J2ME 的 RMS 使用一例：BookStore，rmsbookstore,package ora.

J2ME 的 RMS 使用一例：BookStore，rmsbookstore,package ora.

package ora.ch6;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.DataInputStream;import java.io.DataOutputStream;import java.io.IOException;import javax.microedition.rms.RecordComparator;import javax.microedition.rms.RecordEnumeration;import javax.microedition.rms.RecordFilter;import javax.microedition.rms.RecordListener;import javax.microedition.rms.RecordStore;import javax.microedition.rms.RecordStoreException;// A class that implements a persistent store// of books, keyed by ISBN.public class BookStore implements RecordComparator, RecordFilter {    // The name of the record store used to hold books    private static final String STORE_NAME = "BookStore";    // The record store itself    private RecordStore store;    // ISBN to be used during a filter operation    private String searchISBN;    // Creates a bookstore and opens it    public BookStore() {        try {            store = RecordStore.openRecordStore(STORE_NAME, true);        } catch (RecordStoreException ex) {            System.err.println(ex);        }    }    // Closes the bookstore    public void close() throws RecordStoreException {        if (store != null) {            store.closeRecordStore();        }    }    // Gets the number of books in the book store    public int getBookCount() throws RecordStoreException {        if (store != null) {            return store.getNumRecords();        }        return 0;    }    // Adds a listener to the book store    public void addRecordListener(RecordListener l) {        if (store != null) {            store.addRecordListener(l);        }    }    // Removes a listener from the book store    public void removeRecordListener(RecordListener l) {        if (store != null) {            store.removeRecordListener(l);        }    }    // Gets a sorted list of all of the books in    // the store.    public RecordEnumeration getBooks() throws RecordStoreException {        if (store != null) {            return store.enumerateRecords(null, this, false);        }        return null;    }    // Gets a BookInfo from a store record    // given its ISBN    public BookInfo getBookInfo(String isbn) throws RecordStoreException,                                                    IOException {        BookInfo bookInfo = null;        searchISBN = isbn;        // Look for a book with the given ISBN        RecordEnumeration enum = store.enumerateRecords(                                        this, null, false);        // If found, get its identifier and        // fetch its BookInfo object        if (enum.numRecords() > 0) {            int id = enum.nextRecordId();            bookInfo = getBookInfo(id);        }        // Release the enumeration        enum.destroy();        return bookInfo;    }    // Gets a BookInfo from a store record    // given its record identifier    public BookInfo getBookInfo(int id) throws RecordStoreException,                                                    IOException {        byte[] bytes = store.getRecord(id);        DataInputStream is = new DataInputStream(                            new ByteArrayInputStream(bytes));        String isbn = is.readUTF();        BookInfo info = new BookInfo(isbn);        info.id = id;        info.title = is.readUTF();        info.ranking = is.readInt();        info.reviews = is.readInt();        info.lastRanking = is.readInt();        info.lastReviews = is.readInt();        return info;    }    // Adds an entry to the store or modifies the existing    // entry if a matching ISBN exists.    public void saveBookInfo(BookInfo bookInfo)                                throws IOException, RecordStoreException {        if (store != null) {            searchISBN = bookInfo.getIsbn();            RecordEnumeration enum = store.enumerateRecords(                                        this, null, false);            if (enum.numRecords() > 0) {                // A matching record exists. Set the id                // of the BookInfo to match the existing record                bookInfo.id = enum.nextRecordId();                byte[] bytes = toByteArray(bookInfo);                store.setRecord(bookInfo.id, bytes, 0, bytes.length);            } else {                // Create a new record                bookInfo.id = store.getNextRecordID();                byte[] bytes = toByteArray(bookInfo);                store.addRecord(bytes, 0, bytes.length);            }            // Finally, destroy the RecordEnumeration            enum.destroy();        }    }    // Deletes the entry for a book from the store    public void deleteBook(BookInfo bookInfo) throws RecordStoreException {        if (store != null) {            store.deleteRecord(bookInfo.id);        }    }    // RecordComparator implementation    public int compare(byte[] book1, byte[] book2) {        try {            DataInputStream stream1 =                new DataInputStream(new ByteArrayInputStream(book1));            DataInputStream stream2 =                new DataInputStream(new ByteArrayInputStream(book2));            // Match based on the ISBN, but sort based on the title.            String isbn1 = stream1.readUTF();            String isbn2 = stream2.readUTF();            if (isbn1.equals(isbn2)) {                return RecordComparator.EQUIVALENT;            }            String title1 = stream1.readUTF();            String title2 = stream2.readUTF();            int result = title1.compareTo(title2);            if (result == 0) {                return RecordComparator.EQUIVALENT;            }            return result < 0 ? RecordComparator.PRECEDES :                                RecordComparator.FOLLOWS;        } catch (IOException ex) {            return RecordComparator.EQUIVALENT;        }    }    // RecordFilter implementation    public boolean matches(byte[] book) {        if (searchISBN != null) {            try {                DataInputStream stream =                    new DataInputStream(new ByteArrayInputStream(book));                // Match based on the ISBN.                return searchISBN.equals(stream.readUTF());            } catch (IOException ex) {                System.err.println(ex);            }        }        // Default is not to match        return false;    }    // Writes a record into a byte array.    private byte[] toByteArray(BookInfo bookInfo) throws IOException {        ByteArrayOutputStream baos = new ByteArrayOutputStream();        DataOutputStream os = new DataOutputStream(baos);        os.writeUTF(bookInfo.isbn);        os.writeUTF(bookInfo.title == null ? "" : bookInfo.title);        os.writeInt(bookInfo.ranking);        os.writeInt(bookInfo.reviews);        os.writeInt(bookInfo.lastRanking);        os.writeInt(bookInfo.lastReviews);        return baos.toByteArray();    }}//该片段来自于http://byrx.net