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Spring @PathVariable tutorial

Spring @PathVariable tutorial shows how to read a URL template variable with @PathVariable annotation. We create a Spring RESTful application to demonstrate the annotation.

Spring is a popular Java application framework for creating enterprise applications.

@PathVariable

@PathVariable is a Spring annotation which indicates that a method parameter should be bound to a URI template variable. If the method parameter is Map<String, String> then the map is populated with all path variable names and values.

It has the following optional elements:

Spring @PathVariable example

The following example creates a Spring web application which uses @PathVariable. The values of the variables are logged.

pom.xml
src
├───main
│   ├───java
│   │   └───com
│   │       └───zetcode
│   │           ├───config
│   │           │       MyWebInitializer.java
│   │           │       WebConfig.java
│   │           └───controller
│   │                   MyController.java
│   └───resources
│           logback.xml
└───test
    └───java

This is the project structure of the Spring application.

pom.xml
<?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>

    <groupId>com.zetcode</groupId>
    <artifactId>pathvariableex</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <spring-version>5.1.3.RELEASE</spring-version>
    </properties>

    <dependencies>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-classic</artifactId>
            <version>1.2.3</version>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>javax.servlet-api</artifactId>
            <version>4.0.1</version>
            <scope>provided</scope>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>5.1.3.RELEASE</version>
        </dependency>

    </dependencies>

    <build>
        <plugins>

            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-war-plugin</artifactId>
                <version>3.2.2</version>
            </plugin>

            <plugin>
                <groupId>org.eclipse.jetty</groupId>
                <artifactId>jetty-maven-plugin</artifactId>
                <version>9.4.14.v20181114</version>
            </plugin>

        </plugins>
    </build>
</project>

We declare the project dependencies. The @PathVariable comes from spring-webmvc package.

resources/logback.xml
<?xml version="1.0" encoding="UTF-8"?>
<configuration>
    <logger name="org.springframework" level="ERROR"/>
    <logger name="com.zetcode" level="INFO"/>

    <appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender">
        <encoder>
            <Pattern>%d{HH:mm:ss.SSS} %blue(%-5level) %magenta(%logger{36}) - %msg %n
            </Pattern>
        </encoder>
    </appender>

    <root>
        <level value="INFO" />
        <appender-ref ref="consoleAppender" />
    </root>
</configuration>

The logback.xml is a configuration file for the Logback logging library.

com/zetcode/config/MyWebInitializer.java
package com.zetcode.config;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;

@Configuration
public class MyWebInitializer extends
        AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return null;
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {

        return new Class[]{WebConfig.class};
    }

    @Override
    protected String[] getServletMappings() {

        return new String[]{"/"};
    }
}

DispatcherServlet, which is a front controller for a Spring web application, is registered in MyWebInitializer.

@Override
protected Class<?>[] getServletConfigClasses() {

    return new Class[]{WebConfig.class};
}

The getServletConfigClasses() returns a web configuration class.

com/zetcode/config/WebConfig.java
package com.zetcode.config;

import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = {"com.zetcode"})
public class WebConfig {

}

The WebConfig enables Spring MVC annotations with @EnableWebMvc and configures component scanning for the com.zetcode package.

com/zetcode/MyController.java
package com.zetcode.controller;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpStatus;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.ResponseStatus;
import org.springframework.web.bind.annotation.RestController;

import java.util.Map;

@RestController
public class MyController {

    private static final Logger logger = LoggerFactory.getLogger(MyController.class);

    @ResponseStatus(value = HttpStatus.OK)
    @GetMapping(value = "/user/{name}")
    public void process(@PathVariable String name) {

        logger.info("User name: {}", name);
    }

    @ResponseStatus(value = HttpStatus.OK)
    @GetMapping(value = "/user/{name}/{email}")
    public void process2(@PathVariable String name, @PathVariable String email) {

        logger.info("User name: {} and email: {}", name, email);
    }

    @ResponseStatus(value = HttpStatus.OK)
    @GetMapping(value = "/book/{author}/{title}")
    public void process3(@PathVariable Map<String, String> vals) {

        logger.info("{}: {}", vals.get("author"), vals.get("title"));

    }
}

We have three mappings for GET requests.

@ResponseStatus(value = HttpStatus.OK)
@GetMapping(value = "/user/{name}")
public void process(@PathVariable String name) {

    logger.info("User name: {}", name);
}

In this code, a URI template variable is bound to the name method parameter.

@ResponseStatus(value = HttpStatus.OK)
@GetMapping(value = "/user/{name}/{email}")
public void process2(@PathVariable String name, @PathVariable String email) {

    logger.info("User name: {} and email: {}", name, email);
}

Multiple variables can be bound, too, by specifying multiple @PathVariable annotations.

@ResponseStatus(value = HttpStatus.OK)
@GetMapping(value = "/book/{author}/{title}")
public void process3(@PathVariable Map<String, String> vals) {

    logger.info("{}: {}", vals.get("author"), vals.get("title"));
}

Multiple variables can be bound also with Map<String, String>.

$ mvn jetty:run

We start the Jetty server.

$ curl localhost:8080/user/Peter/peter@gmail.com/

We issue a request with curl.

22:04:35.273 INFO  com.zetcode.controller.MyController - User name: Peter and email: peter@gmail.com

The application logs this message.

In this tutorial, we have created a RESTful web application with Spring framework. We have demonstrated the usage of @PathVariable. You might also be interested in the related tutorials: Spring @RequestMapping tutorial, Spring @RequestHeader tutorial, Java tutorial, or list all Spring tutorials.