Difference between PUT and POST in REST WebService in Java

If you remember REST WebServices uses HTTP methods to map CRUD (create, retrieve, update, delete) operations to HTTP requests. Even though both PUT and POST methods can be used to perform create and update operation in REST WebServices, Idempotency is the main difference between PUT and POST. Similar to the GET request, PUT request is also idempotent in HTTP, which means it will produce the same results if executed once more multiple times. Another practical difference PUT and POST method in the context of REST WebService are that POST is often used to create a new entity, and PUT is often used to update an existing entity. If you replace an existing entity using PUT than you should be aware that if only a subset of data elements is passed then the rest will be replaced by empty or null.

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How to enable SSL debugging in Java JVM?

Dealing with SSL issues in Java web application is no fun, especially when you have no debug logs and all you see is an ugly ‘Page Cannot be displayed’ error message in your browser. Thankfully you can easily enable SSL to debug on your Application to start seeing verbose logs that will clearly show what happens during the SSL handshake process. You can enable SSL debugging logs in your Application Server JVM config by adding the following JVM command line parameter and restart the Application Server:

-Djavax.net.debug=all

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Restlet HelloWorld Example in Java and Eclipse

The Restlet is one of the first open source frameworks to create and deploy RESTful web service in Java. After the release of JAX-RS (Java API for RESTful Web Services) JSR - 317, Restlet also supports JAX-RS annotation and provides a consistent way to create both RESTful Server and Client. HelloWorld program is the traditional way to start with a new technology and continuing to the tradition, we'll write our first Restlet program as HelloWorld. Since Restlet can be used to create on both client and server side, we'll first expose a resource as RESTful web service using Restlet server and then consumer the same RESTful web service by creating a RESTful client. I'll use Maven and Eclipse to create this RESTlet HelloWorld example, if you are not familiar with Maven, it's a build automation tool like ANT for Java projects but also provides dependency management i.e. you don't need to download Restlet JAR manually, Maven will do it for you. To learn more about Maven see here.

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How to get the last modified date and time of a file or directory in Java

Sometimes before processing a file, you want to check it's last modified date to avoid processing an old file. Though some programmers prefer to attach date in the file name itself, I don't find it a cleaner approach. For example, suppose you are downloading closing prices of stocks and processing at the start of the day and loading into the database. In order to accidently process an old file, you can check the last modified date before processing and if it's in the acceptable range, you can process the file. You can get the last modified date of a file in Java by using java.io.File class. This is a class which represents both file and directory in Java. It contains a method called lastModified() which returns the last modified date of the file. This method returns a long millisecond epoch value, which you can convert to more readable dd MM yyyy HH:mm:sss format by using the SimpleDateFormat class of JDK.  In this article, I'll tell you how to get the last modified date of file and directory in Java.

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Difference between GETDATE() vs SYSDATETIME() vs GETUTCDATE() in SQL Server

One of the common question on Microsoft SQL Server interview is, what is the difference between GETDATE(), SYSDATETIME(), and GETUTCDATE(). Even though all three SQL Sever function returns the current date time in SQL Server, there are some subtle differences between them. The main difference between GETDATE() and SYSDATETIME() is that GETDATE returns current date and time as DATETIME but SYSDATETIME returns a DATETIME2 value, which is more precise. The difference between GETDATE() and GETUTCDATE() is in timezone, the GETDATE() function return current date and time in the local timezone, the timezone where your database server is running, but GETUTCDATE() return current time and date in UTC (Universal Time Coordinate) or GMT timezone.

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Top 2 Books for OCPJP8 Certification - Java 8 1Z0-809, 810, 813 Exam

This is the second part of best books for Java 8 certifications. Since you need to pass two exams, OCAJP8 and OCPJP8 to become a Java SE 8 certified developer, I have shared some of the best OCAJP8 books in the last article. In this article, I will tell you more about the second exam OCPJP8 and suggest best books prepare OCPJP8. This exam is known as professional level exam and it's tougher than the associate level exam. The OCPJP8 stands for Oracle Certified Professional Java Programmer. The exam code for this certification is 1Z0-809. This is if you don't have any prior Java certifications but you can still become a Java SE 8 certified developer by giving upgrade exams e.g. 1Z0-810 if you already passed the OCJPJP7 exam and 1z0-813 if you have passed OCPJP6 exams. The books suggested in this article is primarily for the 1Z0-809 exam but it can also be used for upgrade exams e.g. 1Z0-810 (upgrade from Java SE 7 to Java SE 8) and 1Z0-813 (upgrade from Java SE 6 to Java SE 8) certifications.

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2 Ways to find Tomcat and Java Version in Linux and Windows

You can find Tomcat and java version running on Linux either by executing the org.apache.catalina.util.ServerInfo class from catalina.jar or by executing version.sh shell script. The first solution will work on any operating system including Windows and UNIX because it's using a Java class from a catalina.jar file, which is platform independent. Though, if you don't know how to run a class from JAR file, you can check the steps here. Alternatively, you also have a version.bat file inside tomcat/bin directory to check the version of Tomcat in Windows. When you run this script in Linux or Windows it prints information about tomcat version, the java version used to run tomcat, Server built date, OS name, OS Version, architecture, JVM version and JVM vendor etc.

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