Introduction
In the realm of XML, one of the most powerful yet often misunderstood features is the CDATA section. CDATA, short for Character Data, is used in XML documents to include blocks of text that should not be treated as markup. This feature is particularly useful when embedding XML or HTML data within an XML document. Understanding how to work with CDATA sections is crucial for developers dealing with complex XML documents, as it allows for the inclusion of special characters and structured data without the risk of being misinterpreted by the XML parser.
This comprehensive guide will take you through the fundamentals of CDATA in XML, its practical applications, and how it can be effectively used and validated in tools like SoapUI. By the end of this article, you'll have a deep understanding of how to leverage CDATA sections in your XML documents to handle embedded content securely and efficiently.
What is CDATA in XML?
CDATA stands for Character Data, and it is used in XML to include blocks of text that should not be parsed by the XML parser as XML elements or attributes. The main purpose of CDATA is to allow the inclusion of text that contains characters normally treated as markup, such as <, >, and &, without requiring them to be escaped.
Structure of a CDATA Section
A CDATA section begins with <![CDATA[ and ends with ]]>. Everything inside these delimiters is treated as raw text by the XML parser, meaning that even if it contains characters that could be interpreted as XML markup, they are ignored.
Here’s an example:
xml
<message><![CDATA[<data>Some embedded XML</data>]]></message>In this example, the text <data>Some embedded XML</data> is treated as a string, not as XML markup. The parser will not attempt to interpret this content as XML, thus preventing any potential parsing errors.
Why Use CDATA in XML?
CDATA is particularly useful when you need to include content in an XML document that would otherwise interfere with the parsing process. This is common when embedding snippets of HTML, JavaScript, or even another XML document within an XML structure. By using CDATA sections, you can ensure that this content is included as-is, without any risk of it being misinterpreted.
Key Characteristics of CDATA
Non-Parsed: Content inside a CDATA section is not parsed as XML, which means it is not subject to validation or interpretation by the XML parser.
Escape-Free: You do not need to escape special characters like <, >, and & within a CDATA section, making it easier to include complex content.
Limited Nesting: CDATA sections cannot be nested directly because the ]]> sequence terminates the first CDATA section.
Practical Use Cases of CDATA in XML
CDATA sections are used in various scenarios where the content needs to be protected from being parsed as XML. Here are some common use cases:
1. Embedding HTML Content
One of the most common use cases for CDATA is embedding HTML within an XML document. For example, when XML is used to store or transport web content, you might need to include HTML markup within an XML tag.
Example:
xml
<description><![CDATA[<p>This is a <b>bold</b> statement!</p>]]></description>In this example, the HTML content inside the description tag is protected by CDATA, ensuring that it is treated as a plain string.
2. Storing JavaScript Code
When storing JavaScript code in an XML file, CDATA sections can be used to prevent the code from being parsed as XML.
Example:
xml
<script><![CDATA[
function sayHello() {
alert("Hello, World!");
}
]]></script>The JavaScript code within the CDATA section is preserved as-is, without any parsing or escaping.
3. Embedding XML Data
CDATA sections can also be used to embed an entire XML document within another XML document. This is useful when transporting or storing complex data structures.
Example:
xml
<metadata>
<data><![CDATA[<item><name>Example</name><value>123</value></item>]]></data>
</metadata>Here, the embedded XML document inside the data tag is treated as a string and not parsed as part of the outer XML document.
CDATA Sections in SoapUI
When working with SOAP messages or other XML-based protocols in SoapUI, you may encounter scenarios where parts of the payload are encapsulated in CDATA sections. While CDATA can simplify the inclusion of complex data, it also introduces challenges in processing, asserting, and validating XML content.
Handling CDATA in SOAP Messages
In SOAP messages, CDATA sections are often used to embed non-XML content or XML fragments that should not be processed by the parser. This can be both advantageous and challenging:
Advantages: Simplifies the inclusion of complex data without requiring escape sequences.
Challenges: Makes it harder to validate, assert, or manipulate the embedded data using standard XML tools.
