VideoControllerWithDependencyInjection

VideoSvc.java

package org.magnum.mobilecloud.video.controller;

import java.util.Collection;

import org.magnum.mobilecloud.video.client.VideoSvcApi;
import org.magnum.mobilecloud.video.repository.VideoRepository;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestBody;
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.bind.annotation.ResponseBody;

/**
 * This simple VideoSvc allows clients to send HTTP POST requests with
 * videos that are stored in memory using a list. Clients can send HTTP GET
 * requests to receive a JSON listing of the videos that have been sent to
 * the controller so far. Stopping the controller will cause it to lose the history of
 * videos that have been sent to it because they are stored in memory.
 * 
 * Notice how much simpler this VideoSvc is than the original VideoServlet?
 * Spring allows us to dramatically simplify our service. Another important
 * aspect of this version is that we have defined a VideoSvcApi that provides
 * strong typing on both the client and service interface to ensure that we
 * don't send the wrong paraemters, etc.
 * 
 * @author jules
 *
 */

// Tell Spring that this class is a Controller that should 
// handle certain HTTP requests for the DispatcherServlet
@Controller
public class VideoSvc implements VideoSvcApi {
	
	// The VideoRepository that we are going to store our videos
	// in. We don't explicitly construct a VideoRepository, but
	// instead mark this object as a dependency that needs to be
	// injected by Spring. Our Application class has a method
	// annotated with @Bean that determines what object will end
	// up being injected into this member variable.
	//
	// Also notice that we don't even need a setter for Spring to
	// do the injection.
	//
	@Autowired
	private VideoRepository videos;

	// Receives POST requests to /video and converts the HTTP
	// request body, which should contain json, into a Video
	// object before adding it to the list. The @RequestBody
	// annotation on the Video parameter is what tells Spring
	// to interpret the HTTP request body as JSON and convert
	// it into a Video object to pass into the method. The
	// @ResponseBody annotation tells Spring to conver the
	// return value from the method back into JSON and put
	// it into the body of the HTTP response to the client.
	//
	// The VIDEO_SVC_PATH is set to "/video" in the VideoSvcApi
	// interface. We use this constant to ensure that the 
	// client and service paths for the VideoSvc are always
	// in synch.
	//
	@RequestMapping(value=VideoSvcApi.VIDEO_SVC_PATH, method=RequestMethod.POST)
	public @ResponseBody boolean addVideo(@RequestBody Video v){
		return videos.addVideo(v);
	}
	
	// Receives GET requests to /video and returns the current
	// list of videos in memory. Spring automatically converts
	// the list of videos to JSON because of the @ResponseBody
	// annotation.
	@RequestMapping(value=VideoSvcApi.VIDEO_SVC_PATH, method=RequestMethod.GET)
	public @ResponseBody Collection<Video> getVideoList(){
		return videos.getVideos();
	}
	
	// Receives GET requests to /video/find and returns all Videos
	// that have a title (e.g., Video.name) matching the "title" request
	// parameter value that is passed by the client
	@RequestMapping(value=VideoSvcApi.VIDEO_TITLE_SEARCH_PATH, method=RequestMethod.GET)
	public @ResponseBody Collection<Video> findByTitle(
			// Tell Spring to use the "title" parameter in the HTTP request's query
			// string as the value for the title method parameter
			@RequestParam(TITLE_PARAMETER) String title
	){
		return videos.findByTitle(title);
	}

}

package org.magnum.mobilecloud.video.controller;

import java.util.Collection;

import org.magnum.mobilecloud.video.client.VideoSvcApi;

import org.magnum.mobilecloud.video.repository.VideoRepository;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Controller;

import org.springframework.web.bind.annotation.RequestBody;

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.bind.annotation.ResponseBody;

/**

* This simple VideoSvc allows clients to send HTTP POST requests with

* videos that are stored in memory using a list. Clients can send HTTP GET

* requests to receive a JSON listing of the videos that have been sent to

* the controller so far. Stopping the controller will cause it to lose the history of

* videos that have been sent to it because they are stored in memory.

* Notice how much simpler this VideoSvc is than the original VideoServlet?

