Eyal Lupu Software Blog

Introduction - AAD  AWS KMS API supports authenticated encryption using additional authentication data (AAD). The concept of AAD is explained in AWS’ documentation. However, as this is not trivial, I have decided to put that into a live example in this blog post and a simple web application example (available at this GitHub repository).

The lack of Base64 encoding API in Java is, in my opinion, by far one of the most annoying holes in the libraries. Finally Java 8 includes a decent API for it in the java.util package. Here is a short introduction of this new API (apparently it has a little more than the regular encode/decode API).

I started to experience the Java 8 new APIs (still Early Access at the moment of writing this post) and the first thing I looked into was the new date and time API ( JSR 310 ). As there is much to cover in this new long awaited API I think it worth few posts with some examples. This post would be the first in a series, starting with some basic classes of the package: Instant, LocalDate, LocalTime, and LocalDateTime.

Java 7 is out there for such a long time now so this post is even not fashionably late but still there is one aspect of the try-with-resource construct which, in my opinion, is sometimes overlooked: In this post I would like to point out some behavioral change related to exception suppression which might affect code migrating from older Java versions.

Introduction Lately I encountered a configuration tweak I was not aware of, the problem: I had a single Java installation on a Linux machine from which I had to start two JVM instances - each using a different set of JCE providers. A reminder: the JVM loads its security configuration, including the JCE providers list, from a master security properties file within the JRE folder (JRE_HOME/lib/security/java.security), the location of that file is fixed in the JVM and cannot be modified. Going over the documentation (not too much helpful, I must admit) and the code (more helpful, look for Security.java, for example  here ) reveled the secret.

Introduction As a software architect one of the common tasks I have to deal with is web applications security. Usually I would try to make sure that security is automatically enforced by the infrastructure, however this is not always that easy – sometimes the underlying frameworks don’t provide any built in support or configuration which globally turns on a security attribute. This is why the new org.springframework.web.servlet.support.RequestDataValueProcessor interface in Spring MVC 3.1 seems to be very interesting: it provides a clean way to implement automatic CSRF protection.

My previous post was about Java 7's new java.nio.file.Path class  this time I want to continue and explorer some of the other new file system related APIs in Java 7. java.nio.file.DirectoryStream DirectoryStream provides an easy way to iterate over directories content, but more than that it introduces a solution for a long existing problem of listing within very large directories. If I wanted to list folder entries using previous Java versions I had to use one of the java.io.File's list() or listFiles() overloaded methods: // Pre Java 7 Directory Listing Example File f = new File("c:/tmp"); String[] names = f.list(); // At this point Java listed all files in c:/tmp and loaded their names into an array of Strings for (String name : names) { System.out.println(name); } The problem with the old API is that once I asked a File object to list its entries it would immediately scan the folder creating an array of strings (or file objects if l...

Lately I had the feeling it's about time to starts looking into Java 7 EA, it has been under development for some time now and by the latest news it should be released soon. So I downloaded JDK 7-EA and Netbeans 7 (Eclipse doesn't support Java 7 language changes yet) and looked for interesting changes in the release notes, the first few I've noticed are the I/O enhancements on which I decided to write a post or two starting with a short coverage of the new APIs for path manipulation in the new java.nio.file.Path interface.

Introduction As usually it has been a long time since I have last posted in my blog, and even longer (about half a year) since the last time I wrote about Hibernate but finally I have fond the tome for that. This post is about Hibernate standard compatible (TABLE, SEQUENCE, IDENTITY, and AUTO) identity generators: it explains what the identity generators are and illustrated the different considerations need to be taken when choosing identity generation strategy. Environment Hibernate - 3.5.6-Final PostgreSQL - 8.4

Introduction In my previous post I covered some of the more sophisticated Java strings management issues (Collators, Normalizer, interning, substring). Few of the readers of that post left comments asking about StringBuilder vs. StringBuffer vs. the built-in concatenation (+) operator performance. To have a closure to the subject I decided to elaborate on Java strings concatenating. Is It Important? In java we talk a lot about strings concatenating which brings up questions about the importance of that. As always the answer depends on the scenario, if we just want to take two strings and print a message composed out of these strings it is probably doesn't matter - we can use the + operator or String.concat() method and get it done. It is more important when we are processing mass of data and loop a logic performing strings concatenating.

Hi, Usually this (and my old ) blog is more Hibernate, Spring and other JEE/Server side technologies. Still on my day to day work (and mainly when I lecture) I see a lot of misunderstanding/misconception about basic Java tasks. I decided to drop some notes about such subjects from time to time - and today four issues about java.lang.String: Strings are immutable - a very basic one, just a reminder  Strings Equality, Normalizer, and Collator - an overview of strings equality in a Locale sensitive  environments (including accented forms) The substring() method might cause memory leaks - in some scenarios the usage of String.substring() method can cause memory leaks String.intern() - how to improve strings equality performance and memory footprint using String.intern()

Hi all, As usual it took me a long time to write to my blog again but finally here it is - in this post I continue writing about JPA 2.0 (my previous post is here ), more than that this is the first entry I'm publishing in my new (the old one is here ) blog - Congratulations to me :-). Anyhow in this post I'm trying to go over some of the new functions introduced by JPA 2.0 to the JPA query language. As always my platform is Hibernate but I am using only JPA standard annotation and query syntax. The post includes the following: The INDEX function (and the @OrderColumn annotation) The TYPE expression, and The four types of case expressions My environment Hibernate 3.5.2-Final PostgreSQL 8.3

