How to fix error: snap “telegram-desktop” has “install-snap” change in progress

I enconter this error message when installing a Snap app Telegram for Desktop from the terminal command line. I followed instructions on how to do this from the Install button of the snapcraft.io website.

First one I select is use the GUI app store. But nothing happens when click install button. Installing progress starts but go back to install. Click again and same thing is happens.

When using the command line that is I got the error of:

error: snap "telegram-desktop" has "install-snap" change in progress

How to fix?

ANSWER

The error is because you are telling Snap to install an app that has already been scheduled for installation. It’s in the queue. The GUI app store is not very informative about this scenario. Hence, it will seem like the installation process failed when in fact that is not the case.

My guess is it is put on schedule for installation because a higher priority install needs to be done first, most likely Snap core updates that have not yet been applied to the system yet.

Either wait for the core updates to finish and wait for Telegram to get installed after, or force it to update right away.

At the command line, do:

:~$ snap changes

It will show something such as:

ID Status Spawn Ready Summary
101 Done yesterday at 20:33 PST yesterday at 20:34 PST Auto-refresh snap "intellij-idea-community"
102 Doing today at 11:36 PST - Install "slack" snap

Abort the scheduled install for the app listed there, in your case “telegram-desktop” snap using the following command:

:~$ sudo snap abort 102

In the example above, I chose to abort install scheduled with ID 102. Choose the ID of the app you are trying to install that you will see on your terminal after the command above.

Then install the snap app manually:

:~$ sudo snap install telegram-desktop

This should force snap to go ahead with the install, but first it may start with its core updates, followed by the telegram-desktop snap app.

Change default app to open torrent magnet link

I installed a Popcorn-time desktop software on my Ubuntu linux to try that out. It appears to use a torrent technology to stream content as it downloads at the same time. Somehow that now gets the default to open magnet links for torrent files. Have not remembered any setting asking me to make the app open by default during installation or at download.

I don’t want this, don’t know how to change to my default torrent software – Transmission BitTorrent.

How to change back?

ANSWER

Add/edit it into the following files. Either or both is fine, but better to have it in for the system-wide list if you have multiple users.

  • System-wide: /usr/share/applications/defaults.list
  • User-specific: ~/.local/share/applications/mimeapps.list

The value of this entry – x-scheme-handler/magnet – needs to be set to the application you prefer.

For example, since you want it to be Transmission it will be similar as shown below:


x-scheme-handler/magnet=transmission-gtk.desktop

Just make sure the .desktop file for the desired application is correct. Again you can check for that file in the same directory where this list is found.

As an alternative, the following terminal commands will also help.

Find out what is the existing default app that will handle such mime-type for your existing user:

:~$ xdg-mime query default x-scheme-handler/magnet

Replace that by using the next command:

:-$ xdg-mime default transmission-gtk.desktop x-scheme-handler/magnet

Lastly, you can check again if the last command was successful by running the first one.

Base64-encoded value is slightly different at the end of string

Why is there slight differences in base64 encoding at the end of the encoded string. It could be one or more of characters that’s different.

Here an example done on base64encode.org using this text – Hey, Diddle Diddle – the output value is:

SGV5LCBEaWRkbGUgRGlkZGxl

But when I do same in base64 command line, I get this instead:

SGV5LCBEaWRkbGUgRGlkZGxlCg==

It is 4 more characters longer. Which one is correct encoding?

ANSWER

The most likely answer is caused by a non-visible character, or characters, being appended at the end of the text you are trying to encode that is causing the slight variation.

Normally this would be caused by the new line, or line feed character, that you won’t see but is there at the end of the text. It is a valid character that the base64 command will include when it encodes the text you give it.

It is not wrong, but most times it is not the intention to have the new line character encoded with it.

Thus, when doing so in command line make sure the new line character is trimmed off. It can be done this way,

:~$ echo -n "hello world" | base64

The result would be: aGVsbG8gd29ybGQ=

Without it, the output is: aGVsbG8gd29ybGQK

Of course, the case of the character/characters being encoded will also matter.

There any free, lightweight app to merge PDF files as one?

As the name of the title in this post says it all. Okay, maybe not all it says because I want it on Linux desktop.

