Introducing Jexer

  

Modern software applications are often associated with graphical user interfaces (GUIs) that rely on windows, buttons, menus, and rich graphics. However, long before graphical interfaces became widespread, many powerful applications were built to run directly inside the terminal. These applications are known as Text User Interface (TUI) programs. Despite the dominance of GUIs and web applications today, TUIs continue to play an important role in development, system administration, and server environments.

 

In the Java ecosystem, one of the most powerful libraries for building terminal-based applications is Jexer. Jexer allows developers to create rich, interactive terminal applications that resemble desktop style programs. Instead of printing simple text output to the console, developers can build interfaces that contain multiple windows, menus, dialogs, input fields, and interactive components. This makes it possible to design complex applications that run entirely within a terminal.

 

At its core, Jexer provides a framework for building Text User Interfaces (TUIs) in Java. A TUI is an interface that uses characters, colors, and keyboard interactions to create structured screens inside a terminal. Unlike basic command-line programs that simply accept commands and print results, TUI applications provide an interactive environment where users can navigate menus, edit fields, open windows, and interact with the application in a more visual way.

 

Although modern development heavily focuses on web and graphical interfaces, TUIs still remain highly relevant. Many server environments do not have graphical desktops available, especially in cloud or containerized deployments. In such cases, terminal applications become the primary way to interact with systems. TUIs provide a balance between simple command-line tools and full graphical applications by offering structured and interactive interfaces while remaining lightweight and efficient.

 

Because of these advantages, TUIs are commonly used in a variety of real-world scenarios. For example, system dashboards built as terminal applications can display real-time metrics such as CPU usage, memory consumption, and network activity. Database management tools can allow users to browse tables, execute queries, and inspect results directly within a terminal window. Similarly, server monitoring applications often provide interactive dashboards that help administrators track system health without needing a graphical interface.

 

Many well-known tools in the software ecosystem are built using TUI concepts. These tools demonstrate how powerful terminal applications can be when designed with interactive components and structured layouts. Inspired by these ideas, libraries like Jexer make it possible for Java developers to build similar applications without having to manually manage terminal rendering or keyboard handling.

 

In this post, we will explore how Jexer enables developers to build modern terminal applications with features such as windows, dialogs, widgets, and event-driven input handling. By understanding the fundamentals of Jexer and Text User Interfaces, you will be able to create powerful console based applications that provide rich interaction while remaining lightweight and portable.

 

To give a quick idea of what a Jexer application looks like, imagine a terminal screen that contains multiple movable windows, menus at the top, status bars at the bottom, and interactive components inside each window. Even though the application runs inside a terminal, it behaves very similarly to a desktop application, providing a familiar and structured user experience.

 

1. What is Jexer?

Jexer is a Java library designed for building advanced terminal-based user interfaces. It provides a framework that allows developers to create structured and interactive applications inside a terminal window.

 

Unlike traditional console programs that simply print lines of text, Jexer introduces a window-based interface inside the terminal. Developers can create multiple windows, menus, dialog boxes, input fields, and widgets that users can interact with using the keyboard or mouse.

 

Some key capabilities of Jexer include:

 

·      Window-based UI inside a terminal

·      Event-driven keyboard and mouse input handling

·      Built-in UI components like buttons, menus, and dialogs

·      Support for terminal rendering and screen management

·      Ability to run both in terminal environments and Swing

 

Because of these features, applications built with Jexer can behave very similarly to desktop programs, even though they run entirely inside a terminal.

 

2. What is a TUI (Text User Interface)

A Text User Interface (TUI) is a type of user interface that displays structured screens using characters and text instead of graphical elements.

 

In a TUI application, the interface is created using:

 

·      characters

·      colors

·      keyboard input

·      cursor positioning

 

Rather than entering commands line-by-line like in a command-line interface (CLI), users interact with menus, forms, and windows displayed directly in the terminal.

 

For example, a typical TUI application might contain:

 

·      a menu bar at the top

·      multiple windows displaying different information

·      input fields for user data

·      navigation using arrow keys or keyboard shortcuts

 

TUIs were very common before graphical operating systems became widespread, but they continue to be widely used because of their efficiency and simplicity.

 

3. Why TUIs Still Matter

Even though graphical interfaces dominate modern applications, TUIs remain extremely valuable in many scenarios.

 

One of the main reasons is that many systems operate in environments where graphical interfaces are not available. Servers, containers, and remote systems are often accessed through terminal sessions where GUI applications cannot run.

 

TUIs offer several advantages in these environments.

 

·      Lightweight: TUI applications consume far fewer resources compared to graphical applications. They do not require graphical rendering engines or desktop environments.

 

·      Remote Friendly: Terminal-based applications work well over remote connections such as SSH. This makes them ideal for server management and cloud environments.

