DataExport


1   package org.tigris.scarab.screens;
2   
3   /* ================================================================
4    * Copyright (c) 2003 CollabNet.  All rights reserved.
5    * 
6    * Redistribution and use in source and binary forms, with or without
7    * modification, are permitted provided that the following conditions are
8    * met:
9    * 
10   * 1. Redistributions of source code must retain the above copyright
11   * notice, this list of conditions and the following disclaimer.
12   * 
13   * 2. Redistributions in binary form must reproduce the above copyright
14   * notice, this list of conditions and the following disclaimer in the
15   * documentation and/or other materials provided with the distribution.
16   * 
17   * 3. The end-user documentation included with the redistribution, if
18   * any, must include the following acknowlegement: "This product includes
19   * software developed by CollabNet <http://www.collab.net/>."
20   * Alternately, this acknowlegement may appear in the software itself, if
21   * and wherever such third-party acknowlegements normally appear.
22   * 
23   * 4. The hosted project names must not be used to endorse or promote
24   * products derived from this software without prior written
25   * permission. For written permission, please contact info@collab.net.
26   * 
27   * 5. Products derived from this software may not use the "Tigris" or 
28   * "Scarab" names nor may "Tigris" or "Scarab" appear in their names without 
29   * prior written permission of CollabNet.
30   * 
31   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
32   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
33   * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
34   * IN NO EVENT SHALL COLLABNET OR ITS CONTRIBUTORS BE LIABLE FOR ANY
35   * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
36   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
37   * GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
38   * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
39   * IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
40   * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41   * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42   *
43   * ====================================================================
44   * 
45   * This software consists of voluntary contributions made by many
46   * individuals on behalf of CollabNet.
47   */ 
48  
49  import java.io.Writer  ;
50  import java.io.IOException  ;
51  import java.io.PrintWriter  ;
52  import java.io.OutputStreamWriter  ;
53  import java.util.List  ;
54  
55  import org.apache.commons.lang.StringUtils;
56  
57  import org.apache.turbine.Turbine;
58  import org.apache.turbine.RunData;
59  import org.apache.turbine.TemplateContext;
60  
61  import org.tigris.scarab.util.ScarabUtil;
62  import org.tigris.scarab.util.export.ExportFormat;
63  
64  
65  /**
66   * <p>Sends file contents directly to the output stream, setting the
67   * <code>Content-Type</code> and writing back to the browser a
68   * tab-delimited file (Excel digests this fine).  We used to use <a
69   * HREF="http://jakarta.apache.org/poi/">POI</a> to compose an Excel
70   * binary data file, but its outrageous memory consumption didn't
71   * scale for large result sets. POI assembles the its output in
72   * memory.  After study of the native OLE2 Excel file format, it
73   * appears very difficult to generate the file in another fashion.</p>
74   *
75   * <p>Regards output encoding, for now we're assuming the response
76   * stream is appropriately set upon fetching. Also, we're assuming
77   * that Excel will do the right thing on receipt of our TSV file with
78   * Japanese or other multibyte characters (we're not setting an
79   * encoding on the <code>Content-Type</code> we return).  Both of the
80   * above to be verified.</p>
81   *
82   * @author <a HREF="mailto:jmcnally@collab.net">John McNally</a>
83   * @author <a HREF="mailto:stack@collab.net">St.Ack</a>
84   * @author <a HREF="mailto:dlr@collab.net">Daniel Rall</a>
85   * @since Scarab 1.0
86   */
87  class DataExport extends Default
88  {
89      /**
90       * What to show if a cell is empty.  The empty string is dealt
91       * with best by spreadsheet applications.
92       */
93      protected static final String   NO_CONTENT = "";
94  
95      /**
96       * Sets the <code>Content-Type</code> header for the response.
97       * Since this assumes we're writing the reponse ourself, indicates
98       * no target to render by setting it to <code>null</code>.
99       */
100     public void doBuildTemplate(RunData data, TemplateContext context)
101         throws Exception   
102     {
103         super.doBuildTemplate(data, context);
104         String   format = ScarabUtil.findValue(data, ExportFormat.KEY_NAME);
105 
106         // look for a configuration toggle for the encoding to which to
107         // export.  TODO : make this per request configurable (with a per-
108         // language default) to allow use of scarab in a multilingual 
109         // environment.
110         if (ExportFormat.EXCEL_FORMAT.equalsIgnoreCase(format))
111         {
112             data.getResponse().setContentType("application/vnd.ms-excel");
113         }
114         else
115         {
116             // we want to set a charset on the response -- so clients
117             // can detect it properly -- if we have a known encoding
118             String   encoding = getEncodingForExport(data);
119             String   contentType = "text/plain";
120             if (encoding != null && !encoding.equals(""))
121             {
122                 contentType = contentType + "; charset=" + encoding;
123             }
124             data.getResponse().setContentType(contentType);
125         }
126         // Since we're streaming the TSV content directly from our
127         // data source, we don't know its length ahead of time.
