Add a streaming Json item reader

This commit adds a new Json item reader with two implementations based
on Jackson and Gson.

Resolves BATCH-2691

build.gradle

@@ -74,6 +74,7 @@ allprojects {
 		hibernateValidatorVersion = '6.0.4.Final'
 		hsqldbVersion = '2.4.0'
 		jackson2Version = '2.9.2'
+		gsonVersion = '2.8.5'
 		javaMailVersion = '1.6.0'
 		javaxBatchApiVersion = '1.0'
 		javaxInjectVersion = '1'
@@ -326,6 +327,7 @@ project('spring-batch-infrastructure') {
 
 		optional "javax.jms:javax.jms-api:$jmsVersion"
 		optional "com.fasterxml.jackson.core:jackson-databind:${jackson2Version}"
+		optional "com.google.code.gson:gson:${gsonVersion}"
 		compile("org.hibernate:hibernate-core:$hibernateVersion") { dep ->
 			optional dep
 			exclude group: 'org.jboss.spec.javax.transaction', module: 'jboss-transaction-api_1.1_spec'

spring-batch-infrastructure-tests/src/test/java/org/springframework/batch/item/json/GsonJsonItemReaderFunctionalTests.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2018 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.json;
+
+import com.google.gson.JsonSyntaxException;
+
+import org.springframework.batch.item.json.domain.Trade;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public class GsonJsonItemReaderFunctionalTests extends JsonItemReaderFunctionalTests {
+
+	@Override
+	protected JsonObjectReader<Trade> getJsonObjectReader() {
+		return new GsonJsonObjectReader<>(Trade.class);
+	}
+
+	@Override
+	protected Class<? extends Exception> getJsonParsingException() {
+		return JsonSyntaxException.class;
+	}
+
+}

spring-batch-infrastructure-tests/src/test/java/org/springframework/batch/item/json/JacksonJsonItemReaderFunctionalTests.java

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2018 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.json;
+
+import com.fasterxml.jackson.core.JsonParseException;
+
+import org.springframework.batch.item.json.domain.Trade;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public class JacksonJsonItemReaderFunctionalTests extends JsonItemReaderFunctionalTests {
+
+	@Override
+	protected JsonObjectReader<Trade> getJsonObjectReader() {
+		return new JacksonJsonObjectReader<>(Trade.class);
+	}
+
+	@Override
+	protected Class<? extends Exception> getJsonParsingException() {
+		return JsonParseException.class;
+	}
+
+}

spring-batch-infrastructure-tests/src/test/java/org/springframework/batch/item/json/JsonItemReaderFunctionalTests.java

