Read XML Resource in Oracle Service Bus 11g

Some time ago I was thinking in how to read XML Resources available in OSB projects at runtime. It would be very useful to hold some configuration data to be read by the proxy services through XPath or Java Call. After many searches in Google, I did not find any documentation or example in how to read OSB resources content programmatically at runtime. The popular OSB APIs and MBeans do not provide any method to get the resources content, but only their references. The question was how to get the resources content through their references.

With the help of JShrink I spent some time decompiling the OSB native jar functions and making a reverse engineering to discover how to do this. Fortunately, after some good tries I found what I was looking for. Using some internal OSB built-in libraries we can access any project resource at runtime.

In this article I will show how to read a sample XML Resource programmatically at runtime. In this sample I will use a Custom XPath to read a XML resource that holds application configuration parameters. Obs.: the same API shown here can also be used into a Java Call.

The sample project structure will look like this:

File “xsd/Parameters.xsd”: a simple schema that we’ll use in this scenario to describe the XML structure that holds the parameters:

<xsd:complexType name="Parameters">
	<xsd:sequence>
		<xsd:element name="ParameterList" type="tns:ParameterList"/>
	</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="ParameterList">
	<xsd:sequence>
		<xsd:element name="Parameter" type="tns:Parameter" minOccurs="0" maxOccurs="unbounded"/>
	</xsd:sequence>
</xsd:complexType>
<xsd:complexType name="Parameter">
	<xsd:sequence>
		<xsd:element name="Key" type="xsd:string"/>
		<xsd:element name="Value" type="xsd:string"/>
	</xsd:sequence>
</xsd:complexType>

File “xml/Parameters.xml”: the sample XML that will be read by our XPath function at runtime:

<ns0:Parameters xmlns:ns0="https://gibaholms.wordpress.com/samples/xsd/2012/02/parameters">
	<ns0:ParameterList>
		<ns0:Parameter>
			<ns0:Key>Color</ns0:Key>
			<ns0:Value>Blue</ns0:Value>
		</ns0:Parameter>
		<ns0:Parameter>
			<ns0:Key>Size</ns0:Key>
			<ns0:Value>500</ns0:Value>
		</ns0:Parameter>
	</ns0:ParameterList>
</ns0:Parameters>

File “xq/ReadXmlParameters.xq”: a sample test XQuery that calls our XPath function passing as argument the full reference path to the XML parameters file:

xquery version "1.0" encoding "Cp1252";
(:: pragma bea:schema-type-return type="ns0:Parameters" location="../xsd/Parameters.xsd" ::)

declare namespace xf = "http://tempuri.org/ReadXmlResource/xq/ReadXmlParameters/";
declare namespace ns0 = "https://gibaholms.wordpress.com/samples/xsd/2012/02/parameters";
declare namespace param = "https://gibaholms.wordpress.com/xpath/ReadXmlResource";

declare function xf:ReadXmlParameters() as element() {
    param:readXml("ReadXmlResource/xml/Parameters")
};

xf:ReadXmlParameters()

Now, let’s create the custom XPath that does the magic. Create a simple Java project and add the following compile dependencies:

• <MIDDLEWARE_HOME>\Oracle_OSB1\modules\com.bea.common.configfwk_1.5.0.0.jar
• <MIDDLEWARE_HOME>\Oracle_OSB1\modules\com.bea.core.xml.xmlbeans_2.1.0.0_2-5-1.jar
• <MIDDLEWARE_HOME>\Oracle_OSB1\lib\modules\com.bea.alsb.resources.core.jar
• <MIDDLEWARE_HOME>\Oracle_OSB1\lib\modules\com.bea.alsb.resources.xml.jar

The XPath project structure is shown below:

In the file “osb-readxmlresourcefunction.xml” we describe the XPath functions contract. This file is a requirement of OSB and must be copied to the functions directory with the generated jar file:

<xpf:xpathFunctions xmlns:xpf="http://www.bea.com/wli/sb/xpath/config">
	<xpf:category id="Custom Functions">
		<xpf:function>
			<xpf:name>readXml</xpf:name>
			<xpf:comment>This function reads a XML Resource file from OSB</xpf:comment>
			<xpf:namespaceURI>https://gibaholms.wordpress.com/xpath/ReadXmlResource</xpf:namespaceURI>
			<xpf:className>com.wordpress.gibaholms.xpath.ReadXmlResource</xpf:className>
			<xpf:method>org.apache.xmlbeans.XmlObject readXml(java.lang.String)</xpf:method>
			<xpf:isDeterministic>true</xpf:isDeterministic>
			<xpf:scope>Pipeline</xpf:scope>
			<xpf:scope>SplitJoin</xpf:scope>
		</xpf:function>
	</xpf:category>
</xpf:xpathFunctions>

The secret to access OSB resources at runtime is the various “*Repository” classes. The code of our “readXml” XPath function is shown below:

package com.wordpress.gibaholms.xpath;

import org.apache.xmlbeans.XmlException;
import org.apache.xmlbeans.XmlObject;

import com.bea.wli.config.Ref;
import com.bea.wli.config.component.NotFoundException;
import com.bea.wli.sb.resources.config.XmlEntryDocument;
import com.bea.wli.sb.resources.xml.XmlRepository;

public class ReadXmlResource {

	public static XmlObject readXml(String xmlRefPath) {
		Ref ref = new com.bea.wli.config.Ref("XML", Ref.getNames(xmlRefPath));
		XmlObject xmlObject = null;
		try {
			XmlEntryDocument xmlEntryDocument = XmlRepository.get().getEntry(ref);
			String xmlContent = xmlEntryDocument.getXmlEntry().getXmlContent();
			xmlObject = XmlObject.Factory.parse(xmlContent);
		} catch (NotFoundException e) {
			e.printStackTrace();
			throw new RuntimeException("XML Resource not found.");
		} catch (XmlException e) {
			e.printStackTrace();
			throw new RuntimeException("Error parsing XML content.", e);
		}
		return xmlObject;
	}
	
}

As we can see in the code, the class “com.bea.wli.sb.resources.xml.XmlRepository” does the magic of retrieve the XML resource content through it “com.bea.wli.config.Ref” reference. Following the same principle, we can use the other various “*Repository” classes to access other types of resources in projects at runtime, like Schemas, XSLTs, WSDLs and so on.

To test the function, just run the XQuery “xq/ReadXmlParameters.xq” in the sbconsole:

The test XQuery has no parameters, so just execute it:

Then you must see the parameters XML loaded at runtime, like shown below:

I’m glad to share this discovery with other ALSB / OSB developers and I hope help you to do more useful things with this knowledge.

If someone already has another solution to read OSB project resources at runtime or already use this API for some other purpose, please share the experience with us through comments. Thanks.

Attachments

Source Code:
https://github.com/gibaholms/articles/tree/master/Read_XML_Resource_in_OSB

Gilberto Holms