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AVRO-4242: [Java] Fix NPE in DataFileStream and DataFileReader when schema metadata is missing #3726

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Merged
iemejia merged 1 commit into from
Jul 11, 2026
Merged

AVRO-4242: [Java] Fix NPE in DataFileStream and DataFileReader when schema metadata is missing #3726

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11 changes: 7 additions & 4 deletions lang/java/avro/src/main/java/org/apache/avro/file/DataFileReader12.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,8 +17,8 @@
*/
package org.apache.avro.file;

import java.io.IOException;
import java.io.Closeable;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.util.Arrays;
Expand All @@ -27,12 +27,11 @@
import java.util.Map;

import org.apache.avro.InvalidAvroMagicException;
import org.apache.avro.JsonSchemaParser;
import org.apache.avro.Schema;
import org.apache.avro.UnknownAvroCodecException;
import org.apache.avro.io.BinaryDecoder;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DecoderFactory;
import org.apache.avro.io.BinaryDecoder;

/** Read files written by Avro version 1.2. */
public class DataFileReader12<D> implements FileReader<D>, Closeable {
Expand Down Expand Up @@ -89,7 +88,7 @@ public DataFileReader12(SeekableInput sin, DatumReader<D> reader) throws IOExcep
if (codec != null && !codec.equals(NULL_CODEC)) {
throw new UnknownAvroCodecException("Unknown codec: " + codec);
}
this.schema = JsonSchemaParser.parseInternal(getMetaString(SCHEMA));
this.schema = parseSchema();
this.reader = reader;

reader.setSchema(schema);
Expand All @@ -116,6 +115,10 @@ public synchronized long getMetaLong(String key) {
return Long.parseLong(getMetaString(key));
}

private Schema parseSchema() throws IOException {
return DataFileStream.parseSchemaFromMetadata(getMetaString(SCHEMA), SCHEMA);
}

/** Return the schema used in this file. */
@Override
public Schema getSchema() {
Expand Down
17 changes: 16 additions & 1 deletion lang/java/avro/src/main/java/org/apache/avro/file/DataFileStream.java
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Expand Up @@ -141,7 +141,7 @@ void initialize(InputStream in, byte[] magic) throws IOException {

// finalize the header
header.metaKeyList = Collections.unmodifiableList(header.metaKeyList);
header.schema = JsonSchemaParser.parseInternal(getMetaString(DataFileConstants.SCHEMA));
header.schema = parseHeaderSchema();
this.codec = resolveCodec();
reader.setSchema(header.schema);
}
Expand Down Expand Up @@ -198,6 +198,21 @@ public long getMetaLong(String key) {
return Long.parseLong(getMetaString(key));
}

static Schema parseSchemaFromMetadata(String schemaJson, String schemaMetadataKey) throws IOException {
if (schemaJson == null) {
throw new IOException("Missing required metadata: " + schemaMetadataKey);
}
try {
return JsonSchemaParser.parseInternal(schemaJson);
} catch (AvroRuntimeException e) {
throw new IOException("Invalid schema in metadata: " + schemaMetadataKey, e);
}
}

private Schema parseHeaderSchema() throws IOException {
return parseSchemaFromMetadata(getMetaString(DataFileConstants.SCHEMA), DataFileConstants.SCHEMA);
}

/**
* Returns an iterator over entries in this file. Note that this iterator is
* shared with other users of the file: it does not contain a separate pointer
Expand Down
83 changes: 83 additions & 0 deletions lang/java/avro/src/test/java/org/apache/avro/TestDataFileReader.java
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Expand Up @@ -24,19 +24,27 @@
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.lang.management.ManagementFactory;
import java.lang.management.OperatingSystemMXBean;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import com.sun.management.UnixOperatingSystemMXBean;
import org.apache.avro.file.DataFileReader;
import org.apache.avro.file.DataFileConstants;
import org.apache.avro.file.DataFileReader12;
import org.apache.avro.file.DataFileStream;
import org.apache.avro.file.DataFileWriter;
import org.apache.avro.file.FileReader;
import org.apache.avro.file.SeekableByteArrayInput;
import org.apache.avro.file.SeekableFileInput;
import org.apache.avro.file.SeekableInput;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.io.BinaryEncoder;
import org.apache.avro.io.EncoderFactory;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.io.TempDir;