@@ -0,0 +1,118 @@
+/*
+ * Copyright 2018 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.json;
+
+import java.math.BigDecimal;
+
+import org.hamcrest.Matchers;
+import org.junit.Assert;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamException;
+import org.springframework.batch.item.ParseException;
+import org.springframework.batch.item.json.builder.JsonItemReaderBuilder;
+import org.springframework.batch.item.json.domain.Trade;
+import org.springframework.core.io.ByteArrayResource;
+import org.springframework.core.io.ClassPathResource;
+
+import static org.hamcrest.Matchers.instanceOf;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public abstract class JsonItemReaderFunctionalTests {
+
+	@Rule
+	public ExpectedException expectedException = ExpectedException.none();
+
+	protected abstract JsonObjectReader<Trade> getJsonObjectReader();
+
+	protected abstract Class<? extends Exception> getJsonParsingException();
+
+	@Test
+	public void testJsonReading() throws Exception {
+		JsonItemReader<Trade> itemReader = new JsonItemReaderBuilder<Trade>()
+				.jsonObjectReader(getJsonObjectReader())
+				.resource(new ClassPathResource("org/springframework/batch/item/json/trades.json"))
+				.name("tradeJsonItemReader")
+				.build();
+
+		itemReader.open(new ExecutionContext());
+
+		Trade trade = itemReader.read();
+		Assert.assertNotNull(trade);
+		Assert.assertEquals("123", trade.getIsin());
+		Assert.assertEquals("foo", trade.getCustomer());
+		Assert.assertEquals(new BigDecimal("1.2"), trade.getPrice());
+		Assert.assertEquals(1, trade.getQuantity());
+
+		trade = itemReader.read();
+		Assert.assertNotNull(trade);
+		Assert.assertEquals("456", trade.getIsin());
+		Assert.assertEquals("bar", trade.getCustomer());
+		Assert.assertEquals(new BigDecimal("1.4"), trade.getPrice());
+		Assert.assertEquals(2, trade.getQuantity());
+
+		trade = itemReader.read();
+		Assert.assertNull(trade);
+	}
+
+	@Test
+	public void testEmptyResource() throws Exception {
+		JsonItemReader<Trade> itemReader = new JsonItemReaderBuilder<Trade>()
+				.jsonObjectReader(getJsonObjectReader())
+				.resource(new ByteArrayResource("[]".getBytes()))
+				.name("tradeJsonItemReader")
+				.build();
+
+		itemReader.open(new ExecutionContext());
+
+		Trade trade = itemReader.read();
+		Assert.assertNull(trade);
+	}
+
+	@Test
+	public void testInvalidResourceFormat() {
+		this.expectedException.expect(ItemStreamException.class);
+		this.expectedException.expectMessage("Failed to initialize the reader");
+		this.expectedException.expectCause(instanceOf(IllegalStateException.class));
+		JsonItemReader<Trade> itemReader = new JsonItemReaderBuilder<Trade>()
+				.jsonObjectReader(getJsonObjectReader())
+				.resource(new ByteArrayResource("{}, {}".getBytes()))
+				.name("tradeJsonItemReader")
+				.build();
+
+		itemReader.open(new ExecutionContext());
+	}
+
+	@Test
+	public void testInvalidResourceContent() throws Exception {
+		this.expectedException.expect(ParseException.class);
+		this.expectedException.expectCause(Matchers.instanceOf(getJsonParsingException()));
+		JsonItemReader<Trade> itemReader = new JsonItemReaderBuilder<Trade>()
+				.jsonObjectReader(getJsonObjectReader())
+				.resource(new ByteArrayResource("[{]".getBytes()))
+				.name("tradeJsonItemReader")
+				.build();
+		itemReader.open(new ExecutionContext());
+
+		itemReader.read();
+	}
+}

spring-batch-infrastructure-tests/src/test/java/org/springframework/batch/item/json/domain/Trade.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright 2018 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.json.domain;
+
+import java.math.BigDecimal;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public class Trade {
+
+	private String isin = "";
+
+	private long quantity = 0;
+
+	private BigDecimal price = new BigDecimal(0);
+
+	private String customer = "";
+
+	public Trade() {
+	}
+
+	public Trade(String isin, long quantity, BigDecimal price, String customer) {
+		this.isin = isin;
+		this.quantity = quantity;
+		this.price = price;
+		this.customer = customer;
+	}
+
+	public void setCustomer(String customer) {
+		this.customer = customer;
+	}
+
+	public void setIsin(String isin) {
+		this.isin = isin;
+	}
+
+	public void setPrice(BigDecimal price) {
+		this.price = price;
+	}
+
+	public void setQuantity(long quantity) {
+		this.quantity = quantity;
+	}
+
+	public String getIsin() {
+		return isin;
+	}
+
+	public BigDecimal getPrice() {
+		return price;
+	}
+
+	public long getQuantity() {
+		return quantity;
+	}
+
+	public String getCustomer() {
+		return customer;
+	}
+
+	@Override
+	public String toString() {
+		return "Trade: [isin=" + this.isin + ",quantity=" + this.quantity + ",price=" + this.price + ",customer="
+				+ this.customer + "]";
+	}
+
+	@Override
+	public int hashCode() {
+		final int prime = 31;
+		int result = 1;
+		result = prime * result + ((customer == null) ? 0 : customer.hashCode());
+		result = prime * result + ((isin == null) ? 0 : isin.hashCode());
+		result = prime * result + ((price == null) ? 0 : price.hashCode());
+		result = prime * result + (int) (quantity ^ (quantity >>> 32));
+		return result;
+	}
+
+	@Override
+	public boolean equals(Object obj) {
+		if (this == obj)
+			return true;
+		if (obj == null)
+			return false;
+		if (getClass() != obj.getClass())
+			return false;
+		Trade other = (Trade) obj;
+		if (customer == null) {
+			if (other.customer != null)
+				return false;
+		}
+		else if (!customer.equals(other.customer))
+			return false;
+		if (isin == null) {
+			if (other.isin != null)
+				return false;
+		}
+		else if (!isin.equals(other.isin))
+			return false;
+		if (price == null) {
+			if (other.price != null)
+				return false;
+		}
+		else if (!price.equals(other.price))
+			return false;
+		if (quantity != other.quantity)
+			return false;
+		return true;
+	}
+
+}

