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Fix #275: add test to show usage (#634)
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‎avro/src/test/java/com/fasterxml/jackson/dataformat/avro/schemaev/EnumEvolutionTest.java‎

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@@ -33,7 +33,7 @@ protected static class Employee {
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public Gender gender;
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}
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private final AvroMapper MAPPER = new AvroMapper();
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private final AvroMapper MAPPER = newMapper();
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@Test
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public void testSimple() throws Exception

‎avro/src/test/java/com/fasterxml/jackson/dataformat/avro/schemaev/Evolution275Test.java‎

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package com.fasterxml.jackson.dataformat.avro.schemaev;
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import org.junit.jupiter.api.Test;
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import com.fasterxml.jackson.annotation.JsonInclude;
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import com.fasterxml.jackson.core.io.JsonEOFException;
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import com.fasterxml.jackson.dataformat.avro.*;
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import static org.junit.jupiter.api.Assertions.*;
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/**
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* Test for issue #275: Avro backward compatibility when adding fields with default values.
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* <p>
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* This test demonstrates that Jackson Avro DOES support backward compatibility correctly,
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* but users MUST use the {@code withReaderSchema()} method to enable schema resolution.
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* <p>
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* The key insight is that Avro binary format does not include schema metadata in the
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* serialized data. Therefore, when reading data that was written with schema A using
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* schema B, the library needs to be explicitly told about both schemas through the
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* {@code withReaderSchema()} API.
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* <p>
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* Common mistake: Trying to read old data with a new schema directly leads to
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* "Unexpected end-of-input" errors because the parser tries to read fields that
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* don't exist in the binary data.
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* <p>
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* Correct usage pattern:
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* <pre>
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* // Write with old schema
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* AvroSchema writerSchema = mapper.schemaFrom(OLD_SCHEMA_JSON);
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* byte[] data = mapper.writer(writerSchema).writeValueAsBytes(object);
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*
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* // Read with new schema (that has additional fields with defaults)
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* AvroSchema readerSchema = mapper.schemaFrom(NEW_SCHEMA_JSON);
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* AvroSchema resolved = writerSchema.withReaderSchema(readerSchema);
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* MyObject result = mapper.readerFor(MyObject.class)
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* .with(resolved) // Use resolved schema, not readerSchema directly!
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* .readValue(data);
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* </pre>
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*/
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public class Evolution275Test extends AvroTestBase
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{
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// Original schema with 8 fields (simulating the issue scenario)
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static String SCHEMA_V1_JSON = aposToQuotes("{\n"+
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" 'type':'record',\n"+
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" 'name':'Employee',\n"+
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" 'fields':[\n"+
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" { 'name':'code', 'type':'string' },\n"+
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" { 'name':'countryCode', 'type':'string' },\n"+
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" { 'name':'createdBy', 'type':'string' },\n"+
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" { 'name':'createdDate', 'type':'string' },\n"+
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" { 'name':'id', 'type':'long' },\n"+
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" { 'name':'lastModifiedBy', 'type':'string' },\n"+
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" { 'name':'lastModifiedDate', 'type':'string' },\n"+
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" { 'name':'name', 'type':'string' }\n"+
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" ]\n"+
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"}\n");
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// Updated schema adding a 9th field with null default at the end
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static String SCHEMA_V2_JSON = aposToQuotes("{\n"+
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" 'type':'record',\n"+
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" 'name':'Employee',\n"+
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" 'fields':[\n"+
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" { 'name':'code', 'type':'string' },\n"+
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" { 'name':'countryCode', 'type':'string' },\n"+
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" { 'name':'createdBy', 'type':'string' },\n"+
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" { 'name':'createdDate', 'type':'string' },\n"+
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" { 'name':'id', 'type':'long' },\n"+
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" { 'name':'lastModifiedBy', 'type':'string' },\n"+
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" { 'name':'lastModifiedDate', 'type':'string' },\n"+
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" { 'name':'name', 'type':'string' },\n"+
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" { 'name':'phone', 'type':['null', 'string'], 'default':null }\n"+
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" ]\n"+
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"}\n");
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// Simpler test with just 2 fields + new field with null default
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static String SCHEMA_SIMPLE_V1_JSON = aposToQuotes("{\n"+
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" 'type':'record',\n"+
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" 'name':'SimpleRecord',\n"+
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" 'fields':[\n"+
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" { 'name':'id', 'type':'int' },\n"+
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" { 'name':'name', 'type':'string' }\n"+
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" ]\n"+
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"}\n");
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static String SCHEMA_SIMPLE_V2_JSON = aposToQuotes("{\n"+
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" 'type':'record',\n"+
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" 'name':'SimpleRecord',\n"+
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" 'fields':[\n"+
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" { 'name':'id', 'type':'int' },\n"+
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" { 'name':'name', 'type':'string' },\n"+
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" { 'name':'phone', 'type':['null', 'string'], 'default':null }\n"+
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" ]\n"+
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"}\n");
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@JsonInclude(JsonInclude.Include.NON_NULL)
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static class Employee {
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public String code;
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public String countryCode;
