Pro XML Development with Java Technology 2006 phần 6 pptx

For example, for the complex type catalogType, shown in Listing 6-33, the value class CatalogType.java gets generated.. Listing 6-35 shows public class ObjectFactory { private final sta

Binding Catalog Schema to Java Classes

In this section, you will bind the catalog schema shown in Listing 6-6 to its Java content classes

You’ll subsequently use the Java content classes to marshal and unmarshal the XML document

shown in Listing 6-7 You will run xjc from within Eclipse Therefore, configure xjc as an external

tool in Eclipse, similar to the JAXB 1.0 project configuration The only difference for the JAXB 2.0

project is that the xjc batch file Location field is set to the JAXB 2.0 xjc batch file You set the

envi-ronment variables JAVA_HOME and JAXB_HOME similar to JAXB 1.0 Set JAXB_HOME for Chapter6-JAXB2.0

to C:\Sun\jwsdp-2.0\jaxb To add the xjc configuration to the External Tools menu, select the

Common tab, and select the check box External Tools in the Display in Favorites menu area, as

shown in Figure 6-7

To run the xjc compiler on the example schema, catalog.xsd, select the catalog.xsd file in the

Package Explorer and then select Run ➤ External Tools ➤ XJC Schema-derived classes get generated in

the gen_source folder, as shown in Figure 6-12

Figure 6-12 Schema-derived Java content classes generated by xjc

Java classes and interfaces are generated in the package generated by default Fewer classes are

generated with JAXB 2.0 than with JAXB 1.0 For each xsd:complexType schema component, one

value class gets generated, instead of an interface and an implementation class For example, for the

complex type catalogType, shown in Listing 6-33, the value class CatalogType.java gets generated

Listing 6-33 The Complex Type catalogType

<xsd:complexType name="catalogType">

<xsd:sequence>

<xsd:element ref="journal" minOccurs="0" maxOccurs="unbounded"/>

</xsd:sequence>

<xsd:attribute name="section" type="xsd:string"/>

<xsd:attribute name="publisher" type="xsd:string"/>

</xsd:complexType>

172 C H A P T E R 6 ■ O B J E C T B I N D I N G W I T H J A X B

The CatalogType.java class consists of getter and setter methods for each of the attributes of the catalogType complex type A getter method for the complex type journalType with the return type List<JournalType> also gets generated Listing 6-34 shows CatalogType.java

public class CatalogType {

protected List<JournalType> journal;

@XmlAttribute

protected String publisher;

@XmlAttribute

protected String section;

public List<JournalType> getJournal() {

public void setSection(String value) {

this.section = value;

}

}

Similarly, the value class JournalType.java gets generated for the complex type journalType,

and the value class ArticleType.java gets generated for the complex type articleType An

ObjectFactory.java factory class gets generated, which consists of the create methods for each of

the complex type and element declarations in the example schema For example, the ObjectFactory

class method for the complex type catalogType is createCatalogType(), and its return type is

CatalogType The ObjectFactory class method for the element catalog is

createCatalog(CatalogType), and its return type is JAXBElement<CatalogType> Listing 6-35 shows

public class ObjectFactory {

private final static QName _Article_QNAME = new QName("", "article");

private final static QName _Journal_QNAME = new QName("", "journal");

private final static QName _Catalog_QNAME = new QName("", "catalog");

public ObjectFactory() {

}

public JournalType createJournalType() {

return new JournalType();

}

public ArticleType createArticleType() {

return new ArticleType();

}

public CatalogType createCatalogType() {

return new CatalogType();

}

@XmlElementDecl(namespace = "", name = "article")

public JAXBElement<ArticleType> createArticle(ArticleType value) {

return new JAXBElement<ArticleType>

(_Article_QNAME, ArticleType.class, null, value);

}

174 C H A P T E R 6 ■ O B J E C T B I N D I N G W I T H J A X B

@XmlElementDecl(namespace = "", name = "journal")

public JAXBElement<JournalType> createJournal(JournalType value) {

return new JAXBElement<JournalType>

(_Journal_QNAME, JournalType.class, null, value);

}

@XmlElementDecl(namespace = "", name = "catalog")

public JAXBElement<CatalogType> createCatalog(CatalogType value) {

return new JAXBElement<CatalogType>

(_Catalog_QNAME, CatalogType.class, null, value);

}

}

Marshaling an XML Document

Marshaling an XML document means creating an XML document from a Java object representation

of the XML document In the use case example, the web services client has to marshal the XML ment shown in Listing 6-7 In this section, we will show how to marshal such a document from a Java object tree that contains objects that are instances of schema-derived classes, generated with JAXB 2.0

docu-To marshal the example document, you need to follow these steps:

