[GitHub] [flink] dawidwys commented on a change in pull request #10342: [FLINK-14967][table] Add a utility for creating data types via reflection

[GitBox <gi...@apache.org>]

dawidwys commented on a change in pull request #10342: [FLINK-14967][table] Add a utility for creating data types via reflection
URL: https://github.com/apache/flink/pull/10342#discussion_r352522927
 
 

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 File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/types/extraction/DataTypeExtractor.java
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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.table.types.extraction;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.table.annotation.DataTypeHint;
+import org.apache.flink.table.api.DataTypes;
+import org.apache.flink.table.catalog.DataTypeLookup;
+import org.apache.flink.table.types.DataType;
+import org.apache.flink.table.types.FieldsDataType;
+import org.apache.flink.table.types.extraction.utils.DataTypeTemplate;
+import org.apache.flink.table.types.extraction.utils.ExtractionUtils;
+import org.apache.flink.table.types.logical.LogicalType;
+import org.apache.flink.table.types.logical.RawType;
+import org.apache.flink.table.types.logical.StructuredType;
+import org.apache.flink.table.types.logical.StructuredType.StructuredAttribute;
+import org.apache.flink.table.types.utils.ClassDataTypeConverter;
+
+import javax.annotation.Nullable;
+
+import java.lang.reflect.Field;
+import java.lang.reflect.GenericArrayType;
+import java.lang.reflect.Method;
+import java.lang.reflect.Parameter;
+import java.lang.reflect.ParameterizedType;
+import java.lang.reflect.Type;
+import java.lang.reflect.TypeVariable;
+import java.math.BigDecimal;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.collectStructuredFields;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.collectTypeHierarchy;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.createRawType;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.extractAssigningConstructor;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.extractionError;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.isStructuredFieldMutable;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.resolveVariable;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.toClass;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.validateStructuredClass;
+import static org.apache.flink.table.types.extraction.utils.ExtractionUtils.validateStructuredFieldReadability;
+
+/**
+ * Reflection-based utility that analyzes a given {@link java.lang.reflect.Type}, method, or class to
+ * extract a (possibly nested) {@link DataType} from it.
+ */
+@Internal
+public final class DataTypeExtractor {
+
+	private final DataTypeLookup lookup;
+
+	private DataTypeExtractor(DataTypeLookup lookup) {
+		this.lookup = lookup;
+	}
+
+	/**
+	 * Extracts a data type from a type without considering surrounding classes or templates.
+	 */
+	public static DataType extractFromType(
+			DataTypeLookup lookup,
+			Type type) {
+		return extractDataTypeWithClassContext(
+			lookup,
+			DataTypeTemplate.fromDefaults(),
+			null,
+			type,
+			"");
+	}
+
+	/**
+	 * Extracts a data type from a type without considering surrounding classes but templates.
+	 */
+	public static DataType extractFromType(
+			DataTypeLookup lookup,
+			DataTypeTemplate template,
+			Type type) {
+		return extractDataTypeWithClassContext(
+			lookup,
+			template,
+			null,
+			type,
+			"");
+	}
+
+	/**
+	 * Extracts a data type from a type variable at {@code genericPos} of {@code baseClass} using
+	 * the information of the most specific type {@code contextType}.
+	 */
+	public static DataType extractFromGeneric(
+			DataTypeLookup lookup,
+			Class<?> baseClass,
+			int genericPos,
+			Type contextType) {
+		final TypeVariable<?> variable = baseClass.getTypeParameters()[genericPos];
+		return extractDataTypeWithClassContext(
+			lookup,
+			DataTypeTemplate.fromDefaults(),
+			contextType,
+			variable,
+			String.format(
+				" in generic class '%s' in %s",
+				baseClass.getName(),
+				contextType.toString()));
+	}
+
+	/**
+	 * Extracts a data type from a method parameter by considering surrounding classes and parameter
+	 * annotation.
