So I decided to try some game programming in Unity1.
Since it's all new to me, I'd thought I'd write some notes here, to remember how I did some things.
add here how to add a skybox
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Interesting.
There's a tech preview in the latest Payara 5 application server1, that allows deploying Jakarta EE 9 applications.
The Eclipse Transformer basically auto transforms the classes and resource files back to the old packages, upon deployment.
There are basically three ways to deal with an optional, when receiving one.
I'm writing it down here, because each of these three cases is highly dependent on context.
And I've noticed in my work that I have a tendency to take option 2, even though it might be considered an error.
So, I recently had a need to find out the index of an element in a List.
I could take the traditional approach, and use a for loop.
But I was wondering if I could use Streams, and if I could, would that be "better" (for some vague notion of "Better").
Any comments on what you would prefer, and why?
I recently came across a small problem. The program ran fine, but my IDE had it underlined as being highly dodgy.
It is the same for Collection.contains and Map.get
Just see the references why this is.
So I decided to try running some of my stuff in the cloud, instead of having to hire a Virtual Machine type thing.
In order to have to limit my changes, I decided to go with Jelastic1.
I decided to try out hosting provider EAPPS2, because they are one of the providers of PaaS3 with Jelastic4.
They suggested I'd read up on [5].
Some requirements I'd like:
It supports all of those, and relieves me of some server administration and maintenance.
Download nodejs from nodejs.org
Unpack nodejs
Install nodejs (and NPM to go with it automatically) locally.
Add "export PATH=/Users/mrbear/nodejs/bin:$PATH" to .bashrc
Install Angular CLI1.
I found this interesting article1 on clock drifts and hardware clocks and OS clocks and Java and logging.
I really liked the quote in there:
“A person with a watch knows what time it is. A person with two watches is never sure.”- Segal's Law
It's possible to create a global .gitignore file1 that is automatically shared among all your repositories.
Why should I do this in the first place? Well, there are a couple of reasons.
One example is of course, I want the same rules to apply to all my repositories.
But, in my case, at work, we are actually using Subversion and not Git. But I do use Git.
And I do not want to pollute the entire Subversion repository with my .gitignore files.
So for me, this is a valid solution.
Let's check that I do not already have this configuration setting active:
You'll notice that among my properties, I already have a core.excludesfile=/home/mrbear/.gitignore_global.
I added it as follows:
Than just populate it like you do with any .gitignore file.
So I decided to try some game programming in Unity1.
Unity is a crossplatform game engine with scripting in C#.
Now, as I cannot design graphical assets to save my life, I decided to buy some off the shelve ones, and free ones, and see how far I can get.
So, this blog post is basically for me, to remember what kind of things I used/needed or might possibly use/need.
I needed some place to write this down. I don't use it often (or at all) and it has too many advantages for me to ignore it.
Interestically enough, the merge statement sometimes seems to have a huge performance advantage when needing to perform operations in bulk.
But this effect can be absent, when attempting merge statements on individual entries.
I happen to come across this priceless piece of text1 from Linus Torvals, that I feel should have a mention here.
So I am using AssertJ1 to verify results of my Unit Tests.
I also (after the advice of a colleague) installed a Plugin into my IntelliJ IDEA called Concise AssertJ Optimizing Nitpicker (Cajon)2
So I needed to verify the equivalence of an object. I wanted to make sure it was the exact same object I was expecting.
In my naivite I tried something like this.
My IDE complained that "Moving binary expression out of assertThat() would be more meaningful".
I completely agreed with that.
Then my IDE commplained that "Moving get() expression out of assertThat() would be more concise", which of course is obvious.
Then, of course, Multiple assertThat() statements can be joined together
Which means that Implicit isPresent() assertion is covered by containsSame()
And that's what I ended up with.
Truly, sometimes my IDE has some good ideas.
Of course, there are easier methods, but I wanted to verify that it is the exact same instance.
Otherwise, I could have simply done something like:
Still not entirely sure that this is not better, despite not an exact match check.
So I came across this text1 on the background of the Generics in the Java Platform.
And I thought it worth my while to put it in here in my blog for easy reference.
I recently came across a great example of JavaDoc. It was regarding the AssertJ SoftAssertions class.
It's in the references1.
In short, we have a dinner party hosted at a mansion.
