SSD7 Exercise4 （最新）

package library; import java.util.*; import java.sql.*; import java.text.*; /** * class Library represents the functionality of a library * * @author iCarnegie * @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)"; if (myConnection.runUpdate(sqlQuery) > 0) return true; else return false; } } /** * 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. if (myConnection.runUpdate(sqlQuery) > 0) return true; else return false; } /** * 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); if (myConnection.runUpdate(sqlQuery) > 0) return true; } 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; return myConnection.runChainedUpdate(sqlQuery, Connection.TRANSACTION_SERIALIZABLE); } } return false; } /** * 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 + "'"; if (myConnection.runUpdate(sqlQuery) > 0) return true; else return false; } /** * 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(int 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