+	 */
+	public static DataType extractFromMethodParameter(
+			DataTypeLookup lookup,
+			Class<?> baseClass,
+			Method method,
+			int paramPos) {
+		final Parameter parameter = method.getParameters()[paramPos];
+		final DataTypeHint hint = parameter.getAnnotation(DataTypeHint.class);
+		final DataTypeTemplate template;
+		if (hint != null) {
+			template = DataTypeTemplate.fromAnnotation(lookup, hint);
+		} else {
+			template = DataTypeTemplate.fromDefaults();
+		}
+		return extractDataTypeWithClassContext(
+			lookup,
+			template,
+			baseClass,
+			parameter.getParameterizedType(),
+			String.format(
+				" in parameter %d of method '%s' in class '%s'",
+				paramPos,
+				method.getName(),
+				baseClass.getName()));
+	}
+
+	/**
+	 * Extracts a data type from a method return type by considering surrounding classes and method
+	 * annotation.
+	 */
+	public static DataType extractFromMethodOutput(
+			DataTypeLookup lookup,
+			Class<?> baseClass,
+			Method method) {
+		final DataTypeHint hint = method.getAnnotation(DataTypeHint.class);
+		final DataTypeTemplate template;
+		if (hint != null) {
+			template = DataTypeTemplate.fromAnnotation(lookup, hint);
+		} else {
+			template = DataTypeTemplate.fromDefaults();
+		}
+		return extractDataTypeWithClassContext(
+			lookup,
+			template,
+			baseClass,
+			method.getGenericReturnType(),
+			String.format(
+				" in return type of method '%s' in class '%s'",
+				method.getName(),
+				baseClass.getName()));
+	}
+
+	private static DataType extractDataTypeWithClassContext(
+			DataTypeLookup lookup,
+			DataTypeTemplate outerTemplate,
+			@Nullable Type contextType,
+			Type type,
+			String contextExplanation) {
+		final DataTypeExtractor extractor = new DataTypeExtractor(lookup);
+		try {
+			final List<Type> typeHierarchy;
+			if (contextType != null) {
+				typeHierarchy = collectTypeHierarchy(Object.class, contextType);
+			} else {
+				typeHierarchy = Collections.singletonList(type);
+			}
+			return extractor.extractDataTypeOrRaw(outerTemplate, typeHierarchy, type);
+		} catch (Throwable t) {
+			throw extractionError(
+				t,
+				"Could not extract a data type from '%s'%s. " +
+					"Please pass the required data type manually or allow RAW types.",
+				type.toString(),
+				contextExplanation);
+		}
+	}
+
+	// --------------------------------------------------------------------------------------------
+
+	private DataType extractDataTypeOrRaw(
+			DataTypeTemplate outerTemplate,
+			List<Type> typeHierarchy,
+			Type type) {
+		// best effort resolution of type variables, the resolved type can still be a variable
+		final Type resolvedType;
+		if (type instanceof TypeVariable) {
+			resolvedType = resolveVariable(typeHierarchy, (TypeVariable) type);
+		} else {
+			resolvedType = type;
+		}
+		// merge outer template with template of type itself
+		DataTypeTemplate template = outerTemplate;
+		final Class<?> clazz = toClass(resolvedType);
+		if (clazz != null) {
+			final DataTypeHint hint = clazz.getAnnotation(DataTypeHint.class);
+			if (hint != null) {
+				template = outerTemplate.mergeWithInnerAnnotation(lookup, hint);
+			}
+		}
+		// main work
+		final DataType dataType = extractDataTypeOrRawWithTemplate(template, typeHierarchy, resolvedType);
+		// final work
+		return closestBridging(dataType, clazz);
+	}
+
+	private DataType extractDataTypeOrRawWithTemplate(
+			DataTypeTemplate template,
+			List<Type> typeHierarchy,
+			Type type) {
+		// template defines a data type
+		if (template.dataType != null) {
+			return template.dataType;
+		}
+		try {
+			return extractDataTypeOrError(template, typeHierarchy, type);
