library.java

一个关于图书馆的服务器的管理程序

package library;
import java.util.*;
import java.sql.*;
import java.text.*;

/**
 * class Library represents the functionality of a library
 *
 * @author CTE
 * @version 1.0
 */
public class Library
{
    // singleton DBWrapper
    private DBWrapper myConnection = null;
    
    /**
     * class Library constructor
     */
    public Library() 
	throws Exception {
	
	myConnection = DBWrapper.Instance();
    }

    /**
     * holdBook places a hold on book with given call number for the given member
     * @param callNumber String call number of book to hold
     * @param member Member member who wishes to hold the book.
     * @return boolean
     */
    public boolean holdBook( String callNumber, Member member ) 
	throws Exception {
	
	String sqlQuery = "select count(*) as counted from hold where callnumber='" + callNumber + "' and ssn='" + member.getSSN() + "'" ;
	boolean alreadyHeld = false;
	ResultSet r = null;
	// Select the count of the books.  If it is 1, this book is already held.
	r = myConnection.runQuery( sqlQuery );
	if (r.next()) {
	    if (r.getInt("counted") == 1) {
		alreadyHeld = true;
	    }
	}
	// if alreadyHeld is true, then don't place a hold.  Place a hold otherwise.
	if (alreadyHeld) {
	    return true;
	} else {
	    sqlQuery = "INSERT INTO Hold VALUES (" + member.getSSN() + ", '" + callNumber + "', CURRENT_TIMESTAMP)";
	    return myConnection.runUpdate( sqlQuery );
	}
    }

    /**
     * checkinBook checks the book with the specified book id into the library.
     * @param bookId int id of book to check in
     * @return boolean
     */
    public boolean checkInBook( int bookId ) 
	throws Exception {

	// Build the sql query.
	String sqlQuery =  "UPDATE Book SET borrowerssn = null, librarianssn = null, duedate = null WHERE BookID = " + bookId;
	// Run the update.
	return myConnection.runUpdate( sqlQuery );
    }

    /**
     * approve a check out for book with given book id for a member with given member ssn
     * @param bookId int id of book to check out
     * @param memberSSN int ssn of member who wants to check book out
     * @return boolean
     */
    private boolean approveCheckout( int bookId, int memberSSN ) 
	throws Exception {
	
	boolean canCheckOut = true;
	
	// check to see if that book is already checked out
	boolean checkedOut = LibraryBook.isCheckedOut( bookId );
	
	if ( checkedOut ) {
	    canCheckOut = false;
	} else {
	    //see if another member has higher priority on this book
	    
	    // We have to check the holds, if the number of
	    // holds on this title exceeds the number of
	    // available copies.
	    
	    String callNumber = LibraryBook.getBook( bookId ).getCallNumber();
	    int availableCopyCount = LibraryBookTitle.getAvailableTitleCopyCount( callNumber );
	    int heldCopyCount = LibraryBookTitle.getTitleHoldCount( callNumber );
	    
	    String MemberSSN = new String(""+memberSSN);
	    HoldSet holds = LibraryBookTitle.getTitleHolds( callNumber );
	    heldCopyCount = holds.getHoldCount();
	    
	    if ( (heldCopyCount > 0) && (availableCopyCount < heldCopyCount) ) {
		int i = 0;
		boolean highEnoughPriority = false;
		while ((i < holds.getHoldCount()) && (i < availableCopyCount)) {
		    if (holds.getHoldAt(i).getHolderSSN().equals(MemberSSN)) {
			canCheckOut = true;
			break;
		    }
		    i++;
		}
	    }
	}
	return canCheckOut;
    }
    
    /**
     * checkMemberHold checks in the member with ssn memberSSN has a hold on book with id bookId
     * @param bookId int id of book
     * @param memberSSN int ssn of member
     * @return boolean
     */
    private boolean checkMemberHold( int bookId, int memberSSN )
	throws Exception {
	boolean isHeld = false;
	
	Member member = LibraryMember.getMember( memberSSN );
	HoldSet holds = LibraryMember.getMemberHolds( member );
	String callNumber = LibraryBook.getBook( bookId ).getCallNumber();
	
	for( int i=0; i<holds.getHoldCount(); i++ ) {
	    if (callNumber.equals(holds.getHoldAt(i).getCallNumber())) {
		isHeld = true;
		break;
	    }
	}
	return isHeld;
    }
    
    /**
     * checkOutBook checks out the book with bookId for the member with ssn memberSSN by the Librarian librarian
     * @param bookId int id of book
     * @param memberSSN int ssn of member
     * @param librarian Librarian librarian who is checking this book out
     * @return boolean
     */
    public boolean checkOutBook( int bookId, int memberSSN, Librarian librarian ) 
	throws Exception {
	boolean heldByMember = false;
	boolean checkedOut = false;
	
