doPut

doPut is a method in the Java Servlet API used to handle HTTP PUT requests. It is declared in the HttpServlet class and is invoked by the servlet container when a client sends a PUT request to a URL mapped to the servlet. If not overridden, the default HttpServlet doPut implementation responds with 405 Method Not Allowed.

Semantics: HTTP PUT targets a specific resource URI and is generally idempotent. The request body carries a representation of the resource to be stored at that URI. A successful call updates an existing resource or creates a new one at that path. Repeating the same PUT with the same payload must produce the same result.

Implementation: override the method with the standard signature protected void doPut(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException. Within it, read the request body (for example via req.getInputStream()), determine the resource location from the request path (req.getPathInfo()), perform the store or update, and set an appropriate response status (for example 200/204 for success, 201 if a new resource was created).

Relation to other methods: PUT targets a known URI and is distinct from POST, which is not idempotent and may create sub-resources or trigger actions. In RESTful design, PATCH may be used for partial updates, while PUT often implies a full replacement of the resource content.

Example scenario: a RESTful file store may accept PUT /files/notes.txt with a payload containing file data; the server writes the content to the file and returns 204 No Content on success or 201 Created if the file did not previously exist.