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Yatin
The author is graduated in Electronics & Telecommunication. During his studies, he has been involved with a significant number of projects ranging from programming and software engineering to telecommunications analysis. He works as a technical lead in the information technology sector where he is primarily involved with projects based on Java/J2EE technologies platform and novel UI technologies.

Spring @RequestParam Annotation Example

In this post, we feature a comprehensive Example on Spring @RequestParam Annotation. In spring, the @RequestParam annotation is used to bind the values of a query string to a controller method in the Spring MVC framework. In this tutorial, we will show how to implement this annotation with the Spring MVC framework.

1. Introduction

1.1 Spring Framework

  • Spring is an open-source framework created to address the complexity of an enterprise application development
  • One of the chief advantages of the Spring framework is its layered architecture, which allows a developer to be selective about which of its components they can use while providing a cohesive framework for J2EE application development
  • Spring framework provides support and integration to various technologies for e.g.:
    • Support for Transaction Management
    • Support for interaction with the different databases
    • Integration with the Object Relationship frameworks for e.g. Hibernate, iBatis etc
    • Support for Dependency Injection which means all the required dependencies will be resolved with the help of containers
    • Support for REST style web-services

1.2 Spring Mvc Framework

Model-View-Controller (Mvc) is a well-known design pattern for designing the GUI based applications. It mainly decouples the business logic from UI by separating the roles of Model, View, and Controller in an application. This pattern divides the application into three components to separate the internal representation of the information from the way it is being presented to the user. The three components are:

  • Model (M): Model’s responsibility is to manage the application’s data, business logic, and the business rules. It is a POJO class which encapsulates the application data given by the controller
  • View (V): A view is an output representation of the information, such as displaying information or reports to the user either as a text-form or as charts. Views are usually the JSP templates written with Java Standard Tag Library (JSTL)
  • Controller (C): Controller’s responsibility is to invoke the Models to perform the business logic and then update the view based on the model’s output. In the spring framework, the controller part is played by the Dispatcher Servlet
Spring @RequestParam Annotation - Model View Controller (MVC) Overview

Fig. 1: Model View Controller (MVC) Overview

1.3 Spring @RequestParam Annotation

The @RequestParam annotation in spring binds the parameter values of a query string to the method argument of a controller. The query string is in the following format:

field1=value1&field2=value2&field3=value3

The @RequestParam annotation in spring mvc consists of the following optional attributes i.e.:

  • name: It is the String type attribute and is the name of the query string parameter. This is what the code snippet looks like:
    @RequestMapping(value="/sample/request1", method=RequestMethod.GET)
    public ModelAndView handleRequest(@RequestParam(name="site") String site_name) {
    
    	….
    }
    
  • defaultValue: It is a String type attribute and is used as a fallback when the request parameter is not provided or has an empty value. The advantage of using this attribute is that it implicitly sets the required attribute to false. This is what the code snippet looks like:
    @RequestMapping(value="/sample/request1", method=RequestMethod.GET)
    public ModelAndView handleRequest(@RequestParam(defaultValue="www.javacodegeeks.com") String site_name) {
    
    	….
    }
    
  • required: It is a Boolean type attribute and is used when the parameter value is required. If the required parameter is missing in the query string then the application will return an HTTP status 400 error page (i.e. a bad request). The default value of this attribute is true but it can be overridden to false. This is what the code snippet looks like:
    @RequestMapping(value="/sample/request1", method=RequestMethod.GET)
    public ModelAndView handleRequest(@RequestParam(required=false) String site_name) {
    
    	….
    }
    
  • value: It is a String type attribute and is an alias for the name attribute. This is what the code snippet looks like:
    @RequestMapping(value="/sample/request1", method=RequestMethod.GET)
    public ModelAndView handleRequest(@RequestParam(value="site") String site_name) {
    
    	….
    }
    

    Do note, developers can skip this attribute if the variable name of the handler method matches the query string parameter name i.e.:

    @RequestMapping(value="/sample/request1", method=RequestMethod.GET)
    public ModelAndView handleRequest(@RequestParam String site_name) {
    
    	….
    }
    

1.3.1 Using multiple @RequestParam annotations

Sometimes a handler method can have any number of the @RequestParam annotation. Let’s assume we have the following URL to your Web Service endpoint.

