Oracle XML DB and Native Web Serviceskopecky/vyuka/oracle2/1213/xmldb.pdf · Oracle XML DBOracle XML DB RepositoryOracle XML DB Native Web Services XML/SQL Duality XML/SQL Duality

Oracle XML DB Oracle XML DB Repository Oracle XML DB Native Web Services

Oracle XML DB and Native Web Services

Ondrej Kupka

December 3, 2012


Section Layout

1 Oracle XML DBOverviewCore Ideas and ArchitectureStoring XML DataExampleStructured Model and XML SchemasXML/SQL Duality

2 Oracle XML DB Repository

3 Oracle XML DB Native Web Services


Overview

Overview and Architecture

Oracle XML DB is a set of technologies for handling of XML data:

Storing

Generating

Accessing

Searching

Validating

Transforming

Indexing

The goal is to provide both XML and SQL access to the data(XML/SQL duality). XML data can be accessed using SQL, XMLcan be generated from relational data.


Core Ideas and Architecture

Challenges and Ideas

We have a RDBMS and we have XML data. That is a completelydifferent thing. Relations and hierarchy is like apples and oranges.But we still have this RDBMS, so we should use it as much aspossible.

But we cannot say anything about a XML document’s structure.Unless we know the schema, that is!

Oracle XML DB: Abstract XMLType database object type, whichbasically behaves differently according to how much it knows aboutthe data. The access is the same, but the storage is optimisedwhen the structure is known.


Storing XML Data

Storing XML DataXMLType

XMLType is an abstract data type for native handling of XML datain the database.

It is a database object type - tables of XMLType.

It can be used as a column type.

It can be passed into and out of PL/SQL procedures.

It can use various storage models according to the situation.

. . .

Native XML operations (XMLType methods):

extract() - extract a subset of nodes

existsNode() - check if particular node exists in a XMLTypeinstance

schemaValidate() - validate the content of a XMLTypeinstance against a schema

transform() - XSLT


Storing XML Data

XMLType Storage Model

XMType tables and columns may be stored in these ways:

1 Structured storage (also object-relational, object-basedpersistence)

2 Unstructured storage (also CLOB, text-based persistence)

3 Binary XML (also post-parse persistence)

4 Hybrid of structured and unstructured


Storing XML Data

Intermezzo - Data-Centric vs. Document-CentricThe Interesting Part

What are those various backend models good for? Well, it dependson how you approach your data and how you use it!

Data-Centric

XML schema-based dataLittle variation and little change over timeLeads to Object-Relational approach, B-treeindices . . .

Document-Centric

Variable, free-form dataLeads to CLOB or Binary XML, XMLIndexindices . . .


Storing XML Data

Storage Models in Details - Structured Storage

Pros

Queries fast - relational query performanceUpdates fast - only the part affectedSpace efficiencyB-tree index

Cons

ThroughputData flexibility - schema conformanceSchema flexibility - one XMLType = singleschema


Storing XML Data

Storage Models in Details - XML Binary Storage

Pros

Throughput - just encode/decodeQueries - streaming XPath eval, multiple atonce, fast access using XMLIntexSpace efficiencyFlexibilityFull schema validation

Cons

Not really any significant disadvantage


Storing XML Data

Storage Models in Details - Unstructured Storage

Pros

ThroughputFlexibilityStreams-based replication

Cons

Queries slow - constructing DOM every timeUpdates slow - DOM, then the whole doc mustbe written backSpace inefficient


Example

ExampleCreate and Insert

Insert using SQL, PL/SQL, Java, C . . .

Conventional and Direct-Path Load Mode

CREATE TABLE mytable2 OF XMLType;

CREATE DIRECTORY xmldir AS path_to_folder_containing_XML_file;

INSERT INTO mytable2 VALUES (XMLType(bfilename(’XMLDIR’, ’file.xml’),

nls_charset_id(’AL32UTF8’)));

DECLARE

res BOOLEAN;

BEGIN

res := DBMS_XDB.createResource(’/home/user/...’,

bfilename(’XMLDIR’, ’file.xml’),

nls_charset_id(’AL32UTF8’));

END;/


Example

ExampleSelect

SELECT XMLCast(XMLQuery(’$p/<XPath>’ PASSING OBJECT_VALUE AS "p"

RETURNING CONTENT)

AS VARCHAR2(30)) "Reference"

FROM table

WHERE XMLExists(’$p/<XPath condition>’ PASSING OBJECT_VALUE AS "p");


Structured Model and XML Schemas

Structured Mode and XML Schemas

Oracle decomposes XML into SQL objects according to the XMLschema.

