booknewsdao.java

beginJsp2.0外文书籍源代码

package com.wrox.publish.db;

import com.wrox.publish.om.Book;
import com.wrox.publish.om.BookNews;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.Collection;

/** 
 * Data Access Object responsible for reading, writing and deleting
 * BookNews in the database.
 */
public class BookNewsDAO {
    
    private final Connection conn;
    
    /** 
     * Creates a new BookNewsDAO with the given database connection.
     * @param conn The database connection to use.
     */
    public BookNewsDAO(Connection conn) {
        super();
        this.conn = conn;
    }
    
    /**
     * Creates a new BookNews item in the database.
     * @param news The BookNews item to create.
     * @throws SQLException If there was a problem accessing the database.
     */    
    public void create(BookNews news) throws SQLException {
        PreparedStatement insert = conn.prepareStatement(
            "insert into book_news (book, title, body, user, published)" + 
            "values (?, ?, ?, ?, ?)", Statement.RETURN_GENERATED_KEYS);
        try {
            populate(insert, news);
            insert.executeUpdate();

            ResultSet key = insert.getGeneratedKeys();
            if (!key.next()) {
                throw new RuntimeException(
                    "Can't retrieve generated primary key!");
            }
            news.setId(key.getLong(1));
            key.close();
        } finally {
            insert.close();
        }
    }
    
    /**
     * Updates a BookNews item in the database.
     * @param news The item to update.
     * @throws SQLException If there was a problem accessing the database.
     * @throws EntityNotFoundException If the item was not found.
     */    
    public void update(BookNews news) 
    throws SQLException, EntityNotFoundException {
        PreparedStatement update = conn.prepareStatement(
            "update book_news " + 
            "set book=?, title=?, body=?, user=?, published=? " + 
            "where id=?");
        try {
            populate(update, news);
            update.setLong(6, news.getId());
            if (update.executeUpdate() != 1) {
                throw new EntityNotFoundException(
                    "BookNews " + news.getId() + " not found");
            }
        } finally {
            update.close();
        }
    }
    
    private void populate(PreparedStatement stmt, BookNews news) 
    throws SQLException {
        stmt.setLong(1, news.getBook().getId());
        stmt.setString(2, news.getTitle());
        stmt.setString(3, news.getBody());
        stmt.setString(4, news.getUser());
        stmt.setTimestamp(5, news.getPublished());
    }

    /**
     * Removes a BookNews item from the database.
     * @param news The BookNews item to remove.
     * @throws SQLException If there was a problem accessing the database.
     * @throws EntityNotFoundException If the Book was not found.
     */    
    public void remove(BookNews news) 
    throws SQLException, EntityNotFoundException {
        remove(news.getId());
    }
    
    /**
     * Removes a BookNews item from the database.
     * @param id The id (primary key) of the item to remove.
     * @throws SQLException If there was a problem accessing the database.
     * @throws EntityNotFoundException If the item was not found.
     */    
    public void remove(long id) 
    throws SQLException, EntityNotFoundException {
        PreparedStatement delete = conn.prepareStatement(
            "delete from book_news where id=?");
        try {
            delete.setLong(1, id);
            if (delete.executeUpdate() != 1) {
                throw new EntityNotFoundException(
                    "BookNews " + id + " not found");
            }
        } finally {
            delete.close();
        }
    }
    
    /**
     * Finds a single BookNews item by its id (primary key). This methods 
     * loads the entire object graph including the parent Book object, but
     * not the other dependent BookNews items for that Book.
     * @param id The id value to look for
     * @throws SQLException If there was a problem accessing the database
     * @throws EntityNotFoundException If the BookNews was not found.
     * @return The BookNews object
     */    
    public BookNews findById(long id) 
    throws SQLException, EntityNotFoundException {
        BookDAO bookDAO = new BookDAO(conn);
        PreparedStatement select = conn.prepareStatement(
            "select book, title, body, user, published " + 
            "from book_news where id=?");
        try {
            select.setLong(1, id);
            ResultSet results = select.executeQuery();
            if (!results.next()) {
                throw new EntityNotFoundException(
                    "BookNews " + id + " not found");
            } else {
                BookNews news = new BookNews();
                news.setId(id);
                news.setBook(bookDAO.loadById(results.getLong(1)));
                news.setTitle(results.getString(2));
                news.setBody(results.getString(3));
                news.setUser(results.getString(4));
                news.setPublished(results.getTimestamp(5));
                return news;
            }
        } finally {
            select.close();
        }
    }
    
    /** 
     * Multi-object finder method which finds the BookNews items
     * associated with a Book. Used by BookDAO.
     * @param book The book to find news items for.
     * @return A Collection of BookNews objects.
     * @throws SQLException If there was a problem accessing the database
     */
    public Collection findByBook(Book book) throws SQLException {
        PreparedStatement select = conn.prepareStatement(
            "select id, title, body, user, published " + 
            "from book_news where book=?");
        try {
            select.setLong(1, book.getId());
            ResultSet results = select.executeQuery();
            Collection items = new ArrayList();
            while (results.next()) {
                BookNews news = new BookNews();
                news.setId(results.getLong(1));
                news.setBook(book);
                news.setTitle(results.getString(2));
                news.setBody(results.getString(3));
                news.setUser(results.getString(4));
                news.setPublished(results.getTimestamp(5));
                items.add(news);
            }
            return items;
        } finally {
            select.close();
        }
    }
}