com.xerox.bantam
Class Schema

java.lang.Object
  |
  +--com.xerox.bantam.Schema

All Implemented Interfaces:

Serializable

Direct Known Subclasses:

SchemaSchema

public class Schema

extends Object

implements Serializable

A Schema object is an immutable representation of a Bantam schema.

The Schema object allows the user to specify the enforcement of both the presence and type of document properties. To define a schema in code, create a subclass of Schema according to the following guidelines:

Define a method static public Schema getSchema() that returns an instance of the schema, preferably the same instance every time it is called. Repetitively generating new instances not only wastes memory but will prevent efficient validation, slowing down many operations.

Arrange to use the no-arguments constructor of Schema, preferably by creating the subclass with an empty no-argument constructor

Define a class variable for every schema field, with type exactly public static final com.xerox.bantam.FieldDescriptor and an initializer using one of the constructors of FieldDescriptor. With this form of definition, code can use the class variables to identify individual fields, and the single schema object to identify the schema with compile-time type checking. The no-argument public constructor of Schema will introspect to gather all required information. Alternatively, a subclass constructor can call a Schema constructor with an explicit list of FieldDescriptors.

To enable efficient validation of Schema objects when they are passed in Bantam methods, Schema objects must be immmutable. This is the reason why subclasses are not permitted to override getFields() or to access internal field records.

Version:

$Revision: 1.12 $, $Date: 2000/08/11 07:16:21 $

Author:

Keith Edwards

See Also:

Serialized Form

Inner Class Summary

protected class

Schema.fieldCompare Comparator for partial ordering by field name This comparator is inconsistent with equals for FieldDescriptor

Field Summary

protected String	name Name of the schema.
protected long	version Version of the schema.

Constructor Summary

protected	Schema() Constructor for subclasses which define a schema in code.
	Schema(String schemaName, FieldDescriptor[] f) Construct from field descriptors.

Method Summary

boolean	equals(Object obj) Equality test
FieldDescriptor[]	getFields() Return all field definitions in the schema
String	getName() Return schema name.
static Schema	getSchema(Class clazz) Retrieve the canonical instance of a schema by class
static Schema	getSchema(String name) Retrieve the canonical instance of a schema by name
static List	getSchemaFields(Class clazz) Get all the FieldDescriptors from clazz which are used to describe the schema they represent.
long	getVersion() Return a version stamp which is a signature value for this schema.
Schema	parse(String text) Create a Schema from a text definition
int	size() Return the number of entries in this schema.
String	toString()

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

name

protected String name

Name of the schema. Schemas are uniquely identified by name.

version

protected long version

Version of the schema. Schema version number is used for quick validation that two Schema objects with the same name represent precisely the same schema.

Constructor Detail

Schema

protected Schema()

Constructor for subclasses which define a schema in code. Automatically gathers FieldDescriptor definitions from public static final slots.

Schema

public Schema(String schemaName,
              FieldDescriptor[] f)

Construct from field descriptors.

Method Detail

getSchemaFields

public static List getSchemaFields(Class clazz)

Get all the FieldDescriptors from clazz which are used to describe the schema they represent.

getSchema

public static Schema getSchema(Class clazz)

Retrieve the canonical instance of a schema by class

Parameters:

name - the name of the schema to retrieve

getSchema

public static Schema getSchema(String name)

Retrieve the canonical instance of a schema by name

Parameters:

name - the name of the schema to retrieve

size

public int size()

Return the number of entries in this schema.

Returns:

int the number of SchemaEntries we hold

getName

public String getName()

Return schema name. A schema is uniquely identified by name.

getVersion

public long getVersion()

Return a version stamp which is a signature value for this schema. The signature is computed similarly to the computation of Java serialVersionUIDs.

getFields

public final FieldDescriptor[] getFields()

Return all field definitions in the schema

toString

public final String toString()

Overrides:

toString in class Object

parse

public Schema parse(String text)

Create a Schema from a text definition

equals

public boolean equals(Object obj)

Equality test

Overrides:

equals in class Object