java ee servlet response

HttpServletResponse 物件是用來傳回結果到 browser，有些方法常用的方法：

設定 mime type：以下為 open office 的 odt 文件的 mime type
res.setContentType("application/vnd.oasis.opendocument.text");
設定編碼：
res.setCharacterEncoding("utf-8");
設定元件檔名：
res.addHeader("Content-Disposition", "attachment; filename=project-plan-book.odt");

hql 結合 distinct 過瀘重復的查詢結果

有些情況下，會有查詢到重復物件的問題，
舉一個例子直接說明：
A -> B ：1 -> 多
from A as a left join fetch a.b as b
由於A與B是一對多的關係，即許多個B可能以外鍵指向同一個A
以上的hql查詢結果會返回許多重覆的A物件，
假設某A有3個B指向他，則會返回3個某A物件。
這時可以透過distinct將重復的A物件去除，如下：
select distinct a from A as a left join fetch a.b as b

debian 簡易檔案加密解密 ccrypt

安裝：
sudo aptitude install ccrypt

加密：
ccencrypt target-file
Enter encryption key:
Enter encryption key: (repeat)
target-file -> 變成 target-file.cpt 檔案

解密：
ccdecrypt target-file.cpt
Enter decryption key:
target-file.cpt -> 變成 target-file 檔案

顯示加密檔的內容但不解密：
ccat target-file.cpt
Enter decryption key:
.....秘密的資料內容....#@$
target-file.cpt 維持不變。

使用JFreeChart畫甘特圖(gantt)範例

JFreeChart主要分為 JFreeChart 物件表示圖表 及 Dataset 物件表示資料
不同的圖表物由 ChartFactory 不同的 static 方法建立，而不同的圖表物件也需要不同的 Dataset
來儲存資料，如甘特圖的 Dataset 為 IntervalCategoryDataset ：

/**
*主程式進入點
*/
public static void main(String[] args){

final IntervalCategoryDataset dataset = createFakeDataset();
final JFreeChart chart = createChart(dataset);
// 輸出圖表成png檔(如果是web servlet可以輸出到response.getOutputStream())
ChartUtilities.writeChartAsPNG(target.getOutputStream(), outputChart, 2000, 600);
}

/**
* 建立甘特圖資料
*
* @return The dataset.
*/
public IntervalCategoryDataset createDataset() {

final TaskSeries s1 = new TaskSeries("計劃");
s1.add(new Task("許功蓋中文測試", new SimpleTimePeriod(date(1, Calendar.APRIL, 2001), date(5, Calendar.APRIL, 2001))));
s1.add(new Task("Obtain Approval", new SimpleTimePeriod(date(9, Calendar.APRIL, 2001), date(9, Calendar.APRIL, 2001))));
s1.add(new Task("Requirements Analysis", new SimpleTimePeriod(date(10, Calendar.APRIL, 2001), date(5, Calendar.MAY, 2001))));
s1.add(new Task("Design Phase", new SimpleTimePeriod(date(6, Calendar.MAY, 2001), date(30, Calendar.MAY, 2001))));
s1.add(new Task("Design Signoff", new SimpleTimePeriod(date(2, Calendar.JUNE, 2001), date(2, Calendar.JUNE, 2001))));
s1.add(new Task("Alpha Implementation", new SimpleTimePeriod(date(3, Calendar.JUNE, 2001), date(31, Calendar.JULY, 2001))));
s1.add(new Task("Design Review", new SimpleTimePeriod(date(1, Calendar.AUGUST, 2001), date(8, Calendar.AUGUST, 2001))));
s1.add(new Task("Revised Design Signoff", new SimpleTimePeriod(date(10, Calendar.AUGUST, 2001), date(10, Calendar.AUGUST, 2001))));
s1.add(new Task("Beta Implementation", new SimpleTimePeriod(date(12, Calendar.AUGUST, 2001), date(12, Calendar.SEPTEMBER, 2001))));
s1.add(new Task("Testing", new SimpleTimePeriod(date(13, Calendar.SEPTEMBER, 2001), date(31, Calendar.OCTOBER, 2001))));
s1.add(new Task("Final Implementation", new SimpleTimePeriod(date(1, Calendar.NOVEMBER, 2001), date(15, Calendar.NOVEMBER, 2001))));
s1.add(new Task("Signoff", new SimpleTimePeriod(date(28, Calendar.NOVEMBER, 2001), date(30, Calendar.NOVEMBER, 2001))));

