Java tutorial
/* Copyright 2013 Peter Laird 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 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 com.storageroomapp.client; import java.util.ArrayList; import java.util.Iterator; import java.util.List; import org.json.simple.JSONArray; import org.json.simple.JSONObject; import org.json.simple.JSONValue; import com.storageroomapp.client.util.Http; import com.storageroomapp.client.util.JsonSimpleUtil; import com.storageroomapp.client.util.StorageRoomUtil; /** * Encapsulates a page of live results from a query to the StorageRoom * API. It is initially obtained via the query methods on the CollectionEntries * object. Navigating to other pages of the results is done with the * jumpPage() method on this object. * */ public class PageOfEntries { // INPUT into server protected Collection parentCollection = null; protected CollectionQuery queryOptions = null; protected int currentPage = 0; // OUTPUT from server protected int numResultsPages = 0; protected int currentPageSize = 0; protected List<Entry> currentPageEntries = null; // ITERATOR protected int iteratorIndex = 0; // CONSTRUCTION /** * Parses a String of json text and returns an PageOfEntries object. * It will correctly parse the PageOfEntries object if it is toplevel, * or also if nested in an 'array' key-value pair. * * @param json the String with the json text * @return an PageOfEntries object, or null if the parsing failed */ static public PageOfEntries parseJSON(Collection parent, String json) { if (json == null) { return null; } JSONObject jsonObj = (JSONObject) JSONValue.parse(json); if (jsonObj == null) { return null; } JSONObject jsonArrayObj = (JSONObject) jsonObj.get("array"); if (jsonArrayObj != null) { jsonObj = jsonArrayObj; } return parseJSONObject(parent, jsonObj); } /** * Unmarshalls an PageOfEntries object from a JSONObject. This method * assumes the name-values are immediately attached to the passed object * and not nested under a key (e.g. 'array') * @param jsonObj the JSONObject * @return an PageOfEntries object, or null if the unpacking failed */ static public PageOfEntries parseJSONObject(Collection parent, JSONObject jsonObject) { if (jsonObject == null) { return null; } JSONArray jsonArray = (JSONArray) jsonObject.get("resources"); if (jsonArray == null) { return null; } PageOfEntries el = new PageOfEntries(); el.currentPage = JsonSimpleUtil.parseJsonIntValue(jsonObject, "@page", 0); el.currentPageSize = JsonSimpleUtil.parseJsonIntValue(jsonObject, "@total_resources", 20); el.numResultsPages = JsonSimpleUtil.parseJsonIntValue(jsonObject, "@pages", 1); el.currentPageEntries = new ArrayList<Entry>(); @SuppressWarnings("unchecked") Iterator<JSONObject> iter = jsonArray.iterator(); while (iter.hasNext()) { JSONObject entryObj = iter.next(); Entry entry = Entry.parseJSONObject(parent, entryObj); if (entry != null) { el.currentPageEntries.add(entry); } } return el; } // OPERATIONS /** * Performs the actual query against the SR API. This is a protected method, * it is accessed via jumpPage() on this object or via the CollectionEntries * query methods. * <p> * SERVER ROUND TRIP: this is a live API call * * @param parent the Collection * @param query the query definition * @param page the page to retrieve, 0 for the first page * @return the PageOfEntries result, or null if a problem occurred */ static protected PageOfEntries doLiveQuery(Collection parent, CollectionQuery query, int page) { if (parent == null) { return null; } Application pa = parent.getParentApplication(); String entriesUrl = parent.getEntriesUrl(); String extraQueryParams = null; if (query != null) { extraQueryParams = query.generateQueryString(page); } String queryUrl = StorageRoomUtil.decorateUrl(entriesUrl, pa.getAuthToken(), true, extraQueryParams); String results = Http.getAsString(queryUrl); if (results == null) { return null; } PageOfEntries el = PageOfEntries.parseJSON(parent, results); if (el == null) { return null; } el.parentCollection = parent; el.queryOptions = query; el.currentPage = page; return el; } /** * Jump to a new page in the results, using the same query * <p> * SERVER ROUND TRIP: this is a live API call * * @param newPage the new page in the results to fetch * @return the PageOfEntries result, or null if a problem occurred */ public PageOfEntries jumpPage(int newPage) { return doLiveQuery(this.parentCollection, this.queryOptions, newPage); } // GETTERS public Collection getParentCollection() { return parentCollection; } public CollectionQuery getQueryOptions() { return queryOptions; } public int getCurrentPage() { return currentPage; } public int getNumResultsPages() { return numResultsPages; } public int getCurrentPageSize() { return currentPageSize; } /** * Returns the list of Entry objects as an Iterable * @return the Iterable, or null if no entries exist */ public Iterable<Entry> asIterable() { if (currentPageEntries == null) { return null; } return java.util.Collections.unmodifiableList(currentPageEntries); } /** * Returns the list of Entry objects as a List * @return the List, or null if no entries exist */ public List<Entry> asList() { if (currentPageEntries == null) { return null; } return java.util.Collections.unmodifiableList(currentPageEntries); } }