Version 8.3.4
 —  PDF and FOP Services  —

Introduction

This document covers the following topics:


FOP - Formatting Objects Project

There is a series of accepted standard modules coming from the Apache Group that form the base of Application Designer's PDF services. The so-called FOP standard (Formatting Objects Processor) is - though still in evolution - a healthy base for generating PDF documents through a certain XML-based specification: XSLFO. XSLFO consists out of a number of XML tag definitions by which a document is described. The XML definition is processed by a transform processor that produces PDF as output.

Formatting objects

Though clear in concept and flexible in usage, XSLFO has a certain complexity: the number of tags and the number of properties inside the tags is quite high. Therefore, the effort for writing XSLFO-based XML documents is high and requires a profound understanding of FOP.

In addition, XSLFO is a pure output protocol - it describes a document before being transferred to PDF. The task of building the document and filling the right data in is not covered by FOP. This is where Application Designer's services come in.

Application Designer Services in Front of FOP

The following image summarizes the architecture of Application Designer's FOP services:

Formatting objects

An application passes an XML form and a data object to the PDF/FOP services.

The XML form contains:

The data object (adapter) contains:

The Application Designer PDF/FOP services build proper XSLFO out of the form and the data object. The XSLFO is passed to the normal FOP processing. The result is a PDF stream that is passed back to the calling application.

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Output Formats

FOP is an abstract document definition. It is not bound to PDF. Application Designer offers both interfaces to create FOP-XSLO documents by the use of forms and it offers interfaces for printing FOP to a printer.

You can use other FOP output formats as well. Application Designer offers to you to directly generate the XSLFO result and pass it back to you as string.

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Printing

Printing of application forms can be done in two ways:

The server side PDF creation is what this document is about. Your server program uses the Application Designer APIs for creating PDF via FOP. The PDF files can be made available for the client (i.e. reachable by URL) and the client can integrate the files into its pages. Typically, the Adobe Reader is started on the client and the user can decide whether to print the document.

The server side printing is available by using a corresponding API. You can create an FOP document and call the print API. You have to define the printer on which you want to print.

Note:
Server side printing requires JDK 1.4 to be used inside your application server. (JDK 1.3. only allows to print on the standard printer of your application server.)

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Typical Example

The following image shows an example of how the framework is applied:

Example

You see that the binding between the form's XML and the data object is the same as you know from the binding between Application Designer HTML pages and adapter objects. In fact, it is the same technology now transferred to PDF output scenarios.

The following topics are covered below:

Data Object (Adapter)

At runtime, the data object provides the data that is filled into the form. The same rules that you already know from the Application Designer adapter objects also apply to the data object:

For detailed information, see Binding between Page and Adapter in the Special Development Topics.

Ways of Usage

There are several ways of using the Application Designer PDF/FOP services.

It is up to you to decide.

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Browser Output of PDF Documents

After having created a PDF document, you typically want to output it somewhere in the browser. There are two questions that you have to consider:

The following topics are covered below:

Storing the Generated PDF

The Application Designer PDF APIs will generate a PDF byte stream. You have to store this byte stream in a certain way so that it can be reached by a URL from the browser. There are several ways to do so:

If using the second option and embedding PDF into Application Designer page processing, then Application Designer already provides a so-called "session buffer". Inside the session buffer, you can store any object under a certain name. It will return a URL that you can pass to the browser as the URL to the stored content.

An example is provided in the section The First PDF Document.

Embedding the PDF into your Application Designer Page

An example is provided in the section The First PDF Document.

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