 

·      Faster Interaction: Many experienced users prefer keyboard-driven interfaces because they allow faster navigation and interaction compared to mouse-based systems.

 

·      Simplicity: TUI applications are easier to deploy and maintain because they have fewer dependencies compared to graphical applications.

 

Because of these benefits, TUIs remain widely used in system administration, DevOps tooling, and monitoring dashboards.

 

4. Typical Use Cases of TUI Applications

TUI applications are commonly used in environments where graphical interfaces are unnecessary or unavailable. Below are some typical scenarios where TUIs are particularly useful.

 

4.1 System Dashboards

Terminal dashboards can display real-time system information such as CPU usage, memory consumption, and network activity. These dashboards allow administrators to monitor system health without leaving the terminal.

 

For example, a TUI dashboard might show:

 

·      CPU utilization graphs

·      memory usage statistics

·      active processes

·      network traffic

 

With libraries like Jexer, developers can build similar dashboards for their own applications.

 

4.2 Database Tools

Database management often requires executing queries, browsing tables, and inspecting results. A TUI-based database tool allows developers or administrators to perform these tasks directly from the terminal.

 

Such tools may provide:

 

·      table navigation

·      query editors

·      result viewers

·      schema browsers

 

Because TUIs are lightweight, they are ideal for managing databases on remote servers.

 

4.3 Server Monitoring

Monitoring servers and services is another common use case for TUI applications. Administrators frequently need to monitor logs, track metrics, and inspect system behavior in real time.

 

A TUI monitoring application might display:

 

·      service status

·      log streams

·      resource usage

·      alerts and warnings

 

These applications are especially useful in production environments where remote access is common.

 

5. Example Applications Built with TUIs

Many well-known developer tools use TUI interfaces. These tools demonstrate how powerful terminal applications can be when designed with interactive components.

 

Examples include:

·      htop: an interactive process monitoring tool

·      Midnight Commander: a terminal-based file manager

·      nmtui: a network configuration interface

 

These applications provide rich user experiences even though they run entirely inside the terminal.

 

Libraries like Jexer allow Java developers to build similar applications without having to manually handle terminal rendering, keyboard events, or screen updates.

 

Find the below working Application.

 

DashboardApp.java

package com.sample.app.chapter3;

import static jexer.TCommand.cmHelp;
import static jexer.TCommand.cmMenu;
import static jexer.TCommand.cmQuit;
import static jexer.TKeypress.kbCtrlQ;
import static jexer.TKeypress.kbF1;
import static jexer.TKeypress.kbF10;

import jexer.TApplication;
import jexer.TMessageBox;
import jexer.TStatusBar;
import jexer.TWindow;
import jexer.event.TMenuEvent;

public class DashboardApp extends TApplication {

    private static final int MENU_EXIT = 2001;
    private static final int MENU_ABOUT = 2100;

    public DashboardApp() throws Exception {

        super(TApplication.BackendType.SWING);

        createMenuBar();
        createDashboardWindow();
    }

    private void createMenuBar() {

        addMenu("&File").addItem(MENU_EXIT, "E&xit");

        addMenu("&Edit");

        addMenu("&View");

        addMenu("&Help").addItem(MENU_ABOUT, "&About");
    }

    private void createDashboardWindow() {

        TWindow dashboard = addWindow("System Dashboard", 2, 2, 60, 16);

        dashboard.addLabel("CPU Usage: 32%", 2, 2);
        dashboard.addLabel("Memory: 4.1 GB / 16 GB", 2, 4);
        dashboard.addLabel("Active Connections: 12", 2, 6);
        dashboard.addLabel("Server Status: Running", 2, 8);

        dashboard.addLabel("Use menu or keyboard shortcuts to interact.", 2, 11);

        TStatusBar statusBar = dashboard.newStatusBar("Connected to server");

        statusBar.addShortcutKeypress(kbF1, cmHelp, "Help");
        statusBar.addShortcutKeypress(kbF10, cmMenu, "Menu");
        statusBar.addShortcutKeypress(kbCtrlQ, cmQuit, "Quit");
    }

    @Override
    protected boolean onMenu(TMenuEvent event) {

        if (event.getId() == MENU_EXIT) {

            TMessageBox confirm = messageBox("Exit Application", "Do you really want to exit?", TMessageBox.Type.YESNO);

            if (confirm.isYes()) {
                exit();
            }

            return true;
        }

        if (event.getId() == MENU_ABOUT) {

            messageBox("About", "System Dashboard\nBuilt using Jexer\nTerminal UI Demo", TMessageBox.Type.OK);

            return true;
        }

        return super.onMenu(event);
    }

    public static void main(String[] args) throws Exception {

        DashboardApp app = new DashboardApp();
        app.run();
    }
}

Output

  

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