Java Web Services – bottom-top-down approach

There are two approaches to developing web services: bottom-up and top-down. In the bottom-up approach, annotated Java classes are created first, and the WSDL is generated from these classes using wsgen tool.

Bottom-up approach.

In the top-down approach, the WSDL is created first, and the Java artifacts are generated using wsimport tool.

Top-down approach.

As a Java developer, I find the bottom-up approach simpler and quicker because:

• Java classes are faster to create than XML schema
• Creating a skeleton for a service endpoint interface (SEI) is faster than creating a WSDL skeleton.

However, top-down approach is the recommended approach as it provides better control over design, and consequently greater degree of interoperability. Therefore, to develop web services quickly without compromising interoperability, I use what I call the bottom-top-down approach.

In this approach, I very quickly create Java classes including the skeleton for the SEI, annotate them with basic JAX-WS annotations and generate a WSDL. Then, I customize the generated WSDL to be WS-I compliant (see also Which style of WSDL should I use?) and regenerate Java classes using wsimport.

An example using Maven

Let's create a simple maven project with several model classes and a SEI implementation class:

	@WebService
	@SOAPBinding(style = SOAPBinding.Style.DOCUMENT, use = SOAPBinding.Use.LITERAL, parameterStyle = SOAPBinding.ParameterStyle.WRAPPED)
	public class MovieSearchServiceImpl implements MovieSearchService {
	@WebMethod
	@Override
	public SearchResult search(Filter filter) {
	throw new UnsupportedOperationException("Not supported yet.");
	}
	}

view raw MovieSearchServiceImpl.java hosted with ❤ by GitHub

Then, we generate the WSDL using jaxws-maven-plugin. Build section of the pom is shown below:

	<build>
	<plugins>
	<plugin>
	<groupId>org.jvnet.jax-ws-commons</groupId>
	<artifactId>jaxws-maven-plugin</artifactId>
	<version>2.1</version>
	<executions>
	<execution>
	<goals>
	<goal>wsgen</goal>
	</goals>
	</execution>
	</executions>
	<configuration>
	<genWsdl>true</genWsdl>
	<verbose>true</verbose>
	<sei>com.example.MyServiceImpl</sei>
	</configuration>
	<dependencies>
	<dependency>
	<groupId>com.sun.xml.ws</groupId>
	<artifactId>jaxws-rt</artifactId>
	<version>2.1.7</version>
	</dependency>
	</dependencies>
	</plugin>
	<plugin>
	<artifactId>maven-compiler-plugin</artifactId>
	<version>3.0</version>
	<configuration>
	<source>1.6</source>
	<target>1.6</target>
	</configuration>
	</plugin>
	</plugins>
	</build>

view raw pom.xml hosted with ❤ by GitHub

The generated WSDL file can be found under target/jaxws/wsgen/wsdl.

Then, we customize the namespaces and verify that the WSDL doesn't have Java specific parts. Then, we are ready to re-generate our Java classes.

	<build>
	<plugins>
	<plugin>
	<groupId>org.jvnet.jax-ws-commons</groupId>
	<artifactId>jaxws-maven-plugin</artifactId>
	<version>2.1</version>
	<executions>
	<execution>
	<goals>
	<goal>wsimport</goal>
	</goals>
	</execution>
	</executions>
	<configuration>
	<keep>true</keep>>
	<verbose>true</verbose>
	<wsdlDirectory>src/main/resources/wsdl</wsdlDirectory>
	<!--
	<bindingDirectory>src/main/resources/binding</bindingDirectory>
	-->
	</configuration>
	<dependencies>
	<dependency>
	<groupId>com.sun.xml.ws</groupId>
	<artifactId>jaxws-rt</artifactId>
	<version>2.1.7</version>
	</dependency>
	</dependencies>
	</plugin>
	<plugin>
	<artifactId>maven-compiler-plugin</artifactId>
	<version>3.0</version>
	<configuration>
	<source>1.6</source>
	<target>1.6</target>
	</configuration>
	</plugin>
	</plugins>
	</build>

view raw pom.xml hosted with ❤ by GitHub

Generated Java classes use XMLGregorianCalendar instead of java.util.Calendar for XML date and time types. This can be customized using a binding file. In addition, we can make our generated classes implement the Serializable interface. An example binding file is illustrated below:

	<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
	<jaxb:bindings xmlns:jaxb="http://java.sun.com/xml/ns/jaxb"
	xmlns:xs="http://www.w3.org/2001/XMLSchema"
	xmlns:xjc="http://java.sun.com/xml/ns/jaxb/xjc"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://java.sun.com/xml/ns/jaxb http://java.sun.com/xml/ns/jaxb/bindingschema_2_0.xsd"
	version="2.1" jaxb:extensionBindingPrefixes="xjc">
	<jaxb:globalBindings>
	<!-- Use java.util.Calendar instead of javax.xml.datatype.XMLGregorianCalendar for xs:dateTime -->
	<jaxb:javaType name="java.util.Calendar" xmlType="xs:dateTime"
	parseMethod="javax.xml.bind.DatatypeConverter.parseDateTime"
	printMethod="javax.xml.bind.DatatypeConverter.printDateTime" />
	<!-- Use java.util.Calendar instead of javax.xml.datatype.XMLGregorianCalendar for xs:date -->
	<jaxb:javaType name="java.util.Calendar" xmlType="xs:date"
	parseMethod="javax.xml.bind.DatatypeConverter.parseDateTime"
	printMethod="javax.xml.bind.DatatypeConverter.printDateTime" />
	<!-- Generated classes should implement Serializable interface -->
	<xjc:serializable uid="1" />
	<xjc:simple />
	</jaxb:globalBindings>
	</jaxb:bindings>

view raw binding.xml hosted with ❤ by GitHub

Source code for these projects can be found in the quickstarts repository at GitHub.