final TaskSeries s2 = new TaskSeries("實際");
s2.add(new Task("許功蓋中文測試", new SimpleTimePeriod(date(1, Calendar.APRIL, 2001), date(5, Calendar.APRIL, 2001))));
s2.add(new Task("Obtain Approval", new SimpleTimePeriod(date(9, Calendar.APRIL, 2001), date(9, Calendar.APRIL, 2001))));
s2.add(new Task("Requirements Analysis", new SimpleTimePeriod(date(10, Calendar.APRIL, 2001), date(15, Calendar.MAY, 2001))));
s2.add(new Task("Design Phase", new SimpleTimePeriod(date(15, Calendar.MAY, 2001), date(17, Calendar.JUNE, 2001))));
s2.add(new Task("Design Signoff", new SimpleTimePeriod(date(30, Calendar.JUNE, 2001), date(30, Calendar.JUNE, 2001))));
s2.add(new Task("Alpha Implementation", new SimpleTimePeriod(date(1, Calendar.JULY, 2001), date(12, Calendar.SEPTEMBER, 2001))));
s2.add(new Task("Design Review", new SimpleTimePeriod(date(12, Calendar.SEPTEMBER, 2001), date(22, Calendar.SEPTEMBER, 2001))));
s2.add(new Task("Revised Design Signoff", new SimpleTimePeriod(date(25, Calendar.SEPTEMBER, 2001), date(27, Calendar.SEPTEMBER, 2001))));
s2.add(new Task("Beta Implementation", new SimpleTimePeriod(date(27, Calendar.SEPTEMBER, 2001), date(30, Calendar.OCTOBER, 2001))));
s2.add(new Task("Testing", new SimpleTimePeriod(date(31, Calendar.OCTOBER, 2001), date(17, Calendar.NOVEMBER, 2001))));
s2.add(new Task("Final Implementation", new SimpleTimePeriod(date(18, Calendar.NOVEMBER, 2001), date(5, Calendar.DECEMBER, 2001))));
s2.add(new Task("Signoff", new SimpleTimePeriod(date(10, Calendar.DECEMBER, 2001), date(11, Calendar.DECEMBER, 2001))));

final TaskSeriesCollection collection = new TaskSeriesCollection();
collection.add(s1);
collection.add(s2);

return collection;
}

/**
* 方便建立日期
*
* @param day
* the date.
* @param month
* the month.
* @param year
* the year.
*
* @return a date.
*/
public Date date(final int day, final int month, final int year) {
Calendar calendar = Calendar.getInstance();
calendar.set(year, month, day);
Date result = calendar.getTime();
return result;
}

/**
* 產生甘特圖物件
*
* @param dataset
* the dataset.
*
* @return The chart.
*/
public JFreeChart createChart(final IntervalCategoryDataset dataset) {
final JFreeChart chart = ChartFactory.createGanttChart("測試甘特圖 Demo", // chart title
"事件", // domain axis label
"日期", // range axis label
dataset, // data
true, // include legend
true, // tooltips
false // urls
);
//設定各處的字型(需設定為支援中文的字型，才不會造成中文亂碼)
Font font = new Font("標楷體", Font.BOLD, 16);
chart.getLegend().setItemFont(font);
chart.getTitle().setFont(font);
chart.getCategoryPlot().getDomainAxis().setLabelFont(font);
chart.getCategoryPlot().getDomainAxis().setTickLabelFont(font);
chart.getCategoryPlot().getRangeAxis().setLabelFont(font);
chart.getCategoryPlot().getRangeAxis().setTickLabelFont(font);
return chart;
}

結果如下(web)