• Create a JAXBContext object, and use this object to create a Marshaller object

• Create an ObjectFactory object to create instances of the relevant generated Java content classes

• Using the ObjectFactory object, create an object tree with CatalogType as the root object Populate these tree objects with the relevant data using the appropriate setter methods

• Create a JAXBElement<CatalogType> object from the CatalogType object

JAXBElement<CatalogType> represents the catalog element in XML document

An application creates a new instance of the JAXBContext class with the static method

newInstance(String contextPath), where contextPath specifies a list of Java packages for the schema-derived classes In this case, generated contains the schema-derived classes, and you create this object as follows:

ObjectFactory factory=new ObjectFactory();

For each schema-derived Java class, a static factory method to create an object of that class

is defined in the ObjectFactory class The Java value class corresponding to the root element catalog complex type catalogType is CatalogType; therefore, create a CatalogType object with the createCatalogType() method of the ObjectFactory class:

CatalogType catalog = factory.createCatalogType();

The root element in the XML document to be marshaled has the attributes section and publisher

The CatalogType value class provides the setter methods setSection() and setPublisher() for these

attributes You can set the section and publisher attributes with these setter methods, as shown in

Listing 6-36

Listing 6-36 Setting the section and publisher Attributes

catalog.setSection("Java Technology");

catalog.setPublisher("IBM developerWorks");

The Java value class for the journalType complex type is JournalType You create a JournalType

object with createJournalType(), as shown here:

JournalType journal = factory.createJournalType();

To add a JournalType object to a CatalogType object, obtain a parameterized type

List<JournalType> object for a CatalogType object and add the JournalType object to this List,

as shown in Listing 6-37

Listing 6-37 Adding a journal Element to the catalog Element

List<JournalType> journalList = catalog.getJournal();

journalList.add(journal);

The Java value object for the complex type articleType is ArticleType You create an ArticleType

object with the createArticleType() method of the ObjectFactory class:

ArticleType article = factory.createArticleType();

The element article has the attributes level and date for which the corresponding setter

methods in the ArticleType value object are setLevel() and setDate() You can set the attributes

level and date for an article element with these setter methods, as illustrated in Listing 6-38

Listing 6-38 Setting the Attributes level and date

article.setLevel("Intermediate");

article.setDate("January-2004");

The element article has the subelements title and author The ArticleType value object has

setter methods, setTitle() and setAuthor(), for setting the title and author elements, as shown in

Listing 6-39

Listing 6-39 Setting the title and author Elements

article.setTitle("Service Oriented Architecture Frameworks");

article.setAuthor("Naveen Balani");

To add an ArticleType object to a JournalType object, obtain a parameterized type

List<ArticleType> object from a JournalType object, and add the ArticleType object to this List,

as shown in Listing 6-40

Listing 6-40 Adding an article Element to a journal Element

List<ArticleType> articleList = journal.getArticle();

articleList.add(article);

To marshal the Java object representation CatalogType to an XML document, you need to

create a JAXBElement object of type CatalogType with the createCatalog(CatalogType) method’s

public class JAXBMarshaller {

public void generateXMLDocument() {

try {

JAXBContext jaxbContext = JAXBContext.newInstance("generated");

Marshaller marshaller = jaxbContext.createMarshaller();

generated.ObjectFactory factory = new generated.ObjectFactory();

CatalogType catalog = factory.createCatalogType();

catalog.setSection("Java Technology");

catalog.setPublisher("IBM developerWorks");

JournalType journal = factory.createJournalType();

ArticleType article = factory.createArticleType();

public static void main(String[] argv) {

JAXBMarshaller jaxbMarshaller = new JAXBMarshaller();

jaxbMarshaller.generateXMLDocument();

}

}

Unmarshaling an XML Document

Unmarshaling means creating a Java object tree from an XML document In the example use case,

the website receives an XML document containing catalog information, and it needs to unmarshal

this document before it can process the catalog information contained within the document In this

section, we’ll show first how to unmarshal the example XML document using the JAXB 2.0 API, and

subsequently we’ll show how to access various element and attribute values in the resulting Java

object tree

To unmarshal, follow these steps:

1. The example XML document, catalog.xml (Listing 6-7), is the starting point for unmarshaling

Therefore, import catalog.xml to the Chapter6-JAXB2.0 project in Eclipse by selecting File ➤ Import

