dbforum.java

这是学习Java必须读懂两套源代码

     * Updates the modified date but doesn't require a security check since
     * it is a protected method.
     */
    protected void updateModifiedDate(java.util.Date modifiedDate) {
        this.modifiedDate = modifiedDate;
        Connection con = null;
        PreparedStatement pstmt = null;
        try {
            con = DbConnectionManager.getConnection();
            pstmt = con.prepareStatement(UPDATE_FORUM_MODIFIED_DATE);
            pstmt.setString(1, ""+modifiedDate.getTime());
            pstmt.setInt(2, id);
            pstmt.executeUpdate();
        }
        catch( SQLException sqle ) {
            System.err.println("Error in DbForum:updateModifiedDate()-" + sqle);
            sqle.printStackTrace();
        }
        finally {
            try {  pstmt.close(); }
            catch (Exception e) { e.printStackTrace(); }
            try {  con.close();   }
            catch (Exception e) { e.printStackTrace(); }
        }
    }

    /**
     * Loads forum properties from the database.
     */
    private void loadProperties() {
        synchronized(saveLock) {
            Properties newProps = new Properties();
            Connection con = null;
            PreparedStatement pstmt = null;
            try {
                con = DbConnectionManager.getConnection();
                pstmt = con.prepareStatement(LOAD_PROPERTIES);
                pstmt.setInt(1, id);
                ResultSet rs = pstmt.executeQuery();
                while(rs.next()) {
                    String name = rs.getString("name");
                    String value = rs.getString("propValue");
                    newProps.put(name, value);
                }
            }
            catch( SQLException sqle ) {
                System.err.println("Error in DbForum:loadProperties():" + sqle);
                sqle.printStackTrace();
            }
            finally {
                try {  pstmt.close(); }
                catch (Exception e) { e.printStackTrace(); }
                try {  con.close();   }
                catch (Exception e) { e.printStackTrace(); }
            }
            this.properties = newProps;
        }
    }

    /**
     * Saves forum properties to the database.
     */
    private void saveProperties() {
        synchronized(saveLock) {
            Connection con = null;
            PreparedStatement pstmt = null;
            try {
                con = DbConnectionManager.getConnection();
                //Delete all old values.
                pstmt = con.prepareStatement(DELETE_PROPERTIES);
                pstmt.setInt(1, id);
                pstmt.execute();
                pstmt.close();
                //Now insert new values.
                pstmt = con.prepareStatement(INSERT_PROPERTY);
                Enumeration enum = properties.keys();
                while (enum.hasMoreElements()) {
                    String name = (String)enum.nextElement();
                    String value = (String)properties.get(name);
                    pstmt.setInt(1, id);
                    pstmt.setString(2, name);
                    pstmt.setString(3, value);
                    pstmt.executeUpdate();
                }
            }
            catch( SQLException sqle ) {
                System.err.println(sqle);
            }
            finally {
                try {  pstmt.close(); }
                catch (Exception e) { e.printStackTrace(); }
                try {  con.close();   }
                catch (Exception e) { e.printStackTrace(); }
            }
        }
    }

    /**
     * Loads filters from the database.
     */
    private void loadFiltersFromDb() {
        ArrayList newFilters = new ArrayList();
        Connection con = null;
        PreparedStatement pstmt = null;
        try {
            con = DbConnectionManager.getConnection();
            pstmt = con.prepareStatement(LOAD_FILTERS);
            pstmt.setInt(1,id);
            ResultSet rs = pstmt.executeQuery();
            while(rs.next()) {
                try {
                    ObjectInputStream in = new ObjectInputStream(rs.getBinaryStream("filterObject"));
                    newFilters.add(in.readObject());
                }
                catch (ClassCastException cce) {
                    //ignore for now since the filter might be updated. we
                    //need a solution for this. probably custom class loading
                    //of filter classes to protect against failure like this.
                }
                catch (Exception e) {
                    e.printStackTrace();
                }
            }
        }
        catch( SQLException sqle ) {
            sqle.printStackTrace();
        }
        finally {
            try {  pstmt.close(); }
            catch (Exception e) { e.printStackTrace(); }
            try {  con.close();   }
            catch (Exception e) { e.printStackTrace(); }
        }
        filters = new ForumMessageFilter[newFilters.size()];
        for (int i=0; i<filters.length; i++) {
            filters[i] = (ForumMessageFilter)newFilters.get(i);
        }
        //Finally, save filters back to Db. Effectively, this deletes filters
        //from the database that failed to load. See note above.
        //saveFiltersToDb(); <<-- commenting out to try to fix filters bug.
    }