Looking for a tool that can combine different PDF into one big PDF file. I don’t need to modify the content of the PDFs. All important is merging them together as a group.

Sorting it probably comes as second important feature. But I can get on without that as long as it stays in sequence however I added each PDF file.

Lastly simple. No over the top effects. Prefer GUI app. Open to command line.

ANSWER

For that purpose, I have personally used PDF-Shuffler, It is a GUI desktop application on Linux. I used it back then on Ubuntu, but it should be available in all other major distros. Google for it. I know it is included in the official package management repositories of Ubuntu.

PDF-Shuffler can collate, sort (through drag and drop) and rotate the PDF files individually. As an added bonus, it can crop PDFs too.

It is a straightforward app. Stable for all those times I’ve used. But my usage is fairly moderate only.

I also suggest using pdftk for command line if you fancy that kind of stuff. You can combine PDFs into one as simple as:

:~$ pdftk file-1.pdf file-2.df file-3.pdf output my-merged.pdf

This tool can do other stuff. You can read its manual for more information. Google about pdftk too for more examples.

Support for Ubuntu Unity Desktop after 16.04 LTS

Can still use the Unity Desktop after Ubuntu 16.04 Xenial Xerus? Is it still supported?

I like the Unity desktop way of things. Been using it many years now. Read about and tried the new Ubuntu that with Gnome Shell, but I don’t like it much at all. It look clunky with many of missing things from it.

Come April 2021 Ubuntu 16.04 will EOL. Starting to find alternatives, but if Unity is still out there, I’d pick it over the others.

ANSWER

In one word, Yes.

Still can run on both LTS versions of 18.04 and 20.04. Go ahead and install it with:

sudo apt install ubuntu-unity-desktop

Choose Lightdm display manager when asked during install. Best to restart your computer afterwards. Then enjoy.

Consider that many people have said some weird looks of Unity when installed on said LTS versions appear. I forget, but I think its the window decorations and such. This is supposedly caused by the newer Gnome versions, and unpatched by Ubuntu. Unlike before.

You may also like to try out an alternative in the Ubuntu Unity Desktop spinoff. Can be found at this website – https://ubuntuunity.org/

It is not official Ubuntu flavor, but being maintained by some other 3rd party group. The experience is different from just installing 20.04 and then install Unity DE afterwards. Try it out if it suits you.

How to convert For loop using Stream in Java

Creating a Map of Applicant object, where I filter out on the applicant’s age. I only need the first name and last name of the applicant. Using the application ID as the key. The ID is generated integer and unique. Also, testing for null, don’t want that in there. I am using a traditional for loop where I am most comfortable at. But I want to use the Java 8 Stream instead. How is it done?

My code for this is below:

        Applicant a1 = new Applicant();
        a1.setId(1001);
        a1.setFirstName("Joseph");
        a1.setLastName("Dey");
        a1.setAge(25);

        Applicant a2 = new Applicant();
        a2.setId(2001);
        a2.setFirstName("Maxine");
        a2.setLastName("Summers");
        a2.setAge(21);

        Applicant a3 = new Applicant();
        a3.setId(3001);
        a3.setFirstName("Jimmy");
        a3.setLastName("Cox");
        a3.setAge(17);

        Applicant a4 = null;

        List<Applicant> list = new ArrayList<>();
        list.add(a1);
        list.add(a2);
        list.add(a3);
        list.add(a4);

        Map<Integer, String> map = new HashMap<>();
        for (Applicant a : list) {
            if (a != null && a.getAge() > 18) {
                map.put(a.getId(), a.getFirstName() + " " + a.getLastName());
            }
        }

ANSWER

By Statement Lambda in Collectors.toMap – right-hand side is a block. This can become longer to write but sometimes when you have to do more transformations, then it can’t be avoided.

1       Map<Integer, String> map = list.stream()
2                .filter(applicant -> applicant != null)
3                .filter(applicant -> applicant.getAge() >= 18)
4                .collect(Collectors.toMap(applicant -> applicant.getId(), applicant -> {
5                    return applicant.getFirstName() + " " + applicant.getLastName();
6                }));

By Expression Lambda in Collectors.toMap – right-hand side is an expression.