And we're going to use a UnitTest with Assertions to determine if one of the guests has been murdered and who dun it.
It made me smile.
I am busy trying to learn Kotlin.
It's important as my company decided to accept the use of Kotlin for new development.
As a matter of fact, I'm currently implementing an API with a colleague and he already started creating it in Kotlin.
So I'm kinda having to play catchup.
Time to get to work!
So, you're at home all day, because of all the COVID stuff, and in order to stay sane, you sometimes have to do things that are out of the ordinary.
Below is my attempt.
The problems with Doubles and Floats are already well documented, but sometimes we fall into the trap again.
In short, the representation of a real number1 in Float and Double is not precise2.
Normally, I am well aware of this limitation, but sometimes I get tripped up by already receiving Doubles and Floats as input.
In this case, it involved Geometrie coordinates, in doubles of course.
The following Unit Test shows the problem:
Just decided to do a followup on Adding MariaDB JDBC Connector to Payara 51.
I wanted to see if it was possibly very easy to do this using the command line.
The syntax:
Note the following:
Let's test it!
In case you wish to delete it, try:
It seems to be going well, mostly because the only thing that has changed are the names of the Maven dependencies1. (for now)
So for now the only changes take place in the pom.xml files.
Here are the changes:
I did notice that I could remove one Java EE spec in one of my Maven modules. The servlet-spec. Perhaps because I am using something special in there that's included in the default by now?
Noticed some stuff I no longer need. Probable leftovers from early days.
So my versions have changed as follows:
The old:
The new:
That seems to be all.
So, I've been baking cakes for a long time. I got the recipe from my mum, who has also been baking cakes for a long time.
This recipe is basically flower, eggs, butter, bakingpowder, and lots of sugar. You know, the old fashioned way.
Well, a couple of years ago, suddenly my cakes started failing mysteriously.
So I started trying to fix this, by changing stuff randomly. I started downloading recipes from the Internet, to see if they worked better. I bought a cake-flour package from the supermarket, perhaps that worked. I even changed ovens.
None of these things worked.
So, I sat down, and thought about it. And then I realised, I didn't try and find the problem as I would have if I looked at the problem as a bloody Software Designer (which is what I am).
Well, debugging a cake turns out to be hard. System.out.println or logging or breakpoints are quite impossible.
As they say, you have to find the problem during actual production.
If you did not make any changes to your recipe, and suddenly your cakes start to fail, either one of your ingredients has changed or your process/tools for making the cake. This is an obvious conclusion.
I was going to assume that my tools and process were more or less the same.
The only thing that really works, is to change one ingredient at a time.
In other words:
“How often have I said to you that when you have eliminated the impossible, whatever remains, however improbable, must be the truth? ”- Sherlock Holmes, The Sign of the Four (1890)
It also helps to understand the process. What kind of ingredients in a cake are essential and what kind of role do they play?
Well, after a lot of experimenting, and, quite frankly, a lot of dismal ruined cakes, I found the cause to be the butter.
The butter I used, Blue Band, must have changed at the time. So I did a little digging.
I noticed that there are no longer any dairy products in this butter.
And when I use butter made from dairy products, the cakes turn out fine.
Also, when I started checking the supermarket, I did notice that Blue Band also (at around the same time) came out with a new product called "Butter for cookies and cake". I checked, and it did indeed contain dairy products.
Am I just being paranoid in thinking this is not a coincidence?
I've used the guide in [1].
Just writing down my notes on what I encountered.
So let's try to update using [2].
Update to the latest 8 version.
This upgraded my version of Angular from 8.3.23 to 8.3.26
Update to the 9 version.
This upgraded my version from 8.3.26 (obviously) to 9.1.3 .
Of course, this means it's probably a good idea to upgrade to the lastest libraries I also use.
These are (in no particular order):
I've removed jquery and popper.js, these are no longer necessary as I am using ng-bootstrap.
There's an article [1] here. I thought I'd bookmark it, for easy reference.
So the numpad arrow keys do not work in my IntelliJ editor under Fedora Core 31.
I read about similar issues on the Internet.
One of the solutions that worked for me, was to change the file /usr/share/X11/xkb/symbols/keypad.
First off copying the original file seems like a good idea, something like keypad.original.