* Spring allows us to dramatically simplify our service. Another important

* aspect of this version is that we have defined a VideoSvcApi that provides

* strong typing on both the client and service interface to ensure that we

* don't send the wrong paraemters, etc.

* @author jules

// Tell Spring that this class is a Controller that should

// handle certain HTTP requests for the DispatcherServlet

@Controller

public class VideoSvc implements VideoSvcApi {

// The VideoRepository that we are going to store our videos

// in. We don't explicitly construct a VideoRepository, but

// instead mark this object as a dependency that needs to be

// injected by Spring. Our Application class has a method

// annotated with @Bean that determines what object will end

// up being injected into this member variable.

// Also notice that we don't even need a setter for Spring to

// do the injection.

@Autowired

private VideoRepository videos;

// Receives POST requests to /video and converts the HTTP

// request body, which should contain json, into a Video

// object before adding it to the list. The @RequestBody

// annotation on the Video parameter is what tells Spring

// to interpret the HTTP request body as JSON and convert

// it into a Video object to pass into the method. The

// @ResponseBody annotation tells Spring to conver the

// return value from the method back into JSON and put

// it into the body of the HTTP response to the client.

// The VIDEO_SVC_PATH is set to "/video" in the VideoSvcApi

// interface. We use this constant to ensure that the

// client and service paths for the VideoSvc are always

// in synch.

@RequestMapping(value=VideoSvcApi.VIDEO_SVC_PATH, method=RequestMethod.POST)

public @ResponseBody boolean addVideo(@RequestBody Video v){

return videos.addVideo(v);

}

// Receives GET requests to /video and returns the current

// list of videos in memory. Spring automatically converts

// the list of videos to JSON because of the @ResponseBody

// annotation.

@RequestMapping(value=VideoSvcApi.VIDEO_SVC_PATH, method=RequestMethod.GET)

public @ResponseBody Collection<Video> getVideoList(){

return videos.getVideos();

}

// Receives GET requests to /video/find and returns all Videos

// that have a title (e.g., Video.name) matching the "title" request

// parameter value that is passed by the client

@RequestMapping(value=VideoSvcApi.VIDEO_TITLE_SEARCH_PATH, method=RequestMethod.GET)

public @ResponseBody Collection<Video> findByTitle(

// Tell Spring to use the "title" parameter in the HTTP request's query

// string as the value for the title method parameter

@RequestParam(TITLE_PARAMETER) String title

){

return videos.findByTitle(title);

}

Video.java

package org.magnum.mobilecloud.video.controller;

import com.google.common.base.Objects;

/**
 * A simple object to represent a video and its URL for viewing.
 * 
 * @author jules
 * 
 */
public class Video {

	private String name;
	private String url;
	private long duration;

	public Video(){}
	
	public Video(String name, String url, long duration) {
		super();
		this.name = name;
		this.url = url;
		this.duration = duration;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getUrl() {
		return url;
	}

	public void setUrl(String url) {
		this.url = url;
	}

	public long getDuration() {
		return duration;
	}

	public void setDuration(long duration) {
		this.duration = duration;
	}

	/**
	 * Two Videos will generate the same hashcode if they have exactly
	 * the same values for their name, url, and duration.
	 * 
	 */
	@Override
	public int hashCode() {
		// Google Guava provides great utilities for hashing 
		return Objects.hashCode(name,url,duration);
	}

	/**
	 * Two Videos are considered equal if they have exactly
	 * the same values for their name, url, and duration.
	 * 
	 */
	@Override
	public boolean equals(Object obj) {
		if(obj instanceof Video){
			Video other = (Video)obj;
			// Google Guava provides great utilities for equals too! 
			return Objects.equal(name, other.name) 
					&& Objects.equal(url, other.url)
					&& duration == other.duration;
		}
		else {
			return false;
		}
	}

}

package org.magnum.mobilecloud.video.controller;

import com.google.common.base.Objects;

/**

* A simple object to represent a video and its URL for viewing.

