Hands-on with Dropwizard REST APIs

Action two is to sign up the handler class with the application. Let’s acquire these two measures in convert.

Produce a route handler class

By conference, Dropwizard endpoint handlers go in the /src/major/java/com/infoworld/sources folder (or what ever team ID you decide on). We’re heading to include an endpoint handler for returning a record of songwriters. As you can see in Listing two, we’ll return only the greatest. Produce a new SongWriters.java file in the /sources directory.

Listing two. The SongWriters endpoint

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

Listing two is relatively simple. The class itself is presented a route via the @Path annotation, and JSON is specified as the media form via the @Produces annotation. Following, the getBrands() system, which returns a string, is mapped to the GET HTTP system via the @GET annotation. The system just returns a tricky-coded string symbolizing the set of songwriters.

Register the handler

Now to sign up the handler. Open up the /src/major/java/com/infoworld/DemoApplication.java file and modify the operate() system to appear like Listing three.

Listing three. Registering the SongWriters handler

import com.infoworld.sources.SongWriters
// ...
public void operate(final DemoConfiguration configuration, final Natural environment environment) 
        SongWriters songWriters = new SongWriters()
        environment.jersey().sign up(songWriters)
    

Again, relatively simple. Listing three imports the class you just established, then makes use of the Natural environment object to entry Jersey and sign up the handler. Recognize the operate system also receives a DemoConfiguration object, which you will see in motion momentarily.

Take a look at the handler

Now if you visit localhost:8080/songwriters, you will get the JSON that you tricky coded. Recognize the process has seamlessly dealt with returning the string as JSON.

Model the area

Now you want to shift from a tricky-coded string to utilizing real area objects. Start off by generating a /src/major/java/com/infoworld/area/SongWriter.java file, and give it the contents of Listing 4.

Listing 4. The SongWriter area model class

package deal com.infoworld.area
import java.util.ArrayList
import java.util.List
public class SongWriter 
    non-public final String name
    non-public List tunes = new ArrayList<>()
    public SongWriter(final String name, final List tunes) 
        this.name = name
        this.tunes = tunes
    
    public String getName() 
      return name
    
    public List getSongs()
      return this.tunes
    

Incorporate a repository class

Now we’ll include a repository class to represent the information entry layer. Produce a new folder and file: /src/major/java/com/infoworld/repo/SongWriterRepo.java.

Listing five. The SongWriterRepo class

package deal 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 class SongWriterRepo 
  non-public final List songWriters
  public SongWriterRepo()
    this.songWriters = new ArrayList()     
  
  public SongWriterRepo(List songWriters)
    this.songWriters = songWriters
  
  public List findAll()
    return songWriters
  
  public Optional getByName(final String name)
    return songWriters.stream().filter(sw -> sw.getName().equals(name)).findFirst()
  

As you can see in Listing five, SongWriterRepo is responsible for returning all the SongWriter objects in a List via the findAll() system, whilst the getByName() system grabs the songwriter specified by the handed in string name.

Use the area layer

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

Listing 6. The modified SongWriters class

package deal com.infoworld.sources
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
@Path("/songwriters")
@Produces(MediaType.Application_JSON)
public class SongWriters 
   non-public final SongWriterRepo repo
    public SongWriters(SongWriterRepo repo) 
      this.repo = repo
    
    @GET
   
public List getBrands() 
        return repo.findAll()
    

Listing 6 has removed the tricky-coded string in favor of referencing the SongWriterRepo class, which is set in the constructor. Now acquire a appear at Listing 7, exactly where these lessons are wired alongside one another in the DemoApplication class.

Listing 7. Wiring the area class in DemoApplication

package deal com.infoworld
import io.dropwizard.Application
import io.dropwizard.setup.Bootstrap
import io.dropwizard.setup.Natural environment
import com.infoworld.sources.SongWriters
import com.infoworld.repo.SongWriterRepo
public class DemoApplication extends Application 
// ...
    @Override
    public void operate(final DemoConfiguration configuration, final Natural environment environment) 
        SongWriterRepo swRepo = new SongWriterRepo()
        SongWriters songWriters = new SongWriters(swRepo)
        environment.jersey().sign up(songWriters)
    

Return to the DemoApplication class, and modify it as revealed in Listing 7. Recognize that you now instantiate the SongWriterRepo object and parameterize the SongWriters source object before handing it off to Jersey.

Now if you rebuild the task and visit localhost:8080/songwriters, you will uncover an vacant array. Let’s include a tricky-coded songwriter as revealed in Listing eight.

Listing eight. Including a songwriter

public void operate(final DW2Configuration configuration,
                    final Natural environment environment) 
        List preload = new ArrayList()
        preload.include(new SongWriter("Mark Knopfler", new ArrayList()))
        SongWriterRepo swRepo = new SongWriterRepo(preload)
        SongWriters songWriters = new SongWriters(swRepo)
        environment.jersey().sign up(songWriters)
    

Now you will get a end result when you strike the endpoint.

Use the config file

Incorporate a new config file at src/major/sources/Demo-Config.yml and set the contents of Listing 9 in it.

Listing 9. The config YAML

---
songWriters:
  - John Lennon
  - Jeff Lynne

Now modify the com.infoworld.DemoConfiguration.java file to appear like Listing ten. This file is utilized to model the config file via Jackson.

Listing ten. Config java

package deal 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 class 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. Applying the config file to preload songwriters in DemoApplication.java

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

The major position of the modify in Listing 11 is that the configuration file is hydrated into the DemoConfiguration class, populating the getSongWriters() system that is utilized to preload the repository class.

Operate the application with the config file

A compact modify is demanded to operate this application with the config file. Recognize in Listing twelve that the file is referenced right after the contact to server.

Listing twelve. Functioning the application with the config file

java -jar target/DW2-one.-SNAPSHOT.jar server src/major/sources/DW2-config.yml

Now when you visit the application at localhost:8080/songwriters, you will see the preloaded songwriters.

Dropwizard is a lean choice to Spring-centered RESTful APIs. As you have seen below, it focuses on furnishing a simple but ample stack to deal with these requires.