An Entity Manager is a core component of ORM (Object-Relational Mapping) frameworks, especially in Java (JPA – Java Persistence API), but also in other languages like PHP (Doctrine ORM).
Persisting:
Finding/Loading:
Retrieves an object by its ID or other criteria.
Example: $entityManager->find(User::class, 1);
Updating:
Tracks changes to objects and writes them to the database (usually via flush()).
Removing:
Deletes an object from the database.
Example: $entityManager->remove($user);
Managing Transactions:
Begins, commits, or rolls back transactions.
Handling Queries:
Executes custom queries, often using DQL (Doctrine Query Language) or JPQL.
The Entity Manager tracks the state of entities:
managed (being tracked),
detached (no longer tracked),
removed (marked for deletion),
new (not yet persisted).
$user = new User();
$user->setName('Max Mustermann');
$entityManager->persist($user); // Mark for saving
$entityManager->flush(); // Write to DBThe Entity Manager is the central component for working with database objects — creating, reading, updating, deleting. It abstracts SQL and provides a clean, object-oriented way to interact with your data layer.
Design by Contract (DbC) is a concept in software development introduced by Bertrand Meyer. It describes a method to ensure the correctness and reliability of software by defining clear "contracts" between different components (e.g., methods, classes).
In DbC, every software component is treated as a contract party with certain obligations and guarantees:
Preconditions
Conditions that must be true before a method or function can execute correctly.
→ Responsibility of the caller.
Postconditions
Conditions that must be true after the execution of a method or function.
→ Responsibility of the method/function.
Invariant (Class Invariant)
Conditions that must always remain true throughout the lifetime of an object.
→ Responsibility of both the method and the caller.
Clear specification of responsibilities.
More robust and testable software.
Errors are detected early (e.g., through contract violations).
class BankAccount {
private double balance;
// Invariant: balance >= 0
void withdraw(double amount) {
// Precondition: amount > 0 && amount <= balance
if (amount <= 0 || amount > balance) throw new IllegalArgumentException();
balance -= amount;
// Postcondition: balance has been reduced by amount
}
}Clear contracts reduce misunderstandings.
Easier debugging, as violations are detected immediately.
Supports defensive programming.
Requires extra effort to define contracts.
Not directly supported by all programming languages (e.g., Java and C++ via assertions, Python with decorators; Eiffel supports DbC natively).
Perl Compatible Regular Expressions (PCRE) are a type of regular expression syntax and engine that follows the powerful and flexible style of the Perl programming language. They offer advanced features that go beyond the basic regular expressions found in many older systems.
Perl was one of the first languages to introduce highly expressive regular expressions. The PCRE library was created to bring those capabilities to other programming languages and tools, including:
Python (similar via the re module)
JavaScript (with slight differences)
pcregrep (a grep version supporting PCRE)
Editors like VS Code, Sublime Text, etc.
✅ Lookahead & Lookbehind:
(?=...) – positive lookahead
(?!...) – negative lookahead
(?<=...) – positive lookbehind
(?<!...) – negative lookbehind
✅ Non-greedy quantifiers:
*?, +?, ??, {m,n}?
✅ Named capturing groups:
(?P<name>...) or (?<name>...)
✅ Unicode support:
\p{L} matches any kind of letter in any language
✅ Assertions and anchors:
\b, \B, \A, \Z, \z
✅ Inline modifiers:
(?i) for case-insensitive
(?m) for multiline matching, etc.
(?<=\buser\s)\w+This expression matches any word that follows "user " using a lookbehind assertion.
PCRE are like the "advanced edition" of regular expressions — highly powerful, widely used, and very flexible. If you're working in an environment that supports PCRE, you can take advantage of rich pattern matching features inspired by Perl.
Salesforce Apex is an object-oriented programming language specifically designed for the Salesforce platform. It is similar to Java and is primarily used to implement custom business logic, automation, and integrations within Salesforce.
Cloud-based: Runs exclusively on Salesforce servers.
Java-like Syntax: If you know Java, you can learn Apex quickly.
Tightly Integrated with Salesforce Database (SOQL & SOSL): Enables direct data queries and manipulations.
