Web Services with Apache CXF Part 2: JAXB and WSDL to Java Robert Thornton

Notes This is a training, NOT a presentation Please ask questions This is being recorded Prerequisites – Maven, Spring, and Web Application Development – Web Services, Part I: SOAP – A general familiarity with XML simple and complex schema types.

Objectives At the end of this presentation, the participant will be able to: Understand the role of JAXB as a web service data binding solution. Model data entities using JAXB annotations. Understand the purpose and usage of the CXF WSDL2Java tool. Be able to use WSDL2Java to generate a client proxy in a stand- alone Java application. Be able to configure Spring to manage and consume a generated WSDL2Java client proxy.

Web Services with Apache CXF Java XML Binding Modeling Web Service Messages with JAXB

Java and XML The Marriage of XML and Java: XML is a data markup language. – Used for long or short-term data storage. – Useful for data transfer between vastly different architectures. – Particularly useful for web service architectures. Java is an object-oriented programming language. – Unmarshalls (reads) data from existing XML into Java data objects. – Performs manipulations on Java objects via services. – Marshalls (writes) Java objects into a new XML representation.

Java and XML: Choices, choices…. The marriage of Java and XML has produced a large family of technologies, strategies, and libraries: DOM StAX JAXP DOM4J JAXB XML Beans JDOM XStream and many more….

Java and XML: Overview Most Java XML strategies fall into three spaces: DOM (Document Object Model) – Entire document model is held in memory as nodes in a document tree. Streaming – An event-based API for operating on each piece of the XML document individually and in sequence. Often used to stream XML for building DOM trees or construct XML Object bindings. XML-to-Object Binding – XML types and elements are bound to Java types and fields. In practice, most solutions use some combination of these.

JAXB: A Data Binding Solution The JAXB API is the standard solution provided by the JDK for Java XML data binding: Java classes are bound to XML types, elements, and attributes through Java annotations. A XML streaming event-based (StAX) parser is used to parse XML documents and construct Java objects as well as to write Java objects back to XML. The XJC tool (included in the JDK) can generate JAXB annotated classes from an existing XML Schema. The Schemagen tool (also included in the JDK) can generate an XML schema from JAXB annotated classes.

JAXB and Web Services As a data modeling API, JAXB is particularly useful to web services, because: XML is the most common form of data transport. Annotated Java classes can be made to represent XML schema types. JAXB APIs can unmarshall XML into Java data objects and back again. Fits into an RPC-style of service method invocation with POJO parameters and results. * Note that the CXF web service framework automatically handles the marshalling and unmarshalling of XML data to and from JAXB annotated Java classes.

JAXB: Marshalling and Unmarshalling Although CXF handles the marshalling and unmarshalling of serviced XML, it can be helpful to know how CXF does it. A web service developer occasionally needs to experiment with how JAXB annotations affect the parsing and rendering of XML. A web service developer often needs to debug issues that arise from data being marshalled or unmarshalled incorrectly. The JAXB Marshalling/Unmarshalling APIs can be used to apply additional validation or to generate a schema.

JAXB: Unmarshalling JAXB makes unmarshalling from XML easy: // Just create a JAXB context for your Java data classes JAXBContext jaxb = JAXBContext.newInstance(myClasses); // Then unmarshall the XML document into instances of // those classes. MyClass obj = (MyClass) jaxb.createUnmarshaller().unmarshall(xml) The Unmarshaller can accept XML input as a character stream, a file, a DOM node, or several other input types.

JAXB: Marshalling Marshalling objects into XML is just as easy: // Create a JAXB context for your Java data classes JAXBContext jaxb = JAXBContext.newInstance(myClasses); // Marshall your Java object hierarchy into an XML document. jaxb.createMarshaller().marshall(myObject, output); The Marshaller can serialize the XML to a character stream, a file, a DOM node, or several other output types.

JAXB: The Context Instances of the JAXBContext class effectively represent an “in-memory” schema of your data: It is a registry of all the classes that can be bound to XML types. It is a factory for Marshaller and Unmarshaller instances. It can be supplied listeners and a Schema for additional validation. It can be used to generate an XML Schema from your JAXB annotated classes.

JAXB: Non-annotated Class Demo

JAXB: Annotations Although JAXB can bind almost any Java data object with little or no annotations, annotations are typically desirable, for example: They can tell JAXB whether to unmarshal a field into an attribute or an element. They can inform JAXB of ID fields, element order, and other schema constraints. They can be used to identify or customize schema types, element names, attribute names, element wrapping, etc.

JAXB: Common Annotations JAXB defines many annotations to customize Java XML data binding. Here are just @XmlElementRef These and more can be found in the following package: javax.xml.bind.annotation

JAXB: Annotated Class Demo

JAXB: Rules and Conventions Some general rules about JAXB annotations: Concrete classes must have a public default no-arg constructor. Properties that reference interfaces must be annotated with one or annotations that identify the possible concrete types. Annotations may be placed on the fields or on the setters but not on both. By convention, annotating fields is preferable for simple POJOs. Properties not bound to XML values must be annotated

Apache CXF: SOAP: Lab 1 Lab 1: JAXB Data Binding

Web Services with Apache CXF WSDL to Java Consuming 3 rd Party Web Services

WSDL 2 Java Third-party SOAP web services are typically consumed in one of the following ways: Using a client JAR that contains the necessary Java classes and stubs to access the web service. Using a WSDL-to-Java tool to automatically generate the necessary web service stubs from a published WSDL.

WSDL to Java: Code Generation What is generated? How do use what is generated? – Service client – Endpoint interface – JAXB annotated model classes

WSDL to Java: Code Generation IDE Demo

WSDL 2 Java: Code Generation

WSDL to Java CXF provides the wsdl2java tool to consume third- party SOAP services: wsdl2Java

WSDL to Java: Lab 2 Lab 2: Using WSDL to Java

WSDL to Java: Spring Integration When the generated stubs aren’t enough. – Need to apply security (WSS4J/Spring Security) – Need to apply addition in/out interceptors

WSDL to Java: Spring Integration Demo Using an endpoint interface generated by WSDL to Java in a Spring integration test.

Conclusion The standard Java APIs can be used to model your data for use by web services. The JDK, CXF, and the Java Stack provide code generation and configuration utilities to make it easier to consume third-party web services. For more information about JAXB and CXF, please visit the links on the following page.

Resources On the web: rest rest In Print: Developing Web Services with Apache CXF and Axis 2, Kent Kai Iok Tong, TipTech Development, ISBN: