Programming for beginners: Spring mvc: @PathVariable tutorial

@PathVariable annotation is used to bound a method parameter to a URI template variable.

For example, consider below snippet, I bound the URI template variable (Template variable are declared in curly braces) userName to the method parameter name.

@Controller

@RequestMapping("greeting")

public class HelloWorldController {

@RequestMapping("welcome/{userName}")

public ModelAndView getWelcomeMessage(@PathVariable("userName") String name) {

ModelAndView modelAndView = new ModelAndView("hello");

String msg = String.format("Hello %s, Welcome to spring MVC programming", name);

modelAndView.addObject("message", msg);

return modelAndView;

}

If I hit the url 'http://localhost:8080/springdemo/greeting/welcome/krishna', then the method parameter name is bound with value "krishna".

If I hit the url 'http://localhost:8080/springdemo/greeting/welcome/Deeepa', then the method parameter name is bound with value "Deepa".

Find the below working application.

HelloWorldController.java

package com.sample.myApp.controllers;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("greeting")
public class HelloWorldController {

 @RequestMapping("welcome/{userName}")
 public ModelAndView getWelcomeMessage(@PathVariable("userName") String name) {
  ModelAndView modelAndView = new ModelAndView("hello");

  String msg = String.format("Hello %s, Welcome to spring MVC programming", name);
  modelAndView.addObject("message", msg);
  return modelAndView;
 }

}

Create hello.jsp file under WEB-INF/jsp folder.

hello.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
 pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Hello World Spring Web MVC</title>
</head>
<body>
 <h2>${message}</h2>
</body>
</html>

Create web.xml, HelloWorld-servlet.xml files under WEB-INF folder.

web.xml

<web-app id="WebApp_ID" version="2.4"
 xmlns="http://java.sun.com/xml/ns/j2ee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
   http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

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

 <servlet>
  <servlet-name>HelloWorld</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <load-on-startup>1</load-on-startup>
 </servlet>

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

</web-app>

HelloWorld-servlet.xml

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:context="http://www.springframework.org/schema/context"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="
   http://www.springframework.org/schema/beans     
   http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
   http://www.springframework.org/schema/context 
   http://www.springframework.org/schema/context/spring-context-3.0.xsd">

 <context:component-scan
  base-package="com.sample.myApp" />

 <bean
  class="org.springframework.web.servlet.view.InternalResourceViewResolver">
  <property name="prefix" value="/WEB-INF/jsp/" />
  <property name="suffix" value=".jsp" />
 </bean>

</beans>

Create index.jsp file under webapp folder.

index.jsp

<html>
<body>
 <h2>Hello World!</h2>
</body>
</html>

Total project structure looks like below.

Run the application on server and hit the below url.

http://localhost:8080/springdemo/greeting/welcome/krishna

Can I bound multiple path variables in one url?

Yes, you can bound any number of path variables in one url.

For example,

@RequestMapping("welcome/{countryName}/{userName}")

public ModelAndView getWelcomeMessage(@PathVariable("userName") String name, @PathVariable("countryName") String country)

In the above example, countryName is mapped to the method argument country, username is mapped to the method argument country.

Update HelloWorldController class like below and rerun the application.

HelloWorldController.java

package com.sample.myApp.controllers;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("greeting")
public class HelloWorldController {

 @RequestMapping("welcome/{countryName}/{userName}")
 public ModelAndView getWelcomeMessage(@PathVariable("userName") String name,
   @PathVariable("countryName") String country) {
  ModelAndView modelAndView = new ModelAndView("hello");

  String msg = String.format("Hello %s, You are from %s", name, country);
  modelAndView.addObject("message", msg);
  return modelAndView;
 }

}

When you hit the url ‘http://localhost:8080/springdemo/greeting/welcome/India/krishna’.

, you can able to see below kind of message.

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Programming for beginners

Wednesday 21 November 2018

Spring mvc: @PathVariable tutorial

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