* @author jules

public class Video {

private String name;

private String url;

private long duration;

public Video(){}

public Video(String name, String url, long duration) {

super();

this.name = name;

this.url = url;

this.duration = duration;

}

public String getName() {

return name;

}

public void setName(String name) {

this.name = name;

}

public String getUrl() {

return url;

}

public void setUrl(String url) {

this.url = url;

}

public long getDuration() {

return duration;

}

public void setDuration(long duration) {

this.duration = duration;

}

/**

* Two Videos will generate the same hashcode if they have exactly

* the same values for their name, url, and duration.

@Override

public int hashCode() {

// Google Guava provides great utilities for hashing

return Objects.hashCode(name,url,duration);

}

/**

* Two Videos are considered equal if they have exactly

* the same values for their name, url, and duration.

@Override

public boolean equals(Object obj) {

if(obj instanceof Video){

Video other = (Video)obj;

// Google Guava provides great utilities for equals too!

return Objects.equal(name, other.name)

&& Objects.equal(url, other.url)

&& duration == other.duration;

}

else {

return false;

}

Application.java

package org.magnum.mobilecloud.video.controller;

import org.magnum.mobilecloud.video.repository.NoDuplicatesVideoRepository;
import org.magnum.mobilecloud.video.repository.VideoRepository;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;

// Tell Spring that this object represents a Configuration for the
// application
@Configuration
// Tell Spring to turn on WebMVC (e.g., it should enable the DispatcherServlet
// so that requests can be routed to our Controllers)
@EnableWebMvc
// Tell Spring to go and scan our controller package (and all sub packages) to
// find any Controllers or other components that are part of our applciation.
// Any class in this package that is annotated with @Controller is going to be
// automatically discovered and connected to the DispatcherServlet.
@ComponentScan("org.magnum.mobilecloud.video.controller")
// Tell Spring to automatically inject any dependencies that are marked in
// our classes with @Autowired
@EnableAutoConfiguration
public class Application {

	// Tell Spring to launch our app!
	public static void main(String[] args){
		SpringApplication.run(Application.class, args);
	}
	
	// We need to tell Spring which implementation of the VideoRepository
	// that it should use. Spring is going to automatically inject whatever
	// we return into the VideoSvc's videos member variable that is annotated
	// with @Autowired.
	@Bean
	public VideoRepository videoRepository(){
		return new NoDuplicatesVideoRepository();
	}
	
}

package org.magnum.mobilecloud.video.controller;

import org.magnum.mobilecloud.video.repository.NoDuplicatesVideoRepository;

import org.magnum.mobilecloud.video.repository.VideoRepository;

import org.springframework.boot.SpringApplication;

import org.springframework.boot.autoconfigure.EnableAutoConfiguration;

import org.springframework.context.annotation.Bean;

import org.springframework.context.annotation.ComponentScan;

import org.springframework.context.annotation.Configuration;

import org.springframework.web.servlet.config.annotation.EnableWebMvc;

// Tell Spring that this object represents a Configuration for the

// application

@Configuration

// Tell Spring to turn on WebMVC (e.g., it should enable the DispatcherServlet

// so that requests can be routed to our Controllers)

@EnableWebMvc

// Tell Spring to go and scan our controller package (and all sub packages) to

// find any Controllers or other components that are part of our applciation.

// Any class in this package that is annotated with @Controller is going to be

// automatically discovered and connected to the DispatcherServlet.

@ComponentScan("org.magnum.mobilecloud.video.controller")

// Tell Spring to automatically inject any dependencies that are marked in

// our classes with @Autowired

@EnableAutoConfiguration

public class Application {

// Tell Spring to launch our app!

public static void main(String[] args){

SpringApplication.run(Application.class, args);

}

// We need to tell Spring which implementation of the VideoRepository

// that it should use. Spring is going to automatically inject whatever

// we return into the VideoSvc's videos member variable that is annotated

// with @Autowired.