Viewing CDATA in SoapUI
In SoapUI, CDATA sections are treated as strings rather than parsed XML. This means that when you view a SOAP message containing CDATA in the Outline or Overview tabs, the content inside the CDATA section is displayed as plain text. This can make it difficult to work with the embedded data directly.
Here’s an example of a SOAP response containing CDATA:
xml
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:sam="http://www.example.org/sample/">
<soapenv:Body>
<sam:searchResponse>
<item>
<id>1234</id>
<description><![CDATA[<item><width>123</width><height>345</height><length>098</length><isle>A34</isle></item>]]></description>
<price>123</price>
</item>
</sam:searchResponse>
</soapenv:Body>
</soapenv:Envelope>In SoapUI, the content inside the description tag is displayed as a string, not as XML, making it challenging to assert or validate this data using standard methods.
Property Transfers and CDATA Sections in SoapUI
Property Transfers in SoapUI are used to transfer data between test steps, such as copying values from one SOAP request to another. When dealing with CDATA sections, transferring values becomes more complex, as the content is treated as a string.
Transferring Values with CDATA
To transfer values from a CDATA section in one request to another, you can use a combination of temporary properties and the saxon:parse function. This allows you to treat the CDATA content as XML to extract and insert values.
Example Scenario
Suppose you have the following SOAP request and response, and you want to transfer the isle value from the response to the next request:
Response:
xml
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:sam="http://www.example.org/sample/">
<soapenv:Body>
<sam:searchResponse>
<item>
<description><![CDATA[<item><isle>A34</isle></item>]]></description>
</item>
</sam:searchResponse>
</soapenv:Body>
</soapenv:Envelope>Request:
xml
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
xmlns:sam="http://www.example.org/sample/">
<soapenv:Body>
<sam:search>
<searchstring><![CDATA[<isle>?</isle>]]></searchstring>
</sam:search>
</soapenv:Body>
</soapenv:Envelope>Steps to Transfer the Value:
Add a Temporary Property: Create a temporary property in the test case to hold the value extracted from the CDATA section.
First Property Transfer: Transfer the entire CDATA section from the response to the temporary property.
Second Property Transfer: Use the saxon:parse function to extract the desired value (isle) from the temporary property.
Final Property Transfer: Insert the extracted value into the request’s CDATA section.
This method ensures that the isle value is correctly transferred from the response to the next request, even though it is embedded within a CDATA section.
XPath Assertions and CDATA Sections
XPath is commonly used in SoapUI to assert the content of XML documents. However, when dealing with CDATA sections, standard XPath assertions cannot directly access the embedded XML content since it is treated as a string.
Using the saxon:parse Function
The saxon:parse function in XPath allows you to treat the content of a CDATA section as XML, enabling assertions on the embedded content.
Example Assertion
Suppose you want to assert that the isle value in the response is A34. You can use the saxon:parse function to parse the CDATA content and apply an XPath assertion.
XPath Assertion:
xpath
saxon:parse(//description/text())//isle = 'A34'This XPath expression parses the text inside the description tag as XML and then checks if the isle value is equal to A34.
Adding XPath Assertions in SoapUI
In SoapUI, you can add an XPath assertion directly in the Outline view:
Right-Click the Node: Right-click the node in the Outline view where you want to add the assertion.
Select Add Assertion: Choose Add Assertion > for Content.
Specify the XPath Expression: Enter the XPath expression using saxon:parse to validate the CDATA content.
This approach allows you to effectively assert the content of CDATA sections, ensuring that your SOAP messages contain the expected data.
Validation of CDATA Content
Validating the content of a CDATA section against an XML schema can be challenging since the schema typically defines the CDATA content as a simple string, not as a complex XML structure. However, with scripting, you can validate the embedded XML content against a schema.
Validating CDATA Content in SoapUI
To validate the content of a CDATA section, you can write a Groovy script that extracts the content, parses it as XML, and validates it against an XSD schema.
