Accessing a PDF Document with the Acrobat Viewer JavaBean

A PDF document is commonly opened in Acrobat Reader to edit, view, and print. But when you need to open a PDF in a Java application, Acrobat Reader is not accessible. Fortunately, Adobe provides a viewer API, the Acrobat Viewer JavaBean, to view and print PDF documents from Java applications, JavaBeans, or Java applets. The Acrobat classes are provided in the com.adobe.acrobat package of the Acrobat Viewer distribution. In this tutorial, we shall integrate the Acrobat Viewer in a Java application. We'll open an example PDF document in the application with the Acrobat Viewer, and discuss the different features of the Acrobat Viewer.

This tutorial has the following sections:

1. Preliminary Setup
2. Opening a PDF Document
3. Displaying a PDF Document in Acrobat Viewer

Preliminary Setup

The Acrobat Viewer JavaBean API is available from the Acrobat Viewer JavaBean [17] page. Download the bean.zip file. The Acrobat Viewer is available for Windows, Macintosh, Solaris, UNIX, and OS/2 platforms. For the purposes of this tutorial, we'll consider the Acrobat Viewer to be installed on the Windows platform. For installation on other platforms, refer to the installation notes for the specific platform. Extract the bean.zip file to an installation directory. The Acrobat Viewer for JavaBean API classes are included in the %AcrobatViewer%/acrobat.jar file, where the %AcrobatViewer% environment variable represents the directory in which the Acrobat Viewer JavaBean distribution is installed. Add %AcrobatViewer%/acrobat.jar and %AcrobatViewer%/MRJToolkitStubs.zip to the CLASSPATH environment variable.

A Java application with the Acrobat Viewer API may be developed in an IDE such as Eclipse, JDeveloper, or NetBeans, or as a command-line application. In this tutorial, a sample Acrobat Viewer Java application is developed as a command-line application. JRE 1.1.8 or later is recommended for the Acrobat Viewer.

Opening a PDF Document

Having installed the Acrobat Viewer API, we shall open an example PDF document in Acrobat Viewer. The Adobe Document Services PDF [18] document is used as the example document. Store the example PDF document in the C:/Adobe directory.

The Acrobat Viewer for JavaBean API provides methods for displaying a PDF document from a Java application. First, import the com.adobe.acrobat package. Also import the java.awt and java.io packages, which will be used for creating a GUI and loading the PDF file, respectively.

import com.adobe.acrobat.*;
import java.awt.*;
import java.io.*;

Setting the Layout

Create a Frame object, to which the Acrobat Viewer will be added, and set the layout of the frame. Specify BorderLayout as the layout of the frame.

Frame frame = new Frame("PDF Viewer");
frame.setLayout(new BorderLayout());

Viewer viewer = new Viewer();

Add the Viewer object to the frame. Add the Viewer to the center of the frame.

frame.add(viewer, BorderLayout.CENTER);

Setting the Document to Display

Open a FileInputStream to the PDF document that is to be displayed in the Acrobat Viewer.

InputStream input =
    new FileInputStream (new File(
        "C:/Adobe/95004509_AcroDS_SB_UE.pdf"));

Set the FileInputStream as the input to the Acrobat Viewer.

viewer.setDocumentInputStream(input);

A PDF document may also be input with the setDocumentURL(java.lang.String docURL) method.

Setting the Viewer Properties

Acrobat Viewer has several properties to specify the display characteristics of a PDF document. The viewer properties are of two types: static and dynamic. Static properties are set before a viewer is displayed and may not be modified after the viewer is displayed. Dynamic properties may be set and modified after a viewer is displayed. Some of the properties that may be set for the Acrobat Viewer are listed in the following table.

To set the page layout to SinglePage, the zoom type to FitPage, and the magnification to 100 percent, you just make a series of calls to setProperty():

 viewer.setProperty("Default_Page_Layout",
                        "SinglePage");
 viewer.setProperty("Default_Zoom_Type",
                        "FitPage");
 viewer.setProperty("Default_Magnification",
                        "100");

Getting the Current Page

The number of pages in the PDF document and the current page are obtained with the getPageCount() and getCurrentPage() methods. As an example, print out the number of pages in the example document and the current page displayed.

System.out.println("Page Count: "+viewer.getPageCount());
System.out.println("Current Page: "+viewer.getCurrentPage());

Page 0 corresponds to the first page in the document.

Setting the Zoom Level

You can set the zoom level of the current page with the zoomTo() method. Set the zoom magnification to 100 percent by specifying 1.0 as a double in the zoomTo() method.

viewer.zoomTo(1.0);

Displaying the Document

Create the layout of the viewer components and activate the viewer as follows:

viewer.activate();

Next, set the frame size in which the viewer is to be added, and display the frame.

frame.setSize(400, 500);
frame.pack(); 
frame.show();

You'll find the example application PDFViewer.java in the Resources [19] section. Run the Java application in a command-line window. The number of pages for the example PDF document is 3 and the current page is 0, the index of the first page of the PDF document. The example PDF document gets displayed in the Acrobat Viewer. As the zoom level is set to 1.0 in the Java application, the PDF document is displayed with 1.0 magnification. Figure 1 illustrates the PDF document in Acrobat Viewer.