2. Create a JAXBContext object, and use this object to create an UnMarshaller object

3. The Unmarshaller class converts an XML document to a JAXBElement object of type CatalogType

4. Create a CatalogType object from the JAXBElement object

As discussed earlier, create a JAXBContext object, which implements the JAXB binding

frame-work unmarshal() operation

You need an Unmarshaller object to unmarshal an XML document to a Java object Therefore,

create an Unmarshaller object with the createUnmarshaller() method of the JAXBContext class, as

shown here:

Unmarshaller unMarshaller=jaxbContext.createUnmarshaller();

178 C H A P T E R 6 ■ O B J E C T B I N D I N G W I T H J A X B

JAXB 2.0 deprecates the setValidating() method to validate the XML document being shaled in favor of the setSchema(Schema schema) method, whereby you can set the schema that should be used for validation during unmarshaling

unmar-To create a Java object representation of an XML document, unmarshal the XML document to obtain a JAXBElement object of type CatalogType Subsequently, obtain a CatalogType object from the JAXBElement object with the getValue() method, as shown in Listing 6-42

Listing 6-42 Unmarshaling an XML Document

Listing 6-43 Outputting the section and publisher Attributes

System.out.println("Section: "+catalog.getSection());

System.out.println("Publisher: "+catalog.getPublisher());

You can obtain a List<JournalType> object of JournalType objects for a CatalogType object with the getJournal() method of the CatalogType value object:

List<JournalType> journalList = catalog.getJournal();

Iterate over the List to obtain the JournalType objects, which correspond to the journal element in the XML document, catalog.xml, as shown in Listing 6-44

Listing 6-44 Retrieving Journal Objects for a Catalog Object

for (int i = 0; i < journalList.size(); i++) {

JournalType journal = (JournalType) journalList.get(i);

}

You can obtain a List of ArticleType objects with the getArticle() method of the JournalType value object, as shown here:

List<ArticleType> articleList = journal.getArticle();

To obtain ArticleType objects in an ArticleType List, iterate over the List, and retrieve ArticleType objects, as shown in Listing 6-45

Listing 6-45 Retrieving Article Objects from a List

for (int j = 0; j < articleList.size(); j++) {

ArticleType article = (ArticleType)articleList.get(j);

}

An article element has the attributes level and date and the subelements title and author

You can access the values for the article element attributes and subelements with getter methods

for these attributes and elements, as shown in Listing 6-46

Listing 6-46 Outputting article Element Attributes and Subelements

System.out.println("Article Date: "+article.getDate());

System.out.println("Level: "+article.getLevel());

System.out.println("Title: "+article.getTitle());

System.out.println("Author: "+article.getAuthor());

The complete program, JAXBUnMarshaller.java, shown in Listing 6-47, demonstrates how to

unmarshal the example XML document following the steps outlined earlier The unmarshaling

application has the method unMarshall(File), which takes a File object as input The input file

should be the document to be unmarshaled

public class JAXBUnMarshaller {

public void unMarshall(File xmlDocument) {

try {

JAXBContext jaxbContext = JAXBContext.newInstance("generated");

Unmarshaller unMarshaller = jaxbContext.createUnmarshaller();

JAXBElement<CatalogType> catalogElement = (JAXBElement<CatalogType>)

unMarshaller.unmarshal(xmlDocument);

CatalogType catalog=catalogElement.getValue();

System.out.println("Section: " + catalog.getSection());

System.out.println("Publisher: " + catalog.getPublisher());

List<JournalType> journalList = catalog.getJournal();

for (int i = 0; i < journalList.size(); i++) {

JournalType journal = (JournalType) journalList.get(i);

List<ArticleType> articleList = journal.getArticle();

for (int j = 0; j < articleList.size(); j++) {

ArticleType article = (ArticleType)articleList.get(j);

System.out.println("Article Date: " + article.getDate());

System.out.println("Level: " + article.getLevel());

System.out.println("Title: " + article.getTitle());

System.out.println("Author: " + article.getAuthor());

public static void main(String[] argv) {

File xmlDocument = new File("catalog.xml");

JAXBUnMarshaller jaxbUnmarshaller = new JAXBUnMarshaller();

jaxbUnmarshaller.unMarshall(xmlDocument);

}

}

The output from unmarshaling the example XML document is the same as for the JAXB 1.0 project

Binding Java Classes to XML Schema

JAXB 2.0 supports bidirectional mapping between the XML Schema content and Java classes So far, you have looked at binding the XML Schema content to Java classes In this section, you will generate XML Schema content from a Java class using the JAXB 2.0 binding annotations Therefore, you need

to define an annotated class: Catalog.java To this class, you will apply the schemagen tool to generate

a schema definition

In the Catalog.java class, import the javax.xml.bind.annotation package that includes the binding annotation types Define the root element with the @XmlRootElement annotation Create a complex type using the @XmlType annotation:

@XmlRootElement

@XmlType(name="", propOrder={"publisher", "edition", "title", "author"})

You specify the annotation element name as an empty string because the complex type is defined anonymously within an element You specify the element order using the propOrder anno-tation element In the Catalog class, define constructors for the class, and define the different JavaBean properties (publisher, edition, title, author) The root element catalog has an attribute journal Define the journal attribute using the @XmlAttribute annotation:

@XmlAttribute

public String journal;

You also need to define getter and setter methods for the different properties and the journal attribute Listing 6-48 shows the complete Catalog.java class

@XmlType(name = "", propOrder = { "publisher", "edition", "title", "author" })

public class Catalog {

private String publisher;

private String edition;

private String title;

private String author;

public Catalog() {

}

public Catalog(String journal, String publisher, String edition,

String title, String author) {

public String journal;

private String getJournal() {

Figure 6-13 SCHEMAGEN configuration

To generate the XML Schema from the annotated class Catalog.java, select Catalog.java in the Package Explorer, and run the SCHEMAGEN configuration An XML Schema gets generated from the annotated class, as shown in Figure 6-14

Figure 6-14 XML Schema generated from the annotated class Catalog.java

Summary

JAXB 1.0 specifies XML Schema binding to Java representation JAXB 2.0 specifies a bidirectional

XML Schema to Java representation Both specifications provide a binding compiler for generating

schema-derived Java content classes and a runtime framework for the marshaling and unmarshaling of

XML documents

You can customize the XML Schema binding to Java types through external or inline binding

declarations The external binding declarations allow the schema definition and customizations to

be cleanly separated and offer the advantage of applying different customizations to the same schema

definition to satisfy different binding objectives However, external binding declarations rely on

XPath expressions to address binding nodes for customizations and are therefore relatively more

complex to specify than inline bindings, which are specified within the schema definition and thus

address binding nodes implicitly

JAXB 2.0 provides following advantages over JAXB 1.0:

• Support for all the schema constructs

• A relatively compact binding of a schema definition to Java content classes

• Bidirectional mapping between schema definition and Java types

We strongly recommend using JAXB 2.0, unless you explicitly need to stay with JAXB 1.0, such

as for backward compatibility

■ ■ ■

C H A P T E R 7

Binding with XMLBeans

XMLBeans,1 just like JAXB, is an XML-to-Java binding and runtime framework You can use the

binding framework to bind an XML Schema to Java types; you can use the runtime framework to

unmarshal and marshal an XML document to and from its Java binding classes If you are wondering

why you are studying another XML-to-Java binding, the answer lies in the following reasons:

• XMLBeans provides full support for XML Schema binding to Java types across multiple versions

of the Java platform Even though JAXB 2.0 provides full support for XML Schema, it requires

J2SE 5.0; XMLBeans is the only XML-to-Java binding with full schema support that works with

J2SE 1.4.x, as well as with J2SE 5.0.

• XMLBeans predates JAXB, and perhaps because of that, it has found its way into many more

commercial products than JAXB, although, admittedly, if JAXB 2.0 is widely adopted, this may

not last into the future

• XMLBeans defines the XmlObject API for access to XML information content through

type-safe Java classes XMLBeans also defines the XmlCursor API that provides cursor-based access to

the XML InfoSet that underlies an XML document This means by using XMLBeans, you can

access and manipulate information content through type-safe Java classes, and you can do so

in a manner that is related to the low-level details within the document, such as the order of

elements or attributes

• XMLBeans defines the SchemaType API that provides a schema object model for metadata

contained within an XML Schema This is useful if you want to dynamically create an XML

document that conforms to a schema

In our opinion, JAXB should be the default choice for a binding framework, because it is part of

the Java Platform Standard Edition However, in certain situations, for reasons discussed previously

and summarized in Table 7-1, XMLBeans may be the more pragmatic choice

In this chapter, we will primarily focus on the XMLBeans binding and runtime frameworks We

will also discuss the XmlCursor API related to the XML InfoSet; however, the APIs related to the

schema object model are beyond the scope of this chapter, mainly because we want to keep the

focus on the binding framework and because the SchemaType API is not central to this focus