    /**
     * Saves filters to the database. Filter saving works by serializing
     * each filter to a byte stream and then inserting that stream into
     * the database.
     */
    protected void saveFiltersToDb() {
        boolean abort = false;
        boolean supportsTransactions = false;
        synchronized (saveLock) {
            Connection con = null;
            PreparedStatement pstmt = null;
            try {
                con = DbConnectionManager.getConnection();

                supportsTransactions = con.getMetaData().supportsTransactions();
                if (supportsTransactions) {
                    con.setAutoCommit(false);
                }

                pstmt = con.prepareStatement(DELETE_FILTERS);
                pstmt.setInt(1,id);
                pstmt.execute();
                //Now insert new list of filters.
                pstmt.close();
                pstmt = con.prepareStatement(ADD_FILTER);
                for (int i=0; i<filters.length; i++) {
                    try {
                        ByteArrayOutputStream byteOut = new ByteArrayOutputStream();
                        ObjectOutputStream out = new ObjectOutputStream(byteOut);
                        out.writeObject(filters[i]);
                        pstmt.setInt(1,id);
                        pstmt.setInt(2,i);
                        pstmt.setBytes(3,byteOut.toByteArray());
                        pstmt.execute();
                    }
                    catch (Exception e) {
                        abort = true;
                        e.printStackTrace();
                    }
                }
                pstmt.close();
            }
            catch( SQLException sqle ) {
                abort = true;
                sqle.printStackTrace();
            }
            finally {
                try {
                    if (supportsTransactions) {
                        if (abort == true) {
                            con.rollback();
                        }
                        else {
                            con.commit();
                        }
                    }
                }
                catch (Exception e) { e.printStackTrace(); }
                try {
                    if (supportsTransactions) {
                        con.setAutoCommit(true);
                    }
                }
                catch (Exception e) { e.printStackTrace(); }
                try {  con.close();   }
                catch (Exception e) { e.printStackTrace(); }
            }
        }
    }

    /**
     * Loads forum data from the database.
     */
    private void loadFromDb() throws ForumNotFoundException {
        Connection con = null;
        PreparedStatement pstmt = null;
        try {
            con = DbConnectionManager.getConnection();
            //See if we should load by forumID or by name
            if (id == -1) {
                pstmt = con.prepareStatement(LOAD_FORUM_BY_NAME);
                pstmt.setString(1,name);
            }
            else {
                pstmt = con.prepareStatement(LOAD_FORUM_BY_ID);
                pstmt.setInt(1, id);
            }
            ResultSet rs = pstmt.executeQuery();
            if( !rs.next() ) {
                throw new ForumNotFoundException("Forum " + getID() +
                    " could not be loaded from the database.");
            }
            id = rs.getInt("forumID");
            name = rs.getString("name");
            description = rs.getString("description");
            this.creationDate =
                new java.util.Date(Long.parseLong(rs.getString("creationDate").trim()));
            this.modifiedDate =
                new java.util.Date(Long.parseLong(rs.getString("modifiedDate").trim()));
            moderated = rs.getInt("moderated");
        }
        catch( SQLException sqle ) {
            sqle.printStackTrace();
            throw new ForumNotFoundException("Forum " + getID() +
                " could not be loaded from the database.");
        }
        catch (NumberFormatException nfe) {
            System.err.println("WARNING: In DbForum.loadFromDb() -- there " +
                "was an error parsing the dates returned from the database. Ensure " +
                "that they're being stored correctly.");
        }
        finally {
            try {  pstmt.close(); }
            catch (Exception e) { e.printStackTrace(); }
            try {  con.close();   }
            catch (Exception e) { e.printStackTrace(); }
        }
    }

    /**
     * Inserts a new record into the database.
     */
    private void insertIntoDb() {
        Connection con = null;
        PreparedStatement pstmt = null;
        try {
            con = DbConnectionManager.getConnection();
            pstmt = con.prepareStatement(ADD_FORUM);
            pstmt.setInt(1,id);
            pstmt.setString(2,name);
            pstmt.setString(3,description);
            pstmt.setString(4, Long.toString(creationDate.getTime()));
            pstmt.setString(5, Long.toString(modifiedDate.getTime()));
            pstmt.setInt(6, moderated);
            pstmt.executeUpdate();
        }
        catch( SQLException sqle ) {
            System.err.println("Error in DbForum:insertIntoDb()-" + sqle);
            sqle.printStackTrace();
        }
        finally {
            try {  pstmt.close(); }
            catch (Exception e) { e.printStackTrace(); }
            try {  con.close();   }
            catch (Exception e) { e.printStackTrace(); }
        }
    }

    /**
     * Saves forum data to the database.
     */
    private synchronized void saveToDb() {
        Connection con = null;
        PreparedStatement pstmt = null;
        try {
            con = DbConnectionManager.getConnection();
            pstmt = con.prepareStatement(SAVE_FORUM);
            pstmt.setString(1, name);
            pstmt.setString(2, description);
            pstmt.setString(3, Long.toString(creationDate.getTime()));
            pstmt.setString(4, Long.toString(modifiedDate.getTime()));
            pstmt.setInt(5, moderated);
            pstmt.setInt(6, id);
            pstmt.executeUpdate();
        }
        catch( SQLException sqle ) {
            System.err.println("Error in DbForum:saveToDb()-" + sqle);
            sqle.printStackTrace();
        }
        finally {
            try {  pstmt.close(); }
            catch (Exception e) { e.printStackTrace(); }
            try {  con.close();   }
            catch (Exception e) { e.printStackTrace(); }
        }
    }
}