1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 |
|
Review Running FOP for important information that applies to embedded applications as well as command-line use, such as options and performance.
To embed Apache FOP in your application, instantiate org.apache.fop.apps.Fop. You'll tell FOP in the constructor which output format (i.e. Renderer) to use. Afterwards, you'll set the OutputStream to use to output the results of the rendering (where applicable). You can customize FOP's behaviour by supplying your own FOUserAgent instance. The FOUserAgent can, for example, be used to set your own Renderer instance (details below). Finally, you retrieve a SAX DefaultHandler instance from the Fop instance to which you can send your FO file.
Apache FOP relies heavily on JAXP. It uses SAX events exclusively to receive the XSL-FO input document. It is therefore a good idea that you know a few things about JAXP (which is a good skill anyway). Let's look at the basic usage pattern for FOP...
Here is the basic pattern to render an XSL-FO file to PDF:
Let's discuss these 5 steps in detail:
transform() method returns FOP will also have finished converting
the FO file to a PDF file and you can close the OutputStream.
If you're not totally familiar with JAXP Transformers, please have a look at the Embedding examples below. The section contains examples for all sorts of use cases. If you look at all of them in turn you should be able to see the patterns in use and the flexibility this approach offers without adding too much complexity.
This may look complicated at first, but it's really just the combination of an XSL transformation and a FOP run. It's also easy to comment out the FOP part for debugging purposes, for example when you're tracking down a bug in your stylesheet. You can easily write the XSL-FO output from the XSL transformation to a file to check if that part generates the expected output. An example for that can be found in the Embedding examples (See "ExampleXML2FO").
Logging is now a little different than it was in FOP 0.20.5. We've switched from Avalon Logging to Jakarta Commons Logging. While with Avalon Logging the loggers were directly given to FOP, FOP now retrieves its logger(s) through a statically available LogFactory. This is similar to the general pattern that you use when you work with Apache Log4J directly, for example. We call this "static logging" (Commons Logging, Log4J) as opposed to "instance logging" (Avalon Logging). This has a consequence: You can't give FOP a logger for each processing run anymore. The log output of multiple, simultaneously running FOP instances is sent to the same logger.
By default, Jakarta Commons Logging uses JDK logging (available in JDKs 1.4 or higher) as its backend. You can configure Commons Logging to use an alternative backend, for example Log4J. Please consult the documentation for Jakarta Commons Logging on how to configure altentive backends.
Once the Fop instance is set up, call getDefaultHandler() to obtain a SAX
DefaultHandler instance to which you can send the SAX events making up the XSL-FO
document you'd like to render. FOP processing starts as soon as the DefaultHandler's
startDocument() methods is called. Processing stops again when the
DefaultHandler's endDocument() method is called. Please refer to the basic
usage pattern shown above to render a simply XSL-FO document.
If you want to process XSL-FO generated from XML using XSLT we recommend again using standard JAXP to do the XSLT part and piping the generated SAX events directly through to FOP. The only thing you'd change to do that on the basic usage pattern above is to set up the Transformer differently:
The input XSL-FO document is always handled internally as SAX (see the Parsing Design Document for the rationale).
However, you may not always have your input document available as a SAX stream. But with JAXP it's easy to convert different input sources to a SAX stream so you can pipe it into FOP. That sounds more difficult than it is. You simply have to set up the right Source instance as input for the JAXP transformation. A few examples:
Source src = new StreamSource("http://localhost:8080/testfile.xml");
Source src = new StreamSource(new File("C:/Temp/myinputfile.xml"));
Source src = new StreamSource(new StringReader(myString)); //myString is a String
Source src = new StreamSource(new MyInputStream(something));
Source src = new StreamSource(new ByteArrayInputStream(myBuffer)); //myBuffer is a byte[] here
Source src = new DOMSource(myDocument); //myDocument is a Document or a Node
There are a variety of upstream data manipulations possible. For example, you may have a DOM and an XSL stylesheet; or you may want to set variables in the stylesheet. Interface documentation and some cookbook solutions to these situations are provided in Xalan Basic Usage Patterns.
Apache FOP provides a class called FOUserAgent which is used to customize FOP's behaviour. If you wish to do that, the first step is to create your own instance of FOUserAgent and pass that to the Fop constructor:
You can do all sorts of things on the user agent:
The base URL to use when resolving relative URLs. Example:
Disable strict validation. When disabled FOP is less strict about the rules established by the XSL-FO specification. Example:
Set the producer of the document. This is metadata information that can be used for certain output formats such as PDF. The default producer is "Apache FOP". Example:
Set the creating user of the document. This is metadata information that can be used for certain output formats such as PDF. Example:
Set the author of the document. This is metadata information that can be used for certain output formats such as PDF. Example:
Override the creation date and time of the document. This is metadata information that can be used for certain output formats such as PDF. Example:
Set the title of the document. This is metadata information that can be used for certain output formats such as PDF. Example:
Set the keywords of the document. This is metadata information that can be used for certain output formats such as PDF. Example:
Set the internal resolution for the document. This is used when creating bitmap images, for example. Example:
Set your own Renderer instance. If you want to supply your own renderer or configure a Renderer in a special way you can give the instance to the FOUserAgent. Normally, the Renderer instance is created by FOP. Example:
Set your own FOEventHandler instance. If you want to supply your own FOEventHandler or configure an FOEventHandler subclass in a special way you can give the instance to the FOUserAgent. Normally, the FOEventHandler instance is created by FOP. Example:
Manually add a ElementMapping instance. If you want to supply a special FOP extension you can give the instance to the FOUserAgent. Normally, the FOP extensions can be automatically detected (see the documentation on extension for more info).
