Java tutorial
/* * Copyright (c) 2014-2015 Red Hat, Inc. and/or its affiliates. * * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html * * Contributors: * Cheng Fang - Initial API and implementation */ package org.jberet.support.io; import java.io.OutputStream; import java.io.Serializable; import java.util.List; import java.util.Map; import javax.batch.api.BatchProperty; import javax.batch.api.chunk.ItemWriter; import javax.enterprise.context.Dependent; import javax.inject.Inject; import javax.inject.Named; import com.fasterxml.jackson.core.JsonFactory; import com.fasterxml.jackson.core.JsonGenerator; import com.fasterxml.jackson.core.PrettyPrinter; import com.fasterxml.jackson.core.io.OutputDecorator; import org.jberet.support._private.SupportLogger; import org.jberet.support._private.SupportMessages; /** * An implementation of {@code javax.batch.api.chunk.ItemWriter} that writes a list of same-typed objects to Json resource. * Each object is written as part of the root Json array. * * @see JsonItemReader * @see JsonItemReaderWriterBase * @since 1.0.2 */ @Named @Dependent public class JsonItemWriter extends JsonItemReaderWriterBase implements ItemWriter { /** * Instructs this class, when the target Json resource already exists, whether to append to, or overwrite * the existing resource, or fail. Valid values are {@code append}, {@code overwrite}, and {@code failIfExists}. * Optional property, and defaults to {@code append}. */ @Inject @BatchProperty protected String writeMode; /** * A comma-separated list of key-value pairs that specify {@code com.fasterxml.jackson.core.JsonGenerator} features. * Optional property and defaults to null. Keys and values must be defined in * {@code com.fasterxml.jackson.core.JsonGenerator.Feature}. For example, * <p/> * <pre> * WRITE_BIGDECIMAL_AS_PLAIN=true, WRITE_NUMBERS_AS_STRINGS=true, QUOTE_NON_NUMERIC_NUMBERS=false * </pre> * * @see "com.fasterxml.jackson.core.JsonGenerator.Feature" */ @Inject @BatchProperty protected Map<String, String> jsonGeneratorFeatures; /** * Fully-qualified name of a class that implements {@code com.fasterxml.jackson.core.PrettyPrinter}, which * implements pretty printer functionality, such as indentation. Optional property and defaults to null (the * system default pretty printer is used). For example, * <p/> * <pre> * com.fasterxml.jackson.core.util.MinimalPrettyPrinter * </pre> * * @see "com.fasterxml.jackson.core.PrettyPrinter" * @see "com.fasterxml.jackson.core.JsonGenerator#setPrettyPrinter(com.fasterxml.jackson.core.PrettyPrinter)" */ @Inject @BatchProperty protected Class prettyPrinter; /** * Fully-qualified name of a class that implements {@code com.fasterxml.jackson.core.io.OutputDecorator}, which * can be used to decorate output destinations. Typical use is to use a filter abstraction (filtered output stream, * writer) around original output destination, and apply additional processing during write operations. * Optional property and defaults to null. For example, * <p/> * <pre> * org.jberet.support.io.JsonItemReaderTest$NoopOutputDecorator * </pre> * * @see "com.fasterxml.jackson.core.io.OutputDecorator" * @see "com.fasterxml.jackson.core.JsonFactory#setOutputDecorator(com.fasterxml.jackson.core.io.OutputDecorator)" */ @Inject @BatchProperty protected Class outputDecorator; protected JsonGenerator jsonGenerator; @Override public void open(final Serializable checkpoint) throws Exception { SupportLogger.LOGGER.tracef( "Open JsonItemWriter with checkpoint %s, which is ignored for JsonItemWriter.%n", checkpoint); initJsonFactoryAndObjectMapper(); jsonGenerator = configureJsonGenerator(jsonFactory, getOutputStream(writeMode), outputDecorator, jsonGeneratorFeatures); SupportLogger.LOGGER.openingResource(resource, this.getClass()); if (prettyPrinter == null) { jsonGenerator.useDefaultPrettyPrinter(); } else { jsonGenerator.setPrettyPrinter((PrettyPrinter) prettyPrinter.newInstance()); } //write { regardless of the value of skipWritingHeader, since any existing content already ends with } jsonGenerator.writeStartArray(); } @Override public void writeItems(final List<Object> items) throws Exception { for (final Object o : items) { jsonGenerator.writeObject(o); } jsonGenerator.flush(); } @Override public Serializable checkpointInfo() throws Exception { return null; } @Override public void close() throws Exception { if (jsonGenerator != null) { SupportLogger.LOGGER.closingResource(resource, this.getClass()); jsonGenerator.close(); jsonGenerator = null; } } protected static JsonGenerator configureJsonGenerator(final JsonFactory jsonFactory, final OutputStream outputStream, final Class<?> outputDecorator, final Map<String, String> jsonGeneratorFeatures) throws Exception { if (outputDecorator != null) { jsonFactory.setOutputDecorator((OutputDecorator) outputDecorator.newInstance()); } final JsonGenerator jsonGenerator = jsonFactory.createGenerator(outputStream); if (jsonGeneratorFeatures != null) { for (final Map.Entry<String, String> e : jsonGeneratorFeatures.entrySet()) { final String key = e.getKey(); final String value = e.getValue(); final JsonGenerator.Feature feature; try { feature = JsonGenerator.Feature.valueOf(key); } catch (final Exception e1) { throw SupportMessages.MESSAGES.unrecognizedReaderWriterProperty(key, value); } if ("true".equals(value)) { if (!feature.enabledByDefault()) { jsonGenerator.configure(feature, true); } } else if ("false".equals(value)) { if (feature.enabledByDefault()) { jsonGenerator.configure(feature, false); } } else { throw SupportMessages.MESSAGES.invalidReaderWriterProperty(null, value, key); } } } return jsonGenerator; } }