@Bean

public VideoRepository videoRepository(){

return new NoDuplicatesVideoRepository();

}

VideoSvcApi.java

package org.magnum.mobilecloud.video.client;

import java.util.Collection;

import org.magnum.mobilecloud.video.controller.Video;

import retrofit.http.Body;
import retrofit.http.GET;
import retrofit.http.POST;
import retrofit.http.Query;

/**
 * This interface defines an API for a VideoSvc. The
 * interface is used to provide a contract for client/server
 * interactions. The interface is annotated with Retrofit
 * annotations so that clients can automatically convert the
 * 
 * 
 * @author jules
 *
 */
public interface VideoSvcApi {
	
	public static final String TITLE_PARAMETER = "title";

	// The path where we expect the VideoSvc to live
	public static final String VIDEO_SVC_PATH = "/video";

	// The path to search videos by title
	public static final String VIDEO_TITLE_SEARCH_PATH = VIDEO_SVC_PATH + "/find";

	@GET(VIDEO_SVC_PATH)
	public Collection<Video> getVideoList();
	
	@POST(VIDEO_SVC_PATH)
	public boolean addVideo(@Body Video v);
	
	@GET(VIDEO_TITLE_SEARCH_PATH)
	public Collection<Video> findByTitle(@Query(TITLE_PARAMETER) String title);
	
}

package org.magnum.mobilecloud.video.client;

import java.util.Collection;

import org.magnum.mobilecloud.video.controller.Video;

import retrofit.http.Body;

import retrofit.http.GET;

import retrofit.http.POST;

import retrofit.http.Query;

/**

* This interface defines an API for a VideoSvc. The

* interface is used to provide a contract for client/server

* interactions. The interface is annotated with Retrofit

* annotations so that clients can automatically convert the

* @author jules

public interface VideoSvcApi {

public static final String TITLE_PARAMETER = "title";

// The path where we expect the VideoSvc to live

public static final String VIDEO_SVC_PATH = "/video";

// The path to search videos by title

public static final String VIDEO_TITLE_SEARCH_PATH = VIDEO_SVC_PATH + "/find";

@GET(VIDEO_SVC_PATH)

public Collection<Video> getVideoList();

@POST(VIDEO_SVC_PATH)

public boolean addVideo(@Body Video v);

@GET(VIDEO_TITLE_SEARCH_PATH)

public Collection<Video> findByTitle(@Query(TITLE_PARAMETER) String title);

}

VideoRepository.java

package org.magnum.mobilecloud.video.repository;

import java.util.Collection;

import org.magnum.mobilecloud.video.controller.Video;

/**
 * An interface for a repository that can store Video
 * objects and allow them to be searched by title.
 * 
 * @author jules
 *
 */
public interface VideoRepository {

	// Add a video
	public boolean addVideo(Video v);
	
	// Get the videos that have been added so far
	public Collection<Video> getVideos();
	
	// Find all videos with a matching title (e.g., Video.name)
	public Collection<Video> findByTitle(String title);
	
}

package org.magnum.mobilecloud.video.repository;

import java.util.Collection;

import org.magnum.mobilecloud.video.controller.Video;

/**

* An interface for a repository that can store Video

* objects and allow them to be searched by title.

* @author jules

public interface VideoRepository {

// Add a video

public boolean addVideo(Video v);

// Get the videos that have been added so far

public Collection<Video> getVideos();

// Find all videos with a matching title (e.g., Video.name)

public Collection<Video> findByTitle(String title);

}

AllowsDuplicatesVideoRepository.java

package org.magnum.mobilecloud.video.repository;

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArrayList;

import org.magnum.mobilecloud.video.controller.Video;

/**
 * An implementation of the VideoRepository that allows duplicate
 * Videos. 
 * 
 * Yes...there is a lot of code duplication with NoDuplicatesVideoRepository
 * that could be refactored into a base class or helper object. The
 * goal was to have as few classes as possible in the example and so
 * we did not do that refactoring.
 * 
 * @author jules
 *
 */
public class AllowsDuplicatesVideoRepository implements VideoRepository {

	// Lists allow duplicate objects that are .equals() to
	// each other
	//
	// Assume a lot more reads than writes
	private List<Video> videoList = new CopyOnWriteArrayList<Video>();
	
