fix(loader): avoid NPE in FileLineFetcher close method & update HDFS test

[bajisn-666]

What is the purpose of the change
This PR fixes a NullPointerException in FileLineFetcher.java. The NPE occurred when the close() method was called, but the reader was null. This usually happens in multi-threaded environments or when file initialization fails.

Also updated HDFSLoadTest.java to use 4 threads to verify the fix in a concurrent scenario.

Related issues

Fixes #706

[Copilot]

Pull request overview

This PR addresses a NullPointerException issue in FileLineFetcher.java that occurred in multi-threaded environments when parser threads > 1. The fix adds null checks in the fetch(), skipOffset(), and checkMatchHeader() methods to handle cases where the reader might be null during concurrent execution.

Changes:

• Added null safety checks in FileLineFetcher.java to prevent NPE in multi-threaded scenarios
• Updated HDFS tests to use 4 parser threads to verify the fix works under concurrent load
• Refactored HDFSUtil.java test utility to simplify HDFS configuration handling
• Added .editorconfig rules for Parquet binary files to prevent editor corruption
• Added a test Parquet file

Reviewed changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
hugegraph-loader/src/main/java/org/apache/hugegraph/loader/reader/file/FileLineFetcher.java	Added null checks in fetch(), skipOffset(), and checkMatchHeader() methods to handle null reader scenarios
hugegraph-loader/src/test/java/org/apache/hugegraph/loader/test/functional/HDFSLoadTest.java	Increased parser thread count to 4 to test concurrent scenarios
hugegraph-loader/src/test/java/org/apache/hugegraph/loader/test/functional/HDFSUtil.java	Simplified HDFS configuration and refactored utility methods
.editorconfig	Added configuration for Parquet files to prevent binary file corruption
hugegraph-loader/src/test/resources/parquet_compress_file/vertex_person.parquet	Added test Parquet file for testing

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[Copilot]

Contradictory null checking logic: Line 201 enforces that reader must not be null with E.checkState(this.reader != null, ...), but then lines 206-209 add a null check inside the loop. If the reader can become null during iteration (e.g., in a multi-threaded environment), the initial check at line 201 is insufficient. If it cannot, then the null check inside the loop is unnecessary. Consider either: 1) removing the check at line 201 and relying on the null check in the loop, or 2) using synchronized access if reader can be modified by other threads.

Suggested change

	// Fix NPE: check reader again inside loop
	if (this.reader == null) {
	throw new LoadException("Reader is null when skipping offset of file %s",
	readable);
	}

[Copilot]

PR title mentions "avoid NPE in FileLineFetcher close method" but no changes were made to the closeReader() method (lines 151-155), which already has a null check for this.reader. The actual changes are in fetch(), skipOffset(), and checkMatchHeader() methods. Consider updating the PR title to accurately reflect what was changed, e.g., "fix: add null checks in FileLineFetcher fetch/skipOffset/checkMatchHeader methods".

[Copilot]

Comment contains Chinese text in a codebase that appears to use English for comments. For consistency, consider translating to English, e.g., "Modification point 1: Increase concurrent parser thread count".

[Copilot]

Comment contains Chinese text in a codebase that appears to use English for comments. For consistency, consider translating to English, e.g., "Modification point 2: Increase concurrent parser thread count".

[Copilot]

Comment contains Chinese text in a codebase that appears to use English for comments. For consistency, consider translating to English, e.g., "Usually in test scenarios, upload local files to HDFS".

Suggested change

	// 通常测试场景是将本地文件上传到 HDFS
	// Usually in test scenarios, upload local files to HDFS

[Copilot]

Comment contains Chinese text. For consistency with the rest of the file and international collaboration, consider using English, e.g., "Key change: Prevent editor from corrupting Parquet binary files".

Suggested change

	# 关键修改：防止编辑器破坏 Parquet 二进制文件
	# Key change: Prevent editor from corrupting Parquet binary files

[imbajin]

use style file to avoid code format diff

https://github.com/apache/incubator-hugegraph-toolchain/blob/master/.editorconfig (use it to override original IDE format)

[imbajin]

hit 100 chars in one line here?

[imbajin]

seems the judgement logic in method is not precise & duplicated

maybe we have a better solution for it

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 51.49%. Comparing base (b066b80) to head (c6a2b0d).
⚠️ Report is 66 commits behind head on master.

Files with missing lines	Patch %	Lines
.../hugegraph/loader/reader/file/FileLineFetcher.java	25.00%	4 Missing and 2 partials ⚠️

❗ There is a different number of reports uploaded between BASE (b066b80) and HEAD (c6a2b0d). Click for more details.

HEAD has 1 upload less than BASE

Flag	BASE (b066b80)	HEAD (c6a2b0d)
	2	1

Additional details and impacted files

@@              Coverage Diff              @@
##             master     #710       +/-   ##
=============================================
- Coverage     62.49%   51.49%   -11.01%     
+ Complexity     1903      973      -930     
=============================================
  Files           262      111      -151     
  Lines          9541     5861     -3680     
  Branches        886      755      -131     
=============================================
- Hits           5963     3018     -2945     
+ Misses         3190     2580      -610     
+ Partials        388      263      -125     

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