|By Ben Litchfield||
|March 24, 2005 12:00 AM EST||
Since Adobe released the first public PDF Reference in 1993, a number of PDF utilities and libraries, supporting all kinds of languages and platforms, have been made available to users and developers alike. However, support for Adobe's technology has lagged in Java application development. And this is curious because PDF documents tend to be a popular way of storing and interchanging information when dealing with enterprise information systems - an application domain that Java technology is particularly well suited to. Yet it seems that, until recently, mature, capable PDF support wasn't readily available to Java applications developers.
PDFBox (an Open Source project released under the BSD license) is a pure Java library that lets developers read and create PDF documents. It has features such as:
- Extracting text, including Unicode characters
- Easy integration with text search engines like Jakarta Lucene
- Encryption/Decryption of PDF documents
- Importing/Exporting of form data in FDF and XFDF formats
- Appending to existing PDF documents
- Splitting a single PDF into multiple documents
- Overlaying one PDF document on top of another
PDFBox has been designed to represent PDF documents using familiar object-oriented paradigms. The data contained in a PDF document is a collection of basic object types: arrays, booleans, dictionaries, numbers, strings and binary streams. PDFBox captures these basic object types in the org.pdfbox.cos package (the COS Model). While it's possible to create any desired interactions with a PDF document using only these objects, it requires an intimate knowledge of the internals of PDF documents and the techniques used to represent higher-level concepts. For example, objects such as pages and fonts are represented as dictionaries with specialized attributes; deciphering all these various attributes and their types requires tedious consultation of the PDF Reference.
For this reason, the org.pdfbox.pdmodel package (the PD Model) sits on top the COS Model and provides a high-level API that accesses PDF document objects in a more familiar manner (see Figure 1). Objects such as PDPage and PDFont can be found in this package, which encapsulates their lower-level COS model counterparts.
A word of caution to developers: the PD Model offers many nice features but is still a work in progress. In some instances, use of the COS Model may be required to access a particular piece of PDF functionality. Consequently, all PD Model objects can retrieve the corresponding COS Model object that they represent, so it's always possible to start with the PD Model and drop down to the COS Model when the required piece of functionality is found to be missing.
Now that the general capabilities of PDFBox have been discussed a few examples of its use are appropriate. We will start by reading an existing PDF document:
PDDocument document =
PDDocument.load( "./test.pdf" );
This operation will cause the PDF file to be parsed and an in-memory representation of the document will be created. To facilitate the efficient handling of large documents, PDFBox only stores the document structure in memory; objects such as images, embedded fonts and page content are cached in a temporary file.
Note: When finished using a PDDocument object, care should be taken to invoke the close() method on the document object to release resources used during its creation.
Text Extraction and Lucene Integration
In an information retrieval age when applications are expected to have searching and indexing capabilities regardless of the medium, the ability to organize and catalog information into a searchable format is critical. This is simple for text and HTML documents, but PDF documents have more structure and meta-information that makes it difficult to extract the underlying text. The PDF language is similar to Postscript in that objects are drawn as vectors on the page at certain positions. For example:
/Helv 12 Tf
0 13.0847 Td
(Hello World) Tj
This set of instructions changes the font to Helvetica size 12, moves the caret to the next line and renders the string "Hello World." These command streams are usually compressed and the order in which the glyphs are displayed on the screen is not necessarily the order in which the characters appear in the file, so it isn't always possible to simply extract text strings directly from the raw PDF document. However, PDFBox has a sophisticated text-extraction algorithm that deals with this and other complexities, letting a developer get the text of the document as if reading off its rendered form.
Lucene, which is part of the Apache Jakarta project, is a popular Open Source search engine library. Lucene lets developers create an index and do complex searches on a large volume of textual content based on that index. Since Lucene has adopted text as the common denominator for content, it's the developer's responsibility to convert the data contained in other desired file formats to text to use Lucene. For example, file formats such as Microsoft Word and StarOffice documents have to be converted to text before they can be added to a Lucene index.
