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Add a streaming Json item reader
This commit adds a new Json item reader implementation based on Jackson. Resolves BATCH-2691
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‎spring-batch-infrastructure-tests/src/test/java/org/springframework/batch/item/json/JsonItemReaderFunctionalTests.java

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/*
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* Copyright 2018 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.batch.item.json;
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import java.math.BigDecimal;
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import com.fasterxml.jackson.core.JsonParseException;
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import org.junit.Assert;
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import org.junit.Rule;
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import org.junit.Test;
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import org.junit.rules.ExpectedException;
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import org.springframework.batch.item.ExecutionContext;
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import org.springframework.batch.item.ItemStreamException;
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import org.springframework.batch.item.json.domain.Trade;
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import org.springframework.core.io.ByteArrayResource;
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import org.springframework.core.io.ClassPathResource;
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import static org.hamcrest.Matchers.instanceOf;
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/**
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* @author Mahmoud Ben Hassine
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*/
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public class JsonItemReaderFunctionalTests {
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@Rule
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public ExpectedException expectedException = ExpectedException.none();
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@Test
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public void testJsonReading() throws Exception {
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JsonItemReader<Trade> itemReader = new JsonItemReader<>();
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itemReader.setItemType(Trade.class);
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itemReader.setResource(new ClassPathResource("org/springframework/batch/item/json/trades.json"));
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itemReader.setName("tradeJsonItemReader");
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itemReader.afterPropertiesSet();
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itemReader.open(new ExecutionContext());
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Trade trade = itemReader.read();
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Assert.assertNotNull(trade);
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Assert.assertEquals("123", trade.getIsin());
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Assert.assertEquals("foo", trade.getCustomer());
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Assert.assertEquals(new BigDecimal("1.2"), trade.getPrice());
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Assert.assertEquals(1, trade.getQuantity());
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trade = itemReader.read();
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Assert.assertNotNull(trade);
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Assert.assertEquals("456", trade.getIsin());
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Assert.assertEquals("bar", trade.getCustomer());
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Assert.assertEquals(new BigDecimal("1.4"), trade.getPrice());
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Assert.assertEquals(2, trade.getQuantity());
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trade = itemReader.read();
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Assert.assertNull(trade);
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}
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@Test
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public void testEmptyResource() throws Exception {
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JsonItemReader<Trade> itemReader = new JsonItemReader<>();
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itemReader.setItemType(Trade.class);
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itemReader.setResource(new ByteArrayResource("[]".getBytes()));
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itemReader.setName("tradeJsonItemReader");
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itemReader.afterPropertiesSet();
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itemReader.open(new ExecutionContext());
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Trade trade = itemReader.read();
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Assert.assertNull(trade);
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}
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@Test
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public void testInvalidResourceFormat() throws Exception {
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this.expectedException.expect(ItemStreamException.class);
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this.expectedException.expectMessage("Failed to initialize the reader");
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this.expectedException.expectCause(instanceOf(IllegalStateException.class));
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JsonItemReader<Trade> itemReader = new JsonItemReader<>();
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itemReader.setItemType(Trade.class);
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itemReader.setResource(new ByteArrayResource("{}, {}".getBytes()));
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itemReader.afterPropertiesSet();
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itemReader.open(new ExecutionContext());
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}
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@Test
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public void testInvalidResourceContent() throws Exception {
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this.expectedException.expect(JsonParseException.class);
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JsonItemReader<Trade> itemReader = new JsonItemReader<>();
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itemReader.setItemType(Trade.class);
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itemReader.setResource(new ByteArrayResource("[{]".getBytes()));
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itemReader.setName("tradeJsonItemReader");
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itemReader.afterPropertiesSet();
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itemReader.open(new ExecutionContext());
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itemReader.read();
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}
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}

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

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/*
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* Copyright 2018 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.batch.item.json.domain;
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import java.math.BigDecimal;
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/**
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* @author Mahmoud Ben Hassine
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*/
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public class Trade {
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private String isin = "";
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private long quantity = 0;
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private BigDecimal price = new BigDecimal(0);
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private String customer = "";
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public Trade() {
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}
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public Trade(String isin, long quantity, BigDecimal price, String customer) {
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this.isin = isin;
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this.quantity = quantity;
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this.price = price;
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this.customer = customer;
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}
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public void setCustomer(String customer) {
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this.customer = customer;
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}
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public void setIsin(String isin) {
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this.isin = isin;
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}
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public void setPrice(BigDecimal price) {
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this.price = price;
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}
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public void setQuantity(long quantity) {
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this.quantity = quantity;
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}
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public String getIsin() {
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return isin;
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}
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public BigDecimal getPrice() {
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return price;
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}
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public long getQuantity() {
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return quantity;
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}
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public String getCustomer() {
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return customer;
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}
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@Override
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public String toString() {
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return "Trade: [isin=" + this.isin + ",quantity=" + this.quantity + ",price=" + this.price + ",customer="
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+ this.customer + "]";
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}
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@Override
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public int hashCode() {
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final int prime = 31;
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int result = 1;
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result = prime * result + ((customer == null) ? 0 : customer.hashCode());
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result = prime * result + ((isin == null) ? 0 : isin.hashCode());
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result = prime * result + ((price == null) ? 0 : price.hashCode());
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result = prime * result + (int) (quantity ^ (quantity >>> 32));
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return result;
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}
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@Override
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public boolean equals(Object obj) {
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if (this == obj)
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return true;
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if (obj == null)
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return false;
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if (getClass() != obj.getClass())
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return false;
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Trade other = (Trade) obj;
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if (customer == null) {
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if (other.customer != null)
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return false;
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}
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else if (!customer.equals(other.customer))
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return false;
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if (isin == null) {
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if (other.isin != null)
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return false;
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}
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else if (!isin.equals(other.isin))
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return false;
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if (price == null) {
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if (other.price != null)
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return false;
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}
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else if (!price.equals(other.price))
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return false;
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if (quantity != other.quantity)
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return false;
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return true;
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}
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}

