AbstractPdfView


1   /*
2    * Copyright 2002-2005 the original author or authors.
3    * 
4    * Licensed under the Apache License, Version 2.0 (the "License");
5    * you may not use this file except in compliance with the License.
6    * You may obtain a copy of the License at
7    * 
8    *      http://www.apache.org/licenses/LICENSE-2.0
9    * 
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS,
12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13   * See the License for the specific language governing permissions and
14   * limitations under the License.
15   */
16  
17  package org.springframework.web.servlet.view.document;
18  
19  import java.io.ByteArrayOutputStream  ;
20  import java.io.OutputStream  ;
21  import java.util.Map  ;
22  
23  import javax.servlet.ServletOutputStream  ;
24  import javax.servlet.http.HttpServletRequest  ;
25  import javax.servlet.http.HttpServletResponse  ;
26  
27  import com.lowagie.text.Document;
28  import com.lowagie.text.DocumentException;
29  import com.lowagie.text.PageSize;
30  import com.lowagie.text.pdf.PdfWriter;
31  
32  import org.springframework.web.servlet.view.AbstractView;
33   
34  /**
35   * Abstract superclass for PDF views, using Bruno Lowagie's
36   * <a HREF="http://www.lowagie.com/iText">iText</a> package.
37   * Application-specific view classes will extend this class.
38   * The view will be held in the subclass itself, not in a template.
39   *
40   * <p>Note: Internet Explorer requires a ".pdf" extension, as
41   * it doesn't always respect the declared content type.
42   *
43   * @author Rod Johnson
44   * @author Jean-Pierre Pawlak
45   * @author Juergen Hoeller
46   */
47  public abstract class AbstractPdfView extends AbstractView {
48      
49      private static final int OUTPUT_BYTE_ARRAY_INITIAL_SIZE = 4096;
50  
51  
52      /**
53       * This constructor sets the appropriate content type "application/pdf".
54       * Note that IE won't take much notice of this, but there's not a lot we
55       * can do about this. Generated documents should have a ".pdf" extension.
56       */
57      public AbstractPdfView() {
58          setContentType("application/pdf");
59      }
60  
61  
62      protected final void renderMergedOutputModel(
63              Map   model, HttpServletRequest   request, HttpServletResponse   response) throws Exception   {
64  
65          // The following simple method doesn't work in IE, which
66          // needs to know the content length.
67  
68          // PdfWriter writer = PdfWriter.getInstance(document, response.getOutputStream());
69          // document.open();
70          // buildPdfDocument(model, document, writer, request, response);
71          // document.close();
72  
73          // See http://www.lowagie.com/iText/faq.html#msie
74          // for an explanation of why we can't use the obvious form above.
75  
76          // IE workaround: write into byte array first.
77          ByteArrayOutputStream   baos = new ByteArrayOutputStream  (OUTPUT_BYTE_ARRAY_INITIAL_SIZE);
78          Document document = newDocument();
79          PdfWriter writer = newWriter(document, baos);
80  
81          // Apply preferences and build metadata.
82          prepareWriter(model, writer, request);
83          buildPdfMetadata(model, document, request);
84  
85          // Build PDF document.
86          document.open();
87          buildPdfDocument(model, document, writer, request, response);
88          document.close();
89  
90          // Write content type and also length (determined via byte array).
91          response.setContentType(getContentType());
92          response.setContentLength(baos.size());
93  
94          // Flush byte array to servlet output stream.
95          ServletOutputStream   out = response.getOutputStream();
96          baos.writeTo(out);
97          out.flush();
98      }
99  
100     /**
101      * Create a new document to hold the PDF contents.
102      * <p>By default returns an A4 document, but the subclass can specify any
103      * Document, possibly parameterized via bean properties defined on the View.
104      * @return the newly created iText Document instance
105      * @see com.lowagie.text.Document#Document(com.lowagie.text.Rectangle)
106      */
107     protected Document newDocument() {
108         return new Document(PageSize.A4);
109     }
110 
111     /**
112      * Create a new PdfWriter for the given iText Document.
