MLE-26838: Added null check for conf.getStrings() method in various files

[SiddharthMaheshB]

As part of Polaris Null Pointer Dereference issues cleanup, I have added null checks for the conf.getStrings() method in the following files:

    InternalUtilities.java
    PermissionUtil.java
    RDFReader.java
    InputType.java
    ThreadManager.java
    TransformOutputFormat.java
    ContentOutputFormat.java

[Copilot]

Pull request overview

Adds defensive checks around Configuration#getStrings(...) results to avoid null pointer dereferences during host resolution/config parsing across MapReduce + Content Pump components.

Changes:

• Add null/empty-array validation for INPUT_HOST / OUTPUT_HOST before indexing [0].
• Fail fast with IllegalArgumentException when required host lists are missing.
• Apply the pattern across utilities, readers, formats, and thread management.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/main/java/com/marklogic/mapreduce/utilities/InternalUtilities.java	Guards getStrings(INPUT_HOST) before indexing to avoid NPE.
src/main/java/com/marklogic/mapreduce/ContentOutputFormat.java	Validates OUTPUT_HOST when restrictHosts is enabled.
src/main/java/com/marklogic/contentpump/utilities/PermissionUtil.java	Validates OUTPUT_HOST before selecting first host for session creation.
src/main/java/com/marklogic/contentpump/TransformOutputFormat.java	Validates OUTPUT_HOST before attempting to query MIME types.
src/main/java/com/marklogic/contentpump/ThreadManager.java	Validates OUTPUT_HOST list before iterating for host checks.
src/main/java/com/marklogic/contentpump/RDFReader.java	Validates OUTPUT_HOST before selecting first host for permissions initialization.
src/main/java/com/marklogic/contentpump/InputType.java	Validates OUTPUT_HOST before iterating through hosts for connection attempts.

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[Copilot]

This change prevents NPE on a null/empty array, but it also removes the previous validation that hosts[0] itself is non-null/non-empty. As a result, a config like INPUT_HOST= (or an array containing null) will pass the new guard and can still fail later (or attempt to connect with an invalid hostname). Consider restoring a value-level check (e.g., null/blank after trimming) for hosts[0], or switch to a trimmed-string API and validate the first entry.

Suggested change

	if (host == null || host.trim().isEmpty()) {
	throw new IllegalArgumentException(INPUT_HOST +
	" is not specified.");
	}

[Copilot]

The new guard ensures the array exists, but individual entries may still be blank/whitespace (or null), which can cause connection attempts with invalid hostnames inside the loop. Add validation inside the loop (or pre-filter/normalize the array) to reject/skip empty hosts deterministically.

Suggested change

	}
	for (String host : hosts) {
	}
	List<String> validHosts = new ArrayList<String>();
	for (String host : hosts) {
	if (host != null && !host.trim().isEmpty()) {
	validHosts.add(host);
	}
	}
	if (validHosts.isEmpty()) {
	throw new IllegalArgumentException(MarkLogicConstants.OUTPUT_HOST +
	" does not contain any valid non-empty host values.");
	}
	for (String host : validHosts) {

[Copilot]

The same getStrings(...) null/length check + identical exception message is now repeated across several files in this PR. To reduce duplication and keep host-validation semantics consistent (including trimming/blank checks), consider extracting a shared helper (e.g., in InternalUtilities) that returns a validated host list (or first host) and throws a consistent error when missing/invalid.