Mapping of XML types into SQL types (complexType intoSQL type)

Element or attribute becomes a SQL attribute in that type

Collections as tables or LOBs or out-of-line storage (REFs)

Full utilisation or Oracle database

Additional constrains not possible in a plain XML schemaIt is possible to annotate the XML schema to define storage model,override types mapping and name database objects.

xdb:storeVarrayAsTable="true"

<xs:attribute name="ItemID" type="xs:integer"

xdb:SQLName="ITEMID"

xdb:SQLType="NUMBER"/>


Structured Model and XML Schemas

XML Schemas Registration

You have to register your XML schemas before they can be used tovalidate objects. You need

1 The XML schema document

2 A string to be used as a identifier, typically an URL

BEGIN

DBMS_XMLSCHEMA.registerSchema(

SCHEMAURL => ’http://localhost:8080/src/schemas/xsd/file.xsd’,

SCHEMADOC => XDBURIType(’/src/schemas/xsd/file.xsd’).getCLOB(),

LOCAL => TRUE,

GENTYPES => TRUE,

GENTABLES => TRUE); # USUALLY YOU DON’T WANT THIS!!!

END;


XML/SQL Duality

XML/SQL Duality

The same data can be exposed as either rows in a table, beingmanipulated with SQL, or as nodes in a XML document andmanipulated using DOM, XSLT . . .

Oracle supports SQL/XML standard. This allows you address XMLcontent anywhere in your SQL. It uses XPath or XQuery to identifynodes to operate on.

XPath rewrite optimizes stuff.


XML/SQL Duality

XMLTable

Result of XMLQuery may include multiple elements without theroot node, so-called XML fragments. XMLTable can turn such afragment into multiple rows to perform joins and similar.

SELECT vt.COLUMN_VALUE

FROM table t,

XMLTable(’<XPath>’

PASSING t.OBJECT_VALUE) vt

WHERE XMLExists(’$t/<XPath>’

PASSING OBJECT_VALUE AS "t");

COLUMN_VALUE

------------

<e>...</e>

<e>...</e>

<e>...</e>

3 rows selected.


XML/SQL Duality

Relational Views

It is very simple, just create a view (CREATE OR REPLACEVIEW) using virtual tables!

Completely transparent to the view user


XML/SQL Duality

Generating XML Data from Relational Data

SQL/XML functions to construct XML

XMLElement

XMLAttributes

XMLForest

Use in the SELECT clause - SELECTXMLElement(XMLAttributes(...))

DBURIType

Simple way - convert table name into element, multiple¡ROW¿s containing columns as elements


Section Layout





Oracle XML DB Repository

It is an interface to your XML documents which imitates folder/filehierarchy. Data accessible using FTP, WebDAV, HTTP(S). It isbased on so-called resources. A resource is usually an XMLdocument. It has corresponding metadata file attached to it,holding ACL.


Accessing Repository from SQL

RESOURCE VIEW

Columns: RES, ANY PATH, RESID

PATH VIEW

Columns: PATH, RES, LINK, RESID

SELECT path(1) path, depth(1) depth FROM PATH_VIEW

WHERE under_path(RES, 3, ’/sys’, 1) = 1;


Section Layout





Oracle XML DB Native Web Services

You can enable web access for your XML DB in form of servlets.Log in as SYS. Use either xdbconfig or following. User needsXDB WEBSERVICES. WSDL generated automatically.

DECLARE

SERVLET_NAME VARCHAR2(32) := ’...’;

BEGIN

DBMS_XDB.deleteServletMapping(SERVLET_NAME);

DBMS_XDB.deleteServlet(SERVLET_NAME);

DBMS_XDB.addServlet(NAME => SERVLET_NAME,

LANGUAGE => ’C’,

DISPNAME => ’Web Service’,

DESCRIPT => ’Servlet for queries over the web’,

SCHEMA => ’XDB’);

DBMS_XDB.addServletSecRole(SERVNAME => SERVLET_NAME,

ROLENAME => ’XDB_WEBSERVICES’,

ROLELINK => ’XDB_WEBSERVICES’);

DBMS_XDB.addServletMapping(PATTERN => ’/wsv/*’,

NAME => SERVLET_NAME);

END;

/


Query Over The Web

<?xml version="1.0" ?>

<env:Envelope xmlns:env="http://www.w3.org/2002/06/soap-envelope ">

<env:Body>

<query xmlns="http://xmlns.oracle.com/orawsv">

<query_text type="SQL">

<![CDATA[SELECT * FROM employees WHERE salary = :e]]>

</query_text>

<bind name="e">50</bind>

<pretty_print>true</pretty_print>

</query>

</env:Body>

</env:Envelope>


PL/SQP Over The Web

You can use it, but it is a mess. You basically encode theparameters for the function into a SOAP request and do kind ofRPC, receiving the return value as XML again.


Thank you!

Oracle XML DB and Native Web Serviceskopecky/vyuka/oracle2/1213/xmldb.pdf · Oracle XML DBOracle XML DB RepositoryOracle XML DB Native Web Services XML/SQL Duality XML/SQL Duality

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