Then replace all occurrences of KP_Up, KP_Down, KP_Left, KP_Right with Up, Down, Left, Right respectively.
Either rebooting or executing a setxkbmap should do the trick.
I use these to go to the next or previous call in Intellij. Linux just wants to switch Workspaces, when I do that.
The shortcuts could not be found using the standard Settings tool.
But I found a solution at [2].
With a reset if I decide to need it like:
Hello, again!
This is just a small blog post on how to backup and restore a MariaDB server, without using MysqlDump, but by directly copying the files in /var/lib/mysql.
First of course we need to shutdown mariadb.
Copying files:
When putting things back, things start to go wrong1.
Copying the files to a new host, causes this:
So, if the below code works, than SELinux is causing the issue:
Now you added mysql_t to permissive, as shown by the below printout:
Turning it back to enforcing, means running:
We need to relabel the new /var/lib/mysql directory:
Checking the current file contexts:
I need to check out MariaBackup2 3, as a better solution for creating backups compared to mysqldump.
I was looking up Polish Notation, as I remember hearing about it.
And it turns out Polish Notation is actually, basically, when you think about it, exactly how programming languages in my experience work.
For example:
Is polish notation for:
This is very very difficult to understand for someone like me who is absolutely not used to Polish Notation.
However, when I write this down in programming language method calls, everything becomes crystal clear immediately.
For some reason, the statement above makes perfect sense to me.
Likewise as in the Polish Notation, in software design method-calls, the sequence of statements is unambiguous.
With the infix notation, parentheses are required to override operator precedence rules.
Both in Polish Notation as in programming, this does not seem to be required.
I found the following javadoc in our source code. It makes my head hurt.
It repeats the same thing at least three times, twice in the comments and once in the name of the marker interface.
And still I am no closer to understanding what it does.
This is here for me to remember how much magic is used in inserting spatial (geometry) information into an Oracle database1.
CREATE TYPE sdo_geometry AS OBJECT ( SDO_GTYPE NUMBER, SDO_SRID NUMBER, SDO_POINT SDO_POINT_TYPE, SDO_ELEM_INFO SDO_ELEM_INFO_ARRAY, SDO_ORDINATES SDO_ORDINATE_ARRAY);
A point geometry:
MDSYS.SDO_GEOMETRY(
2001, -- 2-dimensional (2), non-linear referencing geometry or default (0), point (01)
28992, -- Amersfoort / RD New
NULL,
MDSYS.SDO_ELEM_INFO_ARRAY(1, 1, 1),
MDSYS.SDO_ORDINATE_ARRAY(81431.756, 455218.921))
A polygon geometry:
MDSYS.SDO_GEOMETRY(
2003, -- 2-dimensional (2), non-linear referencing geometry or default (0), polygon (03)
28992, -- Amersfoort / RD New
NULL,
MDSYS.SDO_ELEM_INFO_ARRAY(1,1003,1), -- first coordinate (1), exterior (1003), polygon (1)
MDSYS.SDO_ORDINATE_ARRAY(
-1041172.16,1407540.16,
-958596.8,-591471.68,
1363835.2,-625878.08,
1319106.88,1428184,
-1041172.16,1407540.16) -- coordinates
)
A multipolygon geometry:
MDSYS.SDO_GEOMETRY(
2007, -- 2-dimensional (2), non-linear referencing geometry or default (0), MULTIPOLYGON or MULTISURFACE (07)
28992, -- Amersfoort / RD New
NULL,
MDSYS.SDO_ELEM_INFO_ARRAY(1, 1003, 1, 11, 2003, 1),
MDSYS.SDO_ORDINATE_ARRAY(42, 78, 41, 85, 46, 82.7, 45, 79, 42, 78, 43.5, 72.5, 52.5, 72.5, 54.5, 79.5, 79, 60, 93, 46, 53, 32, 54, 25, 49, 22, 45, 17, 41, 16, 37, 23, 33, 24, 25, 20, 33, 46, 39, 53, 43.5, 72.5))
The only thing that makes sense among all the magic numbers are the coordinates. The last coordinate is the same as the first coordinate to close the polygon.
I since have found some more information after some digging regarding the SDO_ELEM_INFO.
It's an array of triplets, where a triplet consists of:
I found more information in [2].
It's possible to create SDO_GEOMETRY in PL/SQL based on WKT strings.
