I don't know if there is any library especially suited for calling SOAP services from a Dropwizard application, but we are using Apache CXF[1] quite successfully. We have the following plugin definition in the build section of our POM file:
<plugin>
<groupId>org.apache.cxf</groupId>
<artifactId>cxf-codegen-plugin</artifactId>
<version>3.1.6</version>
<executions>
<execution>
<id>generate-sources</id>
<phase>validate</phase>
<configuration>
<sourceRoot>${basedir}/generated</sourceRoot>
<wsdlOptions>
<wsdlOption>
<wsdl>WSDL path or URL here</wsdl>
<extraargs>
<extraarg>-impl</extraarg>
<extraarg>-verbose</extraarg>
</extraargs>
</wsdlOption>
</wsdlOptions>
</configuration>
<goals>
<goal>wsdl2java</goal>
</goals>
</execution>
</executions>
</plugin>
The plugin loads the WSDL file and generates Java code for calling the SOAP service. You'll need to add "generated" as a source folder to your project.