Unit and Integration Test with Databases

From an ideological point of view, tests that involve the database may be unit tests are may be integration tests. For many applications the functional logic is quite trivial, so it is quite pointless to write „real unit tests“ that work without the database. Or it may be useful. But there is a category of …

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Spline Approximation (Mathematics II)

This is the third of a series of article about spline approximation. If you have not done so, you should start reading Spline Approximation (Introduction) Spline Approximation (Mathematics) So a function which is supposed to approximate a given set of points as a linear combination     of functions , as described in the previous …

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Spline Approximation (Mathematics)

The goal of spline approximation has already been explained in the previous article „Spline Approximation (Introduction)„. This article will cover the mathematics behind this approximation and develop an approach. If you do not care about the mathematics, just skip this article and read the Spline Approximation (Cookbook)“, that will come soon. Spline Interpolation We have …

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Spline Approximation (Introduction)

We sometimes encounter a situation where a number of points with coordinates are given and we want to find a function such that for all of these points we have (interpolation) or (approximation). Most often we say that we want on average to be as small as possible and for whatever reasons usually the quadratic …

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Just run it twice

Often we use some kind of „clustered“ environment to run our software. This promises higher performance and better availability. And the frameworks seem to suggest that it is just a matter of starting it twice and it will magically work correctly. There is nothing wrong with investing some thoughts on this issue. It can actually …

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Combining multiple scans

When images are scanned multiple times, maybe there is a way to construct an image that is better than any of the scans from them. In this case it is assumed, that one scan has a higher resolution, but another scan got the colors better. It has already been found out, which two scans belong …

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Pagination of Database Query Results

This article is highly inspired by the blog post We need tool support for keyset pagination. Please consider reading the original first and then my interpretation and additional thoughts about this idea. We have a typical database base backed web application. It can be a rich client. It can be a NoSQL database. Whatever, but …

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JSON instead of Java Serialization: The solution?

We start recognizing that Serialization is not such a good idea. It is cool and can really work on a wide range of objects, even including complex and cyclic reference graphs. And it was essential for some older Java frameworks like EJB and RMI, which allowed remote access to Java objects and classes. But it …

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Phone Numbers and E-Mail Addresses

Most data that we deal with are strings or numbers or booleans and combinations of these into classes and collections. Dates can be expressed as string or number, but have enough specific logic to be seen as a fourth group of data. All these have interesting aspects, some of which have been discussed in this …

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Ranges of Dates and Times

In Software we often deal with ranges of dates and times. Let us look at it from the perspective of an end user. When we say something like „from 2020-03-07 to 2019-03-10“ we mean the set of all timestamps such that     or more accurately:     Important is, that we mean to include …

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