Example Script
groovy
import com.eviware.soapui.support.XmlHolder
import javax.xml.XMLConstants
import javax.xml.transform.stream.StreamSource
import javax.xml.validation.SchemaFactory
// Extract the CDATA content
def holder = new XmlHolder(messageExchange.responseContentAsXml)
holder.namespaces["sam"] = "http://www.example.org/sample/"
def node = holder["//description/text()"]
// Load the XSD schema
def factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI)
def schema = factory.newSchema(new StreamSource(new FileReader("path/to/your/schema.xsd")))
// Validate the extracted XML content
def validator = schema.newValidator()
validator.validate(new StreamSource(new StringReader(node)))This script extracts the content from the description tag, parses it as XML, and validates it against the specified XSD schema. This is particularly useful when you need to ensure that the embedded XML content conforms to a defined structure.
Using Schema Validation in Complex Scenarios
For more complex validation scenarios, you can use RelaxNG or DTD, depending on the requirements of your project. Groovy in SoapUI supports these formats, allowing for flexible validation of CDATA content.
Event Handlers to Simplify CDATA Processing
In some cases, you might want to preprocess the response to remove CDATA sections entirely, allowing the XML content to be processed as standard XML. This can be achieved using event handlers in ReadyAPI.
Removing CDATA Sections with an Event Handler
By removing the CDATA markers, you can simplify the process of transferring, asserting, and validating the embedded XML content.
Example Event Handler Script
groovy
def content = context.httpResponse.responseContent
content = content.replaceAll("<!\\[CDATA\\[", "")
content = content.replaceAll("]]>", "")
context.httpResponse.responseContent = contentThis script removes all CDATA markers from the response, enabling SoapUI to process the content as standard XML. While this approach may not be suitable for all scenarios, it can be useful for simplifying certain types of XML processing tasks.
Limitations of This Approach
While removing CDATA markers can make processing easier, it may also lead to issues with schema validation or handling of special characters. Therefore, this approach should be used with caution and only in scenarios where strict schema compliance is not required.
Conclusion
CDATA sections in XML are a powerful tool for embedding complex content within XML documents without risking parsing errors. However, working with CDATA sections requires a solid understanding of their structure, usage, and the challenges they present, particularly when working with tools like SoapUI.
In this guide, we’ve explored the fundamentals of CDATA, its practical applications, and how to manage CDATA sections effectively in SoapUI. By following the best practices and techniques outlined in this article, you can confidently handle CDATA sections in your XML documents, ensuring that your data is both secure and correctly processed.
Whether you’re embedding HTML, JavaScript, or another XML document within your XML structure, mastering CDATA will enhance your ability to work with complex data and improve the robustness of your XML-based applications.
Key Takeaways
CDATA in XML allows the inclusion of special characters and embedded XML without parsing issues.
SoapUI can handle CDATA sections but requires specific approaches for property transfers and assertions.
saxonfunction is crucial for asserting and manipulating CDATA content in SoapUI.
Validation of CDATA content can be achieved through scripting, ensuring compliance with XML schemas.
Event Handlers in ReadyAPI can simplify processing by removing CDATA markers, but this approach has limitations.
FAQs
1. What is CDATA in XML?
CDATA is a section in XML used to include text that should not be parsed by the XML parser, allowing special characters and embedded XML.
2. How do you embed HTML in XML using CDATA?
HTML can be embedded in XML using a CDATA section, which prevents the HTML content from being parsed as XML.
3. Can CDATA sections be nested in XML?
No, CDATA sections cannot be nested directly due to the way they are terminated.
4. How does SoapUI handle CDATA sections?
SoapUI treats CDATA sections as plain strings, which can complicate assertions and validations.
5. What is the saxon function in SoapUI?
The saxon function allows you to parse the content of a CDATA section as XML, enabling more complex assertions and data manipulations.
6. How can I validate CDATA content in SoapUI?
CDATA content can be validated using Groovy scripts that parse the content as XML and validate it against an XSD schema.
7. Is it possible to remove CDATA sections before processing?
Yes, event handlers in ReadyAPI can be used to remove CDATA markers, allowing the content to be processed as standard XML.
8. What are the limitations of using CDATA in XML?
CDATA sections cannot be nested, and removing CDATA markers can lead to issues with schema compliance and special character handling.
Comments