OIC - Handling Base64 Encoded JSON NXSD Parsing Issue in Oracle Integration Cloud (OIC)

📌 Problem Statement

In a Real-Time REST integration in Oracle Integration Cloud, the source system sends Base64 encoded JSON.

Flow:

Receive Base64 payload

Decode using oraext:decodeBase64()

Pass to Stage File → Read as JSON

❗ Issue Faced

After decoding, the JSON becomes invalid because:

The closing curly brace } is missing

This causes NXSD parsing errors in Stage File

🔍 Root Cause

During decoding or transformation:

Extra whitespace / formatting issues

Improper encoding at source

OIC string handling edge cases

👉 Result: JSON becomes malformed, especially missing }

💡 Solution Approach

Instead of directly parsing decoded JSON:

✅ Step 1: Decode Base64

✅ Step 2: Clean the JSON string

✅ Step 3: Validate & fix missing closing brace

✅ Step 4: Re-encode to Base64

✅ Step 5: Pass as Opaque to Stage File

🛠️ Implementation (XSLT Logic)

✅ Step 1: Decode Base64

Xslt

<xsl:variable name="decoded"

 select="oraext:decodeBase64(/nssrcmpr:execute/ns16:request-wrapper/ns16:message)"/>

✅ Step 2: Clean unwanted whitespace

Xslt

<xsl:variable name="cleaned"

  select="replace($decoded, '(:\s*&quot;)\s+', '$1')"/>

👉 Removes unnecessary spaces after : in JSON

✅ Step 3: Fix Missing Closing Brace

Xslt

<xsl:variable name="finalJson">

  <xsl:choose>

    <xsl:when test="contains($cleaned, '}')">

      <xsl:value-of select="$cleaned"/>

    </xsl:when>

    <xsl:otherwise>

      <xsl:value-of select="concat($cleaned, '}')"/>

    </xsl:otherwise>

  </xsl:choose>

</xsl:variable>

👉 Ensures JSON is always valid

✅ Step 4: Encode Back to Base64

Xslt

<xsl:value-of select="oraext:encodeBase64($finalJson)"/>

🔄 Integration Flow Design

🧩 OIC Flow Steps

REST Trigger

Stage File (Write File)

Write as Opaque

Use above XSLT

Stage File (Read File)

Now JSON is valid

Parse using NXSD schema

Continue processing…

🎯 Why Opaque Handling Works

Using opaque avoids:

Early validation failures

NXSD parsing errors on invalid JSON

👉 You fix JSON before parsing

⚠️ Best Practices

Always validate decoded payload:

Use contains() or ends-with() for }

Log decoded payload (for debugging)

Avoid direct parsing of decoded Base64 without validation

🏁 Conclusion

Handling Base64 JSON in OIC can be tricky due to:

Encoding inconsistencies

Transformation side effects

👉 The decode → clean → fix → re-encode → stage as opaque pattern is a reliable solution.

Code screenshots:

Stage write:

Code xslt:

Read json:

Code snippet:

<xsl:template match="/" xml:id="id_11">

  <nstrgmpr:Write xml:id="id_12">

    <ns31:opaqueElement>

      <!-- Step 1: Decode -->

      <xsl:variable name="decoded"     select="oraext:decodeBase64(/nssrcmpr:execute/ns16:request-wrapper/ns16:message)"/>

      <!-- Step 2: Clean whitespace after ":" -->

      <xsl:variable name="cleaned"

        select="replace($decoded, '(:\s*&quot;)\s+', '$1')"/>

      <!-- Step 3: Check and fix closing brace -->

      <xsl:variable name="finalJson">

        <xsl:choose>

          <xsl:when test="contains($cleaned, '}')">

            <xsl:value-of select="$cleaned"/>

          </xsl:when>

          <xsl:otherwise>

            <xsl:value-of select="concat($cleaned, '}')"/>

          </xsl:otherwise>

        </xsl:choose>

      </xsl:variable>

      <!-- Step 4: Encode back -->

      <xsl:value-of select="oraext:encodeBase64($finalJson)"/>

    </ns31:opaqueElement>

  </nstrgmpr:Write>

</xsl:template>