Java tutorial
/* * 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 * * 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.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(); } }