http://localhost:8082/springmvc/tutorial?topic=requestParam&author=daniel&site=jcg

To solve this, developers will have to make a handler method having the same number of the query string parameters i.e.:

@RequestMapping(value="/sample/request1", method=RequestMethod.GET)
public ModelAndView handleRequest(@RequestParam(value="topic") String topic_name, @RequestParam(value="author") String author_name, @RequestParam(value="site") String site_name) {

	….
}

This can be a tedious job if the query string has any number of parameter values. Thus, to save the developers from this tedious work, spring provided the support for binding the query string parameters to a Map or MultiValueMap. Hence, all the query string names and values are populated to a Map and this is what the modified code snippet looks like:

@RequestMapping(value="/sample/request1", method=RequestMethod.GET)
public ModelAndView handleRequest(@RequestParam Map map) {

	String siteName = map.get("site"), topicName = map.get("topic"), authorName = map.get("author");

	….
}

Now, open up the Eclipse IDE and let’s see how to use the @RequestParam annotation in the spring framework!

2. Spring @RequestParam Annotation Example

Here is a step-by-step guide for implementing this annotation in the spring mvc framework.

2.1 Tools Used

We are using Eclipse Kepler SR2, JDK 8 and Maven. Having said that, we have tested the code against JDK 1.7 and it works well.

2.2 Project Structure

Firstly, let’s review the final project structure, in case you are confused about where you should create the corresponding files or folder later!

Spring @RequestParam Annotation - Application Project Structure

Fig. 2: Application Project Structure

2.3 Project Creation

This section will demonstrate how to create a Java-based Maven project with Eclipse. In Eclipse IDE, go to File -> New -> Maven Project.

Spring @RequestParam Annotation - Create a Maven Project

Fig. 3: Create a Maven Project

In the New Maven Project window, it will ask you to select project location. By default, ‘Use default workspace location’ will be selected. Just click on next button to proceed.

Spring @RequestParam Annotation - Project Details

Fig. 4: Project Details

Select the Maven Web App archetype from the list of options and click next.

Spring @RequestParam Annotation - Archetype Selection

Fig. 5: Archetype Selection

It will ask you to ‘Enter the group and the artifact id for the project’. We will input the details as shown in the below image. The version number will be by default: 0.0.1-SNAPSHOT.

Spring @RequestParam Annotation - Archetype Parameters

Fig. 6: Archetype Parameters

Click on Finish and the creation of a maven project is completed. If you observe, it has downloaded the maven dependencies and a pom.xml file will be created. It will have the following code:

pom.xml

<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.mvc.spring</groupId>
	<artifactId>SpringMvcRequestParameter</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>
</project>

We can start adding the dependencies that developers want like Servlet API, Spring Mvc etc. Let’s start building the application!

3. Application Building

Below are the steps involved in developing this application.

3.1 Maven Dependencies

Here, we specify the dependencies for the spring mvc framework. The rest dependencies such as Spring Beans, Spring Core etc. will be automatically resolved by Maven. The updated file will have the following code:

pom.xml

<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.mvc.spring</groupId>
	<artifactId>SpringMvcRequestParameter</artifactId>
	<packaging>war</packaging>
	<version>0.0.1-SNAPSHOT</version>
	<name>SpringMvcRequestParameter Maven Webapp</name>
	<url>http://maven.apache.org</url>
	<dependencies>
		<!-- Servlet API Dependency -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>servlet-api</artifactId>
			<version>3.0-alpha-1</version>
		</dependency>
		<!-- Spring Framework Dependencies -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>5.0.7.RELEASE</version>
		</dependency>
	</dependencies>
	<build>		
		<finalName>${project.artifactId}</finalName>
	</build>
</project>

3.2 Configuration Files

Let’s write all the configuration files involved in this application.

