All posts by mkyong.

MongoDB : write Aggregation result into a new collection

This article shows you 2 ways to export a MongoDB “aggregation” result into another new collection. 1. $out Example This $out operator is New in version 2.6. 1.1 Review a simple grouping example, it writes the result to a new variable “result”. > var result = db.hc_hosting.aggregate( { $group :Continue Reading


Ubuntu : Status 14: The disk contains an unclean file system

Dual boot Windows and Ubuntu, but Ubuntu is unable to access the Windows partition /dev/sdb3, shows the following error message : Error mounting /dev/sdb3 … status 14: The disk contains an unclean file system (0, 0). Metadata kept in Windows cache, refused to mount. Failed to mount ‘/dev/sdb3′: Operation notContinue Reading


Linux : How to gzip a folder

On Linux, gzip is unable to compress a folder, it used to compress a single file only. To compress a folder, you should use tar + gzip, which is tar -z. Note $ tar –help -z, -j, -J, –lzma Compress archive with gzip/bzip2/xz/lzma For example, tar -zcvf outputFileName folderToCompress 1.Continue Reading


mongoimport unable to import $numberLong

A collection with NumberLong type data as follows : > db.hc_whois.findOne(); { "_id" : NumberLong(3000001), "startIpInLong" : NumberLong(1543503872), "endIpInLong" : NumberLong(1544552447), "name" : "ap-net-1", //… } Export it with mongoexport : server1 $ mongoexport -d mydb -c hc_whois -o whois.json whois.json { "_id" : { "$numberLong" : "3000001" }, "startIpInLong"Continue Reading


Java : Unsupported major.minor version 51.0

1. Problem Run a “jar” on Debian 7.5, and hits the following error messages : $ java -jar ripecrawler.jar Exception in thread "main" java.lang.UnsupportedClassVersionError: com/mkyong/whois/job/RipeCrawlJob : Unsupported major.minor version 51.0   at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass( at at at$000( at$ at Method) at atContinue Reading


servlet-api-2.5.jar – jar not loaded

Deployed a “war” file on Tomcat, and hits following error messages : Jul 17, 2014 7:59:55 PM org.apache.catalina.loader.WebappClassLoader validateJarFile INFO: validateJarFile(D:\apache-tomcat-7.0.53\webapps\hc\WEB-INF\lib\servlet-api-2.5.jar) – jar not loaded. See Servlet Spec 3.0, section 10.7.2. Offending class: javax/servlet/Servlet.class Tools used : JDK1.7 Maven 3 Tomcat 7 1. Reason The Tomcat’s container comes with ownContinue Reading

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JSF 2 + Log4j Integration Example

In this tutorial, we will show you how to integrate the log4j framework with the JSF 2.x web application. JSF is using java.util.logging, you need extra works to redirect the logging from JSF’s java.util.logging to log4j, with a serious penalty of performance, make sure use this trick only during localContinue Reading

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Log4j hello world example

In this tutorial, we will show you how to use the classic log4j 1.2.x to log a debug or error message in a Java application. 1. Project Directory Review the final project structure, a standard Maven style Java project. 2. Get Log4j Declares the following dependencies : pom.xml <dependency> <groupId>log4j</groupId>Continue Reading

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Download file from server using SSH

Normally, you use Secure copy or SCP to download a file from another server via SSH connection. For example, scp username@remotehost:remoteFileToDownload localFolderNameToSaveTheFile 1. SCP Examples 1.1 Download File From Server Example to download a log file (hc.audit.log) from server (198.58.x.x), into your current local folder. scp [email protected]:/var/log/tomcat7/hc.audit.log . 1.2 UploadContinue Reading


Debian : Change default Java version

Deployed a Debian 7.5 on Linode server, but the default is using OpenJDK 1.6. How can I upgrade the alternative path to OpenJDK 1.7? $ java -version java version "1.6.0_31" OpenJDK Runtime Environment (IcedTea6 1.13.3) (6b31-1.13.3-1~deb7u1) OpenJDK 64-Bit Server VM (build 23.25-b01, mixed mode) Tracing the java, it’s using theContinue Reading

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log4j.xml Example

Here’s an XML version of log4j properties file, just for sharing. 1. Output to Console Redirect the logging to console. log4j.xml <?xml version="1.0" encoding="UTF-8" ?> <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd"> <log4j:configuration debug="true" xmlns:log4j=’’>   <appender name="console" class="org.apache.log4j.ConsoleAppender"> <layout class="org.apache.log4j.PatternLayout"> <param name="ConversionPattern" value="%d{yyyy-MM-dd HH:mm:ss} %-5p %c{1}:%L – %m%n" /> </layout> </appender>  Continue Reading


Spring Security + Hibernate Annotation Example

In this tutorial, previous Spring Security + Hibernate4 XML example will be reused, and convert it to a annotation-based example. Technologies used : Spring 3.2.8.RELEASE Spring Security 3.2.3.RELEASE Hibernate 4.2.11.Final MySQL Server 5.6 Tomcat 7 (Servlet 3.x container) Quick Note : Create a session factory with LocalSessionFactoryBuilder Inject session factoryContinue Reading


Spring Security + Hibernate XML Example

In this tutorial, we will show you how to integrate Hibernate 4 in Spring Security, XML configuration example. Note For annotation version, please read this Spring Security + Hibernate Annotation Example. Technologies used : Spring 3.2.8.RELEASE Spring Security 3.2.3.RELEASE Hibernate 4.2.11.Final MySQL Server 5.6 JDK 1.6 Maven 3 Eclipse 4.3Continue Reading

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java.lang.ClassNotFoundException: org.hibernate.service.jta.platform.spi.JtaPlatform

Spring 3.2.x + Hibernate 4.3.x integration, hits JtaPlatform ClassNotFoundException, search the project classpath, find out that JtaPlatform is at different package? hibernate-core.4.3.5.Final.jar org.hibernate.engine.transaction.jta.platform.spi.JtaPlatform Error message shows org.hibernate.service.jta.platform.spi.JtaPlatform Caused by: java.lang.NoClassDefFoundError: org/hibernate/service/jta/platform/spi/JtaPlatform at org.springframework.orm.hibernate4.SpringSessionContext.<init>( ~[spring-orm-3.2.8.RELEASE.jar:3.2.8.RELEASE] … 40 common frames omitted Caused by: java.lang.ClassNotFoundException: org.hibernate.service.jta.platform.spi.JtaPlatform //… pom.xml <!– Hibernate ORM –> <dependency>Continue Reading


Spring Security : Encoded password does not look like BCrypt

In Spring Security, database authentication with bcrypt password hashing. import; import; //… String password = “123456″; PasswordEncoder passwordEncoder = new BCryptPasswordEncoder(); String hashedPassword = passwordEncoder.encode(password); spring-security.xml <authentication-manager> <authentication-provider> <password-encoder hash="bcrypt" /> //… </authentication-provider> </authentication-manager> CREATE TABLE users ( username VARCHAR(45) NOT NULL , password VARCHAR(45) NOT NULL ,Continue Reading

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