This tutorial will show you how we use @PathVariable annotation with Regular Expressions in Spring Web MVC. Sometimes we need more precision in defining URI template variables. The @RequestMapping annotation supports the use of regular expressions in URI template variables. The syntax is {varName:regex} where the first part defines the variable name and the second – the regular expression.

For example:

@RequestMapping("/spring-web/{fileName:[a-z-]+}-{version:\d\.\d\.\d}{extension:\.[a-z]+}")
    public void handle(@PathVariable String fileName, @PathVariable String version, @PathVariable String extension) {
        // ...
    }
}

For this tutorial we will create maven based web project in Eclipse.

If you already have an idea on how to create a maven project in Eclipse will be great otherwise I will tell you here how to create a maven project in Eclipse.
Prerequisites

The following configurations are required in order to run the application

Eclipse
JDK 1.7
Tomcat 7
Have maven installed and configured
Spring 4 and JSTL API dependencies in pom.xml

Now we will see the below steps how to create a maven based spring project in Eclipse

Step 1. Create a maven based web project in Eclipse

Go to File -> New -> Other. On popup window under Maven select Maven Project. Then click on Next. Select the workspace location – either default or browse the location. Click on Next. Now in next window select the row as highlighted from the below list of archtypes and click on Next button.

maven-arctype-webapp

Now enter the required fields (Group Id, Artifact Id) as shown below

Group Id : com.roytuts
Artifact Id : spring

Step 2. Modify the pom.xml file as shown below.

<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/maven-v4_0_0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.roytuts</groupId>
    <artifactId>spring</artifactId>
    <packaging>war</packaging>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring</name>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <jdk.version>1.7</jdk.version>
        <spring.version>4.1.6.RELEASE</spring.version>
    </properties>

    <dependencies>

        <!-- spring-context which provides core functionality -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- The spring-aop module provides an AOP(aspect-oriented programming)
            implementation -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- The spring-webmvc module contains Spring’s model-view-controller (MVC)
            and REST Web Services implementation for web applications -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-webmvc</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- The spring-web module provides basic web-oriented integration features
            such as multipart file upload functionality and the initialization of the
            IoC container using Servlet listeners and a web-oriented application context -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>
            <version>${spring.version}</version>
        </dependency>

        <!-- jstl -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
            <version>1.2</version>
        </dependency>
    </dependencies>

    <build>
        <finalName>spring</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${jdk.version}</source>
                    <target>${jdk.version}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

Step 3. If you see JRE System Library[J2SE-1.4] then change the version by below process

Do right-click on the project and go to Build -> Configure build path, under Libraries tab click on JRE System Library[J2SE-1.4], click on Edit button and select the appropriate jdk 1.7 from the next window. Click on Finish then Ok.

Step 4. Create Spring XML configuration file controllers.xml under src/main/resources/spring directory

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xsi:schemaLocation="
        http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context.xsd">

    <!-- Support annotation -->
    <context:annotation-config></context:annotation-config>

    <!-- Scan the package where Spring Controllers are placed -->
    <context:component-scan base-package="com.roytuts.spring.controllers" />

    <!-- Resolves logical String-based view names to actual View types -->
    <bean id="viewResolver"
        class="org.springframework.web.servlet.view.InternalResourceViewResolver">
        <property name="viewClass"
            value="org.springframework.web.servlet.view.JstlView" />
        <!-- Where pages are kept -->
        <property name="prefix" value="/" />
        <!-- What is the page extension -->
        <property name="suffix" value=".jsp" />
    </bean>

</beans>

Step 5. Create Controller class

package com.roytuts.spring.controllers;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class HelloWorldController {

  @RequestMapping(value = "helloWorld/{fileName:[a-z-]+}-{version:\d\.\d\.\d}{extension:\.[a-z]+}")
  public String helloWorld(@PathVariable String fileName, @PathVariable String version, @PathVariable String extension, Model model) {
    model.addAttribute("fileName", fileName + version + extension);
    return "hello";
  }

}

Step 6. Now modify web.xml file

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">

    <display-name>Spring MVC</display-name>

    <!-- dispatcher servlet acts as a front controller for each request/response -->
    <servlet>
        <servlet-name>springmvc</servlet-name>
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <!-- load Spring controllers while dispatcher servlet loads -->
        <init-param>
            <param-name>contextConfigLocation</param-name>
            <param-value>classpath:spring/controllers.xml</param-value>
        </init-param>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <servlet-name>springmvc</servlet-name>
        <url-pattern>/</url-pattern>
    </servlet-mapping>

</web-app>

Step 7. Create hello.jsp file under webapp folder

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>
<html>
<body>
    <strong>@PathVariable</strong> with <strong>Regular Expression value : </strong> ${fileName}
</body>
</html>

Step 8. Now run the application you will see the below output in the browser.

URI template with regular expression

Thanks for reading.

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