Apache FOP 2.2 Test Application

Ok, so far I successfully implemented a PDF generation test web application (vaadin) after getting over many problems with Apache FOP 2.2. Record my progress here:

• Not easy to fully configure FOP 2.2 without using XML configuration file. Although document provides a chapter for configuring it programmatically, in the end, a XML file is needed if to configure fonts
• Resolve path - I put all resources in class path, which is extracted by server. I find out the path of the resources on server with these codes:
  • Use class loader to get resource URL
  • Reconstruct the URI by removing the last part of path, and ADD "/" at the end - otherwise it won't work as base URI for FOP

URL fo = getClass().getClassLoader().getResource("/static/topdf.fo");

String path = fo.getFile().substring(0, fo.getFile().lastIndexOf('/'));

......

base = new URI(fo.getProtocol() + "://" + fo.getHost() + path+"/"); // -- this works

// base = new URI(fo.getProtocol() + "://" + fo.getHost() + path); -- this does not work

......

fopFactory = FopFactory.newInstance(base, stream);

• Generate configuration
  • I used a template engine (handlebars) to put path into the placeholders

baseUri = base.toASCIIString();

........

HashMap model = new HashMap();

model.put("baseurl", baseUri);

model.put("basefonturl", baseUri+"fonts/");

model.put("basefontdir", base.getPath()+"/fonts/");

       ....

• Images
  • with correct base URI set, all the three lines below works (with/without "url()", absolute/relative path)

            <fo:external-graphic src="url(vfs:///home/bing/opt/wildfly-10.1.0.Final/standalone/deployments/V8Experiment-1.0-SNAPSHOT.war/WEB-INF/classes/static/img/miso.png)"></fo:external-graphic>

            <fo:external-graphic src="vfs:///home/bing/opt/wildfly-10.1.0.Final/standalone/deployments/V8Experiment-1.0-SNAPSHOT.war/WEB-INF/classes/static/img/miso.png"></fo:external-graphic>

            <fo:external-graphic src="url(img/miso.png)"></fo:external-graphic>

            <fo:external-graphic src="img/miso.png"></fo:external-graphic>

• Fonts
  • Fonts needs to be installed on server, see FOP document
  • Fonts can only be (at least easily) configured with XML configuration file
  • <directory> works, but there's no debug output so difficult to tell
  • <auto-detect> works
  • It's important
    • to specify the correct font family name - it's case sensitive
    • to make sure the file contains the desired glyph for the char code point (otherwise there's warning from standard error)
    • to specify a font: <fo:block font-family="Noto Sans CJK SC" font-size="150%">
    • Use http://bluejamesbond.github.io/CharacterMap/ to check the file (but they always display upper case font family)
    • If not sure, check FOP font cache
• Piped stream
  • whatever pumped into output stream can be read out from input stream
  • with this, no need to create temp file
  • however, the two streams must be passed to two threads, one read and one write.
    • otherwise, will result deadlock of the single thread (blocked write without read or blocked read without write)
  • also the two stream must be connected

           PipedOutputStream out = new PipedOutputStream();

InputStream in = new PipedInputStream(out);

new Thread(() -> {

try {

transformer.transform(src, result);

} catch (TransformerException e) {

e.printStackTrace();

}

;

// Clean-up, anyway

try {

out.close();

} catch (IOException e1) {

e1.printStackTrace();

}

}).start();

return in;

Complete code: it's ugly but it's just a test

package com.bing.V8Experiment.views;

import java.io.ByteArrayInputStream;

import java.io.IOException;

import java.io.InputStream;

import java.io.PipedInputStream;

import java.io.PipedOutputStream;

import java.net.URI;

import java.net.URISyntaxException;

import java.net.URL;

import java.util.HashMap;

import javax.xml.transform.Result;

import javax.xml.transform.Source;

import javax.xml.transform.Transformer;

import javax.xml.transform.TransformerException;

import javax.xml.transform.TransformerFactory;

import javax.xml.transform.sax.SAXResult;

import javax.xml.transform.stream.StreamSource;

import com.github.jknack.handlebars.Handlebars;

import com.github.jknack.handlebars.Template;

import com.vaadin.server.FileDownloader;

import com.vaadin.server.StreamResource;

import com.vaadin.ui.Button;

import com.vaadin.ui.Label;

import com.vaadin.ui.Notification;

import com.vaadin.ui.TextArea;

import com.vaadin.ui.VerticalLayout;

import org.apache.fop.apps.FopFactory;

import org.apache.fop.apps.FopFactoryBuilder;

import org.apache.avalon.framework.configuration.Configuration;

import org.apache.avalon.framework.configuration.DefaultConfiguration;

import org.apache.fop.apps.FOUserAgent;

import org.apache.fop.apps.Fop;

import org.apache.fop.apps.MimeConstants;

import org.apache.fop.cli.CommandLineOptions;

import org.apache.fop.fonts.DefaultFontConfig;

import org.xml.sax.SAXException;

public class PDFDownload extends VerticalLayout {

public PDFDownload() throws SAXException, IOException {

// preparing the URL and base

URL fo = getClass().getClassLoader().getResource("/static/topdf.fo");

// My implementation of PDF generator

PDFStreamSource pdfsrc = new PDFStreamSource(fo);

StreamResource res = new StreamResource(pdfsrc, "Test.pdf");

// preparing the button

Button act = new Button("Generate some PDF");

FileDownloader fd = new FileDownloader(res);

fd.extend(act);

act.addClickListener(e -> {

PDFDownload.this.addComponent(new Label("We are generating the PDF for you, download should start in a while"));