PDF files are no exception, but PDFBox makes it easy to include a PDF document in a Lucene index by supplying a special object that does the integration. A basic PDF document can be converted to a Lucene document with a single statement:
Document doc = LucenePDFDocument.getDocument( file );
This operation parses the PDF document, extracts the text and creates a Lucene document object that can then be added to the index. As mentioned above, PDF documents also contain metadata such as author information and keywords that are important to track when indexing PDF documents. Table 1 shows the fields that PDFBox will populate while creating the Lucene document.
This integration makes it easy for developers to support simple searching and indexing of PDF documents with Lucene. Of course, some applications require more sophisticated text-extraction methods. In that case, the PDFTextStripper class can be used directly, or extended to handle these complex requirements.
By extending this class and overriding the showCharacter() method, many aspects of text extraction can be controlled. For instance, an implementation of this method can use the x, y positioning information to limit the inclusion of certain blocks of text in the extraction. One use might exclude all of the text above a certain y-coordinate value effectively excluding an unwanted document header.
Another example: Oftentimes a group of PDF documents may have been created from forms and the source data are no longer available. In other words, the documents all have some interesting text at similar locations on the page, but the form data used to fill the document out are no longer available. For example, a collection of cover letters that have the name and address at the same location in the document. In this case, an extension of the PDFTextStripper class can be used as a sort of screen-scraping device to extract the desired fields.
|Lucious 03/23/05 02:27:55 PM EST|
I can't believe I found this!! I was searching for tools to update pdf files in my java programs. All I could find was commercial tools that would charge for single/multiple CPU and development liscenses and then charge MORE for deployment!! I actually gave up and downloaded the pdf specs (over 1200 pages) to develop tools of my own. I can't wait to start using these tools!
|Maulik 03/23/05 08:09:43 AM EST|
Great easy-to-follow article for someone who knows next to nothing about integrating Java and PDF. Good job.
|Richard Bouchard 03/12/05 09:15:57 PM EST|
Excellent article and has great utility.
SYS-CON Events announced today that Luxoft Holding, Inc., a leading provider of software development services and innovative IT solutions, has been named “Bronze Sponsor” of SYS-CON's @ThingsExpo, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Luxoft’s software development services consist of core and mission-critical custom software development and support, product engineering and testing, and technology consulting.
Oct. 7, 2015 01:15 AM EDT Reads: 507
Developing software for the Internet of Things (IoT) comes with its own set of challenges. Security, privacy, and unified standards are a few key issues. In addition, each IoT product is comprised of at least three separate application components: the software embedded in the device, the backend big-data service, and the mobile application for the end user's controls. Each component is developed by a different team, using different technologies and practices, and deployed to a different stack/target - this makes the integration of these separate pipelines and the coordination of software upd...
Oct. 7, 2015 12:45 AM EDT Reads: 121
SYS-CON Events announced today that IBM Cloud Data Services has been named “Bronze Sponsor” of SYS-CON's 17th Cloud Expo, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. IBM Cloud Data Services offers a portfolio of integrated, best-of-breed cloud data services for developers focused on mobile computing and analytics use cases.
Oct. 6, 2015 10:00 PM EDT Reads: 659
In his session at @ThingsExpo, Tony Shan, Chief Architect at CTS, will explore the synergy of Big Data and IoT. First he will take a closer look at the Internet of Things and Big Data individually, in terms of what, which, why, where, when, who, how and how much. Then he will explore the relationship between IoT and Big Data. Specifically, he will drill down to how the 4Vs aspects intersect with IoT: Volume, Variety, Velocity and Value. In turn, Tony will analyze how the key components of IoT influence Big Data: Device, Connectivity, Context, and Intelligence. He will dive deep to the matrix...