Like so:
Convenient if you want to do something quick, but you cannot provide additional information regarding the dimensions, and coordinate system, etc.
Let me rephrase that sentence. It means your resulting geometrie has NO SRID, and you'll get in trouble using it in geometry queries! This is not a joke!
The reverse (if you want to find out the geometrie in WKT format, basically because it reads easier) is of course also possible, like so:
So I was playing around with ConvexHull, ConcaveHull and ConcaveHull-Boundary functions.
I took the MultiPolygon in the paragraph above as an example.
I will expand on this blog post, as my knowledge in this area is expanded.
Wowie! Angular 9 has entered the building!
I am going to be looking long and hard at it and immediately upgrade my existing apps!
I found the following quote on the Wikipedia page on Short-circuit evaluation1.
The quote is from Edger W. Dijkstra2
The conditional connectives — "cand" and "cor" for short — are ... less innocent than they might seem at first sight. For instance, cor does not distribute over cand: compare
(A cand B) cor C with (A cor C) cand (B cor C);
in the case ¬A ∧ C , the second expression requires B to be defined, the first one does not. Because the conditional connectives thus complicate the formal reasoning about programs, they are better avoided.
— Edsger W. Dijkstra[2]
“There be a lot of long words in there; and I'm naught but a humble pirate3.”
Let's break it down.
(A && B) || C
(A || C) && (B || C)
Possibilities are:
| A | B | C | (A && B) || C | (A || C) && (B || C) |
|---|---|---|---|---|
| false | false | false | false | false |
| true | false | false | false | false |
| false | true | false | false | false |
| true | true | false | true | true |
| false | false | true | true | true |
| true | false | true | true | true |
| false | true | true | true | true |
| true | true | true | true | true |
So, for A = false and C = true,
(false && B) || true -> does not need to evaluate B
(false || true) && (B || true) -> does need to evaluate B.
And this while (A && B) || C == (A || C) && (B || C) holds true.
So that's interesting.
But I fear Edger W. Dijkstra may have been needlessly dogmatic here.
I ran into some issues, and I thought I'd document them here.
So changed my persistence.xml and added:
Also:
As the vendor name was not detected, eclipselink switched to a default implementation. The default implementation requires SEQUENCES for the IDENTITY definition.
It turns out the MariaDB implementation of Sequences is not compatible with the standard SQL way of creating sequences.
So I had to add the following property to the JDBC Connection pool:
I recently read [1], and it had a very interesting notion.
The idea is to let the database generate JSON, and provide it straight into your client.
So I decided to find out if MariaDB had some support for this as well.
It does2.
So, it basically was nothing more then calling a NativeQuery on the EntityManager, and returning a concatted resultset with a '['prefix and a ']'postfix and a comma-delimiter and away we go.
The native query looked like the following:
It worked flawlessly!
Caveat: of course, this is only in the case where your middleware (as in this example) really doesn't need to do anything with the result.
I mean, you are going to have to do all checks in the database query.
I think this example shows its strength when you just really want to read a lot of data, and do not need to process it.
The Java language authors have been quite frank that Optional was intended for use only as a return type, as a way to convey that a method may or may not return a value.
At work there are some cases where providing an Optional as a method parameter is a good idea, because QueryDSL has been configured to automatically return an empty resultset if the optional is not present.
But an Optional as a method parameter seems to be a disputed design choice1.
A lot of Java tooling complains about it (SonarLint, Findbugs, etc).
A lot of people mention that method overloading might be a better and clearer choice.
For example:
I took a stab at it:
Than I had to go and throw up, this is ugly as sin!
The best answer I found on StackOverflow3 without Java 9 so far:
Now this seems very interesting, but they needed to invent something better. And they did. In Java 9.
Perhaps this is why in Java 92 there is a new method in the Optional class called ifPresentOrElse.
A colleague is looking to update all inspections in IntelliJ at work, which is commendable.
He referred a link, see [1], to me regarding the use of Booleans as method parameters ("switches"), which is a pet peeve of another colleague of mine.
I thought I'd just mention it here, for who's interested.
Oh, darn. Just got bit by this thing.
The customer had stored documents for which it did not know the date with date 01-01-0007.
When importing it via XML, it turned out wrong.
The reference [1] below explains why.