1       Map<Integer, String> map = list.stream()
2                .filter(applicant -> applicant != null)
3                .filter(applicant -> applicant.getAge() >= 18)
4                .collect(Collectors.toMap(applicant -> applicant.getId(), applicant -> applicant.getFirstName() + " " + applicant.getLastName()));

In both cases above, line #2 the Lambda can be replaced with method reference too. It will look like:

.filter(Objects::nonNull)

And on line #4, the same can be done for the Lamba replacing it with a method reference. It will look like:

.collect(Collectors.toMap(Applicant::getId,  // rest of code ommitted

Avro – Unions

As a boolean:

{
	"fieldOne": "hello world",
	"fieldTwo": true,
	"foobar": {
		"boolean": false
	}
}

If value is null:

{
	"fieldOne": "hello world",
	"fieldTwo": true,
	"foobar": null
}

The above is what a field will look like as output where in Avro that field is defined as one of the Complex Types – Unions. Example below, it declares a schema which may be one of null or boolean.

{
  "type": [
    "null", 
    "boolean"
  ]
}

Convert a Map to POJO in Java

How do I convert a Map object to my other plain old Java object (POJO) without going into loops and having to write a class using Java reflection, or some other?

ANSWER

Well, yes, reflection is one but you didn’t want to do that yourself. For some good reason, I bet. It’s a good exercise if you have all the time in the world. But when faced with deadlines and having to write Unit tests for a whole class you wrote, there must be an easier way.

There is more than one way, but what I normally use is the Jackson ObjectMapper. Yes, the same one from the com.fasterxml.jackson library.

Anyway, with ObjectMapper it is pretty straightforward to do so. If I have a Person class like this:

    public class Person {
        private String firstName;
        private String lastName;
    }

My Map object will look like this:

        Map<String, Object> map = new HashMap<>();
        map.put("firstName", "Johnny");
        map.put("lastName", "Foo");

Then with ObjectMapper one can simply do this:

        ObjectMapper mapper = new ObjectMapper();
        Person person = mapper.convertValue(map, Person.class);

Alternatively, the keys in the Map may not align with the fields in the Person class. Well, I usually encounter this when working with JSON objects with lots of crazy looking field names. Something like this – NZT_Mor_First_Name__c – which I clearly don’t want my class field name to be like.

Well, we can use @JsonProperty annotation which is part of Jackson by the way and assign that our class field. The Person class will now look like:

    public class Person {

        @JsonProperty("NZT_Mor_First_Name__c")
        private String firstName;

        @JsonProperty("NZT_Mor_Last_Name__c")
        private String lastName;
    }

Again the Map will hold these values:

        Map<String, Object> map = new HashMap<>();
        map.put("NZT_Mor_First_Name__c", "Jose");
        map.put("NZT_Mor_Last_Name__c", "Yamut");

Now it will map out those weird looking key names to its corresponding class fields.

One thing to note is you might need to set ObjectMapper features such as ignoring unknown properties and make it case insensitive. Allow it a bit more room to wiggle, wiggle.

        ObjectMapper mapper = new ObjectMapper()
                .configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false)
                .enable(MapperFeature.ACCEPT_CASE_INSENSITIVE_VALUES);

Should I quote Strings in YAML?

Should I or should I not? Is it required? Will it work even without quotes – single or double?

ANSWER

I’ve asked myself these questions several times. Often I end up double-quoting long strings, but not for one word ones or shorter strings. Which makes it rather inconsistent. Especially if that string contains characters like a forward slash, a colon or semi-colon. Like when you have a URL as a value. I suppose it’s out of habit.

Thing is, it is not required. Strings can be quoted or not. There is no difference. It will still work with or without it. Even with spaces in that string. YAML allows it. Below are 2 examples:

phrase: 'The quick brown fox jumps over the lazy dog.'
poem: "Hey, diddle, diddle. The cat and the fiddle. The cow jumped over the moon."

The key part of the key-value pair can also be quoted too. The YAML won’t error out. Again, it’s allowed. So this is valid:

'foo':
  "bar": foobar

Single quote or double quotes don’t matter. It can be mixed. Above examples are both acceptable.

However, not quoting is not true in all cases. There are certain instances when it is required such as when there is a colon in the key. In this case, the key needs to be quoted.

