Added Builder for RepositoryItemWriter

resolves BATCH-2609

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/data/RepositoryItemReader.java

@@ -59,6 +59,10 @@ import org.springframework.util.MethodInvoker;
  * <code>saveState=false</code> if used in a multi-threaded client (no restart available).
  * </p>
  *
+ * <p>
+ * The RepositoryItemReader only reads Java Objects i.e. non primitives.
+ * </p>
+ *
  * @author Michael Minella
  * @since 2.2
  */

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/data/RepositoryItemWriter.java

@@ -47,6 +47,10 @@ import org.springframework.util.MethodInvoker;
  * transactions.
  * </p>
  *
+ * <p>
+ * The RepositoryItemWriter only stores Java Objects i.e. non primitives.
+ * </p>
+ *
  * @author Michael Minella
  * @since 2.2
  */
@@ -59,7 +63,7 @@ public class RepositoryItemWriter<T> implements ItemWriter<T>, InitializingBean
 	private String methodName;
 
 	/**
-	 * Specifies what method on the repository to call.  This method must the type of
+	 * Specifies what method on the repository to call.  This method must have the type of
 	 * object passed to this writer as the <em>sole</em> argument.
 	 *
 	 * @param methodName

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/data/builder/RepositoryItemWriterBuilder.java

@@ -0,0 +1,170 @@
+/*
+ * Copyright 2017 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
+ *
+ *          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.springframework.batch.item.data.builder;
+
+
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+import org.springframework.batch.item.data.RepositoryItemWriter;
+import org.springframework.cglib.proxy.Enhancer;
+import org.springframework.cglib.proxy.MethodInterceptor;
+import org.springframework.cglib.proxy.MethodProxy;
+import org.springframework.data.repository.CrudRepository;
+import org.springframework.util.Assert;
+
+/**
+ * A builder implementation for the {@link RepositoryItemWriter}.
+ *
+ * @author Glenn Renfro
+ * @since 4.0
+ * @see RepositoryItemWriter
+ */
+public class RepositoryItemWriterBuilder<T> {
+
+	private CrudRepository<T, ?> repository;
+
+	private String methodName;
+
+	private RepositoryMethodReference repositoryMethodReference;
+
+	/**
+	 * Specifies what method on the repository to call. This method must have the type of
+	 * object passed to this writer as the <em>sole</em> argument.
+	 *
+	 * @param methodName the name of the method to be used for saving the item.
+	 * @return The current instance of the builder.
+	 * @see RepositoryItemWriter#setMethodName(String)
+	 */
+	public RepositoryItemWriterBuilder<T> methodName(String methodName) {
+		this.methodName = methodName;
+
+		return this;
+	}
+
+	/**
+	 * Set the {@link org.springframework.data.repository.CrudRepository} implementation
+	 * for persistence
+	 *
+	 * @param repository the Spring Data repository to be set
+	 * @return The current instance of the builder.
+	 * @see RepositoryItemWriter#setRepository(CrudRepository)
+	 */
+	public RepositoryItemWriterBuilder<T> repository(CrudRepository<T, ?> repository) {
+		this.repository = repository;
+
+		return this;
+	}
+
+	/**
+	 * Specifies a repository and the type-safe method to call for the writer. The method
+	 * configured via this mechanism must take
+	 * {@link org.springframework.data.domain.Pageable} as the <em>last</em>
+	 * argument. This method can be used in place of {@link #repository(CrudRepository)},
+	 * {@link #methodName(String)}}.
+	 *
+	 * Note: The repository that is used by the repositoryMethodReference must be
+	 * non-final.
+	 *
+	 * @param repositoryMethodReference of the used to get a repository and type-safe
+	 * method for use by the writer.
+	 * @return The current instance of the builder.
+	 * @see RepositoryItemWriter#setMethodName(String)
+	 * @see RepositoryItemWriter#setRepository(CrudRepository)
+	 *
+	 */
+	public RepositoryItemWriterBuilder<T> repository(RepositoryItemWriterBuilder.RepositoryMethodReference repositoryMethodReference) {
+		this.repositoryMethodReference = repositoryMethodReference;
+
+		return this;
+	}
+
+	/**
+	 * Builds the {@link RepositoryItemWriter}.
+	 *
+	 * @return a {@link RepositoryItemWriter}
+	 */
+	public RepositoryItemWriter<T> build() {
+		if (this.repositoryMethodReference != null) {
+			this.methodName = this.repositoryMethodReference.getMethodName();
+			this.repository = this.repositoryMethodReference.getRepository();
+		}
+
+		Assert.hasText(this.methodName, "methodName is required.");
+		Assert.notNull(this.repository, "repository is required.");
+
+		RepositoryItemWriter<T> writer = new RepositoryItemWriter<>();
+		writer.setMethodName(this.methodName);
+		writer.setRepository(this.repository);
+		return writer;
+	}
+
+	/**
+	 * Establishes a proxy that will capture a the Repository and the associated
+	 * methodName that will be used by the writer.
+	 * @param <T> The type of repository that will be used by the writer.  The class must
+	 * not be final.
+	 */
+	public static class RepositoryMethodReference<T> {
+		private RepositoryItemWriterBuilder.RepositoryMethodIterceptor repositoryInvocationHandler;
+
+		private CrudRepository<?, ?> repository;
+
+		public RepositoryMethodReference(CrudRepository<?, ?> repository) {
+			this.repository = repository;
+			this.repositoryInvocationHandler = new RepositoryItemWriterBuilder.RepositoryMethodIterceptor();
+		}
+
+		/**
+		 * The proxy returned prevents actual method execution and is only used to gather,
+		 * information about the method.
+		 * @return T is a proxy of the object passed in in the constructor
+		 */
+		public T methodIs() {
+			Enhancer enhancer = new Enhancer();
+			enhancer.setSuperclass(this.repository.getClass());
+			enhancer.setCallback(this.repositoryInvocationHandler);
+			return (T) enhancer.create();
+		}
+
+		CrudRepository<?, ?> getRepository() {
+			return this.repository;
+		}
+
+		String getMethodName() {
+			return this.repositoryInvocationHandler.getMethodName();
+		}
+	}
+
+	private static class RepositoryMethodIterceptor implements MethodInterceptor {
+		private String methodName;
+
+		@Override
+		public Object intercept(Object o, Method method, Object[] objects,
+				MethodProxy methodProxy) throws Throwable {
+			this.methodName = method.getName();
+			return null;
+		}
+
+		String getMethodName() {
+			return this.methodName;
+		}
+
+	}
+}