Dropwizard – Failed to parse configuration [Could not resolve type id ‘http’ into a subtype]

If you are building REST APIs using dropwizard and you get this error while starting the jetty server, then the given solution may help you.

1. Problem

While starting the server, you are getting this error.

$ java -jar target\DropWizardExample-0.0.1-SNAPSHOT.jar server

default configuration has an error:
  * Failed to parse configuration at: server.applicationConnectors.[0]; Could not resolve type id 'http' into a subtype of [simple type, class io.dropwizard.jetty.ConnectorFactory]: known type ids = [ConnectorFactory]
 at [Source: N/A; line: -1, column: -1] (through reference chain: io.dropwizard.Configuration["server"]->io.dropwizard.server.DefaultServerFactory["applicationConnectors"]->java.util.ArrayList[0])

2. Solution

The above exception is because you are not using ServicesResourceTransformer in your maven shade plugin. It relocates classes in META-INF/services and appends entries in META-INF/services resources into a single resource.

Please correct the shade plugin, and you will be good.

I have this pom.xml working perfectly for me.

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>com.howtodoinjava.app</groupId>
  <artifactId>hello-world-example</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>hello-world-example</name>
  <url>https://howtodoinjava.com</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <java.version>17</java.version>
    <dropwizard.version>1.0.0</dropwizard.version>
  </properties>

  <dependencies>
    <dependency>
      <groupId>io.dropwizard</groupId>
      <artifactId>dropwizard-core</artifactId>
      <version>4.0.0</version>
    </dependency>
    <dependency>
      <groupId>io.dropwizard</groupId>
      <artifactId>dropwizard-client</artifactId>
      <version>4.0.0</version>
    </dependency>
    <dependency>
      <groupId>org.projectlombok</groupId>
      <artifactId>lombok</artifactId>
      <version>1.18.26</version>
      <scope>provided</scope>
    </dependency>
  </dependencies>
  <build>
    <finalName>DropWizardExample-${version}</finalName>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.1</version>
        <configuration>
          <source>11</source>
          <target>11</target>
        </configuration>
      </plugin>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-shade-plugin</artifactId>
        <version>3.2.0</version>
        <executions>
          <execution>
            <phase>package</phase>
            <goals>
              <goal>shade</goal>
            </goals>
            <configuration>
              <transformers>
                <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer"/>
                <transformer implementation="org.apache.maven.plugins.shade.resource.ManifestResourceTransformer">
                  <mainClass>com.howtodoinjava.app.App</mainClass>
                </transformer>
                <transformer implementation="org.apache.maven.plugins.shade.resource.ServicesResourceTransformer">
                </transformer>
              </transformers>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>
</project>

Let me know if it solves your problem.

Happy Learning !!

Sourcecode on Github