});

TextArea foCfg = new TextArea("FO Configuration");

foCfg.setHeight("400px");

foCfg.setWidth("100%");

foCfg.setValue(pdfsrc.foCfgStr);

this.addComponents(

new Label("FO URL:" + fo.toExternalForm()),

new Label("Base URL: "+pdfsrc.baseUri),

foCfg,

act);

}

}

class PDFStreamSource implements StreamResource.StreamSource {

private URL fo;

private URI base;

FopFactoryBuilder builder;

FopFactory fopFactory;

String baseUri;

String foCfgStr;

public PDFStreamSource(URL fo) {

this.fo = fo;

String path = fo.getFile().substring(0, fo.getFile().lastIndexOf('/'));

try {

base = new URI(fo.getProtocol() + "://" + fo.getHost() + path+"/"); // -- this works

// base = new URI(fo.getProtocol() + "://" + fo.getHost() + path); -- this does not work

} catch (URISyntaxException e1) {

e1.printStackTrace();

return;

}

baseUri = base.toASCIIString(); // for showing the uri on interface

// Step 0: construct a configuration file with Handlebar

Handlebars hbr = new Handlebars();

Template foCfg;

HashMap model = new HashMap();

model.put("baseurl", baseUri);

model.put("basefonturl", baseUri+"fonts/");

model.put("basefontdir", base.getPath()+"fonts/");

// DefaultFontConfig df;

try {

foCfg = hbr.compile("static/fop");

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

foCfgStr = "Failed to generate foCfgStr";

return;

}

try {

foCfgStr = foCfg.apply(model);

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

// Step 1: Construct a FopFactory by specifying a reference to

// the configuration file

// (reuse if you plan to render multiple documents!)

InputStream stream = new ByteArrayInputStream(foCfgStr.getBytes());

try {

fopFactory = FopFactory.newInstance(base, stream);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

};

@Override

public InputStream getStream() {

try {

// Step 2: Set up output stream.

PipedOutputStream out = new PipedOutputStream();

InputStream in = new PipedInputStream(out);

// Step 3: Construct fop with desired output format

Fop fop = fopFactory.newFop(MimeConstants.MIME_PDF, out);

System.err.println("User agent URI:"+fop.getUserAgent().getResourceResolver().getBaseURI().toASCIIString());

System.err.println("Factory font manager resource resolver baseUri:"+fopFactory.getFontManager().getResourceResolver().getBaseURI().toASCIIString());

// Step 4: Setup JAXP using identity transformer

TransformerFactory factory = TransformerFactory.newInstance();

Transformer transformer = factory.newTransformer(); // identity

// transformer

// Step 5: Setup input and output for XSLT transformation

// Setup input stream

Source src = new StreamSource(fo.openStream());

// Resulting SAX events (the generated FO) must be piped

// through to FOP

Result result = new SAXResult(fop.getDefaultHandler());

// Step 6: Start XSLT transformation and FOP processing

new Thread(() -> {

try {

transformer.transform(src, result);

} catch (TransformerException e) {

e.printStackTrace();

}

;

// Clean-up, anyway

try {

out.close();

} catch (IOException e1) {

e1.printStackTrace();

}

}).start();

return in;

} catch (Exception e) {

e.printStackTrace();

return null;

}

}

}

Finally generated FOP configuration:

<?xml version="1.0"?>

<fop version="1.0">

  <!-- Strict user configuration -->

  <strict-configuration>true</strict-configuration>

  <!-- Strict FO validation -->

  <strict-validation>false</strict-validation>

  <!-- Base URL for resolving relative URLs -->

  <base>vfs:///home/bing/opt/wildfly-10.1.0.Final/standalone/deployments/V8Experiment-1.0-SNAPSHOT.war/WEB-INF/classes/static/</base>

  <!-- Font Base URL for resolving relative font URLs -->

  <font-base>vfs:///home/bing/opt/wildfly-10.1.0.Final/standalone/deployments/V8Experiment-1.0-SNAPSHOT.war/WEB-INF/classes/static/fonts/</font-base>

  <!-- Source resolution in dpi (dots/pixels per inch) for determining the size of pixels in SVG and bitmap images, default: 72dpi -->

  <source-resolution>72</source-resolution>

  <!-- Target resolution in dpi (dots/pixels per inch) for specifying the target resolution for generated bitmaps, default: 72dpi -->

  <target-resolution>72</target-resolution>

  <!-- default page-height and page-width, in case

       value is specified as auto -->

  <default-page-settings height="11in" width="8.26in"/>

  <!-- Use file name nl_Bel instead of the default nl_BE -->

  <hyphenation-pattern lang="nl" country="BE">nl_Bel</hyphenation-pattern>

  <!-- or for xml file -->

  <hyphenation-pattern lang="fr" extension="xml">lang/fr.xml</hyphenation-pattern>

  <!-- or for binary file -->

  <hyphenation-pattern lang="fr" extension="hyp">lang/fr.hyp</hyphenation-pattern>

  <renderers>

<renderer mime="application/pdf">

<fonts>

<!-- register all the fonts found in a directory -->

<directory>/home/bing/opt/wildfly-10.1.0.Final/standalone/deployments/V8Experiment-1.0-SNAPSHOT.war/WEB-INF/classes/static/fonts/</directory>

<!-- automatically detect operating system installed fonts -->

<!-- auto-detect/ -->

</fonts>

</renderer>

  </renderers>

</fop>