Oct. 6, 2015 08:00 PM EDT Reads: 314
When it comes to IoT in the enterprise, namely the commercial building and hospitality markets, a benefit not getting the attention it deserves is energy efficiency, and IoT’s direct impact on a cleaner, greener environment when installed in smart buildings. Until now clean technology was offered piecemeal and led with point solutions that require significant systems integration to orchestrate and deploy. There didn't exist a 'top down' approach that can manage and monitor the way a Smart Building actually breathes - immediately flagging overheating in a closet or over cooling in unoccupied ho...
Oct. 6, 2015 05:00 PM EDT Reads: 257
SYS-CON Events announced today that Cloud Raxak has been named “Media & Session Sponsor” of SYS-CON's 17th Cloud Expo, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. Raxak Protect automates security compliance across private and public clouds. Using the SaaS tool or managed service, developers can deploy cloud apps quickly, cost-effectively, and without error.
Oct. 6, 2015 04:40 PM EDT Reads: 113
Scott Guthrie's keynote presentation "Journey to the intelligent cloud" is a must view video. This is from AzureCon 2015, September 29, 2015 I have reproduced some screen shots in case you are unable to view this long video for one reason or another. One of the highlights is 3 datacenters coming on line in India.
Oct. 6, 2015 02:00 PM EDT Reads: 234
“The Internet of Things transforms the way organizations leverage machine data and gain insights from it,” noted Splunk’s CTO Snehal Antani, as Splunk announced accelerated momentum in Industrial Data and the IoT. The trend is driven by Splunk’s continued investment in its products and partner ecosystem as well as the creativity of customers and the flexibility to deploy Splunk IoT solutions as software, cloud services or in a hybrid environment. Customers are using Splunk® solutions to collect and correlate data from control systems, sensors, mobile devices and IT systems for a variety of Ind...
Oct. 6, 2015 01:00 PM EDT Reads: 583
SYS-CON Events announced today that ProfitBricks, the provider of painless cloud infrastructure, will exhibit at SYS-CON's 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. ProfitBricks is the IaaS provider that offers a painless cloud experience for all IT users, with no learning curve. ProfitBricks boasts flexible cloud servers and networking, an integrated Data Center Designer tool for visual control over the cloud and the best price/performance value available. ProfitBricks was named one of the coolest Clo...
Oct. 6, 2015 01:00 PM EDT Reads: 743
You have your devices and your data, but what about the rest of your Internet of Things story? Two popular classes of technologies that nicely handle the Big Data analytics for Internet of Things are Apache Hadoop and NoSQL. Hadoop is designed for parallelizing analytical work across many servers and is ideal for the massive data volumes you create with IoT devices. NoSQL databases such as Apache HBase are ideal for storing and retrieving IoT data as “time series data.”
Oct. 6, 2015 12:45 PM EDT Reads: 462
Clearly the way forward is to move to cloud be it bare metal, VMs or containers. One aspect of the current public clouds that is slowing this cloud migration is cloud lock-in. Every cloud vendor is trying to make it very difficult to move out once a customer has chosen their cloud. In his session at 17th Cloud Expo, Naveen Nimmu, CEO of Clouber, Inc., will advocate that making the inter-cloud migration as simple as changing airlines would help the entire industry to quickly adopt the cloud without worrying about any lock-in fears. In fact by having standard APIs for IaaS would help PaaS expl...
Oct. 6, 2015 12:30 PM EDT Reads: 589
Organizations already struggle with the simple collection of data resulting from the proliferation of IoT, lacking the right infrastructure to manage it. They can't only rely on the cloud to collect and utilize this data because many applications still require dedicated infrastructure for security, redundancy, performance, etc. In his session at 17th Cloud Expo, Emil Sayegh, CEO of Codero Hosting, will discuss how in order to resolve the inherent issues, companies need to combine dedicated and cloud solutions through hybrid hosting – a sustainable solution for the data required to manage I...