spring-batch-infrastructure-tests/src/test/resources/org/springframework/batch/item/json/trades.json

@@ -0,0 +1,14 @@
+[
+  {
+    "isin": "123",
+    "quantity": 1,
+    "price": 1.2,
+    "customer": "foo"
+  },
+  {
+    "isin": "456",
+    "quantity": 2,
+    "price": 1.4,
+    "customer": "bar"
+  }
+]

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/GsonJsonObjectReader.java

@@ -0,0 +1,97 @@
+/*
+ * Copyright 2018 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.json;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+
+import com.google.gson.Gson;
+import com.google.gson.JsonIOException;
+import com.google.gson.JsonSyntaxException;
+import com.google.gson.stream.JsonReader;
+import com.google.gson.stream.JsonToken;
+
+import org.springframework.batch.item.ParseException;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+
+/**
+ * Implementation of {@link JsonObjectReader} based on
+ * <a href="https://github.com/google/gson">Google Gson</a>.
+ *
+ * @param <T> type of the target object
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 4.1
+ */
+public class GsonJsonObjectReader<T> implements JsonObjectReader<T> {
+
+	private Class<? extends T> itemType;
+
+	private JsonReader jsonReader;
+
+	private Gson mapper = new Gson();
+
+	private InputStream inputStream;
+
+	/**
+	 * Create a new {@link GsonJsonObjectReader} instance.
+	 * @param itemType the target item type
+	 */
+	public GsonJsonObjectReader(Class<? extends T> itemType) {
+		this.itemType = itemType;
+	}
+
+	/**
+	 * Set the object mapper to use to map Json objects to domain objects.
+	 * @param mapper the object mapper to use
+	 */
+	public void setMapper(Gson mapper) {
+		Assert.notNull(mapper, "The mapper must not be null");
+		this.mapper = mapper;
+	}
+
+	@Override
+	public void open(Resource resource) throws Exception {
+		Assert.notNull(resource, "The resource must not be null");
+		this.inputStream = resource.getInputStream();
+		this.jsonReader = this.mapper.newJsonReader(new InputStreamReader(this.inputStream));
+		Assert.state(this.jsonReader.peek() == JsonToken.BEGIN_ARRAY,
+				"The Json input stream must start with an array of Json objects");
+		this.jsonReader.beginArray();
+	}
+
+	@Override
+	public T read() throws Exception {
+		try {
+			if (this.jsonReader.hasNext()) {
+				return this.mapper.fromJson(this.jsonReader, this.itemType);
+			}
+		} catch (IOException |JsonIOException | JsonSyntaxException e) {
+			throw new ParseException("Unable to read next JSON object", e);
+		}
+		return null;
+	}
+
+	@Override
+	public void close() throws Exception {
+		this.inputStream.close();
+		this.jsonReader.close();
+	}
+
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/JacksonJsonObjectReader.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2018 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.json;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+import com.fasterxml.jackson.core.JsonParser;
+import com.fasterxml.jackson.core.JsonToken;
+import com.fasterxml.jackson.databind.ObjectMapper;
+
+import org.springframework.batch.item.ParseException;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+
+/**
+ * Implementation of {@link JsonObjectReader} based on
+ * <a href="https://github.com/FasterXML/jackson">Jackson</a>.
+ *
+ * @param <T> type of the target object
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 4.1
+ */
+public class JacksonJsonObjectReader<T> implements JsonObjectReader<T> {
+
+	private Class<? extends T> itemType;
+
+	private JsonParser jsonParser;
+
+	private ObjectMapper mapper = new ObjectMapper();
+
+	private InputStream inputStream;
+
+	/**
+	 * Create a new {@link JacksonJsonObjectReader} instance.
+	 * @param itemType the target item type
+	 */
+	public JacksonJsonObjectReader(Class<? extends T> itemType) {
+		this.itemType = itemType;
+	}
+
+	/**
+	 * Set the object mapper to use to map Json objects to domain objects.
+	 * @param mapper the object mapper to use
+	 */
+	public void setMapper(ObjectMapper mapper) {
+		Assert.notNull(mapper, "The mapper must not be null");
+		this.mapper = mapper;
+	}
+
+	@Override
+	public void open(Resource resource) throws Exception {
+		Assert.notNull(resource, "The resource must not be null");
+		this.inputStream = resource.getInputStream();
+		this.jsonParser = this.mapper.getFactory().createParser(this.inputStream);
+		Assert.state(this.jsonParser.nextToken() == JsonToken.START_ARRAY,
+				"The Json input stream must start with an array of Json objects");
+	}
+
+	@Override
+	public T read() throws Exception {
+		try {
+			if (this.jsonParser.nextToken() == JsonToken.START_OBJECT) {
+				return this.mapper.readValue(this.jsonParser, this.itemType);
+			}
+		} catch (IOException e) {
+			throw new ParseException("Unable to read next JSON object", e);
+		}
+		return null;
+	}
+
+	@Override
+	public void close() throws Exception {
+		this.inputStream.close();
+		this.jsonParser.close();
+	}
+
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/JsonItemReader.java

