Next In this post, we will see about Dropwizard tutorial. Dropwizard is java framework to develop high-performance restful web services faster. It will use some of the stable libraries to create simple,light-weight package so that you can actually focus on business logic rather than worrying about configuration. Dropwizard provides out of the box support for configuration, application metrics, logging and many other operational tools.
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Dusan is a back-end Java developer with eight years of experience in Java development and a number of large projects under his belt. In a microservice architecture, Dropwizard commands a very important place. It allows developers quick project bootstrapping. This helps you package your applications to be easily deployable in a production environment as standalone services. If you have ever been in a situation where you need to bootstrap a project in the Spring framework , for example, you probably know how painful it can be.
It just came to mind first. Default Dropwizard Libraries Instead of including all libraries needed to build a REST service separately and configuring each of them, Dropwizard does that for us. Dropwizard embeds the Jetty servlet container for running web applications. Instead of deploying your applications to an application server or web server, Dropwizard defines a main method that invokes the Jetty server as a standalone process. As of now, Dropwizard recommends only running the application with Jetty; other web services like Tomcat are not officially supported.
Metrics: Dropwizard has its own metrics module for exposing the application metrics through HTTP endpoints. Guava: In addition to highly optimized immutable data structures, Guava provides a growing number of classes to speed up development in Java.
Logback and Slf4j: These two are used for better logging mechanisms. Freemarker and Mustache: Choosing template engines for your application is one of the key decisions. The chosen template engine has to be more flexible for writing better scripts.
Dropwizard uses well-known and popular template engines Freemarker and Mustache for building the user interfaces. Maven Configuration Dropwizard officially supports Maven. This is the first step in creating your Dropwizard application. This will download all the required dependencies to your project. The current Dropwizard version is 1.
Now, we can move on to writing our first real Dropwizard application. You will need to have the file configuration. Valid; import javax. NotNull; import com. JsonProperty; import io. Configuration; import io. Define an Application Class We should now go and create the main application class.
This class will bring all the bundles together and bring the application up and get it running for use. Here is an example of an application class in Dropwizard: import io. Application; import io. AuthDynamicFeature; import io. OAuthCredentialAuthFilter; import io. Environment; import javax. DataSource; import org. RolesAllowedDynamicFeature; import org. DBI; import com. DropwizardBlogAuthenticator; import com. DropwizardBlogAuthorizer; import com. User; import com. DropwizardBlogConfiguration; import com.
DropwizardBlogApplicationHealthCheck; import com. PartsResource; import com. All of these will be explained later on. Length; import com. It is nothing but an endpoint URI for accessing the resource on the server.
Here is a resource class for our Dropwizard example: import java. List; import javax. RolesAllowed; import javax. NotNull; import javax. GET; import javax. POST; import javax. PUT; import javax. Path; import javax. PathParam; import javax. Produces; import javax. MediaType; import org.
HttpStatus; import com. Timed; import com. Part; import com. Representation; import com. Registering a Resource I would go back now to the main application class. You can see at the end of that class that we have registered our resource to be initialized with the service run.
We need to do so with all resources we might have in our application. Here is our service class: import java. List; import java.
Objects; import javax. WebApplicationException; import javax. Status; import org. UnableToExecuteStatementException; import org. UnableToObtainConnectionException; import org. CreateSqlObject; import com. PartsDao; import com. The database may be down or there may be network connectivity issues. The database configurations are likely incorrect. I have created a simple MySQL schema with one table only to be used in our example.
You can find the init script for the schema within the source. Here is our DAO interface: import java. List; import org. Bind; import org. BindBean; import org. SqlQuery; import org. SqlUpdate; import org. RegisterMapper; import com. PartsMapper; import com. Part; RegisterMapper PartsMapper. However, we need to map our SQL result sets to a model, which we do by registering a mapper class.
Here is our mapper class: import java. ResultSet; import java. SQLException; import org. StatementContext; import org. ResultSetMapper; import com. In our case, we would probably like to check if the database is up and running before saying that our service is healthy. What we do is actually perform some simple DB action like getting parts from the DB and handling the potential outcomes successful or exceptions. Here is our health check implementation in Dropwizard: import com.
HealthCheck; import com. I will show you how to protect your service with OAuth. However, due to complexity, I have omitted an underlying DB structure and just showed how it is wrapped. Implementing to full scale should not be an issue starting from here.
Dropwizard has two important interfaces we need to implement.
Getting Started with Dropwizard
Dropwizard is kind of ecosystem which contains all the dependencies such as Jersey, jackson or jetty bundled into single package or can be added as separate module. If you are not using dropwizard, you will end up collecting all dependencies yourself and it often results into class loading issues due to version mismatch between various java libraries. Dropwizard solve this problem for you, and pulls together stable, mature libraries into a simple, light-weight package that lets you focus on getting things done. You will need Java 8 to run the examples given in this code which are developed using dropwizard version 1. Libraries included inside dropwizard Once you include dropwizard into your project, you get following libraries added to your classpath.
Or you can just skip to the fun part. Overview Dropwizard straddles the line between being a library and a framework. Its goal is to provide performant, reliable implementations of everything a production-ready web application needs. Because this functionality is extracted into a reusable library, your application remains lean and focused, reducing both time-to-market and maintenance burdens.
Dropwizard Tutorial – Hello World Example
Dusan is a back-end Java developer with eight years of experience in Java development and a number of large projects under his belt. In a microservice architecture, Dropwizard commands a very important place. It allows developers quick project bootstrapping. This helps you package your applications to be easily deployable in a production environment as standalone services. If you have ever been in a situation where you need to bootstrap a project in the Spring framework , for example, you probably know how painful it can be. It just came to mind first.
Get Started With Microservices: A Dropwizard Tutorial