+		} catch (Throwable t) {
+			// ignore the exception and just treat it as RAW type
+			final Class<?> clazz = toClass(type);
+			if (isAllowRawGlobally(template) || isAllowAnyPattern(template, clazz)) {
+				return createRawType(lookup, template.rawSerializer, clazz);
+			}
+			// forward the root cause otherwise
+			throw t;
+		}
+	}
+
+	private DataType extractDataTypeOrError(DataTypeTemplate template, List<Type> typeHierarchy, Type type) {
+		// still a type variable
+		if (type instanceof TypeVariable) {
+			throw extractionError(
+				"Unresolved type variable '%s'. A data type cannot be extracted from a type variable. " +
+					"The original content might have been erased due to Java type erasure.",
+				type.toString());
+		}
+
+		// ARRAY
+		DataType resultDataType = extractArrayType(template, typeHierarchy, type);
+		if (resultDataType != null) {
+			return resultDataType;
+		}
+
+		// skip extraction for enforced patterns early but after arrays
+		resultDataType = extractEnforcedRawType(template, type);
+		if (resultDataType != null) {
+			return resultDataType;
+		}
+
+		// PREDEFINED
+		resultDataType = extractPredefinedType(template, type);
+		if (resultDataType != null) {
+			return resultDataType;
+		}
+
+		// MAP
+		resultDataType = extractMapType(template, typeHierarchy, type);
+		if (resultDataType != null) {
+			return resultDataType;
+		}
+
+		// try interpret the type as a STRUCTURED type
+		try {
+			return extractStructuredType(template, typeHierarchy, type);
+		} catch (Throwable t) {
+			throw extractionError(
+				t,
+				"Could not extract a data type from '%s'. " +
+					"Interpreting it as a structured type was also not successful.",
+				type.toString());
+		}
+	}
+
+	private @Nullable DataType extractArrayType(
+			DataTypeTemplate template,
+			List<Type> typeHierarchy,
+			Type type) {
+		// for T[]
+		if (type instanceof GenericArrayType) {
+			final GenericArrayType genericArray = (GenericArrayType) type;
+			return DataTypes.ARRAY(
+				extractDataTypeOrRaw(template, typeHierarchy, genericArray.getGenericComponentType()));
+		}
+		// for my.custom.Pojo[][]
+		else if (type instanceof Class) {
+			final Class<?> clazz = (Class<?>) type;
+			if (clazz.isArray()) {
+				return DataTypes.ARRAY(
+					extractDataTypeOrRaw(template, typeHierarchy, clazz.getComponentType()));
+			}
+		}
+		return null;
+	}
+
+	private @Nullable DataType extractEnforcedRawType(DataTypeTemplate template, Type type) {
+		final Class<?> clazz = toClass(type);
+		if (template.forceRawPattern == null || clazz == null) {
+			return null;
+		}
+		final String className = clazz.getName();
+		for (String anyPattern : template.forceRawPattern) {
+			if (className.startsWith(anyPattern)) {
+				return createRawType(lookup, template.rawSerializer, clazz);
+			}
+		}
+		return null;
+	}
+
+	private @Nullable DataType extractPredefinedType(DataTypeTemplate template, Type type) {
+		final Class<?> clazz = toClass(type);
+		// all predefined types are representable as classes
+		if (clazz == null) {
+			return null;
+		}
+
+		// DECIMAL
+		if (clazz == BigDecimal.class) {
+			if (template.defaultDecimalPrecision != null && template.defaultDecimalScale != null) {
+				return DataTypes.DECIMAL(template.defaultDecimalPrecision, template.defaultDecimalScale);
+			} else if (template.defaultDecimalPrecision != null) {
+				return DataTypes.DECIMAL(template.defaultDecimalPrecision, 0);
+			}
+			throw extractionError("Values of '%s' need fixed precision and scale.", BigDecimal.class.getName());
+		}
+
+		// TIME
+		else if (clazz == java.sql.Time.class || clazz == java.time.LocalTime.class) {