Set a URIResolver for custom URI resolution. By supplying a JAXP URIResolver you can add custom URI resolution functionality to FOP. For example, you can use Apache XML Commons Resolver to make use of XCatalogs.
Set the parameters for PDF encryption for the document. If you create PDF files you can instantiate and set an org.apache.fop.pdf.PDFEncryptionParams object. Example:
Instead of setting the parameters manually in code as shown above you can also set many values from an XML configuration file:
The layout of the configuration file is described on the Configuration page.
At the moment, the Fop instances shouldn't be reused. Please recreate Fop and FOUserAgent instances for each rendering run until further notice. We will likely add an additional object which will carry information and configuration which can be reused between rendering runs to further optimize this.
If your XSL-FO files contain SVG then Apache Batik will be used. When Batik is
initialised it uses certain classes in java.awt that
intialise the Java AWT classes. This means that a daemon thread
is created by the JVM and on Unix it will need to connect to a
DISPLAY.
The thread means that the Java application may not automatically quit
when finished, you will need to call System.exit(). These
issues should be fixed in the JDK 1.4.
If you run into trouble running FOP on a head-less server, please see the notes on Batik.
To get the number of pages that were rendered by FOP you can call
Fop.getResults(). This returns a FormattingResults object
where you can lookup the number of pages produced. It also gives you the
page-sequences that were produced along with their id attribute and their
number of pages. This is particularly useful if you render multiple
documents (each enclosed by a page-sequence) and have to know the number of
pages of each document.
There are several options to consider:
fop.setOutputStream(new java.io.BufferedOutputStream(out));
Templates object and reuse it each time you do
the XSL transformation. (More information can be found
here.)
Apache FOP may currently not be completely thread safe. FOP uses some static variables (for example for the image cache). This code has not been fully tested for multi-threading issues, yet.
There is also a known issue with fonts being jumbled between threads when using the Java2D/AWT renderer (which is used by the -awt and -print output options). In general, you cannot safely run multiple threads through the AWT renderer.
The directory "{fop-dir}/examples/embedding" contains several working examples. In contrast to the examples above the examples here primarily use JAXP for XML access. This may be easier to understand for people familiar with JAXP.
This example demonstrates the basic usage pattern to transform an XSL-FO file to PDF using FOP.
This example has nothing to do with FOP. It is there to show you how an XML file can be converted to XSL-FO using XSLT. The JAXP API is used to do the transformation. Make sure you've got a JAXP-compliant XSLT processor in your classpath (ex. Xalan).
This example demonstrates how you can convert an arbitrary XML file to PDF using XSLT and XSL-FO/FOP. It is a combination of the first two examples above. The example uses JAXP to transform the XML file to XSL-FO and FOP to transform the XSL-FO to PDF.
The output (XSL-FO) from the XSL transformation is piped through to FOP using SAX events. This is the most efficient way to do this because the intermediate result doesn't have to be saved somewhere. Often, novice users save the intermediate result in a file, a byte array or a DOM tree. We strongly discourage you to do this if it isn't absolutely necessary. The performance is significantly higher with SAX.
This example is a preparatory example for the next one. It's an example that shows how an arbitrary Java object can be converted to XML. It's an often needed task to do this. Often people create a DOM tree from a Java object and use that. This is pretty straightforward. The example here however shows how to do this using SAX which will probably be faster and not even more complicated once you know how this works.
For this example we've created two classes: ProjectTeam and ProjectMember (found in xml-fop/examples/embedding/java/embedding/model). They represent the same data structure found in xml-fop/examples/embedding/xml/xml/projectteam.xml. We want to serialize a project team with several members which exist as Java objects to XML. Therefore we created the two classes: ProjectTeamInputSource and ProjectTeamXMLReader (in the same place as ProjectTeam above).
The XMLReader implementation (regard it as a special kind of XML parser)is responsible for creating SAX events from the Java object. The InputSource class is only used to hold the ProjectTeam object to be used.
Have a look at the source of ExampleObj2XML.java to find out how this is used. For more detailed information see other resources on JAXP (ex. An older JAXP tutorial).
This example combines the previous and the third to demonstrate how you can transform a Java object to a PDF directly in one smooth run by generating SAX events from the Java object that get fed to an XSL transformation. The result of the transformation is then converted to PDF using FOP as before.
This example has FOP use a DOMSource instead of a StreamSource in order to use a DOM tree as input for an XSL transformation.
This example shows use of the PDF Transcoder, a sub-application within FOP. It is used to generate a PDF document from an SVG file.
These examples should give you an idea of what's possible. It should be easy to adjust these examples to your needs. Also, if you have other examples that you think should be added here, please let us know via either the fop-users or fop-dev mailing lists. Finally, for more help please send your questions to the fop-users mailing list.
| summaryrefslogtreecommitdiffstats |