Merge pull request eugenp#17840 from AndreiBranza/BAEL-8046-get-the-s…

…chema-from-an-avro-file

BAEL-8046 | Article code

apache-libraries/pom.xml

@@ -104,7 +104,7 @@
         <bval.version>3.0.1</bval.version>
         <jakarta.validation.validation-api.version>3.1.0</jakarta.validation.validation-api.version><opennlp.opennlp-tools.version>1.8.4</opennlp.opennlp-tools.version>
         <solr.solr-solrj.version>6.4.0</solr.solr-solrj.version>
-        <apache.avro.version>1.11.3</apache.avro.version>
+        <apache.avro.version>1.12.0</apache.avro.version>
     </properties>
 
 </project>

apache-libraries/src/main/java/com/baeldung/apache/avro/schemafromavrofile/AvroSchemaExtractor.java

@@ -0,0 +1,41 @@
+package com.baeldung.apache.avro.schemafromavrofile;
+
+import org.apache.avro.Schema;
+import org.apache.avro.file.DataFileReader;
+import org.apache.avro.generic.GenericDatumReader;
+import org.apache.avro.generic.GenericRecord;
+import org.apache.avro.io.DatumReader;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+public class AvroSchemaExtractor {
+
+    public static Schema extractSchema(String avroFilePath) throws IOException {
+
+        File avroFile = new File(avroFilePath);
+        DatumReader<GenericRecord> datumReader = new GenericDatumReader<>();
+
+        try (DataFileReader<GenericRecord> dataFileReader = new DataFileReader<>(avroFile, datumReader)) {
+            return dataFileReader.getSchema();
+        }
+    }
+
+    public static List<GenericRecord> readAvroData(String avroFilePath) throws IOException {
+
+        File avroFile = new File(avroFilePath);
+        DatumReader<GenericRecord> datumReader = new GenericDatumReader<>();
+        List<GenericRecord> records = new ArrayList<>();
+
+        try (DataFileReader<GenericRecord> dataFileReader = new DataFileReader<>(avroFile, datumReader)) {
+            GenericRecord record = null;
+            while (dataFileReader.hasNext()) {
+                record = dataFileReader.next(record);
+                records.add(record);
+            }
+        }
+        return records;
+    }
+}

apache-libraries/src/test/java/com/baeldung/apache/avro/schemafromavrofile/AvroSchemaExtractorUnitTest.java

@@ -0,0 +1,65 @@
+package com.baeldung.apache.avro.schemafromavrofile;
+
+import org.apache.avro.Schema;
+import org.apache.avro.file.DataFileWriter;
+import org.apache.avro.generic.GenericData;
+import org.apache.avro.generic.GenericDatumWriter;
+import org.apache.avro.generic.GenericRecord;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Path;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+public class AvroSchemaExtractorUnitTest {
+
+    @TempDir
+    Path tempDir;
+
+    private File avroFile;
+    private Schema schema;
+
+    @BeforeEach
+    void setUp() throws IOException {
+        schema = new Schema.Parser().parse("""
+                                        {
+                                            "type": "record",
+                                            "name": "User",
+                                            "fields": [
+                                                {"name": "name", "type": "string"},
+                                                {"name": "age", "type": "int"}
+                                            ]
+                                        }
+                                        """);
+        avroFile = tempDir.resolve("test.avro").toFile();
+
+        GenericRecord user1 = new GenericData.Record(schema);
+        user1.put("name", "John Doe");
+        user1.put("age", 30);
+
+        try (DataFileWriter<GenericRecord> dataFileWriter = new DataFileWriter<>(new GenericDatumWriter<>(schema))) {
+            dataFileWriter.create(schema, avroFile);
+            dataFileWriter.append(user1);
+        }
+    }
+
+    @Test
+    void whenSchemaIsExistent_thenItIsExtractedCorrectly() throws IOException {
+        Schema extractedSchema = AvroSchemaExtractor.extractSchema(avroFile.getPath());
+
+        assertEquals(schema, extractedSchema);
+    }
+
+    @Test
+    void whenAvroFileHasContent_thenItIsReadCorrectly() throws IOException {
+        List<GenericRecord> records = AvroSchemaExtractor.readAvroData(avroFile.getPath());
+
+        assertEquals("John Doe", records.get(0).get(0).toString());
+    }
+}