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MY PROJECTS
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Recent Posts
- SQL.How can you compare two nullable values safely, and how does IS DISTINCT FROM differ from <>?
- SQL.How are NULL values ordered by ORDER BY, how do defaults differ between databases, and how can you control their placement?
- SQL.How does NULL propagate through arithmetic expressions, and how can COALESCE and NULLIF help handle missing values and division by zero?
- SQL.How does NULL affect join conditions, and why can filtering the right-hand table in WHERE remove unmatched rows from a LEFT JOIN?
- SQL.How do GROUP BY and DISTINCT treat NULL values, even though NULL = NULL evaluates to UNKNOWN?
- SQL.How do aggregate functions handle NULL, and what is the difference between COUNT(*), COUNT(column), and COUNT(DISTINCT column)?
- SQL.How does NULL affect IN and NOT IN, and why can NOT EXISTS be a safer choice when a subquery returns nullable values?
- SQL.How do WHERE, HAVING, and CHECK constraints treat conditions that evaluate to UNKNOWN?
- SQL.Why do column = NULL and column <> NULL not work as expected, and when should you use IS NULL and IS NOT NULL?
- SQL.What is SQL’s three-valued logic (TRUE, FALSE, UNKNOWN), and how do AND, OR, and NOT behave with UNKNOWN?
- ChromeDevTools.Watch all failed requests
- SQL.What are domain types (or constraints on data types), and how do they help enforce data correctness?
- SQL.How does SQL handle comparisons between different data types (for example, string vs number), and why is this dangerous?
- SQL.What is the difference between DATE, TIME, TIMESTAMP, and TIMESTAMPTZ, and which one should be used for business events?
- SQL.How do numeric types like INTEGER, BIGINT, DECIMAL, and FLOAT differ in terms of precision and use cases?
- SQL.What problems can arise from implicit type casting in SQL, and how can it affect indexes?
- SQL.How does NULL differ from 0, an empty string, or FALSE in SQL?
- SQL.What is the difference between CHAR, VARCHAR, and TEXT, and when would you choose each?
- SQL.What is MVCC ?
- SQL.What is AutoVacuum Postgres ?
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Author Archives: Stanislav_Panteleev
Java.Servlet.JSP Request-to-Response Lifecycle
🔁 JSP Request-to-Response Lifecycle 1. Client Sends HTTP Request A user visits a URL like: This sends an HTTP GET (or POST) request to the web server. 3. JSP Is Translated into a Servlet If it’s the first time the … Continue reading
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Java.Servlet.Why do we need JSP?
✅ 1. Simplifies Web Development Instead of writing HTML inside Java (as in Servlets), you can write HTML first and just insert Java logic where needed. This makes your code: Easier to write Easier to read Easier to maintain ✅ … Continue reading
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Java.Servlet.What are Java Server Pages (JSP)?
Java Server Pages (JSP) are server-side technologies used to create dynamic web pages by embedding Java code directly into HTML. JSPs are like HTML pages, but with the ability to run Java code inside them. The server compiles JSPs into … Continue reading
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Java.Servlet.What authentication methods are available to a servlet?
✅ Short Answer: In servlets, there are four standard authentication methods, defined by the Servlet Specification (web.xml or annotations). Method Description 1. Basic Authentication Simple login popup from the browser (username/password sent base64-encoded). 2. Digest Authentication Like Basic but sends … Continue reading
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Java.Servlet.What are the main features introduced in the Servlet 3 specification?
✅ Short answer: Servlet 3.0 (finalized in December 2009, part of Java EE 6) brought major improvements to simplify development and support modern web applications. ✅ Main Features introduced in Servlet 3.0: Feature Description 1. Annotation-based Configuration No more messy … Continue reading
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Java.Servlet.Should i close connection in my code if i use connection pool ?
✅ Short and clear answer:YES, you absolutely must close the Connection yourself even when using a connection pool! BUT — and this is very important — Closing a connection from the pool does NOT physically close it to the database. … Continue reading
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Java.Servlet.If i created connection pool, when it should be destroyed ?
✅ Short answer:The connection pool (like HikariDataSource, Tomcat DataSource, etc.) should be destroyed when the web application is shutting down. That means: When Tomcat (or another servlet container) undeploys your app, Or stops, Or reloads the application. Otherwise: Database connections … Continue reading
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Java.Servlet.How can we organize a database connection, provide logging in a servlet?
✅ Problem: You need a database connection in your servlet. You want to log information, warnings, errors (instead of just printing to console). If you just open a Connection inside every servlet → it’s inefficient and dangerous (resource leaks, no … Continue reading
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Java.Servlet.How can we provide transport layer security for our web application?
✅ Short answer:To provide Transport Layer Security (TLS) for your web application, you must use HTTPS instead of HTTP. TLS = modern version of SSL (Secure Sockets Layer).It encrypts all the data sent between the client (browser) and server, preventing: … Continue reading
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Java.Servlet.What is an effective way to ensure that all servlets are accessible only to a user with a valid session?
✅ Short answer:The most effective and standard way is to use a Servlet Filter. A Filter intercepts every request before it reaches the servlet. In the filter, you check if the user has a valid session. If the session is … Continue reading
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