Add initial support for Java 14 records mapping

Issue #3693

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/file/mapping/RecordFieldSetMapper.java

@@ -0,0 +1,83 @@
+/*
+ * Copyright 2020 the original author or authors.
+ *
+ * Licensed 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
+ *
+ *      https://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.springframework.batch.item.file.mapping;
+
+import java.lang.reflect.Constructor;
+
+import org.springframework.batch.item.file.transform.FieldSet;
+import org.springframework.beans.BeanUtils;
+import org.springframework.beans.SimpleTypeConverter;
+import org.springframework.core.convert.ConversionService;
+import org.springframework.core.convert.support.DefaultConversionService;
+import org.springframework.util.Assert;
+
+/**
+ * This is a {@link FieldSetMapper} that supports Java records mapping.
+ * It uses the record's canonical constructor to map components with the
+ * same name as tokens in the {@link FieldSet}.
+ * 
+ * @param <T> type of mapped items
+ * @author Mahmoud Ben Hassine
+ * @since 4.3
+ */
+public class RecordFieldSetMapper<T> implements FieldSetMapper<T> {
+
+	private final SimpleTypeConverter typeConverter = new SimpleTypeConverter();
+	private final Constructor<T> mappedConstructor;
+	private String[] constructorParameterNames;
+	private Class<?>[] constructorParameterTypes;
+
+	/**
+	 * Create a new {@link RecordFieldSetMapper}.
+	 * 
+	 * @param targetType type of mapped items
+	 */
+	public RecordFieldSetMapper(Class<T> targetType) {
+		this(targetType, new DefaultConversionService());
+	}
+
+	/**
+	 * Create a new {@link RecordFieldSetMapper}.
+	 * 
+	 * @param targetType type of mapped items
+	 * @param conversionService service to use to convert raw data to typed fields
+	 */
+	public RecordFieldSetMapper(Class< T> targetType, ConversionService conversionService) {
+		this.typeConverter.setConversionService(conversionService);
+		this.mappedConstructor = BeanUtils.getResolvableConstructor(targetType);
+		if (this.mappedConstructor.getParameterCount() > 0) {
+			this.constructorParameterNames = BeanUtils.getParameterNames(this.mappedConstructor);
+			this.constructorParameterTypes = this.mappedConstructor.getParameterTypes();
+		}
+	}
+
+	@Override
+	public T mapFieldSet(FieldSet fieldSet) {
+		Assert.isTrue(fieldSet.getFieldCount() == this.constructorParameterNames.length,
+				"Fields count must be equal to record components count");
+		Assert.isTrue(fieldSet.hasNames(), "Field names must specified");
+		Object[] args = new Object[0];
+		if (this.constructorParameterNames != null && this.constructorParameterTypes != null) {
+			args = new Object[this.constructorParameterNames.length];
+			for (int i = 0; i < args.length; i++) {
+				String name = this.constructorParameterNames[i];
+				Class<?> type = this.constructorParameterTypes[i];
+				args[i] = this.typeConverter.convertIfNecessary(fieldSet.readRawString(name), type);
+			}
+		}
+		return BeanUtils.instantiateClass(this.mappedConstructor, args);
+	}
+}