When developing applications that interact with databases, Object-Relational Mappers (ORMs) help bridge the gap between relational databases and object-oriented programming. Two of the most popular ORMs are SQLAlchemy (for Python) and Hibernate (for Java). While both serve the same purpose, they have different approaches, strengths, and best use cases.
Amazon Web Services (AWS) offers a variety of persistent storage solutions designed to meet different needs, from simple object storage to high-performance databases. Choosing the right data source depends on factors such as scalability, durability, cost, and access patterns. This guide compares the most commonly used persistent data storage options on AWS to help you make an informed decision.
Many developers turn to AI to generate unit tests for existing code, but what if we flipped the process? Instead of using AI to write tests, we can write unit tests first and use AI to generate the implementation that satisfies them. This approach aligns with test-driven development (TDD), ensuring that our code meets predefined requirements and is robust from the start.
The walrus operator (:=) in Python, introduced in Python 3.8, is also known as the assignment expression. It returns the value as well as assigning it. This can reduce many lines of code and greatly simplifies the language.
I recently started using hatch for python projects, and even though hatch will manage and install dependencies for you (just modify the pyproject.toml file), I noticed the import statements could not find the dependencies. This has to do with how Python and Hatch create virtual environments.
Git hooks are scripts that Git automatically executes before or after specific events, such as committing changes or pushing to a repository. They allow you to customize and automate tasks related to these events, such as enforcing code style rules, running tests, or sending notifications. Hooks are useful for maintaining code quality and ensuring consistent workflows across a team. They can be set up in the .git/hooks directory of your repository and include both client-side and server-side hooks.
Hatch is a python packaging tool. Useful for building python projects. Out of the box it supports testing, building, managing dependencies, and linting/formatting support.
Definition of Recursion:
Recursion is a programming technique where a function calls itself in order to solve smaller instances of the same problem until it reaches a base case that does not require further recursion.
To find things quickly - use the silver searcher.
The supplier allows you to pass something but not retrieve it right away. One use case is retrieving a property an object that could throw a null pointer exception. By not retrieving right away, but instead using a supplier, the supplier can be later executed inside a try/catch block and handle any exceptions thrown.
An incredible tool in Java is the ability to create functions and compose them.
In eclipse, if you refactor->move a file from one project to another, it may not show up in your eclipse git staging as deleted from the original project.
Be careful when using setInterval as a timer.
If using the react hook useReducer(reducer, state) and you notice it runs twice after dispatching an action - this is actually by design for development mode.
If you want to maintain the order of a list of objects retrieve from the database using hibernate/jpa, use the @OrderColumn annotation. An additional column will be created in the database (if ddl is set to update) that will keep track of the order/position of an item in a list.
SQL injection occurs when SQL code can be injected into API input. In this injection attack, valid input has SQL commands concatened with SQL execution commands. When the SQL code is executed, the commands are run. In this process data can be mutated and returned to the attacker.
Always remember the CIA triad when securing API’s:
Below is an example of React hook useState to change the state of a boolean.
You can audit any changes to any entity using envers.
“Everybody wants to be a bodybuilder, but nobody wants to lift heavy ass weight”
Simple example on how to send a post request from the client and handle the response.
To add a date to a git commit message from the command line:
In Spring you can enable a component using a profile:
YAGNI is an acronym for “You Aren’t Gonna Need It”.
When making changes to config maps or other things - it’s tempting to restart all the pods for a particular service (select them all, delete, and let them come back up). This may work in the majority of cases, but if something goes wrong, it’ll be hard to tell if the recent change caused it or if it’s unrelated.
To access a shell in a particular pod:
To run a batch job, a JobLauncher needs a batch JobConfiguration and JobParameters. This creates a JobInstance.
If you need to checkout a single file from another branch in git use:
Batch jobs are created in Spring Batch using the JobBuilderFactory. A custom job builder factory can be created and re-used to allow common job configurations to be shared across all batch jobs in a project.
When a batch job fails it’s useful to automatically send a notification or trigger some sort of an action.
public static LocalDate parseDate(String date) {
DateTimeFormatter formatter =
DateTimeFormatter.ofPattern("M/d/y");
return LocalDate.parse(date,formatter);
}
@Test
public void testDateParsing() {
String testDate;
testDate ="01/01/2022";
LocalDate expected = LocalDate.of(2022, 1, 1);
assertEquals(expected, DateParser.parseDate(testDate));
}
@Test
public void testDateParsingSingleDigitMonthAndYear() {
String testDate;
testDate = "1/1/2022";
LocalDate expected = LocalDate.of(2022, 1, 1);
assertEquals(expected, DateParser.parseDate(testDate));
}
Imagine a basic web app (SPA, REST API, Sql database) with a new-user registration form. The form collects a first and last name of a new user. It is decided that the middle name needs to be collected on the form as well.
An key thing to remember in Spring Batch is that an instance of a Spring Batch job can only be restarted if it FAILED. If the job completeds SUCCESSFULLY a new instance of the job will have to be created to run it again.
To create a service in Angular:
In Spring Batch, when configuring a step you can set the chunk size.
If you have a kubernetes pod being terminated due to OOMKilled (Out of Memory Killed), you can monitor the memory usage of the pod during the action that is using too much memory.
To create a brand new spring boot app and deploy to a web server in 8 steps you can use the following:
To Install the Spring Boot Command Line Interface:
If you have a container in kubernetes unexpectedly disconnect with no error in the console log you can check the pod yaml for the last state of the pod.
Spring profiles can be used to toggle behaviors in a spring app. If your app is running in a container in Rancher (Kubernetes) you may need to see what spring profiles are being applied. To check what spring profiles a service is running in Rancher:
When running multiple batch jobs in Spring Batch, the default JobLauncher waits to launch a job until the previous job running is COMPLETE. In order to run multiple batch jobs simultaneously, the JobLauncher must be configured to run jobs asynchronously.
Often in designing batch jobs you want to limit the frequency that a job can run. For example, if you want a batch job to run once a day, you can use @Scheduled annotation to run the batch job once a day. This is enough if you only run one instance of the batch program and there are no other ways to launch the job.
When defining a Spring batch step, often common configurations are added to almost every step. In order to not violate DRY (Don’t Repeat Yourself), a StepBuilder can be customized upstream with all the shared configurations.
for(String name: names) {
System.out.println(name);
}
// This is called a method reference
names.foreach(System.out::println);
When you want to query only on results from today in a Postgres database use the >= now()::date syntax.
To find a file from the command line:
brew tap heroku/brew && brew install heroku
heroku autocomplete
printf "$(heroku autocomplete:script bash)" >> ~/.bashrc; source ~/.bashrc
To use autocomplete type: Heroku and Tab,Tab
In order to view git history from the command line:
Often we have to loop through a list of items and convert it into a map, with the key being some sort of category and the value being a set of the associated items ie Map<Key, Set<Object>>. The old way of doing this looped through the list and before adding checked if the key was present. Using computeIfAbsent we can clean up this syntax considerably.
In Spring Batch, in order to get the job_execution_id of the last batch job instance for a given batch job name use this query:
