Download XML Binding - Chariot Solutions

JavaTM Technology to
XML Binding Tools
JAXB, Castor, XMLBeans, JiBX
Aaron Mulder
Chief Technical Officer
Chariot Solutions
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| 2004 JavaOneSM Conference | Session 2841
java.sun.com/javaone/sf
Goal of This Talk
Moving beyond SAX and DOM
Learn how to use XML binding tools
to read, write, and manipulate XML
documents by interacting with simple
Java objects
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| 2004 JavaOneSM Conference | Session 2841
Agenda
Overview of XML binding tools
Introduction to each tool in this talk
Sample code
Tool comparison
Q&A
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| 2004 JavaOneSM Conference | Session 2841
Credentials & Use Cases
• Aaron Mulder
─ XML binding user
• When XML binding?
─ XML configuration files
─ XML data exchange files
─ Save objects to XML when exceptions crop up,
reload from XML in test cases
─ Anywhere you’d otherwise use a lower-level API
• When not XML binding?
─ Large files (bulk data load)
─ Multiple versions of same XML format (maybe)
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| 2004 JavaOneSM Conference | Session 2841
Agenda Progress
Overview of XML binding tools
Introduction to each tool in this talk
Sample code
Tool comparison
Q&A
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| 2004 JavaOneSM Conference | Session 2841
XML Binding
• JAXP provides SAX and DOM, which are
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manual APIs to extract information from an
XML document
The JAXP spec addresses input; output is
provided indirectly via XSLT
There are higher-level tools like JDOM, but
we’re still dealing with data, not objects
XML binding tools allow us to directly map XML
documents to Java objects without manual
effort
This talk covers 4 tools; there are more.
| 2004 JavaOneSM Conference | Session 2841
XML Binding Example
<customer>
<name>
<first-name>Aaron</first-name>
<last-name>Mulder</last-name>
</name>
<street>165 Indiana Ave</street>
<city>Fort Washington</city>
…
</customer>
• Complex type definitions are
mapped to classes
• Child elements & attributes
are mapped to fields
• May be able to adjust depth
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| 2004 JavaOneSM Conference | Session 2841
Customer
street
city
Name
firstName
lastName
XML Binding Approaches
• May start from:
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Schema
DTD (legacy)
one or more XML Documents
Existing Java classes
• May generate Java classes based on XML
document/DTD/schema
• Any way you slice it, you get marshalling (Java
to XML), unmarshalling (XML to Java),
modification, and validation
• Each tool offers value-added features
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| 2004 JavaOneSM Conference | Session 2841
When to Use These Approaches
• Schema-centric (generating) is best when you:
─ Have a stable Schema
─ Must get up and running quickly
─ Want to validate according to the Schema
• Java technology-centric (mapping) is best
when you:
─ Don’t want object model tied to schema
─ Need to support different versions of the schema
with the same object model
─ Want a common data exchange format for existing
objects
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| 2004 JavaOneSM Conference | Session 2841
What’s the Same Across These Tools
• Schema support
• Can generate new Java objects to represent
an XML document
• Can customize the generated code to some
degree (i.e. package/class names)
• Free to use (though specific license varies)
• Documentation available
• Command-line and Ant tools
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| 2004 JavaOneSM Conference | Session 2841
What’s Different
• Support for XML documents without a
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corresponding schema
Support for DTDs (in some cases via
conversion to schema)
Points at which the tool validates (may be
automatically or programmatically)
Events/listeners for changes to XML objects
Mapping a schema to existing classes without
generating any code
Unmarshalling into existing objects to reuse
memory for multiple documents
| 2004 JavaOneSM Conference | Session 2841
What’s Different, cont.
• Whether you can unmarshal a subset of a
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large document
GUI tools or IDE plugins
Parser/J2SETM platform prerequisites
Speed & memory usage
Size of redistributable JAR(s)
Whether generated classes are plain
JavaBeansTM objects or extend XML-related
base classes
| 2004 JavaOneSM Conference | Session 2841
Agenda Progress
Overview of XML binding tools
Introduction to each tool in this talk
Sample Code
Tool comparison
Q&A
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| 2004 JavaOneSM Conference | Session 2841
Java Architecture for XML Binding (JAXB)
http://java.sun.com/xml/jaxb/
• JAXB 1.0 Specification (JSR 31)
─ Developed within Java Community ProcessSM
(JCPSM)
─ Specification, Reference Implementation (RI) and
Technology Compatibility Kit (TCK)
─ Only supported subset of XML Schema
• JAXB 1.0 RI is tool discussed today
• JAXB 2.0 Specification is under development
(JSR-222)
─ All tools on panel participate in this effort
• Vendor-specific extensions
─ Enable additional schema support than originally
specified
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| 2004 JavaOneSM Conference | Session 2841
JAXB RI v1.0.3 Features
• Supports subset of XML Schema
─ Vendor extensions
─ Element and Type Substitution
─ DTD and RELAX/NG
• Customizable
─ Schema-derived code and XML output format
• Smaller memory footprint
─ JAXB 1.0 does not require XML infoset preservation
• Unmarshal and On-Demand Validation
• Active forums & weekly bugfix releases at
https://jaxb.dev.java.net/
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| 2004 JavaOneSM Conference | Session 2841
JAXB 2.0 Specification Goals
• Full XML Schema support
• Java technology-centric Binding Model
─ Bind Java class to XML Schema
─ Customize binding with annotations
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Leverage J2SE 5.0 platform features
Provide JAX-RPC 2.0 databinding
Updateable Partial Binding
Schema Evolution
JAXB 2.0 Early Draft available for review at
http://jcp.org/aboutJava/communityprocess/edr/jsr222
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| 2004 JavaOneSM Conference | Session 2841
The Castor Project
http://www.castor.org/
• Can map existing classes to XML
• XML documents can be unmarshalled directly into
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JavaBeans components without preconfigured
mapping
Likewise, any JavaBeans component can be
marshalled to XML via introspection without
preconfigured mapping
Includes a tool to generate a schema from a DTD or
existing XML documents
XML documents can be unmarshalled into existing
objects to save memory
Reflection based, but able to call custom getters and
setters as well
| 2004 JavaOneSM Conference | Session 2841
Castor, cont.
• Generated classes are plain JavaBeans
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components, along with generated or manually
provided compile-time descriptor classes
Developer can customize generated source
code via the binding file, including event
support (namely, bound properties)
Developer can customize the marshalled XML
formatting via the mapping file
Supports custom FieldHandlers for extensibility
Supports optional validation including invoking
the validator by hand
| 2004 JavaOneSM Conference | Session 2841
XMLBeans
http://xmlbeans.apache.org/
• Originally a BEA tool, then incubated at
Apache, now a top-level Apache project
• Version 1.03 just approved, Version 2 in
development
• Supports all of XML Schema
• Provides full schema object model API
• Preserves the full XML Infoset
• Can validate after any change to the objects
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| 2004 JavaOneSM Conference | Session 2841
XMLBeans, cont.
• Generated code extends XML base classes with
special XML/Schema features
─ Provides access to XmlCursor API
─ Developer can switch between XML/Java technology features
• Does not create Java objects at parse time
─ Java objects created lazily as necessary
• Upcoming version 2:
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Reduces JAR and memory footprint
Adds DOM Level II support over XML Store
Adds support for Java technology-centric approach
Ability to extend generated objects with custom functionality
Pre- and post- events on generated methods
| 2004 JavaOneSM Conference | Session 2841
JiBX
http://www.jibx.org/
• JiBX uses binding definitions
─ You define how XML relates to Java objects
─ Allows structural changes going to and from XML
─ Start from schema, code, or both
• Binding code compiled into your class files
─ At build time, or on-the-fly at runtime
─ Allows compact and fast runtime
• Fundamentally a Java technology-centric
approach
• Current beta 3c release in widespread
production use
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| 2004 JavaOneSM Conference | Session 2841
JiBX Binding Definition Flexibility
• Current code supports:
─ Complex types with simple content, mixed content,
etc.
─ Input-output, input-only, or output-only bindings
─ Multiple bindings, even for the same classes
─ Easy extension hooks (pre-set, post-set, pre-get)
─ Custom marshallers / unmarshallers
─ Selective marshalling / unmarshalling, streaming
• More features planned for future...
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| 2004 JavaOneSM Conference | Session 2841
Agenda Progress
Overview of XML binding tools
Introduction to each tool in this talk
Sample code
Tool comparison
Q&A
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| 2004 JavaOneSM Conference | Session 2841
Scenario
• I’m working on an application server or
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deployment tool
I am given a J2EE 1.4 application with
deployment descriptors (based on XML
Schema)
I need to extract the information from those
deployment descriptors
To narrow it down even further, I’m working
with a J2EE Connector 1.5 deployment
descriptor (ra.xml)
This is a complex set of schemas!
| 2004 JavaOneSM Conference | Session 2841
J2EE 1.4 Schemas
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application_1_4.xsd
application-client_1_4.xsd
connector_1_5.xsd
ejb-jar_2_1.xsd
j2ee_1_4.xsd
j2ee_web_services_1_1.xsd
j2ee_web_services_client_1_1.xsd
jsp_2_0.xsd
web-app_2_4.xsd
web-jsptaglibrary_2_0.xsd
xml.xsd
| 2004 JavaOneSM Conference | Session 2841
Sample Deployment Descriptor (ra.xml)
<?xml version="1.0" encoding="UTF-8" ?>
<connector xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/connector_1_5.xsd"
version="1.5">
<description>Resource Adapter to interact with an RFID savant. Currently supports SOAP over HTTP savant
MTB.</description>
<display-name>Chariot RFID Adapter</display-name>
<vendor-name>Chariot Solutions LLC</vendor-name>
<eis-type>Auto-ID Savant v1.0</eis-type>
<resourceadapter-version>1.0</resourceadapter-version>
<resourceadapter>
<resourceadapter-class>com.chariotsolutions.rfid.ra.RFIDAdapter</resourceadapter-class>
<config-property>
<description>The TCP/IP hostname where the savant can be reached</description>
<config-property-name>HostName</config-property-name>
<config-property-type>java.lang.String</config-property-type>
</config-property>
<config-property>
<description>The TCP/IP port where the savant can be reached. Used for HTTP transport.</description>
<config-property-name>Port</config-property-name>
<config-property-type>java.lang.Integer</config-property-type>
</config-property>
<connector>
<inbound-resourceadapter>
<messageadapter>
<messagelistener>
<messagelistener-type>com.chariotsolutions.rfid.event.RFIDListener</messagelistener-type>
<activationspec>
<activationspec-class>com.chariotsolutions.rfid.ra.in.ScanSpec</activationspec-class>
<required-config-property>
<description>Network port to listen on for incoming messages</description>
<config-property-name>Port</config-property-name>
</required-config-property>
</activationspec>
</messagelistener>
</messageadapter>
</inbound-resourceadapter>
</resourceadapter>
</connector>
<description>…</description>
<display-name>…</display-name>
…
</connector>
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| 2004 JavaOneSM Conference | Session 2841
Sample Code
• Run the schema compiler to generate the code
• Load from an XML file into Java objects
• Print the object representing the Connector
element
─ For XMLBeans, this prints an XML fragment
including the entire contents of that element
─ Other tools print the object class/ID
• Print the values of the description and display
name child elements
• Customized mapping avoided where possible
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| 2004 JavaOneSM Conference | Session 2841
XMLBeans Schema Compiler
export XMLBEANS_HOME=/usr/local/java/xmlbeans-1.0.3
export PATH=$PATH:$XMLBEANS_HOME/bin
scomp -src java/xmlbeans -out
lib/xmlbeans/schema.jar -verbose schema/
• Compiled all schemas at once!
• No complaints or problems
• Generates a JAR containing the necessary
runtime “stuff”, plus source code for reference
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| 2004 JavaOneSM Conference | Session 2841
XMLBeans Usage
ConnectorDocument doc =
ConnectorDocument.Factory.parse(new
FileReader("ra.xml"));
ConnectorType con = doc.getConnector();
System.out.println("Connector: "+con);
System.out.println("Description: "
+con.getDescriptionArray()[0].getStringValue());
System.out.println("Display Name: "
+con.getDisplayNameArray()[0].getStringValue());
• No casts!
• Generated code has interface/implementation
separation
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| 2004 JavaOneSM Conference | Session 2841
JAXB Schema Compiler
export JWSDP_HOME=/usr/local/java/jwsdp-1.4
export PATH=$PATH:$JWSDP_HOME/jaxb/bin
xjc.sh -extension -d java/jaxb
schema/connector_1_5.xsd
• Takes one schema at a time
• Did not successfully compile ejb-jar_2_1.xsd
• Needed an updated weekly build to handle
other J2EE schemas
• Generates Java code for us to compile
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| 2004 JavaOneSM Conference | Session 2841
JAXB Usage
JAXBContext jc = JAXBContext.newInstance(
"com.sun.java.xml.ns.j2ee" );
Unmarshaller u = jc.createUnmarshaller();
Connector con = (Connector)u.unmarshal(new FileInputStream(
"ra.xml" ) );
System.out.println("Connector: "+con);
System.out.println("Description: "
+((DescriptionType)con.getDescription().get(0)).getValue());
System.out.println("Display Name: "
+((DisplayNameType)con.getDisplayName().get(0)).getValue());
• Needed to cast from a List
• Generated code has interface/implementation
separation with very clean interfaces
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| 2004 JavaOneSM Conference | Session 2841
Castor Schema Compiler
export CASTOR_HOME=/usr/local/java/castor-0.9.5.3
export PATH=$PATH:$CASTOR_HOME
export CLASSPATH=.../xercesImpl.jar
sourceGen -i schema/connector_1_5.xsd -dest
java/castor -verbose -f
• Takes one schema at a time
• Did not successfully compile ejb-jar_2_1.xsd
• Needed to override endless prompting and
ignore a number of warnings
• Generates code for us to compile (however,
required manual mapping for it to compile!)
