Spring 4 MVC Atom and RSS Feed Example with ROME using JavaConfig

By Arvind Rai, October 01, 2015

This page will walk through Spring 4 MVC Atom and RSS feed example with ROME using JavaConfig. Spring provides AbstractAtomFeedView and AbstractRssFeedView for Atom and RSS feed respectively. To generate Atom feed we need to define buildFeedMetadata() and buildFeedEntries() methods provided by AbstractAtomFeedView. To generate RSS feed we need to define buildFeedMetadata() and buildFeedItems() methods provided by AbstractRssFeedView. In JavaConfig, we will register our view classes using ViewResolverRegistry which will select proper view on user request for Atom and RSS feed. Find the complete example.

Differences between Atom and RSS Feed

1. Atom is called Atom Syndication Format whereas RSS is called Really Simple Syndication
2. Atom feed can be HTML, XHTML, XML etc and RSS feed is plain TEXT or escaped HTML.
3. Atom feed can specify language for each entry whereas RSS feed can not specify language for each item.
4. The elements of Atom can be used in other XML whereas RSS are nor generally reusable in other XML.

Software Used

Find the software used in our demo.
1. Java 7
2. Spring 4
3. ROME 1.5.1
4. Gradle
5. Eclipse
6. Tomcat 8

Project Structure in Eclipse

Find the project structure in eclipse.

Spring 4 MVC Atom and RSS Feed Example with ROME using JavaConfig

Gradle for Spring 4 and ROME API

Find the gradle build file for Spring and ROME API.
build.gradle

apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'war'
archivesBaseName = 'Spring4'
version = '1' 
repositories {
    mavenCentral()
}
dependencies {
    compile 'org.springframework.boot:spring-boot-starter-web:1.2.3.RELEASE'
    compile 'com.rometools:rome:1.5.1'
    providedRuntime 'org.springframework.boot:spring-boot-starter-tomcat:1.1.5.RELEASE'
}

Atom Feed: Implement AbstractAtomFeedView

ContentAtomView.java

package com.concretepage.view;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.view.feed.AbstractAtomFeedView;
import com.concretepage.bean.MyFeed;
import com.rometools.rome.feed.atom.Content;
import com.rometools.rome.feed.atom.Entry;
import com.rometools.rome.feed.atom.Feed;
import com.rometools.rome.feed.atom.Link;
public class ContentAtomView extends AbstractAtomFeedView {
	@Override
	protected void buildFeedMetadata(Map<String, Object> model, Feed feed, 
			HttpServletRequest request) {
		feed.setId("id1234");
		feed.setTitle("Concretepage.com");
		List<Link> links = new ArrayList<>();
		Link link = new Link();
		link.setHref("http://www.concretepage.com");
		links.add(link);
		feed.setAlternateLinks(links);
	}
	@Override
	protected List<Entry> buildFeedEntries(Map<String, Object> model,
			HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		List<Entry> entries = new ArrayList<Entry>();
		Object ob = model.get("feeds");
		if (ob instanceof List){
	           for(int i = 0; i < ((List<?>)ob).size(); i++){
	                Object feedObj = ((List<?>) ob).get(i);
	                MyFeed myFeed = (MyFeed)feedObj;
	    		Entry entry = new Entry();
	    		entry.setId(myFeed.getFeedId());
	    		entry.setPublished(myFeed.getPubDate());
	    		entry.setTitle(myFeed.getTitle());
	    		List<Link> links = new ArrayList<>();
	    		Link link = new Link();
	    		link.setHref(myFeed.getLink());
	    		links.add(link);
	    		entry.setAlternateLinks(links);
	    		Content content = new Content();
	    		content.setValue(myFeed.getDescription());
	    		entry.setSummary(content);
	    		entries.add(entry);
	         }
	      }
	      return entries;
	}
}

