Hands-on with Dropwizard REST APIs

Action two is to sign-up the handler course with the app. Let us consider these two steps in change.

Build a route handler course

By conference, Dropwizard endpoint handlers go in the /src/primary/java/com/infoworld/assets folder (or whichever team ID you opt for). We’re heading to increase an endpoint handler for returning a listing of songwriters. As you can see in Listing two, we’ll return only the ideal. Build a new SongWriters.java file in the /assets listing.

Listing two. The SongWriters endpoint

bundle com.infoworld.assets
import javax.ws.rs.*
import javax.ws.rs.main.MediaType
import java.util.List
import java.util.Optional
@Route("/songwriters")
@Produces(MediaType.Application_JSON)
public course SongWriters 
    public SongWriters() 
    
    @GET
    public String getBrands() 
        return "'name':'Roger Waters','name':'Tom Petty'"
    

Listing two is pretty straightforward. The course by itself is given a route by using the @Route annotation, and JSON is specified as the media variety by using the @Produces annotation. Subsequent, the getBrands() method, which returns a string, is mapped to the GET HTTP method by using the @GET annotation. The method just returns a hard-coded string symbolizing the set of songwriters.

Sign up the handler

Now to sign-up the handler. Open the /src/primary/java/com/infoworld/DemoApplication.java file and modify the run() method to glance like Listing 3.

Listing 3. Registering the SongWriters handler

import com.infoworld.assets.SongWriters
// ...
public void run(ultimate DemoConfiguration configuration, ultimate Natural environment environment) 
        SongWriters songWriters = new SongWriters()
        environment.jersey().sign-up(songWriters)
    

Once more, pretty straightforward. Listing 3 imports the course you just made, then takes advantage of the Natural environment object to obtain Jersey and sign-up the handler. Discover the run method also gets a DemoConfiguration object, which you’ll see in action momentarily.

Test the handler

Now if you visit localhost:8080/songwriters, you’ll get the JSON that you hard coded. Discover the method has seamlessly dealt with returning the string as JSON.

Design the area

Now you want to shift from a hard-coded string to using precise area objects. Get started by creating a /src/primary/java/com/infoworld/area/SongWriter.java file, and give it the contents of Listing 4.

Listing 4. The SongWriter area model course

bundle com.infoworld.area
import java.util.ArrayList
import java.util.List
public course SongWriter 
    non-public ultimate String identify
    non-public List tracks = new ArrayList<>()
    public SongWriter(ultimate String identify, ultimate List tracks) 
        this.identify = identify
        this.tracks = tracks
    
    public String getName() 
      return identify
    
    public List getSongs()
      return this.tracks
    

Add a repository course

Now we’ll increase a repository course to stand for the knowledge obtain layer. Build a new folder and file: /src/primary/java/com/infoworld/repo/SongWriterRepo.java.

Listing 5. The SongWriterRepo course

bundle com.infoworld.repo
import com.infoworld.area.SongWriter
import java.util.List
import java.util.ArrayList
import java.util.Optional
import java.util.stream.Collectors
public course SongWriterRepo 
  non-public ultimate List songWriters
  public SongWriterRepo()
    this.songWriters = new ArrayList()     
  
  public SongWriterRepo(List songWriters)
    this.songWriters = songWriters
  
  public List findAll()
    return songWriters
  
  public Optional getByName(ultimate String identify)
    return songWriters.stream().filter(sw -> sw.getName().equals(identify)).findFirst()
  

As you can see in Listing 5, SongWriterRepo is dependable for returning all the SongWriter objects in a List by using the findAll() method, when the getByName() method grabs the songwriter specified by the handed in string identify.

Use the area layer

Now we’ll use the new layer to push the JSON returned by the source endpoint. Modify com.infoworld.source.SongWriters to glance like Listing 6.