Version 2.0 of the Java Persistency API (JPA), a.k.a JSR-317 , was released a while ago (10-December-2009) and Hibernate's next version (3.5.0) will implement this version of the specification. In this, and the next, blog entries I'm planning to explorer JPA 2.0 new features and Hibernate implementation of those feature. Since this is the first post in the series I'll focus on environment setup and include only few new mapping options: The orphanRemoval option The ElementCollection annotaiotn, and The CollectionTable annotation On my next posts I'll cover some more options. My Environment Hibernate 3.5.0-CR-2 (Please notice that Hibernate 3.5 is still a candidate release so things written in this blog entry might change in the future) Database PostgreSQL 8.3

One of the new features in Spring 3.0 is the Spring Expression Language (Spring EL or SpEL). While evaluation Spring 3.0 I was also checking out the SpEL capabilities, in this blog entry I'll try to cover some of the more interesting, and less obvious, features and aspects of the SpEL. The Basics In its basics SpEL is yet another Expression Language, similar to Unified EL, it supports expressions (no control statements in the language) mainly used to access bean properties, the Spring Expression Language can be used as part of the Spring bean factory configuration (XML or annotation based) but can also be evaluated directly by the application code - meaning we can read and evaluate expressions at runtime. Here is the most basic example of SpEL used in XML factory bean: <!-- Classic - Simple bean with random value --> <bean id="randomNumber" class="java.lang.Math" factory-method="random"/> <bean id="classicBean" class=...

Hi all, This time about derived properties, maybe this is not a commonly used feature, and maybe even a little bit hidden one (I don't think I have ever been asked about it in any of the Hibernate courses I had lectured in and this usually a sign that people are not familiar with that feature) but once you're familiar with that it is a powerful feature - however, as always, there are considerations regarding of how and when to use it. What Is a Derived Property? A derived, or calculated, property is a read only property which its value is calculated at fetch time using SQL expressions. For example a Product class might have a price and a calculated final price which is the price including VAT. The first (not so good) solution might be something like that: @Entity @Table(name="PRODUCTS") public class Product { @Column(name="PRICE") private float price; public float getFinalPrice() { return VAT*price; } } The getFinalPrice() method...

Hi all, One of the new features in Spring 3.0 is REST support, REST clients can use the restTemplate class and server as part of the MVC framework. In chapter 18 of the 3.0.M3 documentation we can find a section describing content negotiation using the ContentNegotiatingViewResolver class. Lately I was invited to give a lecture about the new Spring 3.0 features and I prepared a detailed HOWTO example (if you want to skip the theory scroll down to HOTWO) of REST content negotiation which I decided to load to my blog, here it is What is Content Negotiation? Sometimes different HTTP clients would like to get different representations of a the same resource, for example the resource http://localhost/app/rest/users will list all of the users in a specific server - however one client would like to get the result as a XML document, another in a JSON format and the third as a human readable fancy HTML table - the process in which a client notifying the server about the preferred format (...

Hi all, The next version of Hibernate Validator (currently 4.0.0 Alpha3) will be the Bean Validation ( JSR-303 ) RI (Hibernate Validator 4.0.0-A3 actually implements the CR1 of the specification), as usually with specifications that interest me I read it and look for interesting changes - in this case changes from the legacy Hibernate Validator. We can easily identify the strong roots of Hibernate Validator in the new specification but it has some new ideas. In this entry I want to focus on one of them - the constraints grouping. But first a basic example. Basic Validation Example The concept of the new API is not very different from the legacy Hibernate Validator (I wrote about it in the past -  here ), basically we have two parts to the API: (1) the bean constraints and (2) the validator. The code fragment bellow illustrates how bean constraints are assigned to properties: package com.jroller.eyallupu; import javax.validation.constraints .Min; import javax.validation...

Two Side Notes About Arrays and Reflection Yesterday I read a  post  by Jakob Jenkov about using reflection to work with Java arrays. It is a nice post but I have two comments about it:

Hi,  Another entry about queries - this time a tuning test case and the relations between simple queries, join fetch queries, paging query results, and batch size. Paging the Query Results Since I have never said anything about paging in this blog I start with a short introduction about paging in EJB3: To support paging the EJB3 Query interface defines the following two methods: setMaxResults - sets the number of maximum rows to retrieve from the database setFirstResult - sets the first row to retrieve

Hi,  The 3.3.1.GA release of Hibernate annotations (released on March) includes a new annotation: the @Any (see  http://opensource.atlassian.com/projects/hibernate/browse/ANN-28 ). This annotation (accomplished with @AnyMetaDef) provides the Hibernate annotation and EntityManager support for the "any" type. The Any Property Type Sometimes we need to map an association property to different types of entities that  don't have  a common ancestor entity - so a plain polymorphic association doesn't do the work. For example let's assume three different applications which manage a media library - the first application manages books borrowing, the second one DVDs, and the third VHSs. The applications have nothing in common. Now we want to develop a new application that manages all three media types and reuses the exiting Book, DVD, and VHS entities. Since Book, DVD, and VHS classes came from different applications they don't have any ancestor entity - the common...