	//can this member borrow the book?
	if ( approveCheckout( bookId, memberSSN ) ) {
	    //check to see if the member is already holding the book...
	    heldByMember = checkMemberHold( bookId, memberSSN );
	    
	    // set the date that the book is due
	    final int MILLISECONDS_IN_THREE_WEEKS = 1000 * 60 * 60 * 24 * 21;
	    java.util.Date d = new java.util.Date(System.currentTimeMillis() + MILLISECONDS_IN_THREE_WEEKS);
	    
	    // Format it nicely into a String.
	    SimpleDateFormat f = new SimpleDateFormat("MM/dd/yyyy");
	    String dd = f.format(d);
	    
	    //if the book is not held by a member, check it out...
	    if ( !heldByMember ) {
		// Build the SQL statement required to check out the book.
		String sqlQuery = null;
		
		sqlQuery = new String( "UPDATE Book SET borrowerssn = " + memberSSN +
				       ", librarianssn = " + librarian.getSSN() +
				       ", duedate = '" + dd + "' " +
				       "WHERE bookid = " + bookId );
		
		checkedOut = myConnection.runUpdate( sqlQuery );
	    } else {
		//otherwise, delete the hold and then check it out
		String callNumber = LibraryBook.getBook( bookId ).getCallNumber();
		String [] sqlQuery = new String[2];
		sqlQuery[0] ="DELETE FROM hold WHERE ssn=" + memberSSN + " and callnumber='" + callNumber + "'";
		sqlQuery[1] =  "UPDATE Book SET borrowerssn = " + memberSSN +
		    ", librarianssn = " + librarian.getSSN() +
		    ", duedate = '" + dd + "' " +
		    "WHERE bookid = " + bookId;
		checkedOut = myConnection.runChainedUpdate( sqlQuery, "SERIALIZABLE" );
	    }
	}
	return checkedOut;
    }
    
    /**
     * releaseHold releases a hold on booktitle with call number callNumber for the specified member.
     * @param callNumber String call number of hold to release
     * @param member Member member who has the hold
     * @return boolean
     */
    public boolean releaseHold( String callNumber, Member member ) 
	throws Exception {
	
	String sqlQuery = "DELETE FROM Hold WHERE ssn = " + member.getSSN() +
	    " AND CallNumber = '" + callNumber + "'";

	return myConnection.runUpdate( sqlQuery );
    }
    
    /**
     * validateLibrarian returns a librarian object for the librarian with the given ssn and password
     * @param ssn String ssn of librarian
     * @param passWord String password of librarian
     * @return Librarian
     */
    public Librarian validateLibrarian( String ssn, String passWord ) 
	throws Exception {
	
	String sql = "SELECT * FROM Librarian WHERE ssn = " + ssn +
	    " AND passwd = '" + passWord + "'";
	
	ResultSet r = myConnection.runQuery(sql);
	if (r==null) {
	    return null;
	}
	if (r.next()) {
	    return LibraryLibrarian.getLibrarian( r.getInt( "ssn" ) );
	} else {
	    return null;
	}
    }
    
    /**
     * validateMember returns a new member for the given ssn and password
     * @param ssn String ssn of member
     * @param passWord String password of member
     * @return Member
     */
    public Member validateMember( String ssn, String passWord ) 
	throws Exception{
	
	String sql = "SELECT * FROM Member WHERE ssn = " + ssn +
	    " AND passwd = '" + passWord + "'";
	
	ResultSet r = myConnection.runQuery(sql);
	
	if (r==null) {
	    return null;
	}
	if (r.next()) {
	    return LibraryMember.getMember( r.getInt( "ssn") );
	} else {
	    return null;
	}
    }
    
    /**
     * getBooks returns all of the books currently in the library
     * @return BookSet
     */
    public BookSet getBooks() 
	throws Exception{
	
	String sqlQuery = "SELECT bookid FROM Book ORDER BY BookID ASC";
	BookSet currentBooks = new BookSet();

	ResultSet r = myConnection.runQuery( sqlQuery );
	while( r.next() ) {
	    currentBooks.addBook( LibraryBook.getBook( r.getInt( "bookid" ) ) );
	    }
	r.close();
	
	return currentBooks;
    }
    
    /**
     * getBookTitles returns the set of all book titles current at the library
     * @return BookTitleSet
     */
    public BookTitleSet getBookTitles() 
	throws Exception{
	
	String sqlQuery = "SELECT callnumber FROM Book ORDER BY BookID ASC";
	BookTitleSet currentBooks = null;

	ResultSet r = myConnection.runQuery( sqlQuery );
	while( r.next() ) {
	    currentBooks.addBookTitle( LibraryBookTitle.getBookTitle( r.getString( "callnumber" ) ) );
	}
	return currentBooks;
    }
}