'key:': value

What about quotes in the value itself?

CORRECT - phrase1: 'The quick ''brown'' fox jumped over the lazy dog.'
WRONG- phrase2: "The quick ""brown"" fox jumped over the lazy dog."
CORRECT - phrase3: "The quick \"brown\" fox jumped over the lazy dog."
WRONG - phrase4: "The quick '"brown"' fox jumped over the lazy dog."
CORRECT - phrase6: The quick 'brown' fox jumped over the lazy dog.
CORRECT - phrase7: The quick "brown" fox jumped over the lazy dog.

Finally, what does YAML mean?

It is short for – YAML Ain’t Markup Language.

What’s my Windows version

You’ll probably get asked this once or twice. Especially when your Windows computer is not working right, and you are running all over the Internet trying to look for answers. Perhaps would-be good Samaritans might ask this off you as well.

And you reply, “Windows 10”. But rightfully so.

After all, isn’t that the Windows that is installed on your machine right now. Well, yes. Then again, no. No not in the sense that you are wrong. But sometimes the answer to the question of what Windows version is installed on your PC might be something else. Sometimes support may ask you this, and likely they will tell you how to give them the answer they are looking for. If you don’t already know this, then this can save time and misunderstanding. Below are the steps on how to get that information.

What version is my Windows?

  • Go to the Start Menu. Click it. Press the Windows key
  • Type “Run”. The shortcut key is Windows key + R.
  • Type “winver” in the field labeled with Open. You may also type winver in the search box on your taskbar if you have that one.
  • Click OK or press enter
  • Small dialog Windows will pop out title – About Windows.

The information will be found on this pop up window. On the first few lines you should see something like:

Microsoft Windows
Version 2004 (OS Build 19041.630)

Note: Don’t include quotes when typing in those words in the steps.

Is there a Clipboard for Windows 10?

What are the freely available Clipboard programs, if any, for Windows 10? Are there such? I don’t want ads in it and I prefer it simple as possible. No crazy or complex features. I’m only after a simple copy-paste of the short history of what I’ve copied on my desktop. I find this useful for my productivity. I somehow always ending up in open a Notepad and copying the items in there. It works but a clipboard would be better in my opinion.

ANSWER

Windows 10 already comes with a built-in Clipboard Manager. This was from an update some time ago. However it is not enabled by default, buried somewhere in the Settings and you will have to activate it. This feature is not very well known. But it is there and it works as expected.

To activate:

Open Settings via any of the following ways:

  • You can either search for it if you have that search bar on your Windows taskbar.
  • Start typing “Settings” when you have the Windows Start Menu opened.
  • Open the Start Menu then, then click on the Gear icon on the left hand side of the menu.
  • Windows + i shortcut key combo.

Once you are in Settings, go to System. That should be the first icon entry at the top.

You will be taken to another page where there are items at the left hand side. Scroll down and find Clipboard.

Under Clipboard history, toggle the button to On.

To get to your clipboard history, simply press Windows + V shortcut key combo. It will appear as a floating box over your last active application. Otherwise, it will show up on the right side of the desktop on top of the system tray.

The clipboard can contain a max of 25 entries. It is a FIFO (first in, first out) stack so the oldest entry will go out first once that entry limit is hit.

It supports plain text, HTML and images up to 4MB size.

Your clipboard history can be synced across your Windows devices. Be warned that if you enable this it means you are allowing Windows to save the history on Microsoft servers. Make sure you don’t have sensitive information in there when the Sync functionality is enabled.

Re-publish Kafka record not setting partition number?

Well, I plan to re-publish Kafka records that my app is consuming to another Kafka topic on another host (internal only). This sort of lets other groups consume data from this topic without having to create connections outside of the private network, since the original data source is a 3rd party vendor. They can then also do their own transformations or other business logic on it as if they were consuming from the original source. Delay from source to re-publish should be minimal. Will still be close to real time.

What I normally do when producing records is not to set a partition by default. Would this be okay when re-publishing records? Will there be conflict with original record partition number to the target topic partition?

ANSWER

How many partitions does your target topic have? Do you have freedom to create as many partitions as the source?