@@ -0,0 +1,126 @@
+/*
+ * Copyright 2018 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.json;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.batch.item.ItemStreamReader;
+import org.springframework.batch.item.file.ResourceAwareItemReaderItemStream;
+import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+
+/**
+ * {@link ItemStreamReader} implementation that reads Json objects from a
+ * {@link Resource} having the following format:
+ * <p>
+ * <code>
+ * [
+ *    {
+ *       // JSON object
+ *    },
+ *    {
+ *       // JSON object
+ *    }
+ * ]
+ * </code>
+ * <p>
+ *
+ * The implementation is <b>not</b> thread-safe.
+ *
+ * @param <T> the type of json objects to read
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 4.1
+ */
+public class JsonItemReader<T> extends AbstractItemCountingItemStreamItemReader<T> implements
+		ResourceAwareItemReaderItemStream<T> {
+
+	private static final Log LOGGER = LogFactory.getLog(JsonItemReader.class);
+
+	private Resource resource;
+
+	private JsonObjectReader<T> jsonObjectReader;
+
+	private boolean strict = true;
+
+	/**
+	 * Create a new {@link JsonItemReader} instance.
+	 * @param resource the input json resource
+	 * @param jsonObjectReader the json object reader to use
+	 */
+	public JsonItemReader(Resource resource, JsonObjectReader<T> jsonObjectReader) {
+		Assert.notNull(resource, "The resource must not be null.");
+		Assert.notNull(jsonObjectReader, "The json object reader must not be null.");
+		this.resource = resource;
+		this.jsonObjectReader = jsonObjectReader;
+	}
+
+	/**
+	 * Set the {@link JsonObjectReader} to use to read and map Json fragments to domain objects.
+	 * @param jsonObjectReader the json object reader to use
+	 */
+	public void setJsonObjectReader(JsonObjectReader<T> jsonObjectReader) {
+		this.jsonObjectReader = jsonObjectReader;
+	}
+
+	/**
+	 * In strict mode the reader will throw an exception on
+	 * {@link #open(org.springframework.batch.item.ExecutionContext)} if the
+	 * input resource does not exist.
+	 * @param strict true by default
+	 */
+	public void setStrict(boolean strict) {
+		this.strict = strict;
+	}
+
+	@Override
+	public void setResource(Resource resource) {
+		this.resource = resource;
+	}
+
+	@Override
+	protected T doRead() throws Exception {
+		return jsonObjectReader.read();
+	}
+
+	@Override
+	protected void doOpen() throws Exception {
+		if (!this.resource.exists()) {
+			if (this.strict) {
+				throw new IllegalStateException("Input resource must exist (reader is in 'strict' mode)");
+			}
+			LOGGER.warn("Input resource does not exist " + this.resource.getDescription());
+			return;
+		}
+		if (!this.resource.isReadable()) {
+			if (this.strict) {
+				throw new IllegalStateException("Input resource must be readable (reader is in 'strict' mode)");
+			}
+			LOGGER.warn("Input resource is not readable " + this.resource.getDescription());
+			return;
+		}
+		this.jsonObjectReader.open(this.resource);
+	}
+
+	@Override
+	protected void doClose() throws Exception {
+		this.jsonObjectReader.close();
+	}
+
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/JsonObjectReader.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright 2018 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.json;
+
+import org.springframework.core.io.Resource;
+
+/**
+ * Strategy interface for Json readers. Implementations are expected to use
+ * a streaming API in order to read Json objects one at a time.
+ *
+ * @param <T> type of the target object
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 4.1
+ */
+public interface JsonObjectReader<T> {
+
+	/**
+	 * Open the Json resource for reading.
+	 * @param resource the input resource
+	 * @throws Exception if unable to open the resource
+	 */
+	default void open(Resource resource) throws Exception {
+
+	}
+
+	/**
+	 * Read the next object in the Json resource if any.
+	 * @return the next object or null if the resource is exhausted
+	 * @throws Exception if unable to read the next object
+	 */
+	T read() throws Exception;
+
+	/**
+	 * Close the input resource.
+	 * @throws Exception if unable to close the input resource
+	 */
+	default void close() throws Exception {
+
+	}
+}

