Javalin framework tutorial and entry guide
Javalin framework tutorial and entry guide
Javalin is a simple and easy -to -use Java back -end framework that is suitable for building lightweight, fast and scalable web applications.This tutorial will introduce the basic concepts and usage methods of the Javalin framework, and provide you with some example code and related configuration about writing the Javalin application.
Preparation:
Before starting this tutorial, you need to install the Java Development Kit (JDK) and Apache Maven to build tools on your computer.Make sure your computer already has these prerequisites.
Install javalin:
1. Open the terminal or command prompt, run the following command to create a new Maven project:
shell
mvn archetype:generate -DgroupId=com.example -DartifactId=javalin-demo -DarchetypeArtifactId=maven-archetype-quickstart -DinteractiveMode=false
2. Enter the project directory:
shell
cd javalin-demo
3. Open the pom.xml file of the project, and add the following content to the `Dependencies>` element:
<dependency>
<groupId>io.javalin</groupId>
<artifactId>javalin</artifactId>
<version>3.13.6</version>
</dependency>
4. Run the following commands to build and run applications:
shell
mvn clean compile exec:java -Dexec.mainClass="com.example.App"
Write the Javalin application:
Now, let's start writing a simple Javalin application.
1. Create a Java class called App.java in the SRC/main/java/com/exmple directory, and add the following:
package com.example;
import io.javalin.Javalin;
public class App {
public static void main(String[] args) {
Javalin app = Javalin.create().start(7000);
app.get("/", ctx -> ctx.result("Hello Javalin!"));
}
}
In this example, we created a Javalin instance and tied it to port 7000.Then, we define a GET request processing program that will return "Hello Javalin!" On the root path ("/").
2. Run application:
In the root directory of the project, run the following commands to build and run applications:
shell
mvn clean compile exec:java -Dexec.mainClass="com.example.App"
Applications will display similar information on the terminal:
INFO: Javalin has started \o/
3. Access application:
Enter "http: // localhost: 7000" in the web browser, and you will see the page with "Hello Javalin!".
Configure Javalin application:
You can perform more Javalin configurations according to the needs of the application.
1. Add routing and middleware to the app.java:
app.get("/hello", ctx -> ctx.result("Hello Route!"));
app.get("/user/:id", ctx -> {
String userId = ctx.pathParam("id");
ctx.result("User ID: " + userId);
});
app.before("/hello", ctx -> {
// Execute the logic before the hello routing
});
app.after("/hello", ctx -> {
// The logic of executing after the hello routing
});
Here are two additional GET request processing programs, a GET path parameter processing program and two middleware functions.The route parameters are specified through the `ID` grammar and obtained through the` ctx.pathparam ("ID") `).
2. Configure static file service:
You can configure the application to provide static files through the following code:
app.enableStaticFiles("/public");
This code provides files in the `/Public` directory to the client.
3. Processing abnormal:
You can use anomalous processing program to process the abnormalities in the application:
app.exception(Exception.class, (e, ctx) -> {
// Treatment of abnormal logic
});
This is just an entry guide for the Javalin framework. You can learn more about routing, middleware, request processing, template engine and other aspects according to your needs.I hope this tutorial can help you start using Javalin to build a web application.