Listing 6. The modified SongWriters course

bundle com.infoworld.assets
import javax.ws.rs.*
import javax.ws.rs.main.MediaType
import java.util.List
import java.util.Optional
import com.infoworld.repo.SongWriterRepo
import com.infoworld.area.SongWriter
@Route("/songwriters")
@Produces(MediaType.Application_JSON)
public course SongWriters 
   non-public ultimate SongWriterRepo repo
    public SongWriters(SongWriterRepo repo) 
      this.repo = repo
    
    @GET
    public List getBrands() 
        return repo.findAll()
    

Listing 6 has eradicated the hard-coded string in favor of referencing the SongWriterRepo course, which is set in the constructor. Now consider a glance at Listing 7, the place these courses are wired with each other in the DemoApplication course.

Listing 7. Wiring the area course in DemoApplication

bundle com.infoworld
import io.dropwizard.Application
import io.dropwizard.set up.Bootstrap
import io.dropwizard.set up.Natural environment
import com.infoworld.assets.SongWriters
import com.infoworld.repo.SongWriterRepo
public course DemoApplication extends Application 
// ...
    @Override
    public void run(ultimate DemoConfiguration configuration, ultimate Natural environment environment) 
        SongWriterRepo swRepo = new SongWriterRepo()
        SongWriters songWriters = new SongWriters(swRepo)
        environment.jersey().sign-up(songWriters)
    

Return to the DemoApplication course, and modify it as proven in Listing 7. Discover that you now instantiate the SongWriterRepo object and parameterize the SongWriters source object just before handing it off to Jersey.

Now if you rebuild the venture and visit localhost:8080/songwriters, you will come across an empty array. Let us increase a hard-coded songwriter as proven in Listing eight.

Listing eight. Introducing a songwriter

public void run(ultimate DW2Configuration configuration,
                    ultimate Natural environment environment) 
        List preload = new ArrayList()
        preload.increase(new SongWriter("Mark Knopfler", new ArrayList()))
        SongWriterRepo swRepo = new SongWriterRepo(preload)
        SongWriters songWriters = new SongWriters(swRepo)
        environment.jersey().sign-up(songWriters)
    

Now you’ll get a end result when you hit the endpoint.

Use the config file

Add a new config file at src/primary/assets/Demo-Config.yml and put the contents of Listing nine in it.

Listing nine. The config YAML

---
songWriters:
  - John Lennon
  - Jeff Lynne

Now alter the com.infoworld.DemoConfiguration.java file to glance like Listing 10. This file is used to model the config file by using Jackson.

Listing 10. Config java

bundle com.infoworld
import io.dropwizard.Configuration
import com.fasterxml.jackson.annotation.JsonProperty
import org.hibernate.validator.constraints.*
import javax.validation.constraints.*
import com.fasterxml.jackson.annotation.JsonCreator
import com.fasterxml.jackson.annotation.JsonProperty
import java.util.List
import java.util.ArrayList
public course DW2Configuration extends Configuration 
  non-public List songWriters
  @JsonCreator
  public DW2Configuration(@JsonProperty("songWriters") List songWriters)
          this.songWriters = songWriters
  
  public List getSongWriters()
          return this.songWriters
  

Now use the file in DemoApplication, as shown in Listing 11.

Listing 11. Using the config file to preload songwriters in DemoApplication.java

    @Override
    public void run(ultimate DemoConfiguration configuration,
                    final Natural environment environment) 
        List preload = new ArrayList()
        configuration.getSongWriters().forEach(sw -> preload.increase(new SongWriter(sw, new ArrayList())))
        SongWriterRepo swRepo = new SongWriterRepo(preload)
        SongWriters songWriters = new SongWriters(swRepo)
        environment.jersey().sign-up(songWriters)
    

The primary place of the alter in Listing 11 is that the configuration file is hydrated into the DemoConfiguration course, populating the getSongWriters() method that is used to preload the repository course.

Operate the app with the config file

A smaller alter is demanded to run this app with the config file. Discover in Listing 12 that the file is referenced immediately after the get in touch with to server.

Listing 12. Managing the app with the config file

java -jar focus on/DW2-1.-SNAPSHOT.jar server src/primary/assets/DW2-config.yml

Now when you visit the app at localhost:8080/songwriters, you’ll see the preloaded songwriters.

Dropwizard is a lean alternative to Spring-centered RESTful APIs. As you’ve witnessed right here, it focuses on delivering a straightforward but sufficient stack to handle these requires.