spring-batch-infrastructure/src/main/java/org/springframework/batch/item/json/builder/JsonItemReaderBuilder.java

@@ -0,0 +1,157 @@
+/*
+ * Copyright 2018 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.json.builder;
+
+import org.springframework.batch.item.json.JsonItemReader;
+import org.springframework.batch.item.json.JsonObjectReader;
+import org.springframework.core.io.Resource;
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
+
+/**
+ * A builder for {@link JsonItemReader}.
+ *
+ * @param <T> type of the target item
+ *
+ * @author Mahmoud Ben Hassine
+ * @since 4.1
+ */
+public class JsonItemReaderBuilder<T> {
+
+	private JsonObjectReader<T> jsonObjectReader;
+
+	private Resource resource;
+
+	private String name;
+
+	private boolean strict = true;
+
+	private boolean saveState = true;
+
+	private int maxItemCount = Integer.MAX_VALUE;
+
+	private int currentItemCount;
+
+	/**
+	 * Set the {@link JsonObjectReader} to use to read and map Json objects to domain objects.
+	 * @param jsonObjectReader to use
+	 * @return The current instance of the builder.
+	 * @see JsonItemReader#setJsonObjectReader(JsonObjectReader)
+	 */
+	public JsonItemReaderBuilder<T> jsonObjectReader(JsonObjectReader<T> jsonObjectReader) {
+		this.jsonObjectReader = jsonObjectReader;
+
+		return this;
+	}
+
+	/**
+	 * The {@link Resource} to be used as input.
+	 * @param resource the input to the reader.
+	 * @return The current instance of the builder.
+	 * @see JsonItemReader#setResource(Resource)
+	 */
+	public JsonItemReaderBuilder<T> resource(Resource resource) {
+		this.resource = resource;
+
+		return this;
+	}
+
+	/**
+	 * The name used to calculate the key within the
+	 * {@link org.springframework.batch.item.ExecutionContext}. Required if
+	 * {@link #saveState(boolean)} is set to true.
+	 * @param name name of the reader instance
+	 * @return The current instance of the builder.
+	 * @see org.springframework.batch.item.ItemStreamSupport#setName(String)
+	 */
+	public JsonItemReaderBuilder<T> name(String name) {
+		this.name = name;
+
+		return this;
+	}
+
+	/**
+	 * Setting this value to true indicates that it is an error if the input
+	 * does not exist and an exception will be thrown. Defaults to true.
+	 * @param strict indicates the input resource must exist
+	 * @return The current instance of the builder.
+	 * @see JsonItemReader#setStrict(boolean)
+	 */
+	public JsonItemReaderBuilder<T> strict(boolean strict) {
+		this.strict = strict;
+
+		return this;
+	}
+
+	/**
+	 * Configure if the state of the {@link org.springframework.batch.item.ItemStreamSupport}
+	 * should be persisted within the {@link org.springframework.batch.item.ExecutionContext}
+	 * for restart purposes.
+	 * @param saveState defaults to true
+	 * @return The current instance of the builder.
+	 */
+	public JsonItemReaderBuilder<T> saveState(boolean saveState) {
+		this.saveState = saveState;
+
+		return this;
+	}
+
+	/**
+	 * Configure the max number of items to be read.
+	 * @param maxItemCount the max items to be read
+	 * @return The current instance of the builder.
+	 * @see org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader#setMaxItemCount(int)
+	 */
+	public JsonItemReaderBuilder<T> maxItemCount(int maxItemCount) {
+		this.maxItemCount = maxItemCount;
+
+		return this;
+	}
+
+	/**
+	 * Index for the current item. Used on restarts to indicate where to start from.
+	 * @param currentItemCount current index
+	 * @return The current instance of the builder.
