Spring Boot

File download means the server finds a stored file and sends it back to the client as the HTTP response, with headers that tell the client the file name, type, and size. The Content-Disposition header decides whether the browser saves the file (attachment) or opens it (inline). It is used for downloading certificates, marksheets, invoices, […]

Multiple file upload means a client sends several files in one multipart/form-data request, and Spring Boot receives them together as a List<MultipartFile> (or an array). Each file is a separate part of the request, so the server can check, store, and record every file one by one. It is used when a record needs more

Single file upload means a client sends exactly one file to the server in a multipart/form-data request, and Spring Boot receives it as a MultipartFile. The application then validates the file, saves it somewhere (a folder, the database, or cloud storage), and keeps the file details for later use. It is used for profile pictures,

DatabaseMetaData is a JDBC interface used to obtain information about the database, JDBC driver, tables, columns, and supported database features. It is obtained from a Connection object using the getMetaData() method. Using DatabaseMetaData, a Java program can dynamically inspect database information without directly querying system tables. This is useful for database administration, debugging, database migration

A standard error response is one fixed JSON structure that your API returns for every kind of failure, whether it is a missing record, invalid input, or a server problem. It is a small class (here ErrorResponse) holding the same fields each time: status, message, timestamp, and request path. It is used so that front-end

Global exception handling means one central class catches the exceptions thrown from every controller in the application and turns them into clean HTTP responses. In Spring Boot you create this class with @RestControllerAdvice, and it holds @ExceptionHandler methods for each kind of error. It is used so that error handling is written once, every API

Controller-level handling means a controller catches and handles exceptions itself, using @ExceptionHandler methods written inside the controller class. When a service throws an exception, Spring looks in that same controller for a matching handler and uses it to build the response. It is used to turn failures such as a missing student or invalid data

A custom exception is your own exception class that describes one specific failure in your application, such as a student who does not exist. It extends RuntimeException (or Exception) and carries a clear name and message, so the problem is obvious in code, logs, and API responses. It is used instead of generic exceptions, because

DatabaseMetaData is a JDBC interface used to obtain information about the database, JDBC driver, tables, columns, and supported database features. It is obtained from a Connection object using the getMetaData() method. Using DatabaseMetaData, a Java program can dynamically inspect database information without directly querying system tables. This is useful for database administration, debugging, database migration

REST API testing means calling your endpoints directly, without a front-end, to check that they return the right data and status codes. An API client such as Postman lets you choose the HTTP method, URL, headers, and body, then shows the response, status code, and time. It is used to find bugs early, confirm that