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Diffstat (limited to 'examples_java/src/persist/EventExample.java')
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diff --git a/examples_java/src/persist/EventExample.java b/examples_java/src/persist/EventExample.java new file mode 100644 index 0000000..5a3ee44 --- /dev/null +++ b/examples_java/src/persist/EventExample.java @@ -0,0 +1,424 @@ +/*- + * See the file LICENSE for redistribution information. + * + * Copyright (c) 2004-2009 Oracle. All rights reserved. + * + * $Id$ + */ + +package persist; + +import java.io.File; +import java.io.FileNotFoundException; +import java.io.Serializable; +import java.util.Calendar; +import java.util.Date; +import java.util.HashSet; +import java.util.Random; +import java.util.Set; + +import com.sleepycat.bind.EntryBinding; +import com.sleepycat.bind.serial.SerialBinding; +import com.sleepycat.bind.serial.StoredClassCatalog; +import com.sleepycat.bind.tuple.IntegerBinding; +import com.sleepycat.bind.tuple.LongBinding; +import com.sleepycat.db.Cursor; +import com.sleepycat.db.Database; +import com.sleepycat.db.DatabaseConfig; +import com.sleepycat.db.DatabaseEntry; +import com.sleepycat.db.DatabaseException; +import com.sleepycat.db.DatabaseType; +import com.sleepycat.db.Environment; +import com.sleepycat.db.EnvironmentConfig; +import com.sleepycat.db.OperationStatus; +import com.sleepycat.db.SecondaryConfig; +import com.sleepycat.db.SecondaryCursor; +import com.sleepycat.db.SecondaryDatabase; +import com.sleepycat.db.SecondaryKeyCreator; +import com.sleepycat.db.Transaction; + +/** + * EventExample is a trivial example which stores Java objects that represent + * an event. Events are primarily indexed by a timestamp, but have other + * attributes, such as price, account reps, customer name and quantity. + * Some of those other attributes are indexed. + * <p> + * The example simply shows the creation of a BDB environment and database, + * inserting some events, and retrieving the events. + * <p> + * This example is meant to be paired with its twin, EventExampleDPL.java. + * EventExample.java and EventExampleDPL.java perform the same functionality, + * but use the Base API and the Direct Persistence Layer API, respectively. + * This may be a useful way to compare the two APIs. + * <p> + * To run the example: + * <pre> + * cd jehome/examples + * javac je/EventExample.java + * java je.EventExample -h <environmentDirectory> + * </pre> + */ +public class EventExample { + + /* + * The Event class embodies our example event and is the application + * data. BDB data records are represented at key/data tuples. In this + * example, the key portion of the record is the event time, and the data + * portion is the Event instance. + */ + static class Event implements Serializable { + + /* This example will add secondary indices on price and accountReps. */ + private int price; + private Set<String> accountReps; + + private String customerName; + private int quantity; + + Event(int price, + String customerName) { + + this.price = price; + this.customerName = customerName; + this.accountReps = new HashSet<String>(); + } + + void addRep(String rep) { + accountReps.add(rep); + } + + @Override + public String toString() { + StringBuilder sb = new StringBuilder(); + sb.append(" price=").append(price); + sb.append(" customerName=").append(customerName); + sb.append(" reps="); + if (accountReps.size() == 0) { + sb.append("none"); + } else { + for (String rep: accountReps) { + sb.append(rep).append(" "); + } + } + return sb.toString(); + } + + int getPrice() { + return price; + } + } + + /* A BDB environment is roughly equivalent to a relational database. */ + private Environment env; + + /* + * A BDB table is roughly equivalent to a relational table with a + * primary index. + */ + private Database eventDb; + + /* A secondary database indexes an additional field of the data record */ + private SecondaryDatabase eventByPriceDb; + + /* + * The catalogs and bindings are used to convert Java objects to the byte + * array format used by BDB key/data in the base API. The Direct + * Persistence Layer API supports Java objects as arguments directly. + */ + private Database catalogDb; + private EntryBinding eventBinding; + + /* Used for generating example data. */ + private Calendar cal; + + + /* + * First manually make a directory to house the BDB environment. + * Usage: java EventExample -h <envHome> + * All BDB on-disk storage is held within envHome. + */ + public static void main(String[] args) + throws DatabaseException, FileNotFoundException { + + if (args.length != 2 || !"-h".equals(args[0])) { + System.err.println + ("Usage: java " + EventExample.class.getName() + + " -h <envHome>"); + System.exit(2); + } + EventExample example = new EventExample(new File(args[1])); + example.run(); + example.close(); + } + + private EventExample(File envHome) + throws DatabaseException, FileNotFoundException { + + /* Open a transactional Berkeley DB engine environment. */ + System.out.println("-> Creating a BDB environment"); + EnvironmentConfig envConfig = new EnvironmentConfig(); + envConfig.setAllowCreate(true); + envConfig.setTransactional(true); + envConfig.setInitializeCache(true); + envConfig.setInitializeLocking(true); + env = new Environment(envHome, envConfig); + + init(); + cal = Calendar.getInstance(); + } + + /** + * Create all primary and secondary indices. + */ + private void init() + throws DatabaseException, FileNotFoundException { + + System.out.println("-> Creating a BDB database"); + DatabaseConfig dbConfig = new DatabaseConfig(); + dbConfig.setTransactional(true); + dbConfig.setAllowCreate(true); + dbConfig.setType(DatabaseType.BTREE); + eventDb = env.openDatabase(null, // use auto-commit txn + "eventDb", // file name + null, // database name + dbConfig); + + + /* + * In our example, the database record is composed of a key portion + * which represents the event timestamp, and a data portion holds an + * instance of the Event class. + * + * BDB's base API accepts and returns key and data as byte arrays, so + * we need some support for marshaling between objects and byte arrays. + * We call this binding, and supply a package of helper classes to + * support this. It's entirely possible to do all binding on your own. + * + * A class catalog database is needed for storing class descriptions + * for the serial binding used below. This avoids storing class + * descriptions redundantly in each record. + */ + DatabaseConfig catalogConfig = new DatabaseConfig(); + catalogConfig.setTransactional(true); + catalogConfig.setAllowCreate(true); + catalogConfig.setType(DatabaseType.BTREE); + catalogDb = env.openDatabase(null, "catalogDb", null, catalogConfig); + StoredClassCatalog catalog = new StoredClassCatalog(catalogDb); + + /* + * Create a serial binding for Event data objects. Serial + * bindings can be used to store any Serializable object. + * We can use some pre-defined binding classes to convert + * primitives like the long key value to the a byte array. + */ + eventBinding = new SerialBinding(catalog, Event.class); + + /* + * Open a secondary database to allow accessing the primary + * database a secondary key value. In this case, access events + * by price. + */ + SecondaryConfig secConfig = new SecondaryConfig(); + secConfig.setTransactional(true); + secConfig.setAllowCreate(true); + secConfig.setType(DatabaseType.BTREE); + secConfig.setSortedDuplicates(true); + secConfig.setKeyCreator(new PriceKeyCreator(eventBinding)); + eventByPriceDb = env.openSecondaryDatabase(null, + "priceDb", + null, + eventDb, + secConfig); + + } + + private void run() + throws DatabaseException { + + Random rand = new Random(); + + /* DatabaseEntry represents the key and data of each record */ + DatabaseEntry key = new DatabaseEntry(); + DatabaseEntry data = new DatabaseEntry(); + + /* + * Create a set of events. Each insertion is a separate, auto-commit + * transaction. + */ + System.out.println("-> Inserting 4 events"); + LongBinding.longToEntry(makeDate(1), key); + eventBinding.objectToEntry(new Event(100, "Company_A"), + data); + eventDb.put(null, key, data); + + LongBinding.longToEntry(makeDate(2), key); + eventBinding.objectToEntry(new Event(2, "Company_B"), + data); + eventDb.put(null, key, data); + + LongBinding.longToEntry(makeDate(3), key); + eventBinding.objectToEntry(new Event(20, "Company_C"), + data); + eventDb.put(null, key, data); + + LongBinding.longToEntry(makeDate(4), key); + eventBinding.objectToEntry(new Event(40, "CompanyD"), + data); + eventDb.put(null, key, data); + + /* Load a whole set of events transactionally. */ + Transaction txn = env.beginTransaction(null, null); + int maxPrice = 50; + System.out.println("-> Inserting some randomly generated events"); + for (int i = 0; i < 25; i++) { + long time = makeDate(rand.nextInt(365)); + Event e = new Event(rand.nextInt(maxPrice),"Company_X"); + if ((i%2) ==0) { + e.addRep("Jane"); + e.addRep("Nikunj"); + } else { + e.addRep("Yongmin"); + } + LongBinding.longToEntry(time, key); + eventBinding.objectToEntry(e, data); + eventDb.put(txn, key, data); + } + txn.commitWriteNoSync(); + + /* + * Windows of events - display the events between June 1 and Aug 31 + */ + System.out.println("\n-> Display the events between June 1 and Aug 31"); + long endDate = makeDate(Calendar.AUGUST, 31); + + /* Position the cursor and print the first event. */ + Cursor eventWindow = eventDb.openCursor(null, null); + LongBinding.longToEntry(makeDate(Calendar.JUNE, 1), key); + + if ((eventWindow.getSearchKeyRange(key, data, null)) != + OperationStatus.SUCCESS) { + System.out.println("No events found!"); + eventWindow.close(); + return; + } + try { + printEvents(key, data, eventWindow, endDate); + } finally { + eventWindow.close(); + } + + /* + * Display all events, ordered by a secondary index on price. + */ + System.out.println("\n-> Display all events, ordered by price"); + SecondaryCursor priceCursor = + eventByPriceDb.openSecondaryCursor(null, null); + try { + printEvents(priceCursor); + } finally { + priceCursor.close(); + } + } + + private void close() + throws DatabaseException { + + eventByPriceDb.close(); + eventDb.close(); + catalogDb.close(); + env.close(); + } + + /** + * Print all events covered by this cursor up to the end date. We know + * that the cursor operates on long keys and Event data items, but there's + * no type-safe way of expressing that within the BDB base API. + */ + private void printEvents(DatabaseEntry firstKey, + DatabaseEntry firstData, + Cursor cursor, + long endDate) + throws DatabaseException { + + System.out.println("time=" + + new Date(LongBinding.entryToLong(firstKey)) + + eventBinding.entryToObject(firstData)); + DatabaseEntry key = new DatabaseEntry(); + DatabaseEntry data = new DatabaseEntry(); + + while (cursor.getNext(key, data, null) == + OperationStatus.SUCCESS) { + if (LongBinding.entryToLong(key) > endDate) { + break; + } + System.out.println("time=" + + new Date(LongBinding.entryToLong(key)) + + eventBinding.entryToObject(data)); + } + } + + private void printEvents(SecondaryCursor cursor) + throws DatabaseException { + DatabaseEntry timeKey = new DatabaseEntry(); + DatabaseEntry priceKey = new DatabaseEntry(); + DatabaseEntry eventData = new DatabaseEntry(); + + while (cursor.getNext(priceKey, timeKey, eventData, null) == + OperationStatus.SUCCESS) { + System.out.println("time=" + + new Date(LongBinding.entryToLong(timeKey)) + + eventBinding.entryToObject(eventData)); + } + } + + /** + * Little utility for making up java.util.Dates for different days, just + * to generate test data. + */ + private long makeDate(int day) { + + cal.set((Calendar.DAY_OF_YEAR), day); + return cal.getTime().getTime(); + } + /** + * Little utility for making up java.util.Dates for different days, just + * to make the test data easier to read. + */ + private long makeDate(int month, int day) { + + cal.set((Calendar.MONTH), month); + cal.set((Calendar.DAY_OF_MONTH), day); + return cal.getTime().getTime(); + } + + /** + * A key creator that knows how to extract the secondary key from the data + * entry of the primary database. To do so, it uses both the dataBinding + * of the primary database and the secKeyBinding. + */ + private static class PriceKeyCreator implements SecondaryKeyCreator { + + private EntryBinding dataBinding; + + PriceKeyCreator(EntryBinding eventBinding) { + this.dataBinding = eventBinding; + } + + public boolean createSecondaryKey(SecondaryDatabase secondaryDb, + DatabaseEntry keyEntry, + DatabaseEntry dataEntry, + DatabaseEntry resultEntry) + throws DatabaseException { + + /* + * Convert the data entry to an Event object, extract the secondary + * key value from it, and then convert it to the resulting + * secondary key entry. + */ + Event e = (Event) dataBinding.entryToObject(dataEntry); + int price = e.getPrice(); + IntegerBinding.intToEntry(price, resultEntry); + return true; + } + } +} |