com.rometools.rome.feed.atom.Feed : ROME API which sets the Atom feed metadata. The setter methods in Feed are setId(), setTitle(), setAlternateLinks() etc.
AbstractAtomFeedView.buildFeedMetadata(): Method is overridden to declare Atom feed metadata. Feed is one of the arguments of this method. We will set metadata using setter methods of Feed.
AbstractAtomFeedView.buildFeedEntries(): Using this method, we prepare the entries of Atoms feeds. Controller passes the feed content instance to it which is accepted by Map<String, Object> model parameter of this method.
com.rometools.rome.feed.atom.Entry : ROME API which creates one entry of Atom feeds. The setter methods of Entry are setId(), setPublished(), setTitle(), setSummary(), setAlternateLinks() etc.

RSS Feed: Implement AbstractRssFeedView

ContentRssView.java

package com.concretepage.view;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.springframework.web.servlet.view.feed.AbstractRssFeedView;
import com.concretepage.bean.MyFeed;
import com.rometools.rome.feed.rss.Channel;
import com.rometools.rome.feed.rss.Content;
import com.rometools.rome.feed.rss.Item;
public class ContentRssView extends AbstractRssFeedView {
	@Override
	protected void buildFeedMetadata(Map<String, Object> model, Channel channel, 
			HttpServletRequest request) {
		channel.setTitle("Concretepage.com");
		channel.setLink("http://www.concretepage.com");
		channel.setDescription("Concretepage.com is a java tutorial.");
	}
	@Override
	protected List<Item> buildFeedItems(
			Map<String, Object> model, HttpServletRequest request, HttpServletResponse response)
			throws Exception {
		List<Item> items = new ArrayList<>();
		Object ob = model.get("feeds");
		if (ob instanceof List){
	           for(int i = 0; i < ((List<?>)ob).size(); i++){
	                Object feedObj = ((List<?>) ob).get(i);
	                MyFeed myFeed = (MyFeed)feedObj;
	    		Item item = new Item();
	    		item.setTitle(myFeed.getTitle());
	    		item.setLink(myFeed.getLink());
	    		item.setPubDate(myFeed.getPubDate());
	    		Content content = new Content();
	    		content.setValue(myFeed.getDescription());
	    		item.setContent(content);
	    		items.add(item);
	           }
		}
		return items;
	}
}

com.rometools.rome.feed.rss.Channel : ROME API which sets the RSS feed metadata. The setter methods in Channel are setTitle(), setLink(), setDescription() etc.
AbstractRssFeedView.buildFeedMetadata(): Method is overridden to declare RSS feed metadata. Channel is one of the arguments of this method. We will set metadata using setter methods of Channel.
AbstractRssFeedView.buildFeedItems(): Using this method, we prepare the items of RSS feeds. Controller passes the feed content instance to it which is accepted by Map<String, Object> model parameter of this method.
com.rometools.rome.feed.rss.Item : ROME API which creates one item of RSS feeds. The setter methods of Item are setTitle(), setLink(), setPubDate(), setContent() etc.

JavaConfig for ViewResolverRegistry

So far we have created two views, one for Atom feed and second for RSS feed. Now we will register these two views with ViewResolverRegistry which will identify the media type of user request and accordingly it will display Atom or RSS feed.
AppConfiguration.java

package com.concretepage.config;  
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ViewResolverRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import com.concretepage.view.ContentAtomView;
import com.concretepage.view.ContentRssView;
@Configuration 
@ComponentScan("com.concretepage") 
@EnableWebMvc
public class AppConfiguration extends WebMvcConfigurerAdapter  {  
    @Override
    public void configureViewResolvers(ViewResolverRegistry registry) {
        registry.enableContentNegotiation(new ContentAtomView(), new ContentRssView());
    }
}

Initializer.java

package com.concretepage.config;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRegistration.Dynamic;
import org.springframework.web.WebApplicationInitializer;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;
public class Initializer implements WebApplicationInitializer {
	public void onStartup(ServletContext servletContext) throws ServletException {  
        AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext();  
        ctx.register(AppConfiguration.class);  
        ctx.setServletContext(servletContext);    
        Dynamic dynamic = servletContext.addServlet("dispatcher", new DispatcherServlet(ctx));  
        dynamic.addMapping("/");  
        dynamic.setLoadOnStartup(1);  
   }  
}