Oct. 6, 2015 12:00 PM EDT Reads: 445
Apps and devices shouldn't stop working when there's limited or no network connectivity. Learn how to bring data stored in a cloud database to the edge of the network (and back again) whenever an Internet connection is available. In his session at 17th Cloud Expo, Bradley Holt, Developer Advocate at IBM Cloud Data Services, will demonstrate techniques for replicating cloud databases with devices in order to build offline-first mobile or Internet of Things (IoT) apps that can provide a better, faster user experience, both offline and online. The focus of this talk will be on IBM Cloudant, Apa...
Oct. 6, 2015 10:45 AM EDT Reads: 456
Mobile messaging has been a popular communication channel for more than 20 years. Finnish engineer Matti Makkonen invented the idea for SMS (Short Message Service) in 1984, making his vision a reality on December 3, 1992 by sending the first message ("Happy Christmas") from a PC to a cell phone. Since then, the technology has evolved immensely, from both a technology standpoint, and in our everyday uses for it. Originally used for person-to-person (P2P) communication, i.e., Sally sends a text message to Betty – mobile messaging now offers tremendous value to businesses for customer and empl...
Oct. 6, 2015 10:45 AM EDT Reads: 188
As more and more data is generated from a variety of connected devices, the need to get insights from this data and predict future behavior and trends is increasingly essential for businesses. Real-time stream processing is needed in a variety of different industries such as Manufacturing, Oil and Gas, Automobile, Finance, Online Retail, Smart Grids, and Healthcare. Azure Stream Analytics is a fully managed distributed stream computation service that provides low latency, scalable processing of streaming data in the cloud with an enterprise grade SLA. It features built-in integration with Azur...
Oct. 6, 2015 10:00 AM EDT Reads: 738
SYS-CON Events announced today that HPM Networks will exhibit at the 17th International Cloud Expo®, which will take place on November 3–5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. For 20 years, HPM Networks has been integrating technology solutions that solve complex business challenges. HPM Networks has designed solutions for both SMB and enterprise customers throughout the San Francisco Bay Area.
Oct. 6, 2015 09:00 AM EDT Reads: 574
The enterprise is being consumerized, and the consumer is being enterprised. Moore's Law does not matter anymore, the future belongs to business virtualization powered by invisible service architecture, powered by hyperscale and hyperconvergence, and facilitated by vertical streaming and horizontal scaling and consolidation. Both buyers and sellers want instant results, and from paperwork to paperless to mindless is the ultimate goal for any seamless transaction. The sweetest sweet spot in innovation is automation. The most painful pain point for any business is the mismatch between supplies a...
Oct. 6, 2015 09:00 AM EDT Reads: 145
The broad selection of hardware, the rapid evolution of operating systems and the time-to-market for mobile apps has been so rapid that new challenges for developers and engineers arise every day. Security, testing, hosting, and other metrics have to be considered through the process. In his session at Big Data Expo, Walter Maguire, Chief Field Technologist, HP Big Data Group, at Hewlett-Packard, will discuss the challenges faced by developers and a composite Big Data applications builder, focusing on how to help solve the problems that developers are continuously battling.
Oct. 6, 2015 04:00 AM EDT Reads: 445
As enterprises capture more and more data of all types – structured, semi-structured, and unstructured – data discovery requirements for business intelligence (BI), Big Data, and predictive analytics initiatives grow more complex. A company’s ability to become data-driven and compete on analytics depends on the speed with which it can provision their analytics applications with all relevant information. The task of finding data has traditionally resided with IT, but now organizations increasingly turn towards data source discovery tools to find the right data, in context, for business users, d...
Oct. 5, 2015 08:00 AM EDT Reads: 382
SYS-CON Events announced today that MobiDev, a software development company, will exhibit at the 17th International Cloud Expo®, which will take place November 3-5, 2015, at the Santa Clara Convention Center in Santa Clara, CA. MobiDev is a software development company with representative offices in Atlanta (US), Sheffield (UK) and Würzburg (Germany); and development centers in Ukraine. Since 2009 it has grown from a small group of passionate engineers and business managers to a full-scale mobile software company with over 150 developers, designers, quality assurance engineers, project manage...
Oct. 5, 2015 05:00 AM EDT Reads: 742