+			if (template.defaultSecondPrecision != null) {
+				return DataTypes.TIME(template.defaultSecondPrecision)
+					.bridgedTo(clazz);
+			}
+		}
+
+		// TIMESTAMP
+		else if (clazz == java.sql.Timestamp.class || clazz == java.time.LocalDateTime.class) {
+			if (template.defaultSecondPrecision != null) {
+				return DataTypes.TIMESTAMP(template.defaultSecondPrecision)
+					.bridgedTo(clazz);
+			}
+		}
+
+		// TIMESTAMP WITH TIME ZONE
+		else if (clazz == java.time.OffsetDateTime.class) {
+			if (template.defaultSecondPrecision != null) {
+				return DataTypes.TIMESTAMP_WITH_TIME_ZONE(template.defaultSecondPrecision);
+			}
+		}
+
+		// TIMESTAMP WITH LOCAL TIME ZONE
+		else if (clazz == java.time.Instant.class) {
+			if (template.defaultSecondPrecision != null) {
+				return DataTypes.TIMESTAMP_WITH_LOCAL_TIME_ZONE(template.defaultSecondPrecision);
+			}
+		}
+
+		// INTERVAL SECOND
+		else if (clazz == java.time.Duration.class) {
+			if (template.defaultSecondPrecision != null) {
+				return DataTypes.INTERVAL(DataTypes.SECOND(template.defaultSecondPrecision));
+			}
+		}
+
+		// INTERVAL YEAR TO MONTH
+		else if (clazz == java.time.Period.class) {
+			if (template.defaultYearPrecision != null && template.defaultYearPrecision == 0) {
+				return DataTypes.INTERVAL(DataTypes.MONTH());
+			} else if (template.defaultYearPrecision != null) {
+				return DataTypes.INTERVAL(DataTypes.YEAR(template.defaultYearPrecision), DataTypes.MONTH());
+			}
+		}
+
+		return ClassDataTypeConverter.extractDataType(clazz).orElse(null);
+	}
+
+	private @Nullable DataType extractMapType(DataTypeTemplate template, List<Type> typeHierarchy, Type type) {
+		final Class<?> clazz = toClass(type);
+		if (clazz != Map.class) {
+			return null;
+		}
+		if (!(type instanceof ParameterizedType)) {
+			throw extractionError("Raw map type needs generic parameters.");
+		}
+		final ParameterizedType parameterizedType = (ParameterizedType) type;
+		final DataType key = extractDataTypeOrRaw(
+			template,
+			typeHierarchy,
+			parameterizedType.getActualTypeArguments()[0]);
+		final DataType value = extractDataTypeOrRaw(
+			template,
+			typeHierarchy,
+			parameterizedType.getActualTypeArguments()[1]);
+		return DataTypes.MAP(key, value);
+	}
+
+	private DataType extractStructuredType(DataTypeTemplate template, List<Type> typeHierarchy, Type type) {
+		final Class<?> clazz = toClass(type);
+		if (clazz == null) {
+			throw extractionError("Not a class type.");
+		}
+
+		validateStructuredClass(clazz);
+
+		final List<Field> fields = collectStructuredFields(clazz);
+
+		if (fields.isEmpty()) {
+			throw extractionError(
+				"Class '%s' has no fields.",
+				clazz.getName());
+		}
+
+		boolean requireAssigningConstructor = false;
+		for (Field field : fields) {
+			validateStructuredFieldReadability(clazz, field);
+			final boolean isMutable = isStructuredFieldMutable(clazz, field);
+			// not all fields are mutable, a default constructor is not enough
+			if (!isMutable) {
+				requireAssigningConstructor = true;
+			}
+		}
+
+		final ExtractionUtils.AssigningConstructor constructor = extractAssigningConstructor(clazz, fields);
+		if (requireAssigningConstructor && constructor == null) {
+			throw extractionError(
+				"Class '%s' has immutable fields and thus requires a constructor that is publicly " +
+					"accessible and assigns all fields: %s",
+				clazz.getName(),
+				fields.stream().map(Field::getName).collect(Collectors.joining(", ")));
+		}
+
+		final Map<String, DataType> fieldDataTypes = extractStructuredTypeFields(
+			template,
+			typeHierarchy,
+			type,
+			fields);
+
+		final StructuredType.Builder builder = StructuredType.newBuilder(clazz);
