag spring:url P.S This project …
This article shows how to solve the java.lang.OutOfMemoryError: Java heap space in Eclipse IDE. Table of contents 1. Eclipse – OutOfMemoryError: Java heap space 2. Temporary fix – Increase the heap size 3. eclipse.ini 4. The solution, find the reason behind the heap size error. 5. References 1. Eclipse – OutOfMemoryError: Java heap space In …
Review following documents : Collection : domain { "_id" : 1001, "domainName" : "google.com" "tag" : [ "search engine", "search", "find anything", "giant" ] }, { "_id" : 1002, "domainName" : "yahoo.com" "tag" : [ "search engine", "online portal", ] }, { "_id" : 1003, "domainName" : "mkyong.com" } 1. Question How to find all …
In this tutorial, we show you how to integrate jQuery autocomplete plugin with Spring MVC. Tools and Libraries used : Spring MVC 3.2 jQuery autocomplete plugin – github Maven 3 Eclipse IDE Review the tutorial’s flows : An HTML page, with a textbox. If the user is tying on the textbox, it will fire an …
This tutorial shows you how to work with java.util.Date and java.util.Calendar. 1. Java Date Examples Few examples to work with Date APIs. Example 1.1 – Convert Date to String. SimpleDateFormat sdf = new SimpleDateFormat("dd/M/yyyy"); String date = sdf.format(new Date()); System.out.println(date); //15/10/2013 Example 1.2 – Convert String to Date. SimpleDateFormat sdf = new SimpleDateFormat("dd-M-yyyy hh:mm:ss"); String …
This article shows you how to attach the JDK source code in Eclipse IDE. In Eclipse, select Windows -> Preferences -> Java -> Installed JREs , expands rt.jar, select “Source attachment” and find the src.zip from your disk drive. P.S JDK source code is inside the src.zip. Note You may interest at this article – …
The JDK source code is inside the src.zip, this article shows you how to get it on Windows, Ubuntu (Linux) and Mac OSX. 1. Windows In Windows, visit the Oracle website and download the JDK (not JRE). Install the JDK and the src.zip is inside the JDK installed folder, for example : C:\Program Files\Java\jdk1.7.0_40\src.zip 2. …
A leap year is a year containing one additional day (366 days a year). Review the leap year algorithm : if year is divisible by 400 then is_leap_year else if year is divisible by 100 then not_leap_year else if year is divisible by 4 then is_leap_year else not_leap_year P.S Algorithm from wikipedia leap year. 1. …
Two Java examples show you how to print the elapsed time in days, hours, minutes and seconds format. 1. Standard JDK Date APIs You need to calculate the elapsed time manually. DateTimeUtils.java package com.mkyong.dateUtils; import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Date; public class DateTimeUtils { public static void main(String[] args) { DateTimeUtils obj = new DateTimeUtils(); …
In Mongodb, you can use sort()to do the date sorting. 1. MongoDB Sorting Examples In Mongodb, to sort a “date” field, issues : //The ‘1’ = sort ascending (oldest to newest) db.domain.find().sort({lastModifiedDate:1}) { "_id" : 1, "lastModifiedDate" : ISODate("2013-08-13T07:18:04.774Z") } { "_id" : 2, "lastModifiedDate" : ISODate("2013-09-03T08:12:16.309Z") } { "_id" : 3, "lastModifiedDate" : ISODate("2013-10-03T08:12:16.309Z") …
In SQL, the ‘like’ query is looks like this : select * from tags where tagName like ‘%apple%’ In MongoDB console, it looks like this : db.tags.find({"tagName": /apple/}) In Spring data mongodb, it implements with Criteria or BasicQuery : String tagName = "apple"; Query query = new Query(); query.limit(10); query.addCriteria(Criteria.where("tagName").regex(tagName)); mongoOperation.find(query, Tags.class); String tagName = …
Review a simple jQuery example to loop over a JavaScript array object. var json = [ {"id":"1","tagName":"apple"}, {"id":"2","tagName":"orange"}, {"id":"3","tagName":"banana"}, {"id":"4","tagName":"watermelon"}, {"id":"5","tagName":"pineapple"} ]; $.each(json, function(idx, obj) { alert(obj.tagName); }); Above code snippet is working fine, prompts the “apple”, “orange” … as expected. Problem : JSON string Review below example, declares a JSON string (enclosed with single …