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public String createdBy;
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public String createdDate;
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public long id;
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public String lastModifiedBy;
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public String lastModifiedDate;
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public String name;
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public String phone;
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protected Employee() { }
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public Employee(String code, String countryCode, String createdBy,
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String createdDate, long id, String lastModifiedBy,
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String lastModifiedDate, String name) {
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this.code = code;
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this.countryCode = countryCode;
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this.createdBy = createdBy;
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this.createdDate = createdDate;
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this.id = id;
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this.lastModifiedBy = lastModifiedBy;
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this.lastModifiedDate = lastModifiedDate;
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this.name = name;
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}
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}
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@JsonInclude(JsonInclude.Include.NON_NULL)
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static class SimpleRecord {
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public int id;
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public String name;
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public String phone;
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protected SimpleRecord() { }
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public SimpleRecord(int id, String name) {
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this.id = id;
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this.name = name;
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}
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}
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private final AvroMapper MAPPER = newMapper();
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@Test
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public void testSimpleAddNullableFieldWithDefault() throws Exception
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{
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final AvroSchema srcSchema = MAPPER.schemaFrom(SCHEMA_SIMPLE_V1_JSON);
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final AvroSchema dstSchema = MAPPER.schemaFrom(SCHEMA_SIMPLE_V2_JSON);
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final AvroSchema xlate = srcSchema.withReaderSchema(dstSchema);
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// Write data using old schema (without phone field)
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byte[] avro = MAPPER.writer(srcSchema).writeValueAsBytes(new SimpleRecord(1, "Alice"));
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// Read using new schema (with phone field defaulting to null)
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// This should NOT throw "Unexpected end-of-input in FIELD_NAME"
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SimpleRecord result = MAPPER.readerFor(SimpleRecord.class)
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.with(xlate)
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.readValue(avro);
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assertEquals(1, result.id);
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assertEquals("Alice", result.name);
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assertNull(result.phone); // Should use default value
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}
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// This test demonstrates INCORRECT usage: trying to read data serialized with an old schema
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// using a new schema directly, without calling withReaderSchema().
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// This is expected to fail because Avro binary format doesn't include schema metadata,
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// so the reader can't know the data was written with a different schema.
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// Users MUST call withReaderSchema() when reading data written with a different schema.
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@Test
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public void testSimpleAddNullableFieldWithDefaultWrongUsage() throws Exception
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{
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final AvroSchema srcSchema = MAPPER.schemaFrom(SCHEMA_SIMPLE_V1_JSON);
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final AvroSchema dstSchema = MAPPER.schemaFrom(SCHEMA_SIMPLE_V2_JSON);
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// Write data using old schema (without phone field)
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byte[] avro = MAPPER.writer(srcSchema).writeValueAsBytes(new SimpleRecord(1, "Alice"));
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// INCORRECT: Try to read with new schema directly without using withReaderSchema
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// This triggers EOF error because the reader expects to find the phone field in binary data
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// but the data doesn't contain it.
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JsonEOFException thrown = assertThrows(JsonEOFException.class, () -> {
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MAPPER.readerFor(SimpleRecord.class)
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.with(dstSchema) // Using dstSchema directly instead of xlate
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.readValue(avro);
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});
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verifyException(thrown, "Unexpected end-of-input in FIELD_NAME");
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}
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@Test
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public void testAddNullableFieldWithDefault() throws Exception
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{
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final AvroSchema srcSchema = MAPPER.schemaFrom(SCHEMA_V1_JSON);
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final AvroSchema dstSchema = MAPPER.schemaFrom(SCHEMA_V2_JSON);
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final AvroSchema xlate = srcSchema.withReaderSchema(dstSchema);
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// Write data using old schema (without phone field)
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Employee emp = new Employee("EMP001", "US", "admin", "2024-01-01",
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123L, "admin", "2024-01-01", "John Doe");
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byte[] avro = MAPPER.writer(srcSchema).writeValueAsBytes(emp);
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// Read using new schema (with phone field defaulting to null)
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// This should NOT throw "Unexpected end-of-input in FIELD_NAME"
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Employee result = MAPPER.readerFor(Employee.class)
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.with(xlate)
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.readValue(avro);
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assertEquals("EMP001", result.code);
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assertEquals("US", result.countryCode);
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assertEquals("admin", result.createdBy);
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assertEquals("2024-01-01", result.createdDate);
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assertEquals(123L, result.id);
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assertEquals("admin", result.lastModifiedBy);
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assertEquals("2024-01-01", result.lastModifiedDate);
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assertEquals("John Doe", result.name);
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assertNull(result.phone); // Should use default value
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}
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}

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