# File Viewer for Vaadin **Browse and search large log files directly in your Vaadin application.** File Viewer makes it easy to inspect application logs and other large text files. Inspired by [glogg](https://github.com/nickbnf/glogg), it brings log viewing and monitoring into your Vaadin UI. ## Live demo A live demo is available at [pacos.dev](https://pacos.dev). Sign in as a guest, then select **Applications → Glogg** from the system’s top menu. ## Getting started Add the component to your Vaadin view and open a file using its path: ```java import java.nio.file.Path; import org.vaadin.addons.viewer.FileViewer; FileViewer fileViewer = new FileViewer(); add(fileViewer); fileViewer.openFile(Path.of("/var/log/application.log")); ``` The file is opened using UTF-8 by default. To open a file with a different character encoding, pass a `Charset`: ```java import java.nio.charset.Charset; import java.nio.charset.StandardCharsets; import java.nio.file.Path; fileViewer.openFile(Path.of("/var/log/application.log"), StandardCharsets.UTF_8); fileViewer.openFile(Path.of("/var/log/legacy.log"), Charset.forName("windows-1250")); ``` ## Configuration You can configure polling, search visibility, and font resizing by passing a `FileViewerConfig` to the viewer. The default configuration enables all three features and uses a polling interval of 3 seconds. ```java import org.vaadin.addons.viewer.DefaultFileViewerConfig; import org.vaadin.addons.viewer.FileViewer; import org.vaadin.addons.viewer.FileViewerConfig; FileViewerConfig config = new DefaultFileViewerConfig() { @Override public boolean pollingEnabled() { return true; } @Override public int pollingInterval() { return 3; // seconds } @Override public boolean searchViewVisible() { return true; } @Override public boolean fontResizeAllowed() { return true; } }; FileViewer fileViewer = new FileViewer(config); add(fileViewer); fileViewer.openFile(Path.of("/var/log/application.log")); ``` Configuration options: | Option | Description | | --- | --- | | `pollingEnabled()` | Enables polling and displays the polling controls. | | `pollingInterval()` | Initial polling interval in seconds. The UI allows values from 1 to 30 seconds. | | `searchViewVisible()` | Shows or hides the search bar and search-results grid. | | `fontResizeAllowed()` | Shows or hides controls for changing font size, line height, and row height. | You can use `new FileViewer()` for the default configuration without explicitly creating a `FileViewerConfig`. ## Features - **Large file browsing** — navigate large text files smoothly. - **Multiple files** — open several files in separate tabs and switch between them. - **Powerful search** — find matching lines using case-sensitive or case-insensitive search, including regular expressions. - **Live updates** — monitor log files for newly appended entries without reopening the file. - **Updated search results** — find new matching lines as log entries arrive. - **Character encoding support** — choose the appropriate encoding for each file. - **Adjustable display** — change font size, line spacing, and row height for comfortable reading. ## Live log monitoring File Viewer is designed for append-only log files. It detects newly appended content; file truncation, replacement, rotation, and overwrites that do not change file size are not detected reliably. For a responsive UI when polling is enabled, configure Vaadin Push in your application. ## Source code [View File Viewer on GitHub](https://github.com/radekpakula/FileViewer)