+	 * @see org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader#setCurrentItemCount(int)
+	 */
+	public JsonItemReaderBuilder<T> currentItemCount(int currentItemCount) {
+		this.currentItemCount = currentItemCount;
+
+		return this;
+	}
+
+	/**
+	 * Validate the configuration and build a new {@link JsonItemReader}.
+	 * @return a new instance of the {@link JsonItemReader}
+	 */
+	public JsonItemReader<T> build() {
+		Assert.notNull(this.jsonObjectReader, "A json object reader is required.");
+		Assert.notNull(this.resource, "A resource is required.");
+		if (this.saveState) {
+			Assert.state(StringUtils.hasText(this.name), "A name is required when saveState is set to true.");
+		}
+
+		JsonItemReader<T> reader = new JsonItemReader<>(this.resource, this.jsonObjectReader);
+		reader.setName(this.name);
+		reader.setStrict(this.strict);
+		reader.setSaveState(this.saveState);
+		reader.setMaxItemCount(this.maxItemCount);
+		reader.setCurrentItemCount(this.currentItemCount);
+
+		return reader;
+	}
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/json/GsonJsonItemReaderCommonTests.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2018 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.json;
+
+import org.springframework.batch.item.sample.Foo;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public class GsonJsonItemReaderCommonTests extends JsonItemReaderCommonTests {
+
+	@Override
+	protected JsonObjectReader<Foo> getJsonObjectReader() {
+		return new GsonJsonObjectReader<>(Foo.class);
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/json/JacksonJsonItemReaderCommonTests.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2018 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.json;
+
+import org.springframework.batch.item.sample.Foo;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public class JacksonJsonItemReaderCommonTests extends JsonItemReaderCommonTests {
+
+	@Override
+	protected JsonObjectReader<Foo> getJsonObjectReader() {
+		return new JacksonJsonObjectReader<>(Foo.class);
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/json/JsonItemReaderCommonTests.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2018 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.json;
+
+import org.springframework.batch.item.AbstractItemStreamItemReaderTests;
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemReader;
+import org.springframework.batch.item.sample.Foo;
+import org.springframework.core.io.ByteArrayResource;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public abstract class JsonItemReaderCommonTests extends AbstractItemStreamItemReaderTests {
+
+	private static final String FOOS = "[" +
+			"  {\"value\":1}," +
+			"  {\"value\":2}," +
+			"  {\"value\":3}," +
+			"  {\"value\":4}," +
+			"  {\"value\":5}" +
+			"]";
+
+	protected abstract JsonObjectReader<Foo> getJsonObjectReader();
+
+	@Override
+	protected ItemReader<Foo> getItemReader() {
+		ByteArrayResource resource = new ByteArrayResource(FOOS.getBytes());
+		JsonObjectReader<Foo> jsonObjectReader = getJsonObjectReader();
+		JsonItemReader<Foo> itemReader = new JsonItemReader<>(resource, jsonObjectReader);
+		itemReader.setName("fooJsonItemReader");
+		return itemReader;
+	}
+
+	@Override
+	protected void pointToEmptyInput(ItemReader<Foo> tested) {
+		JsonItemReader<Foo> reader = (JsonItemReader<Foo>) tested;
+		reader.setResource(new ByteArrayResource("[]".getBytes()));
+
+		reader.open(new ExecutionContext());
+	}
+
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/json/JsonItemReaderTests.java