If user requests /feed.atom then the response will be generated by AbstractAtomFeedView implementation class and if URL is /feed.rss then the response will be generated by AbstractRssFeedView

Create Bean Class

MyFeed.java

package com.concretepage.bean;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;
import org.springframework.stereotype.Repository;
@Repository
public class MyFeed {
	private String feedId;
	private String title;
	private String description;
	private Date pubDate;
	private String link;
	public String getFeedId() {
		return feedId;
	}
	public void setFeedId(String feedId) {
		this.feedId = feedId;
	}
	public String getTitle() {
		return title;
	}
	public void setTitle(String title) {
		this.title = title;
	}
	public String getDescription() {
		return description;
	}
	public void setDescription(String description) {
		this.description = description;
	}
	public Date getPubDate() {
		return pubDate;
	}
	public void setPubDate(Date pubDate) {
		this.pubDate = pubDate;
	}
	public String getLink() {
		return link;
	}
	public void setLink(String link) {
		this.link = link;
	}
	public List<MyFeed> createFeed() {
		List<MyFeed> feeds = new ArrayList<>();
		MyFeed feed1 = new MyFeed();
		feed1.setFeedId("100");
		feed1.setTitle("Title one");
		feed1.setDescription("This is description one");
		feed1.setLink("http://www.urlone.com");
		feed1.setPubDate(new Date());
		feeds.add(feed1);
		MyFeed feed2 = new MyFeed();
		feed2.setFeedId("200");
		feed2.setTitle("Title two");
		feed2.setDescription("This is description two");
		feed2.setLink("http://www.urltwo.com");
		feed2.setPubDate(new Date());
		feeds.add(feed2);
		return feeds;
	}
}

Create Controller Class

FeedController.java

package com.concretepage.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;
import com.concretepage.bean.MyFeed;
@Controller
public class FeedController {
	@Autowired
	private MyFeed myFeed;
	@RequestMapping(value="/feed.*", method=RequestMethod.GET)
	public ModelAndView getContent() {
		ModelAndView mav = new ModelAndView();
		mav.addObject("feeds", myFeed.createFeed());
		return mav;
	}
}

Output

1. For Atom feed.

<?xml version="1.0" encoding="UTF-8"?>
<feed xmlns="http://www.w3.org/2005/Atom">
  <title>Concretepage.com</title>
  <link rel="alternate" href="http://www.concretepage.com" />
  <id>id1234</id>
  <entry>
    <title>Title one</title>
    <link rel="alternate" href="http://www.urlone.com" />
    <id>100</id>
    <published>2015-10-01T04:42:06Z</published>
    <summary>This is description one</summary>
  </entry>
  <entry>
    <title>Title two</title>
    <link rel="alternate" href="http://www.urltwo.com" />
    <id>200</id>
    <published>2015-10-01T04:42:06Z</published>
    <summary>This is description two</summary>
  </entry>
</feed>

2. For RSS feed.

<?xml version="1.0" encoding="UTF-8"?>
<rss xmlns:content="http://purl.org/rss/1.0/modules/content/" version="2.0">
  <channel>
    <title>Concretepage.com</title>
    <link>http://www.concretepage.com</link>
    <description>Concretepage.com is a java tutorial.</description>
    <item>
      <title>Title one</title>
      <link>http://www.urlone.com</link>
      <content:encoded>This is description one</content:encoded>
      <pubDate>Thu, 01 Oct 2015 04:46:16 GMT</pubDate>
    </item>
    <item>
      <title>Title two</title>
      <link>http://www.urltwo.com</link>
      <content:encoded>This is description two</content:encoded>
      <pubDate>Thu, 01 Oct 2015 04:46:16 GMT</pubDate>
    </item>
  </channel>
</rss>