Event-driven: Often executed through Salesforce triggers (e.g., record changes).
Governor Limits: Salesforce imposes limits (e.g., maximum SOQL queries per transaction) to maintain platform performance.
Triggers: Automate actions when records change.
Batch Processing: Handle large data sets in background jobs.
Web Services & API Integrations: Communicate with external systems.
Custom Controllers for Visualforce & Lightning: Control user interfaces.
In software development, syntax refers to the formal rules that define how code must be written so that it can be correctly interpreted by a compiler or interpreter. These rules dictate the structure, arrangement, and usage of language elements such as keywords, operators, brackets, variables, and more.
Language-Specific Rules
Every programming language has its own syntax. What is valid in one language may cause errors in another.
Example:
Python relies on indentation, while Java uses curly braces.
Python:
if x > 0:
print("Positive Zahl")Java:
if (x > 0) {
System.out.println("Positive Zahl");
}Syntax Errors
Syntax errors occur when the code does not follow the language's rules. These errors prevent the program from running.
Example (Syntax error in Python):
print "Hello, World!" # Fehlende Klammern3. Syntax vs. Semantics
4. Tools for Syntax Checking
Variable Naming: Variable names cannot contain spaces or special characters.
Variablenbenennung: Variablennamen dürfen keine Leerzeichen oder Sonderzeichen enthalten.
my_variable = 10 # korrekt
my-variable = 10 # Syntaxfehler{ ... }.
An object-oriented database management system (OODBMS) is a type of database system that combines the principles of object-oriented programming (OOP) with the functionality of a database. It allows data to be stored, retrieved, and managed as objects, similar to how they are defined in object-oriented programming languages like Java, Python, or C++.
Object Model:
Classes and Inheritance:
Encapsulation:
Persistence:
Object Identity (OID):
Complex Data Types:
Object-oriented databases are particularly useful for managing complex, hierarchical, or nested data structures commonly found in modern software applications.
Object Query Language (OQL) is a query language similar to SQL (Structured Query Language) but specifically designed for object-oriented databases. It is used to query data from object-oriented database systems (OODBs), which store data as objects. OQL was defined as part of the Object Data Management Group (ODMG) standard.
Object-Oriented Focus:
SQL-Like Syntax:
Querying Complex Objects:
Support for Methods:
Integration with Object-Oriented Languages:
Suppose there is a database with a class Person that has the attributes Name and Age. An OQL query might look like this:
SELECT p.Name
FROM Person p
WHERE p.Age > 30This query retrieves the names of all people whose age is greater than 30.
In practice, OQL is less popular than SQL since relational databases are still dominant. However, OQL is very powerful in specialized applications that utilize object-oriented data models.
A Remote Function Call (RFC) is a method that allows a computer program to execute a function on a remote system as if it were called locally. RFC is commonly used in distributed systems to facilitate communication and data exchange between different systems.
The Document Object Model (DOM) is a standardized interface provided by web browsers to represent and programmatically manipulate structured documents, especially HTML and XML documents. It describes the hierarchical structure of a document as a tree, where each node represents an element, attribute, or text.
Tree Structure:
<html> element, with child nodes such as <head>, <body>, <div>, <p>, etc.Object-Oriented Representation:
Interactivity:
<p> element or insert a new <div>.Platform and Language Agnostic:
1. Accessing an Element:
let element = document.getElementById("myElement");2. Changing Content:
element.textContent = "New Text";3. Adding a New Element:
let newNode = document.createElement("div");
document.body.appendChild(newNode);The DOM is defined and maintained by the W3C (World Wide Web Consortium) standards and is constantly updated to support modern web technologies.
SonarQube is an open-source tool for continuous code analysis and quality assurance. It helps developers and teams evaluate code quality, identify vulnerabilities, and promote best practices in software development.
Code Quality Assessment:
Detecting Security Vulnerabilities:
Technical Debt Evaluation:
Multi-Language Support:
Reports and Dashboards:
SonarQube is available in a free Community Edition and commercial editions with advanced features (e.g., for larger teams or specialized security analysis).
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