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.olingo.client.api.domain; import org.apache.commons.io.IOUtils; import org.apache.commons.lang3.StringUtils; import org.apache.olingo.client.api.CommonODataClient; import org.apache.olingo.commons.api.Constants; import org.apache.olingo.commons.api.data.Entity; import org.apache.olingo.commons.api.data.ResWrap; import org.apache.olingo.commons.api.domain.CommonODataEntity; import org.apache.olingo.commons.api.domain.CommonODataEntitySet; import org.apache.olingo.commons.api.format.ODataFormat; import org.apache.olingo.commons.api.serialization.ODataDeserializerException; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.URI; import java.util.Iterator; import java.util.NoSuchElementException; /** * OData entity set iterator class. * <br/> * <b>Please don't forget to call the <tt>close()>/</tt> method when not needed any more.</b> * * @param <E> concrete ODataEntity implementation * @param <ES> concrete ODataEntitySet implementation */ public class ODataEntitySetIterator<ES extends CommonODataEntitySet, E extends CommonODataEntity> implements Iterator<E> { /** * Logger. */ private static final Logger LOG = LoggerFactory.getLogger(ODataEntitySetIterator.class); protected final CommonODataClient<?> odataClient; protected ResWrap<Entity> cached; private final InputStream stream; private final ODataFormat format; private ES entitySet; private final ByteArrayOutputStream osEntitySet; private final String namespaces; private boolean available = true; /** * Constructor. * * @param odataClient client instance getting this request * @param stream source stream. * @param format OData format. */ public ODataEntitySetIterator(final CommonODataClient<?> odataClient, final InputStream stream, final ODataFormat format) { this.odataClient = odataClient; this.stream = stream; this.format = format; this.osEntitySet = new ByteArrayOutputStream(); if (format == ODataFormat.ATOM) { namespaces = getAllElementAttributes(stream, "feed", osEntitySet); } else { namespaces = null; try { if (consume(stream, "\"value\":", osEntitySet, true) >= 0) { int c = 0; while (c != '[' && (c = stream.read()) >= 0) { osEntitySet.write(c); } } } catch (IOException e) { LOG.error("Error parsing entity set", e); throw new IllegalStateException(e); } } } /** * {@inheritDoc } */ @Override @SuppressWarnings("unchecked") public boolean hasNext() { if (available && cached == null) { if (format == ODataFormat.ATOM) { cached = nextAtomEntityFromEntitySet(stream, osEntitySet, namespaces); } else { cached = nextJSONEntityFromEntitySet(stream, osEntitySet); } if (cached == null) { available = false; try { entitySet = (ES) odataClient.getReader() .readEntitySet(new ByteArrayInputStream(osEntitySet.toByteArray()), format); } catch (final ODataDeserializerException e) { available = false; } close(); } } return available; } /** * {@inheritDoc } */ @Override public E next() { if (hasNext()) { @SuppressWarnings("unchecked") final E res = (E) odataClient.getBinder().getODataEntity(cached); cached = null; return res; } throw new NoSuchElementException("No entity found"); } /** * Unsupported operation. */ @Override public void remove() { throw new UnsupportedOperationException("Operation not supported"); } /** * Closes the current iterator. */ public void close() { IOUtils.closeQuietly(stream); IOUtils.closeQuietly(osEntitySet); } /** * Gets the next link if exists. * * @return next link if exists; null otherwise. */ public URI getNext() { if (entitySet == null) { throw new IllegalStateException( "Iteration must be completed in order to retrieve the link for next page"); } return entitySet.getNext(); } private ResWrap<Entity> nextJSONEntityFromEntitySet(final InputStream input, final OutputStream osEntitySet) { final ByteArrayOutputStream entity = new ByteArrayOutputStream(); ResWrap<Entity> jsonEntity = null; try { int c; boolean foundNewOne = false; do { c = input.read(); if (c == '{') { entity.write(c); c = -1; foundNewOne = true; } if (c == ']') { osEntitySet.write(c); c = -1; } } while (c >= 0); if (foundNewOne) { int count = 1; c = 0; while (count > 0 && c >= 0) { c = input.read(); if (c == '{') { count++; } else if (c == '}') { count--; } entity.write(c); } if (c >= 0) { jsonEntity = odataClient.getDeserializer(ODataFormat.JSON) .toEntity(new ByteArrayInputStream(entity.toByteArray())); } } else { while ((c = input.read()) >= 0) { osEntitySet.write(c); } } } catch (Exception e) { LOG.error("Error retrieving entities from EntitySet", e); } return jsonEntity; } private ResWrap<Entity> nextAtomEntityFromEntitySet(final InputStream input, final OutputStream osEntitySet, final String namespaces) { final ByteArrayOutputStream entity = new ByteArrayOutputStream(); ResWrap<Entity> atomEntity = null; try { if (consume(input, "<entry>", osEntitySet, false) >= 0) { entity.write("<entry ".getBytes(Constants.UTF8)); entity.write(namespaces.getBytes(Constants.UTF8)); entity.write(">".getBytes(Constants.UTF8)); if (consume(input, "</entry>", entity, true) >= 0) { atomEntity = odataClient.getDeserializer(ODataFormat.ATOM) .toEntity(new ByteArrayInputStream(entity.toByteArray())); } } } catch (Exception e) { LOG.error("Error retrieving entities from EntitySet", e); } return atomEntity; } private String getAllElementAttributes(final InputStream input, final String name, final OutputStream os) { final ByteArrayOutputStream attrs = new ByteArrayOutputStream(); String res; try { byte[] attrsDeclaration = null; final String key = "<" + name + " "; if (consume(input, key, os, true) >= 0 && consume(input, ">", attrs, false) >= 0) { attrsDeclaration = attrs.toByteArray(); os.write(attrsDeclaration); os.write('>'); } res = attrsDeclaration == null ? StringUtils.EMPTY : new String(attrsDeclaration, Constants.UTF8).trim(); } catch (Exception e) { LOG.error("Error retrieving entities from EntitySet", e); res = StringUtils.EMPTY; } return res.endsWith("/") ? res.substring(0, res.length() - 1) : res; } private int consume(final InputStream input, final String end, final OutputStream os, final boolean includeEndKey) throws IOException { final char[] endKey = end.toCharArray(); final char[] endLowerKey = end.toLowerCase().toCharArray(); final char[] endUpperKey = end.toUpperCase().toCharArray(); int pos = 0; int c = 0; while (pos < endKey.length && (c = input.read()) >= 0) { if (c == endLowerKey[pos] || c == endUpperKey[pos]) { pos++; if (includeEndKey && os != null) { os.write(c); } } else if (pos > 0) { if (!includeEndKey && os != null) { for (int i = 0; i < pos; i++) { os.write(endKey[i]); } } if (os != null) { os.write(c); } pos = 0; } else { if (os != null) { os.write(c); } } } return c; } }