Expand Down Expand Up @@ -236,4 +244,79 @@ void invalidMagicBytes() throws IOException {
() -> DataFileReader.openReader(fileInput, new GenericDatumReader<>()));
}
}

@Test
void missingSchemaMetadataDoesNotThrowNullPointerException() throws IOException {
byte[] malformedFile = buildContainerHeaderWithoutSchema();

IOException streamException = assertThrows(IOException.class,
() -> new DataFileStream<>(new ByteArrayInputStream(malformedFile), new GenericDatumReader<>()));
assertNotNull(streamException.getMessage());
assertTrue(streamException.getMessage().contains(DataFileConstants.SCHEMA));

IOException readerException = assertThrows(IOException.class,

@nandorKollar nandorKollar Apr 17, 2026

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You mentioned DataFileReader12 in the PR (and the problem was indeed fixed there too), does this test case give sufficient coverage to verify those changes too?

@iemejia iemejia Jul 11, 2026

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Good point - the existing test only covers DataFileStream and DataFileReader (current format). It does not exercise DataFileReader12 since that class uses a different binary layout (footer-based metadata).

I've now added a dedicated test (missingSchemaMetadataInVersion12DoesNotThrowNullPointerException) that constructs a minimal Avro 1.2 format container with the sync marker but no schema entry, and asserts that DataFileReader12 throws a descriptive IOException rather than an NPE.

() -> new DataFileReader<>(new SeekableByteArrayInput(malformedFile), new GenericDatumReader<>()));
assertNotNull(readerException.getMessage());
assertTrue(readerException.getMessage().contains(DataFileConstants.SCHEMA));
}

private static byte[] buildContainerHeaderWithoutSchema() throws IOException {
ByteArrayOutputStream output = new ByteArrayOutputStream();
output.write(DataFileConstants.MAGIC);

BinaryEncoder encoder = EncoderFactory.get().binaryEncoder(output, null);
encoder.writeMapStart();
encoder.setItemCount(1);
encoder.startItem();
encoder.writeString(DataFileConstants.CODEC);
encoder.writeBytes("null".getBytes(StandardCharsets.UTF_8));
encoder.writeMapEnd();
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encoder.writeFixed(new byte[DataFileConstants.SYNC_SIZE]);
encoder.flush();

return output.toByteArray();
}

@Test
void missingSchemaMetadataInVersion12DoesNotThrowNullPointerException() throws IOException {
byte[] malformedFile = buildVersion12ContainerWithoutSchema();

IOException exception = assertThrows(IOException.class,
() -> new DataFileReader12<>(new SeekableByteArrayInput(malformedFile), new GenericDatumReader<>()));
assertNotNull(exception.getMessage());
assertTrue(exception.getMessage().contains("schema"));
}

/**
* Builds a minimal Avro 1.2 format container with the footer metadata map
* containing only a sync marker but no schema entry.
*/
private static byte[] buildVersion12ContainerWithoutSchema() throws IOException {
ByteArrayOutputStream output = new ByteArrayOutputStream();
// Avro 1.2 magic: 'O' 'b' 'j' 0x00
output.write(new byte[] { (byte) 'O', (byte) 'b', (byte) 'j', 0 });

// Write the footer (metadata map with sync but no schema)
ByteArrayOutputStream footer = new ByteArrayOutputStream();
BinaryEncoder encoder = EncoderFactory.get().binaryEncoder(footer, null);
encoder.writeMapStart();
encoder.setItemCount(1);
encoder.startItem();
encoder.writeString("sync");
encoder.writeBytes(new byte[16]); // 16-byte sync marker
encoder.writeMapEnd();
encoder.flush();

byte[] footerBytes = footer.toByteArray();
// Footer size includes the 4 bytes for the size itself
int footerSize = footerBytes.length + 4;
output.write(footerBytes);
// Write footer size as big-endian 4 bytes at the end
output.write((footerSize >> 24) & 0xFF);
output.write((footerSize >> 16) & 0xFF);
output.write((footerSize >> 8) & 0xFF);
output.write(footerSize & 0xFF);

return output.toByteArray();
}
}
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