1 This is part of the Apache XML Project; you can find detailed information related to this project at

http://xmlbeans.apache.org/overview.html

docu-In this chapter, we will first show how to use the binding compiler to bind an example schema

to its Java types and then show how to use these Java types to marshal and unmarshal an example XML document Listing 7-1 shows the example schema

Table 7-1 XMLBeans vs JAXB

Feature XMLBeans JAXB

Bidirectional

mapping

Does not support bidirectional mapping between the XML Schema and the Java class

JAXB 2.0 supports bidirectional mapping between the XML Schema and the Java class.XML Schema

XML document

navigation

XMLBeans supports XML document navigation with cursors

JAXB does not support cursors

interfaces extend org.apache.xmlbeans.XmlObject

The JAXB JavaBeans interfaces do not extend a root interface

a XQuery 1.0 is an XML-based query language (http://www.w3.org/TR/xquery/)

<xs:element name="article">

<xs:complexType>

<xs:sequence>

<xs:element name="title" type="xs:string"/>

<xs:element name="author" type="xs:string"/>

</xs:sequence>

<xs:attribute name="level" type="xs:string"/>

<xs:attribute name="date" type="xs:string"/>

<xs:attribute name="section" type="xs:string"/>

</xs:complexType>

</xs:element>

Listing 7-2 shows the example XML document we will marshal and unmarshal The structure

and content of the example XML document, of course, conforms to the example XML schema

Listing 7-2 catalog.xml

<?xml version="1.0" encoding="UTF-8"?>

<catalog>

<journal publisher="IBM developerWorks">

<article level="Intermediate" date="January-2004" section="Java Technology">

<title>Service Oriented Architecture Frameworks</title>

<author>Naveen Balani</author> </article>

<article level="Advanced" date="October-2003" section="Java Technology">

<title>Advance DAO Programming</title>

<author>Sean Sullivan</author> </article>

<article level="Advanced" date="May-2002" section="Java Technology">

<title>Best Practices in EJB Exception Handling</title>

<author>Srikanth Shenoy </author> </article>

</journal>

</catalog>

We will show how to compile the example schema with the binding compiler Subsequently, we

will show how to unmarshal and marshal the example XML document using the Java classes

gener-ated from the schema

Setting Up the Eclipse Project

Before you can set up your project, you need to download XMLBeans2 2.0 and extract it to an

instal-lation directory You also need to download the Saxon3 8.1.1 XSLT and the XQuery4 processor; you’ll

use the Saxon 8.1.1 API to query an XML document with the XmlCursor API XMLBeans requires at

least J2SE 1.4.x We are using J2SE 5.0 because we used it for JAXB 2.0, and we think it is convenient

to continue using it for XMLBeans You may choose to follow suit or use J2SE 1.4.x If you follow this

choice, download and install J2SE 5.0, in case you have not already done so

2 You can download the XMLBeans binary version from http://xmlbeans.apache.org/

3 You can download this from http://sourceforge.net/project/

showfiles.php?group_id=29872&package_id=21888

4 We’ll discuss XQuery in the “Querying XML Document with XQuery” section

188 C H A P T E R 7 ■ B I N D I N G W I T H X M L B E A N S

To compile and run the code examples, you will need an Eclipse project Download the project Chapter7 from the Apress website (http://www.apress.com), and import it into your Eclipse work-space, as described in Chapter 1

You need some XMLBeans JAR files in your project’s Java build path; Figure 7-1 shows these JAR files The JAR files required for an XMLBeans application are xbean.jar, which consists of the XMLBeans API, and jsr173_api.jar, which implements JSR-173, Streaming API for XML.5 You also need to set the JRE system library to JRE 5.0,6 as shown in Figure 7-1

Figure 7-1 Chapter7 project Java build path

You will configure the binding compiler scomp to generate Java content classes in the gen_source folder; therefore, add the gen_source folder to the source path on the Source tab in the Java build path area, as shown in Figure 7-2

Figure 7-3 shows the Chapter7 project directory structure

5 JSR-173 defines the StAX API, which we covered in Chapter 2 Information about JSR 173 is available at http://www.jcp.org/en/jsr/detail?id=173

6 As noted, you may choose to use JRE 1.4.x.

Figure 7-2 Source path for the Chapter7 project

Figure 7-3 Chapter7 project directory structure

Compiling an XML Schema

In this section, you will first bind the example schema (catalog.xsd, shown in Listing 7-1) to its

corresponding Java types Subsequently, you will marshal and unmarshal the example XML

docu-ment (catalog.xml, shown in Listing 7-2) As noted earlier, you will use the scomp binding compiler

to bind the example schema There is a choice of syntax for scomp use, as shown in Listing 7-3