Figure 1. PDF Document in Acrobat Viewer

Using the Viewer Commands

The Acrobat Viewer provides some viewer commands to edit the document and to modify the view characteristics of the document. The viewer commands are specified in the ViewerCommand interface, which is implemented by the Viewer class. To run a viewer command, invoke the execMenuItem(java.lang.String viewerCommand) method of the Viewer class. For example, to run the ZoomTo_K command:

Viewer viewer=new Viewer();
viewer.execMenuItem(ViewerCommand.ZoomTo_K);

Some of the commonly used viewer commands are listed in the following table:

The Acrobat Viewer may be displayed with some of the toolbar buttons removed. For example, you can remove the Open and Open URL buttons in the Acrobat Viewer with:

String[] dis = {ViewerCommand.Open_K, ViewerCommand.OpenURL_K};
Viewer viewer = new Viewer(dis);

[20]Displaying a PDF Document in Acrobat Viewer

The Acrobat Viewer has a toolbar to navigate through the PDF document with Next Page, Last Page, Previous Page, and First Page buttons. A PDF document may be zoomed in or zoomed out with the Zoom In or Zoom Out buttons. The Open and Open URL buttons allow you to open a different PDF document, which replaces the document currently displayed the Java AWT Component.

The Acrobat Viewer GUI functionality may also be accessed with the com.adobe.acrobat package API from a Java application. The different viewer commands are invoked with the execMenuItem(java.lang.String viewerCommand) method of the Viewer class. The viewer commands corresponding to some of the Acrobat Viewer buttons are listed in the following table.

Acrobat Viewer Button	Viewer Command
Next Page	ViewerCommand.NextPage_K
Last Page	ViewerCommand.LastPage_K
Previous Page	ViewerCommand.PrevPage_K
First Page	ViewerCommand.FirstPage_K
Zoom In, Zoom Out	ViewerCommand.ZoomTo_K
Open	ViewerCommand.Open_K
Find	ViewerCommand.Find_K

In the Viewer Component, you access the File, Edit, View, Tools, and Help menus by right-clicking in the document. This displays the pop-up menu seen in Figure 2.

Figure 2. PDF document menu

The File and Edit menu items may also be invoked with a viewer command in a Java application. Some of the viewer commands corresponding to the File and Edit menu items are listed in the following table.

Acrobat Viewer Menu Item	Viewer Command
Close	ViewerCommand.Close_K
Copy	ViewerCommand.EditCopy_K
Select All	ViewerCommand.EditSelectAll_K

To display the PDF document at its actual size, select the Actual Size button, as illustrated in Figure 3. The Actual Size button may also be invoked with the viewer command ViewerCommand.ActualSize_K.

Figure 3. Displaying document at actual size

To fit the PDF document in the AWT Component's display space, select Fit Page, as illustrated in Figure 4. The Fit Page button may also be invoked with the viewer command ViewerCommand.FitPage_K.

Figure 4. Displaying document to fit page

To fit the PDF document to the width of the component, select the Fit Width button, as illustrated in Figure 5. The Fit Width button may also be invoked with the viewer command ViewerCommand.FitWidth_K.

Figure 5. Displaying document to fit page width

Opening a Document

To open another PDF document, select the Open URL button, as shown in Figure 6. The Open URL button may also be invoked with the viewer command ViewerCommand.OpenURL_K.

Figure 6. Opening a document from a URL

In the Open URL frame, specify the URL of the PDF document, as illustrated in Figure 7. The input field for the Open URL frame does not accept a ftp-style URL with an escape sequence, such as ftp://host/my%20file.pdf. On the other hand, escapes are OK in http-style URLs.

Figure 7. Open URL

Bookmarking a Document

A PDF document page may be bookmarked in the Acrobat Viewer. The Acrobat Viewer bookmark frame displays the bookmarks to a PDF document with links to the different document pages. To bookmark a page, select the Bookmark button, as illustrated in Figure 8.

Figure 8. Bookmarking a document

This adds a bookmark to the Acrobat Viewer, as shown in Figure 9. You can obtain the root bookmark in the Acrobat Viewer frame from a Java application with the getRootBookmark() method of the Viewer class. The PDFBookmark class represents a bookmark in a PDF document.

Viewer viewer;
PDFBookmark rootBookmark=viewer.getRootBookmark();

Obtain the different bookmarks in a PDF document that is displayed in the Acrobat Viewer with the getBookmarks() method.

java.util.Vector pdfBookmarks=rootBookmark.getBookmarks();

The title of a bookmark can be obtained with the getTitle() method.

PDFBookmark bookmark;
java.lang.String title=bookmark.getTitle();

Figure 9. PDF document with a bookmark

Selecting Text

In the Acrobat Viewer, text may be highlighted with the Select Text button. Select the Select Text button and select the text to be highlighted, as illustrated in Figure 10.

Figure 10. Selecting text

Conclusion

A Java application may need to display PDF documents. The Adobe Acrobat Viewer for JavaBean API makes it feasible to display a PDF document from a Java application.

Resources

• Adobe Acrobat Viewer [17]
• Sample code [21] for this article

Deepak Vohra [1] is a NuBean consultant and a web developer.