Wednesday, 21 November 2018

Spring mvc: @PathVariable: Handling multiple path variables.

This is continuation to my previous post, in my previous post, I explained how to bound path variables to method arguments using @PathVariable annotation. In this post, I am going to show you how can you bound multiple path variables.

If you have multiple path variables in the url, it doesn't looks good if you try to bound them to the method arguments. Suppose if there are 5 path variables, we need to write a method with 5 arguments like below.

@RequestMapping("welcome/{countryName}/{state}/{firstName}/{lastName}/{customMsg}")
public ModelAndView getWelcomeMsg(@PathVariable("countryName") String countryName,
@PathVariable("state") String state, @PathVariable("firstName") String firstName,
@PathVariable("lastName") String lastName, @PathVariable("customMsg") String customMsg) {
         .....
         .....
}

What if you want to bound 10 path variables, would you like to write a method of 10 arguments? Obviously, No.

Spring MVC provides a better way to handle multiple path variable. You can map all the path variables to map like below.

@RequestMapping("welcome/{countryName}/{userName}")
public ModelAndView getWelcomeMessage(@PathVariable Map<String, String> pathVariables) {
         String name = pathVariables.get("userName");
         String country = pathVariables.get("countryName");
         .....
         .....
}

As you see above snippet, I mapped all the path variables to a map and access the path variable value using the map.

Find the below working application.

HelloWorldController.java
package com.sample.myApp.controllers;

import java.util.Map;

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 Map<String, String> pathVariables) {
  String name = pathVariables.get("userName");
  String country = pathVariables.get("countryName");

  ModelAndView modelAndView = new ModelAndView("hello");

  String msg = String.format("Hello %s, You are from %s", name, country);
  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.






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