	@Override
	public boolean addVideo(Video v) {
		return videoList.add(v);
	}

	@Override
	public Collection<Video> getVideos() {
		return videoList;
	}

	// Search the list of videos for ones with
	// matching titles.
	@Override
	public Collection<Video> findByTitle(String title) {
		Set<Video> matches = new HashSet<>();
		for(Video video : videoList){
			if(video.getName().equals(title)){
				matches.add(video);
			}
		}
		return matches;
	}

}

package org.magnum.mobilecloud.video.repository;

import java.util.ArrayList;

import java.util.Collection;

import java.util.HashSet;

import java.util.List;

import java.util.Set;

import java.util.concurrent.CopyOnWriteArrayList;

import org.magnum.mobilecloud.video.controller.Video;

/**

* An implementation of the VideoRepository that allows duplicate

* Videos.

* Yes...there is a lot of code duplication with NoDuplicatesVideoRepository

* that could be refactored into a base class or helper object. The

* goal was to have as few classes as possible in the example and so

* we did not do that refactoring.

* @author jules

public class AllowsDuplicatesVideoRepository implements VideoRepository {

// Lists allow duplicate objects that are .equals() to

// each other

// Assume a lot more reads than writes

private List<Video> videoList = new CopyOnWriteArrayList<Video>();

@Override

public boolean addVideo(Video v) {

return videoList.add(v);

}

@Override

public Collection<Video> getVideos() {

return videoList;

}

// Search the list of videos for ones with

// matching titles.

@Override

public Collection<Video> findByTitle(String title) {

Set<Video> matches = new HashSet<>();

for(Video video : videoList){

if(video.getName().equals(title)){

matches.add(video);

}

return matches;

}

NoDuplicatesVideoRepository.java

package org.magnum.mobilecloud.video.repository;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

import org.magnum.mobilecloud.video.controller.Video;

/**
 * An implementation of the VideoRepository that does not allow duplicate
 * Videos. 
 * 
 * Yes...there is a lot of code duplication with NoDuplicatesVideoRepository
 * that could be refactored into a base class or helper object. The
 * goal was to have as few classes as possible in the example and so
 * we did not do that refactoring.
 * 
 * @author jules
 *
 */
public class NoDuplicatesVideoRepository implements VideoRepository {

	// Sets only store one instance of each object and will not
	// store a duplicate instance if two objects are .equals()
	// to each other.
	//
	private Set<Video> videoSet = Collections.newSetFromMap(
	        new ConcurrentHashMap<Video, Boolean>());
	
	@Override
	public boolean addVideo(Video v) {
		return videoSet.add(v);
	}

	@Override
	public Collection<Video> getVideos() {
		return videoSet;
	}

	// Search the list of videos for ones with
	// matching titles.
	@Override
	public Collection<Video> findByTitle(String title) {
		Set<Video> matches = new HashSet<>();
		for(Video video : videoSet){
			if(video.getName().equals(title)){
				matches.add(video);
			}
		}
		return matches;
	}

}

package org.magnum.mobilecloud.video.repository;

import java.util.Collection;

import java.util.Collections;

import java.util.HashSet;

import java.util.Set;

import java.util.concurrent.ConcurrentHashMap;

import org.magnum.mobilecloud.video.controller.Video;

/**

* An implementation of the VideoRepository that does not allow duplicate

* Videos.

* Yes...there is a lot of code duplication with NoDuplicatesVideoRepository

* that could be refactored into a base class or helper object. The

* goal was to have as few classes as possible in the example and so

* we did not do that refactoring.

* @author jules

public class NoDuplicatesVideoRepository implements VideoRepository {

// Sets only store one instance of each object and will not

// store a duplicate instance if two objects are .equals()

// to each other.

private Set<Video> videoSet = Collections.newSetFromMap(

new ConcurrentHashMap<Video, Boolean>());

@Override

public boolean addVideo(Video v) {

return videoSet.add(v);

}

@Override

public Collection<Video> getVideos() {

return videoSet;

}

// Search the list of videos for ones with

// matching titles.

@Override

public Collection<Video> findByTitle(String title) {

Set<Video> matches = new HashSet<>();

for(Video video : videoSet){

if(video.getName().equals(title)){

matches.add(video);

}

return matches;

}