Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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.apache.batchee.jackson; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.databind.ObjectMapper; import org.apache.batchee.extras.transaction.TransactionalWriter; import javax.batch.api.BatchProperty; import javax.batch.api.chunk.ItemWriter; import javax.batch.operations.BatchRuntimeException; import javax.inject.Inject; import java.io.File; import java.io.Serializable; import java.util.List; public class JacksonJSonWriter implements ItemWriter { @Inject @BatchProperty private String file; @Inject @BatchProperty private String encoding; @Inject @BatchProperty private String configuration; @Inject @BatchProperty private String skipRoot; @Inject @BatchProperty private String fieldNameGeneratorClass; private JsonGenerator generator; private TransactionalWriter writer; private FieldNameGenerator fieldNameGenerator = null; @Override public void open(final Serializable checkpoint) throws Exception { final File outputFile = new File(file); if (!outputFile.getParentFile().exists() && !outputFile.getParentFile().mkdirs()) { throw new BatchRuntimeException("Can't create " + outputFile.getAbsolutePath()); } final ObjectMapper mapper = Jacksons.newMapper(configuration); writer = new TransactionalWriter(outputFile, encoding, checkpoint); generator = mapper.getFactory().createGenerator(writer); if (fieldNameGeneratorClass != null) { if ("default".equals(fieldNameGeneratorClass)) { fieldNameGenerator = new DefaultFieldNameGenerator(); } else { fieldNameGenerator = FieldNameGenerator.class.cast(Thread.currentThread().getContextClassLoader() .loadClass(fieldNameGeneratorClass).newInstance()); } } if (useGlobalWrapper()) { if (fieldNameGenerator != null) { generator.writeStartObject(); } else { generator.writeStartArray(); } } } @Override public void close() throws Exception { if (generator != null) { if (useGlobalWrapper()) { if (fieldNameGenerator != null) { generator.writeEndObject(); } else { generator.writeEndArray(); } } generator.close(); } } @Override public void writeItems(final List<Object> items) throws Exception { for (final Object o : items) { if (fieldNameGenerator != null) { generator.writeFieldName(fieldNameGenerator.nextName()); } generator.writeObject(o); } writer.flush(); } @Override public Serializable checkpointInfo() throws Exception { return writer.position(); } private boolean useGlobalWrapper() { return skipRoot == null || !"true".equalsIgnoreCase(skipRoot); } }