+		builder.attributes(createStructuredTypeAttributes(constructor, fieldDataTypes));
+		builder.setFinal(true); // anonymous structured types should not allow inheritance
+		builder.setInstantiable(true);
+		return new FieldsDataType(builder.build(), clazz, fieldDataTypes);
+	}
+
+	private Map<String, DataType> extractStructuredTypeFields(
+			DataTypeTemplate template,
+			List<Type> typeHierarchy,
+			Type type,
+			List<Field> fields) {
+		final Map<String, DataType> fieldDataTypes = new HashMap<>();
+		final List<Type> structuredTypeHierarchy = collectTypeHierarchy(Object.class, type);
+		for (Field field : fields) {
+			try {
+				final Type fieldType = field.getGenericType();
+				final List<Type> fieldTypeHierarchy = new ArrayList<>();
+				// hierarchy until structured type
+				fieldTypeHierarchy.addAll(typeHierarchy);
+				// hierarchy of structured type
+				fieldTypeHierarchy.addAll(structuredTypeHierarchy);
+				// field type
+				fieldTypeHierarchy.add(fieldType);
+				final DataTypeTemplate fieldTemplate = mergeFieldTemplate(lookup, field, template);
+				final DataType fieldDataType = extractDataTypeOrRaw(fieldTemplate, fieldTypeHierarchy, fieldType);
+				fieldDataTypes.put(field.getName(), fieldDataType);
+			} catch (Throwable t) {
+				throw extractionError(
+					t,
+					"Error in field '%s' of class '%s'.",
+					field.getName(),
+					field.getDeclaringClass().getName());
+			}
+		}
+		return fieldDataTypes;
+	}
+
+	private List<StructuredAttribute> createStructuredTypeAttributes(
+			ExtractionUtils.AssigningConstructor constructor,
+			Map<String, DataType> fieldDataTypes) {
+		// field order is defined by assigning constructor
+		if (constructor != null) {
+			return constructor.parameterNames
+				.stream()
+				.map(name -> {
+					final LogicalType logicalType = fieldDataTypes.get(name).getLogicalType();
+					return new StructuredAttribute(name, logicalType);
+				})
+				.collect(Collectors.toList());
+		}
+		// field order is sorted
+		else {
+			return fieldDataTypes.keySet()
+				.stream()
+				.sorted()
+				.map(name -> {
+					final LogicalType logicalType = fieldDataTypes.get(name).getLogicalType();
+					return new StructuredAttribute(name, logicalType);
+				})
+				.collect(Collectors.toList());
+		}
+	}
+
+	/**
+	 * Merges the template of a structured type with a possibly more specific field annotation.
+	 */
+	private DataTypeTemplate mergeFieldTemplate(DataTypeLookup lookup, Field field, DataTypeTemplate structuredTemplate) {
+		final DataTypeHint hint = field.getAnnotation(DataTypeHint.class);
+		if (hint == null) {
+			return structuredTemplate.copyWithoutDataType();
+		}
+		return structuredTemplate.mergeWithInnerAnnotation(lookup, hint);
+	}
+
+	/**
+	 * Use closest class for data type if possible. Even though a hint might have provided some data
+	 * type, in many cases, the conversion class can be enriched with the extraction type itself.
+	 */
+	@SuppressWarnings("unchecked")
+	private DataType closestBridging(DataType dataType, @Nullable Class<?> clazz) {
+		if (clazz == null) {
+			return dataType;
+		}
+		final LogicalType logicalType = dataType.getLogicalType();
+		final boolean supportsConversion = logicalType.supportsInputConversion(clazz) ||
+			logicalType.supportsOutputConversion(clazz);
+		if (supportsConversion && logicalType instanceof RawType) {
+			return DataTypes.RAW(clazz, ((RawType) logicalType).getTypeSerializer());
 
 Review comment:
   Will it work if it is the other way round? `eval(@DataTypeHing("Raw", bridgedTo = Integer.class) Object o)`

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