3.2.1 Web Deployment Descriptor

The web.xml file declares one servlet (i.e. Dispatcher Servlet) to receive all kind of the requests. Dispatcher servlet here acts as a front controller. Add the following code to it:

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" 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_2_5.xsd">
	
	<display-name>SpringMvcRequestParameter</display-name>
	<servlet>
		<servlet-name>mvcrequestparameterdispatcher</servlet-name>
		<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
	</servlet>

	<servlet-mapping>
		<servlet-name>mvcrequestparameterdispatcher</servlet-name>
		<url-pattern>/</url-pattern>
	</servlet-mapping>
</web-app>

3.2.2 Spring Configuration File

To configure the spring framework, developers need to implement a bean configuration file i.e. mvcrequestparameterdispatcher-servlet.xml which provide an interface between the basic Java class and the outside world. Add the following code to it:

mvcrequestparameterdispatcher-servlet.xml

<?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:context="http://www.springframework.org/schema/context"
	xmlns:mvc="http://www.springframework.org/schema/mvc"
	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
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc.xsd">

	<context:component-scan base-package="com.spring.mvc" />

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

Do note:

  • This file is loaded by the spring’s Dispatcher Servlet which receives all the requests coming into the application and dispatches them to the controller for processing
  • This file has the InternalResourceViewResolver bean declaration that tells the framework how to find the physical JSP files according to the logical view names returned by the controllers, by attaching the prefix and the suffix to a view name

3.3 Java Class Creation

Let’s create a simple controller class where the @Controller annotation specifies this class as a spring controller and is responsible for handling the incoming request which is configured by the by the @RequestMapping annotation. In the showWelcomePage() method, the query string is mapped to two parameter values. Add the following code to it:

Ctrl.java

package com.spring.mvc;

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

@Controller
public class Ctrl {

	@RequestMapping(value="/welcome/user", method=RequestMethod.GET) 
	public ModelAndView showWelcomePage(@RequestParam(value="fName", required=true) String firstname, @RequestParam(value="lName") String lastname) {

		String fullname = firstname + " " + lastname;
		System.out.println("Username is= " + fullname);

		ModelAndView m = new ModelAndView();
		m.addObject("fullname", fullname);
		m.setViewName("success");
		return m;
	}
}

3.4 JSP View

Spring Mvc supports many types of views for different presentation technologies. These include – JSP, HTML, XML etc. So let us write a simple result view in SpringMvcRequestParameter/src/main/webapp/WEB-INF/views. Add the following code to it:

success.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
	pageEncoding="ISO-8859-1"%>
<%@ page isELIgnored="false"%>
<!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>Success</title>
	</head>
	<body>
		<div>Welcome, <span>${fullname}</span></div>
	</body>
</html>

4. Run the Application

As we are ready with all the changes, let us compile the project and deploy the application on the Tomcat7 server. To deploy the application on Tomat7, right-click on the project and navigate to Run as -> Run on Server.

Spring @RequestParam Annotation - Deploy Application on Tomcat

Fig. 7: How to Deploy Application on Tomcat

Tomcat will deploy the application in its web-apps folder and shall start its execution to deploy the project so that we can go ahead and test it on the browser.

5. Project Demo

Open your favorite browser and hit the following URL to display the output page.

http://localhost:8082/SpringMvcRequestParameter/welcome/user?fName=yatin&lName=batra

Server name (localhost) and port (8082) may vary as per your tomcat configuration.

Spring @RequestParam Annotation - Output Page

Fig. 8: Output Page

In case of an error (such as bad request etc.), the 400 error page will be displayed.

Spring @RequestParam Annotation - Error Page

Fig. 9: Error Page

That’s all for this tutorial and I hope the article served you whatever you were looking for. Happy Learning and don’t forget to share!

6. Conclusion

In this section, developers learned how @RequestParam annotation can be used to bind the query string parameters to the handler method arguments. Developers can download the sample application as an Eclipse project in the Downloads section.

7. Download the Eclipse Project

This was an example of Spring @RequestParam Annotation in Spring Mvc.

Download
You can download the full source code of this example here: SpringMvcRequestParameter
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Andrzej SydorDaniel Jipa Recent comment authors
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Daniel Jipa
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Daniel Jipa

After Spring 4.3 specialized annotations were brought to the table that are much more clearer to use than RequestMapping: GetMapping, PostMapping, PutMapping, PatchMapping, DeleteMapping.

Andrzej Sydor
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Andrzej Sydor

why you use weird variable name convention like ‘topic_name’ instead of camel case convention ‘topicName’?