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

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[
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{
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"isin": "123",
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"quantity": 1,
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"price": 1.2,
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"customer": "foo"
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},
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{
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"isin": "456",
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"quantity": 2,
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"price": 1.4,
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"customer": "bar"
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}
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]

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

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/*
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* Copyright 2018 the original author or authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.springframework.batch.item.json;
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import java.io.InputStream;
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import com.fasterxml.jackson.core.JsonParser;
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import com.fasterxml.jackson.core.JsonToken;
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import com.fasterxml.jackson.databind.ObjectMapper;
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import org.apache.commons.logging.Log;
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import org.apache.commons.logging.LogFactory;
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import org.springframework.batch.item.ItemStreamReader;
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import org.springframework.batch.item.file.ResourceAwareItemReaderItemStream;
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import org.springframework.batch.item.support.AbstractItemCountingItemStreamItemReader;
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import org.springframework.beans.factory.InitializingBean;
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import org.springframework.core.io.Resource;
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import org.springframework.util.Assert;
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/**
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* {@link ItemStreamReader} implementation that reads Json objects from a
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* {@link Resource} having the following format:
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* <p>
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* <code>
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* [
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* {
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* // JSON object
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* },
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* {
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* // JSON object
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* }
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* ]
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* </code>
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* <p>
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*
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* The implementation is <b>not</b> thread-safe.
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*
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* @param <T> the type of json objects to read
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*
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* @author Mahmoud Ben Hassine
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* @since 4.1
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*/
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public class JsonItemReader<T> extends AbstractItemCountingItemStreamItemReader<T> implements
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ResourceAwareItemReaderItemStream<T>, InitializingBean {
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private static final Log LOGGER = LogFactory.getLog(JsonItemReader.class);
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private Class<T> itemType;
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private Resource resource;
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private JsonParser parser;
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private ObjectMapper mapper = new ObjectMapper();
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private boolean strict = true;
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/**
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* Set the {@link ObjectMapper} to use to map Json fragments to domain objects.
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* @param mapper to use
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*/
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public void setObjectMapper(ObjectMapper mapper) {
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this.mapper = mapper;
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}
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/**
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* Set the target domain object type.
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* @param itemType the target domain object type
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*/
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public void setItemType(Class<T> itemType) {
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this.itemType = itemType;
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}
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/**
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* In strict mode the reader will throw an exception on
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* {@link #open(org.springframework.batch.item.ExecutionContext)} if the
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* input resource does not exist.
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* @param strict true by default
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*/
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public void setStrict(boolean strict) {
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this.strict = strict;
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}
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@Override
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public void setResource(Resource resource) {
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this.resource = resource;
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}
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@Override
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protected T doRead() throws Exception {
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if (this.parser.nextToken() == JsonToken.START_OBJECT) {
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return this.mapper.readValue(this.parser, this.itemType);
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}
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return null;
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}
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@Override
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protected void doOpen() throws Exception {
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if (!this.resource.exists()) {
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if (this.strict) {
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throw new IllegalStateException("Input resource must exist (reader is in 'strict' mode)");
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}
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LOGGER.warn("Input resource does not exist " + this.resource.getDescription());
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return;
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}
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if (!this.resource.isReadable()) {
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if (this.strict) {
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throw new IllegalStateException("Input resource must be readable (reader is in 'strict' mode)");
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}
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LOGGER.warn("Input resource is not readable " + this.resource.getDescription());
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return;
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}
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InputStream resourceInputStream = this.resource.getInputStream();
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this.parser = this.mapper.getFactory().createParser(resourceInputStream);
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Assert.state(this.parser.nextToken() == JsonToken.START_ARRAY,
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"The resource must start with an array of Json objects");
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}
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@Override
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protected void doClose() throws Exception {
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this.parser.close();
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}
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@Override
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public void afterPropertiesSet() throws Exception {
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Assert.notNull(this.itemType, "The item type must not be null.");
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Assert.notNull(this.resource, "The resource must not be null.");
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}
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}

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