128         //data.getResponse().setContentLength(?);
129         
130         // FIXME: Provide work hooks here...
131         //TSVPrinter printer = new TSVPrinter(data.getResponse().getWriter());
132         //writeHeading(printer, mitlist, l10n, rmuas);
133         //writeRows(printer, mitlist, l10n, scarabR, rmuas);
134 
135         // Above we sent the response, so no target to render
136         data.setTarget(null);
137     }
138 
139     /**
140      * This function encapsulates the logic of determining which encoding 
141      * to use.  Right now, the encoding isn't per-request, but that should
142      * be changed.
143      */
144     protected String   getEncodingForExport(RunData data)
145     {
146         String   encoding = Turbine.getConfiguration()
147             .getString("scarab.dataexport.encoding");
148         return encoding;
149     }
150 
151     /**
152      * This function is available to subclasses -- it is used to provide
153      * a Writer based on the current request and the site configuration,
154      * taking encoding issues into consideration.
155      */
156     protected Writer   getWriter(RunData data)
157         throws IOException  
158     {
159         Writer   writer = null;
160         String   encoding = getEncodingForExport(data);
161         if (encoding != null && !encoding.equals(""))
162         {
163             writer =
164                 new OutputStreamWriter  (data.getResponse().getOutputStream(),
165                                        encoding);
166         }
167         else
168         {
169             writer = data.getResponse().getWriter();
170         }
171         return writer;
172     }
173 
174     /**
175      * Escape any commas in passed string.
176      *
177      * @param s String to check.
178      * @return Passed string with commas escaped.
179      */
180     protected String   escapeCommas(String   s)
181     {
182         // Not sure how to escape commas.  What to use instead?  Quote
183         // for now.
184         return quote(s);
185     }
186 
187     protected final boolean containsElements(List   l)
188     {
189         return l != null && !l.isEmpty();
190     }
191 
192     /**
193      * Quote the string argument.
194      *
195      * @param s Text to quote.
196      * @return Passed string, quoted.
197      */
198     private static String   quote(String   s)
199     {
200         return '"' + StringUtils.replace(s, "\"", "\"\"") + '"';
201     }
202 
203     /**
204      * Uses a <code>PrintWriter</code> internally to do actual
205      * writing.  If content with tabs and newlines in it is
206      * double-quoted, Excel does the Right Thing when parsing.
207      *
208      * @see <a HREF="http://ostermiller.org/utils/ExcelCSVPrinter.java.htm">ExcelCSVPrinter.java</a>
209      */
210     protected class TSVPrinter
211     {
212         /**
213          * Flag indicating start of a new line.
214          */
215         private boolean lineStart = true;
216 
217         /**
218          * Printer write on.
219          */
220         private PrintWriter   printer = null;
221 
222         /**
223          * Creates a new instance.
224          *
225          * @param writer Writer to output to.
226          * @throws IllegalArgumentException If <code>writer</code> is
227          * <code>null</code>.
228          */
229         public TSVPrinter(Writer   writer)
230         {
231             if (writer == null)
232             {
233                 //TODO [HD] Shouldn't this be better a NPE ?
234                 //          That better hits the truth...
235                 throw new IllegalArgumentException  
236                     ("TSVPrinter constructor requires a non-null writer"); //EXCEPTION
237             }
238             
239             if (writer instanceof PrintWriter  )
240             {
241                 this.printer = (PrintWriter  ) writer;
242             }
243             else
244             {
245                 this.printer = new PrintWriter  (writer);
246             }
247         }
248 
249         /**
250          * Prints one field at a time.
251          */
252         public void print(String   s)
253         {
254             if (!lineStart)
255             {
256                 // Print a tab seperator before we print our field content.
257                 printer.print('\t');
258             }
259             lineStart = false;
260 
261             if (StringUtils.isNotEmpty(s))
262             {
263                 printer.print(escape(s));
264             }
265         }
266 
267         /**
268          * Must be called when done writing a line -- this prints a newline
269          * and flushes the printer.
270          */
271         public void println()
272         {
273             printer.println();  
274             printer.flush();
275             lineStart = true;
276         }
277 
278         /**
279          * Quote the string argument.
280          *
281          * @param s Text to quote.
282          * @return Passed string, quoted.
283          */
284         protected String   quote(String   s)
285         {
286             return DataExport.quote(s);
287         }
288 
289         /**
290          * If the passed string has any problematic characters, quote the
291          * whole thing after escaping any quotes already present. Excel
292          * does the right thing parsing if it gets quoted content.
293          *
294          * @param s String to escape.
295          * @return An escaped version of the passed string.
296          */
297         private String   escape(String   s)
298         {
299             if (StringUtils.isNotEmpty(s))
300             {
301                 for (int i = 0; i < s.length(); i++)
302                 {
303                     char c = s.charAt(i);
304                     if (c == '"' || c == '\t' || c == '\n' || c == '\r')
305                     {
306                         s = quote(s);
307                         break;
308                     }
309                 }
310             }
311 
312             return s;
313         }
314     }
315 }
316
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