(1) If you can create 1:1 partitions then my suggestion is to retain the original partition number of that record when you publish to the destination topic.

(2) You can also assign the partition in a round-robin way when you have lesser partitions on your target topic. Save metadata info of that record in the headers, such as original partition assignment and etc. Perhaps that will be useful down the line for your consumers.

(3) Lastly, you can NOT assign a partition number. Instead, let Kafka do the magic for you. When no partitions are set, Kafka will determine the next partition in a round robin method. You can do this with a null value instead of an int for partition number.

Bottom line is that it depends on the project requirements, I suppose, or more so on the infrastructure of your destination Kafka.

Can’t copy text from webpage?

Sometimes I come upon a website that I cannot copy text from a HTML web page. Simply cannot click and highlight the lines I try to select for copying. I thought that my browser/mouse was not working. But I go to other sites, I am able to highlight/copy normally. They must’ve done something on that page probably to prevent content from being lifted of the page easily?

Why is this and how do they do it? Is this a javascript in the page that prevents me from copying?

ANSWER

Could be a script on the webpage. I’m certain that can be done or already been done through Javascript before.

I know that the same effect can be achieved via CSS alone. It is easier, cleaner and does not add to another Javascript messing up or slowing down a site. I prefer this method over the other.

Below are the CSS lines that does what you want. Different ones for different browsers. It is vendor specific for some, but does the same exact thing.

   user-select: none; /* Supported by Chrome, Firefox & Opera */
  -moz-user-select: none; /* Firefox (older) */
  -ms-user-select: none; /* Edge */
  -khtml-user-select: none; /* Konqueror */
  -webkit-touch-callout: none; /* Safari for iOS */
  -webkit-user-select: none; /* Safari for Mac */

Try it out. You can make it for entire page/site.

* {
     /* CSS lines go here */
}

Or you can make it so only targeted content will have it using Class or ID selectors.

#text-no-select {
     /* ID selector -  CSS lines go here */
}

.text-no-select {
     /* Class selector -  CSS lines go here */
}

Be aware this does not totally prevent anyone from copying content on a website. There are many other ways to go around this or even with a Javascript impementation. It is a minor roadblock.

How to make IntelliJ check and create SerialVersionUID

When the class implements Serializable I want the serialVersionUID field to be auto-created by IntelliJ IDE. This feature comes in automatically in Eclipse. But the former does not.

How do I make IntelliJ create the field or warn me that it is not defined in the class yet?

ANSWER

It is not turned on by default in IntelliJ. Can be easily done by going to the following:

File > Settings > Editor > Inspections > Java > Serialization Issues

Then find and select – Serializable class without ‘serialVersionUID’ – by checking on the box to the right of it.

Similarly, you can search for it once in File > Settings. Keyword for search can be – ‘serialVersionUID’ – without the quotes.

The path or location of this feature on IntelliJ may vary. It should be the same on Linux and Windows for versions 2019 and 2020.

This will only throw a warning. It does not magically create the field in all those classes that implements Serializable straight away. But then IntelliJ will help you create it, like any other decent IDE out there. Go to the class name declaration, you may find that it is subtly highlighted in yellow to hint that there is a user action that can be done. Hover then click on the option – Add ‘serialVersionUID’ field – and you will get the desired result like this one:

private static final long serialVersionUID = 6265605531073886420L;

Database tables map One To Many without foreign key in @JoinColumn

Possible to not have foreign key relationship in child table to its parent in the database, while in JPA it will still be able to map out fine? How will this be done?

Can I still use @JoinColumn to define the field for reference back to the parent table?

This is a one-to-many relationship. One parent record, many child records.

I only care about writes to the database tables right now.

ANSWER

Yes, no FKs defined in the database is fine. JPA will still be able to map out there relationships as defined in your entity classes.

In fact, enabling – spring.jpa.generate-ddl – in your application properties file will create the necessary Foreign Key and/or Unique Key constraints in the database. This is vendor dependent however.

For a One To Many relationship, it is straightforward to do. Example below definition below:

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name = "recommendation_id")
    private List<CommentEntity> commentList;

This will map out the entity object values to the Comment table, assuming that is the name of the target table. Each one will be persisted to the child table along with the ID of the parent Recomendation under the recommendation_id column.