SOA Learning Site: August 2014

Configuring datasources for RAC DB

Fast Connection Failover provides failover for a JDBC
connection to a 10g R1 or 10g R2 RAC database. Upon
failure of a RAC node, Oracle Notification Service (ONS) detects the failure
and an SQL exception is thrown to application code. To enable Fast Connection
Failover on APPHOST1 and APPHOST2:

1. Open the ORACLE_HOME/opmn/conf/opmn.xml file.

2. Add the RAC database hostname and remote port
identifiers:

<notification-server>

</topology>

</notification-server>

3. Save and close the file.

4. Open the ORACLE_HOME/j2ee/OC4J_SOA/config/data-sources.xml file.

5. Add the RAC node information and enable Fast Connection Failover.

<managed-data-source jndi-name="jdbc/TestDemoDS" description="Managed
DataSource for TestDemoDS" connection-pool-name="TestDemoDS
Connection Pool" name="TestDemoDS"/>

<connection-pool name="TestDemoDS Connection
Pool" min-connections="10" max-connections="30" inactivity-timeout="30">

<connection-factory factory-class="oracle.jdbc.pool.OracleDataSource" user="system" password="welcome1" url="jdbc:oracle:oci:@(DESCRIPTION=(LOAD_BALANCE=off) (ADDRESS=(PROTOCOL=TCP)(HOST=infradbhost1.mycompany.com)(PORT=1521))(ADDRESS=(PROTOCOL=TCP)(HOST=infradbhost2.mycompany.com)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=loon)))"/>

</connection-factory>

</connection-pool>

6. Save and close the file.

7. Issue this command in ORACLE_HOME/opmn/bin:

Opmnctl reload

Basics of SOA - XML

Before proceeding further to learn SOA, first we have to see what are the basic prerequisite technologies to be learned. The list is as below:

1) XML

2) XML Schema

3) WSDL

4) XPath

5) XSL

Let us start our journey from XML.

XML

----------

XML stands for eXtensible Markup Language and is mainly designed to transport and store data.
XML is a markup language much like HTML but XML tags are not predefined and we can define our own tags
XML is a software- and hardware-independent tool for carrying information

Example XML looks as below:

<?xml version="1.0" encoding="UTF-8"?>
<Letter xmlns=”http://Srini.blogs.com/letter”>
<to>Srini</to>
<from>Vas</from>
<Subject>Hello</Subject>
<body>Hello Everyone !!!</body>
</Letter>

The first line is the XML declaration. It defines the XML version (1.0) and encoding to be used for understanding data in XML.

The next line is Root element i.e <Letter>

Next 4 lines are the elements inside the root element and so they are called as child of the root element.

Last line ( </Letter>) defines the end of the root element.

After looking in to XML we can say it represents a tree structure which contains parent-child relationship.

Next we will see what are the rules to say an XML is well-formed. The conditions to be satisfied are :

All elements must have a closing tag. Eg: <Letter>…….</Letter>
XML tags are case sensitive. The tag <Letter> is different from the tag <letter>

· XML elements must be properly nested.

<Letter><From>abc</Letter></From> is illegal and

<Letter><From>abc</From></Letter> is correct since tags are properly nested.

XML documents must have a root element.

· XML documents must contain one element that is the parent of all other elements. This element is called the root element. In our example <Letter> is root element.

XML attribute values must be quoted

<Letter lang=eng>…</Letter> is illegal and

<Letter lang=”eng”>…</Letter> is correct since attribute value is in quotes.

Let us see some more features of XML below:

Comments in XML should be used as <! -- Comment -- >
White space values are preserved in XML. <name>Sri Ni</name> is preserved with space

Escape characters in XML:

Since XML elements are represented using ‘<’ and ‘>’ if the value of certain element contains ‘<’ or ‘>’ in its value then we need to use escaping to preserve the value correctly.

The below value of body should be as below:

<body> Hello < everyone </body>

‘<’ character in value will be understood as ending tag of body but it is not the one and so to preserve the value we need to write it as below:

<body> Hello < everyone </body> so that ‘<’ character in value is understood correctly by parser.

Similar list of escape characters are as below:

<	<	less than
>	>	greater than
&	&	ampersand
'	'	apostrophe
"	"	quotation mark

Naming rules for XML element value:

· Names can contain letters, numbers, and other characters. Eg: <bod12y>Srini</ bod12y > is valid.

· Names cannot start with a number or punctuation character. Eg: <1body>Srini</1body> is invalid

· Names cannot start with the letters xml (or XML, or Xml, etc) Eg: <xmlbody>Srini</ xmlbody > is invalid.

· Names cannot contain spaces. Eg: <na me>Srini</na me> is invalid

Namespaces:

In sample XML below, we are defining a namespace xmlns=http://srini.blogs.com/letter

<?xml version="1.0" encoding="UTF-8"?>
<Letter xmlns=”http://Srini.blogs.com/letter”>
<to>Srini</to>
<from>Vas</from>
<Subject>Hello</Subject>
<body>Hello Everyone !!!</body>
</Letter>

This namespace is used to resolve conflicts between same names in different XML.

Let us take one more example XML which shows the conflict.

<?xml version="1.0" encoding="UTF-8"?>
<Letter xmlns=”http://Srini.blogs.com/letter1”>
<reach>Srini</reach>
<sent>Vas</sent>
<Shortmessage>Hello</Shortmessage>
<message>Hello Everyone !!!</message>
</Letter>

If I am using both the above XML in one more XML then I will have a conflict if namespace http://srini.blogs.com/letter or http://srini.blogs.com/letter1 are not defined since both are having the same name Letter and we will get a conflict if I refer Letter to which Letter it will exactly refer.

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Wednesday, 20 August 2014

Configuring datasources for RAC DB in SOA 10G

Basics of SOA - XML