113      * @param document the iText Document to create a writer for
114      * @param os the OutputStream to write to
115      * @return the PdfWriter instance to use
116      * @throws DocumentException if thrown during writer creation
117      */
118     protected PdfWriter newWriter(Document document, OutputStream   os) throws DocumentException {
119         return PdfWriter.getInstance(document, os);
120     }
121 
122     /**
123      * Prepare the given PdfWriter. Called before building the PDF document,
124      * that is, before the call to <code>Document.open()</code>.
125      * <p>Useful for registering a page event listener, for example.
126      * The default implementation sets the viewer preferences as returned
127      * by this class's <code>getViewerPreferences()</code> method.
128      * @param model the model, in case meta information must be populated from it
129      * @param writer the PdfWriter to prepare
130      * @param request in case we need locale etc. Shouldn't look at attributes.
131      * @throws DocumentException if thrown during writer preparation
132      * @see com.lowagie.text.Document#open()
133      * @see com.lowagie.text.pdf.PdfWriter#setPageEvent
134      * @see com.lowagie.text.pdf.PdfWriter#setViewerPreferences
135      * @see #getViewerPreferences()
136      */
137     protected void prepareWriter(Map   model, PdfWriter writer, HttpServletRequest   request)
138             throws DocumentException {
139 
140         writer.setViewerPreferences(getViewerPreferences());
141     }
142 
143     /**
144      * Return the viewer preferences for the PDF file.
145      * <p>By default returns <code>AllowPrinting</code> and
146      * <code>PageLayoutSinglePage</code>, but can be subclassed.
147      * The subclass can either have fixed preferences or retrieve
148      * them from bean properties defined on the View.
149      * @return an int containing the bits information against PdfWriter definitions
150      * @see com.lowagie.text.pdf.PdfWriter#AllowPrinting
151      * @see com.lowagie.text.pdf.PdfWriter#PageLayoutSinglePage
152      */
153     protected int getViewerPreferences() {
154         return PdfWriter.AllowPrinting | PdfWriter.PageLayoutSinglePage;
155     }
156 
157     /**
158      * Populate the iText Document's meta fields (author, title, etc.).
159      * <br>Default is an empty implementation. Subclasses may override this method
160      * to add meta fields such as title, subject, author, creator, keywords, etc.
161      * This method is called after assigning a PdfWriter to the Document and
162      * before calling <code>document.open()</code>.
163      * @param model the model, in case meta information must be populated from it
164      * @param document the iText document being populated
165      * @param request in case we need locale etc. Shouldn't look at attributes.
166      * @see com.lowagie.text.Document#addTitle
167      * @see com.lowagie.text.Document#addSubject
168      * @see com.lowagie.text.Document#addKeywords
169      * @see com.lowagie.text.Document#addAuthor
170      * @see com.lowagie.text.Document#addCreator
171      * @see com.lowagie.text.Document#addProducer
172      * @see com.lowagie.text.Document#addCreationDate
173      * @see com.lowagie.text.Document#addHeader
174     */
175     protected void buildPdfMetadata(Map   model, Document document, HttpServletRequest   request) {
176     }
177 
178     /**
179      * Subclasses must implement this method to build an iText PDF document,
180      * given the model. Called between <code>Document.open()</code> and
181      * <code>Document.close()</code> calls.
182      * <p>Note that the passed-in HTTP response is just supposed to be used
183      * for setting cookies or other HTTP headers. The built PDF document itself
184      * will automatically get written to the response after this method returns.
185      * @param model the model Map
186      * @param document the iText Document to add elements to
187      * @param writer the PdfWriter to use
188      * @param request in case we need locale etc. Shouldn't look at attributes.
189      * @param response in case we need to set cookies. Shouldn't write to it.
190      * @throws Exception any exception that occured during document building
191      * @see com.lowagie.text.Document#open()
192      * @see com.lowagie.text.Document#close()
193      */
194     protected abstract void buildPdfDocument(
195             Map   model, Document document, PdfWriter writer,
196             HttpServletRequest   request, HttpServletResponse   response)
197             throws Exception  ;
198 
199 }
200
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