Bootstrap Example

Spring Boot @PathVariable - Read URI Template Variable with @PathVariable

Author: SAI K

In this short article, we will learn how to use Spring Boot @PathVariable annotation to read an URL template variable. We create a Spring Boot RESTful application to demonstrate the annotation.

@PathVariable Annotation

@PathVariable is a Spring annotation which indicates that a method parameter should be bound to a URI template variable.

It has the following optional elements:

name - name of the path variable to bind to
required - tells whether the path variable is required
value - alias for name

With the @PathVariable annotation, we bind the request URL template path variable to the method variable. For instance, with the /100/Ramesh/ URL, the 100 value is bind to the id variable and "Ramesh" value to the name variable.

   @GetMapping(path = "/hello-world/{id}/{name}")
    public HelloWorldBean helloWorldPathVariable(@PathVariable long id, 
        @PathVariable(name = "name") String name) {
        return new HelloWorldBean(id, name);
    }

Spring Boot @PathVariable Annotation Example

The following example creates a Spring Boot web application which uses @PathVariable. The application receives an URL from which it builds a text response to the client.

Development Steps

Create a Spring Boot Application
Project Structure
Pom Dependencies
Java Bean - HelloWorldBean.java
Create REST Controller - HelloWorldController.java
Run Application - Application.java
Testing

1. Create a Spring Boot Application

There are many ways to create a Spring Boot application. You can refer below articles to create a Spring Boot application.

>> Create Spring Boot Project With Spring Initializer
>> Create Spring Boot Project in Spring Tool Suite [STS]

Refer project structure or packaging structure in the next step.

2. Project Structure

This is the project structure of the Spring Boot application that we are going to create -

3. Pom Dependencies

This is the Maven build file. The spring-boot-starter-web is a starter for building web applications using Spring MVC. It uses Tomcat as the default embedded container.

<?xml version="1.0" encoding="UTF-8"?>
<project
    xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.RELEASE</version>
        <relativePath />
        <!-- lookup parent from repository -->
    </parent>
    <groupId>net.javaguides.springboot</groupId>
    <artifactId>springboot-helloworld-app</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>springboot-helloworld-app</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

4. Java Bean - HelloWorldBean.java

Let's create a representation class which we use to return in JSON format:

package net.javaguides.springboot;

public class HelloWorldBean {

    private long id;
    private String message;

    public HelloWorldBean(long id, String message) {
        super();
        this.id = id;
        this.message = message;
    }

    public long getId() {
        return id;
    }
    public void setId(long id) {
        this.id = id;
    }
    public String getMessage() {
        return message;
    }
    public void setMessage(String message) {
        this.message = message;
    }
}

5. Create REST Controller - HelloWorldController.java

Let's create a simple HelloWorldController which exposes hello world rest service:

package net.javaguides.springboot;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloWorldController {

    @GetMapping(path = "/hello-world/{id}/{name}")
    public HelloWorldBean helloWorldPathVariable(@PathVariable long id, 
        @PathVariable(name = "name") String name) {
        return new HelloWorldBean(id, name);
    }
}

With the @PathVariable annotation, we bind the request URL template path variable to the method variable. For instance, with the /100/Ramesh/ URL, the 100 value is bind to the id variable and "Ramesh" value to the name variable.

 @GetMapping(path = "/hello-world/{id}/{name}")
    public HelloWorldBean helloWorldPathVariable(@PathVariable long id, 
        @PathVariable(name = "name") String name) {
        return new HelloWorldBean(id, name);
    }

6. Run Application - Application.java

Application is the entry point which sets up the Spring Boot application. The @SpringBootApplication annotation enables auto-configuration and component scanning.

Let's run this Spring boot application from either Eclipse IDE by right click -> Run As -> Java Application.

Or you can use below maven command to run:

mvn spring-boot:run

7. Testing from Browser

Hit this URL in a browser - http://localhost:8080/hello-world/100/ramesh