@@ -0,0 +1,144 @@
+/*
+ * Copyright 2018 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.json;
+
+import java.io.InputStream;
+
+import org.hamcrest.Matchers;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnitRunner;
+
+import org.springframework.batch.item.ExecutionContext;
+import org.springframework.batch.item.ItemStreamException;
+import org.springframework.core.io.AbstractResource;
+import org.springframework.core.io.ByteArrayResource;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+@RunWith(MockitoJUnitRunner.class)
+public class JsonItemReaderTests {
+
+	@Rule
+	public ExpectedException expectedException = ExpectedException.none();
+
+	@Mock
+	private JsonObjectReader<String> jsonObjectReader;
+
+	private JsonItemReader<String> itemReader;
+
+	@Test
+	public void testValidation() {
+		try {
+			new JsonItemReader<>(null, this.jsonObjectReader);
+			fail("A resource is required.");
+		} catch (IllegalArgumentException iae) {
+			assertEquals("The resource must not be null.", iae.getMessage());
+		}
+
+		try {
+			new JsonItemReader<>(new ByteArrayResource("[{}]".getBytes()), null);
+			fail("A json object reader is required.");
+		} catch (IllegalArgumentException iae) {
+			assertEquals("The json object reader must not be null.", iae.getMessage());
+		}
+	}
+
+	@Test
+	public void testNonExistentResource() {
+		// given
+		this.expectedException.expect(ItemStreamException.class);
+		this.expectedException.expectMessage("Failed to initialize the reader");
+		this.expectedException.expectCause(Matchers.instanceOf(IllegalStateException.class));
+		this.itemReader = new JsonItemReader<>(new NonExistentResource(), this.jsonObjectReader);
+
+		// when
+		this.itemReader.open(new ExecutionContext());
+
+		// then
+		// expected exception
+	}
+
+	@Test
+	public void testNonReadableResource() {
+		// given
+		this.expectedException.expect(ItemStreamException.class);
+		this.expectedException.expectMessage("Failed to initialize the reader");
+		this.expectedException.expectCause(Matchers.instanceOf(IllegalStateException.class));
+		this.itemReader = new JsonItemReader<>(new NonReadableResource(), this.jsonObjectReader);
+
+		// when
+		this.itemReader.open(new ExecutionContext());
+
+		// then
+		// expected exception
+	}
+
+	private static class NonExistentResource extends AbstractResource {
+
+		NonExistentResource() {
+		}
+
+		@Override
+		public boolean exists() {
+			return false;
+		}
+
+		@Override
+		public String getDescription() {
+			return "NonExistentResource";
+		}
+
+		@Override
+		public InputStream getInputStream() {
+			return null;
+		}
+	}
+
+	private static class NonReadableResource extends AbstractResource {
+
+		NonReadableResource() {
+		}
+
+		@Override
+		public boolean isReadable() {
+			return false;
+		}
+
+		@Override
+		public boolean exists() {
+			return true;
+		}
+
+		@Override
+		public String getDescription() {
+			return "NonReadableResource";
+		}
+
+		@Override
+		public InputStream getInputStream() {
+			return null;
+		}
+	}
+}