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| 2004 JavaOneSM Conference | Session 2841
Castor Usage
Connector con = (Connector) Connector.unmarshal(new
FileReader("ra.xml"));
System.out.println("Connector: "+con);
System.out.println("Description: "
+con.getDescriptionGroup().getDescription()[0].getCont
ent());
System.out.println("Display Name: "
+con.getDescriptionGroup().getDisplayName()[0].getCont
ent());
• No casts!
• Generated objects with their own
marshall/unmarshall methods
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| 2004 JavaOneSM Conference | Session 2841
JiBX Schema Compiler
• No such thing!
• I wrote my own POJOs instead
public class Connector {
private String description;
private String displayName;
//getters & setters
}
• Very tight Java code, but…
• …does anyone see the error I’ve introduced
already? Schemas are hard to read and XML
files aren’t representative.
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| 2004 JavaOneSM Conference | Session 2841
JiBX Mapping File
<binding>
<mapping name="connector"
class="example.jibx.Connector">
<namespace uri="http://java.sun.com/xml/ns/j2ee"
default="elements" />
<value name="description" field="description" />
<value name="display-name" field="displayName" />
<structure name="vendor-name" usage="optional"/>
<structure name="eis-type" usage="optional"/>
<structure name="resourceadapter-version"
usage="optional"/>
<structure name="resourceadapter" usage="optional"/>
</mapping>
</binding>
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| 2004 JavaOneSM Conference | Session 2841
JiBX Binding Tool
export JIBX_HOME=/usr/local/java/jibx-beta3c
export
CLASSPATH=$JIBX_HOME/lib/bcel.jar:$JIBX_HOME/lib/
jibx-bind.jar:$JIBX_HOME/lib/jibxrun.jar:$JIBX_HOME/lib/xpp3.jar:classes
java org.jibx.binding.Compile jibx.binding
• First compile the Java code
• Then run this tool to mangle the classes
• Now binding features are available at runtime
(but not directly at development time)
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| 2004 JavaOneSM Conference | Session 2841
JiBX Usage
IBindingFactory bfact =
BindingDirectory.getFactory(Connector.class);
IUnmarshallingContext uctx =
bfact.createUnmarshallingContext();
Object obj = uctx.unmarshalDocument(new
FileInputStream("ra.xml"), null);
Connector con = (Connector) obj;
System.out.println("Connector: "+con);
System.out.println("Description: "+con.getDescription());
System.out.println("Display Name: "
+con.getDisplayName());
• I get to use my lovely POJOs (bugs and all!)
• Use JiBX API calls to marshall/unmarshall
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| 2004 JavaOneSM Conference | Session 2841
Agenda Progress
Overview of XML binding tools
Introduction to each tool in this talk
Sample code
Tool Comparison
Q&A
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| 2004 JavaOneSM Conference | Session 2841
XMLBeans Thoughts
• Advantages
─ Full schema support
─ Navigation & query of documents
─ Lots of metadata available
• Disadvantages
─ More overhead at runtime
─ Likes its generated JAR, doesn’t like it so much if
you just compile the code it generates
• Overall
─ My favorite when starting with complex schemas
and generating code ahead of time
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| 2004 JavaOneSM Conference | Session 2841
JAXB RI Thoughts
• Advantages
─ Standards-based (other implementations out there,
or coming)
─ Supports DTDs, Relax-NG, etc.
─ Interfaces look quite nice
• Disadvantages
─ Incomplete schema support
─ Generated code required casts (JAXB 2 should be
better with Generics, etc.)
• Overall
─ Not my first choice… yet.
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| 2004 JavaOneSM Conference | Session 2841
Castor Thoughts
• Advantages
─ Can operate without the schema compiler step
(using reflection only)
─ All generated code goes in one package, no class
bloat
─ Castor offers O/R features too
• Disadvantages
─ Incomplete schema support
─ Required manual mapping; some rough edges
• Overall
─ First choice for for on-the-fly mapping
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| 2004 JavaOneSM Conference | Session 2841
JiBX Thoughts
• Advantages
─ Small & fast
─ You write the code
• Disadvantages
─ You write the code – hopefully the right code
─ Bytecode mangling makes debugging hard
─ Still under active development (mapping file format
changes between beta releases, etc.)
• Overall
─ Best for small schemas, existing Java code, version
conflicts, etc.
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| 2004 JavaOneSM Conference | Session 2841
Agenda Progress
Overview of XML binding tools
Introduction to each tool in this talk
Sample code
Tool comparison
Q&A
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| 2004 JavaOneSM Conference | Session 2841
Q&A
http://java.sun.com/xml/jaxb/
http://www.castor.org/
http://xml.apache.org/xmlbeans/
http://www.jibx.org/
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| 2004 JavaOneSM Conference | Session 2841
Java to XML
Binding Tools
JAXB, Castor, XMLBeans, JiBX
Aaron Mulder
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| 2004 JavaOneSM Conference | Session 2841
java.sun.com/javaone/sf