spring-batch-infrastructure/src/test/java/org/springframework/batch/item/json/builder/JsonItemReaderBuilderTest.java

@@ -0,0 +1,105 @@
+/*
+ * Copyright 2018 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.json.builder;
+
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import org.springframework.batch.item.json.JsonItemReader;
+import org.springframework.batch.item.json.JsonObjectReader;
+import org.springframework.core.io.Resource;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
+import static org.springframework.test.util.ReflectionTestUtils.getField;
+
+/**
+ * @author Mahmoud Ben Hassine
+ */
+public class JsonItemReaderBuilderTest {
+
+	@Mock
+	private Resource resource;
+	@Mock
+	private JsonObjectReader<String> jsonObjectReader;
+
+	@Before
+	public void setUp() {
+		MockitoAnnotations.initMocks(this);
+	}
+
+	@Test
+	public void testValidation() {
+		try {
+			new JsonItemReaderBuilder<String>()
+					.build();
+			fail("A json object reader is required.");
+		}
+		catch (IllegalArgumentException iae) {
+			assertEquals("A json object reader is required.",
+					iae.getMessage());
+		}
+
+		try {
+			new JsonItemReaderBuilder<String>()
+					.jsonObjectReader(this.jsonObjectReader)
+					.build();
+			fail("A resource is required.");
+		}
+		catch (IllegalArgumentException iae) {
+			assertEquals("A resource is required.",
+					iae.getMessage());
+		}
+
+		try {
+			new JsonItemReaderBuilder<String>()
+					.jsonObjectReader(this.jsonObjectReader)
+					.resource(this.resource)
+					.build();
+			fail("A name is required when saveState is set to true.");
+		}
+		catch (IllegalStateException iae) {
+			assertEquals("A name is required when saveState is set to true.",
+					iae.getMessage());
+		}
+	}
+
+	@Test
+	public void testConfiguration() {
+		JsonItemReader<String> itemReader = new JsonItemReaderBuilder<String>()
+				.jsonObjectReader(this.jsonObjectReader)
+				.resource(this.resource)
+				.saveState(true)
+				.strict(true)
+				.name("jsonItemReader")
+				.maxItemCount(100)
+				.currentItemCount(50)
+				.build();
+
+		Assert.assertEquals(this.jsonObjectReader, getField(itemReader, "jsonObjectReader"));
+		Assert.assertEquals(this.resource, getField(itemReader, "resource"));
+		Assert.assertEquals(100, getField(itemReader, "maxItemCount"));
+		Assert.assertEquals(50, getField(itemReader, "currentItemCount"));
+		Assert.assertTrue((Boolean) getField(itemReader, "saveState"));
+		Assert.assertTrue((Boolean) getField(itemReader, "strict"));
+		Object executionContext = getField(itemReader, "executionContextUserSupport");
+		Assert.assertEquals("jsonItemReader", getField(executionContext, "name"));
+	}
+}