Loading velocity template inside a jar file

Question

I have a project where I want to load a velocity template to complete it with parameters. The whole application is packaged as a jar file. What I initially thought of doing was this:

VelocityEngine ve = new VelocityEngine();

   URL url = this.getClass().getResource("/templates/");

   File file = new File(url.getFile());

   ve = new VelocityEngine();
   ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "file");
   ve.setProperty(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, file.getAbsolutePath());
   ve.setProperty(RuntimeConstants.FILE_RESOURCE_LOADER_CACHE, "true");

   ve.init();

   VelocityContext context = new VelocityContext();

   if (properties != null) {
    stringfyNulls(properties);
    for (Map.Entry<String, Object> property : properties.entrySet()) {
     context.put(property.getKey(), property.getValue());
    }
   }

   final String templatePath = templateName + ".vm";
   Template template = ve.getTemplate(templatePath, "UTF-8");
   String outFileName = File.createTempFile("report", ".html").getAbsolutePath();
   BufferedWriter writer = new BufferedWriter(new FileWriter(new File(outFileName)));

   template.merge(context, writer);

   writer.flush();
   writer.close();

And this works fine when I run it in eclipse. However, once I package the program and try to run it using the command line I get an error because the file could not be found.

I imagine the problem is in this line:

ve.setProperty(RuntimeConstants.FILE_RESOURCE_LOADER_PATH, file.getAbsolutePath());

Because in a jar the absolute file does not exist, since it's inside a zip, but I couldn't yet find a better way to do it.

Anyone has any ideas?

for the love of god, highlight the code in your post and click the code button so that its formatted properly! :) — vicatcu, May 28 '10 at 18:28
Are you quite certain that the /templates/ directory is getting exported into your jar? You have to mark it as part of your build settings and stuff. — vicatcu, May 28 '10 at 18:29
didn't known about the code button, thanks. Yes, the templates dir is getting into the jar file. — Rafael, May 28 '10 at 18:35

score 77 · Accepted Answer · edited Apr 24 '23 at 15:00

77

If you want to use resources from classpath, you should use resource loader for classpath:

ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "classpath"); 
ve.setProperty("classpath.resource.loader.class", ClasspathResourceLoader.class.getName());
ve.init();

edited Apr 24 '23 at 15:00

Sathiamoorthy

8,831
9
65
77

answered May 28 '10 at 20:18

axtavt

239,438
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482

I will test it! do you know where I can find documentation to each RuntimeContants and its possible values? – Rafael May 28 '10 at 20:48
Couldn't make it work, it doesn't find the file in neither eclipse nor in the jar. – Rafael May 28 '10 at 20:56
@Rafael: Fixed. `ClasspathResourceLoader` is not registered by default. – axtavt May 28 '10 at 21:28
Thanks, it did work when I used this along with the idea presented by ZZ Coder below. – Rafael May 31 '10 at 13:41
Works as written with v 1.7. Thanks. ` VelocityEngine ve = new VelocityEngine(); ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "classpath"); ve.setProperty("classpath.resource.loader.class", ClasspathResourceLoader.class.getName()); ve.init(); ` – David Williams Sep 22 '13 at 17:22
Also look at ve.evaluate(..) which allows a java.io.Reader to be passed – John Deverall Mar 04 '15 at 15:10
1

It is unfortunate that [Javadocs of ClasspathResourceLoader](https://velocity.apache.org/engine/devel/apidocs/org/apache/velocity/runtime/resource/loader/ClasspathResourceLoader.html) wrongly says that resource loader value should be "class" - I tried that and it did not work, only to discover later that it should be "classpath" as mentioned in this answer – Wand Maker Apr 18 '16 at 09:23

score 24 · Answer 2 · edited Jun 13 '18 at 18:12

Final code, developed using the ideas presented in both answers above:

VelocityEngine ve = new VelocityEngine();
ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "classpath");
ve.setProperty("classpath.resource.loader.class", ClasspathResourceLoader.class.getName());

ve.init();

final String templatePath = "templates/" + templateName + ".vm";
InputStream input = this.getClass().getClassLoader().getResourceAsStream(templatePath);
if (input == null) {
    throw new IOException("Template file doesn't exist");
}

InputStreamReader reader = new InputStreamReader(input);

VelocityContext context = new VelocityContext();

if (properties != null) {
    stringfyNulls(properties);
    for (Map.Entry<String, Object> property : properties.entrySet()) {
        context.put(property.getKey(), property.getValue());
    }
}

Template template = ve.getTemplate(templatePath, "UTF-8");
String outFileName = File.createTempFile("report", ".html").getAbsolutePath();
BufferedWriter writer = new BufferedWriter(new FileWriter(new File(outFileName)));

if (!ve.evaluate(context, writer, templatePath, reader)) {
    throw new Exception("Failed to convert the template into html.");
}

template.merge(context, writer);

writer.flush();
writer.close();

Thank you, this helped me a great deal! Might be that my adapation works just a bit different, but using VelocityEngine#evaluate(...), I could leave out the instantiation of the Template and the call to Template#merge(...) — Argelbargel, Jun 23 '11 at 23:56
works like a charm. The RuntimeInstance solved my problem allowing me to load the template in my bundle. Best solution for OSGI — iberbeu, Dec 11 '14 at 09:25
This solution worked well, except I did not need the merge part at the end. — Mr. Polywhirl, Dec 13 '19 at 13:06

score 10 · Answer 3 · answered May 28 '10 at 20:55

Unless JAR is exploded, you can't read the resource in JAR as file. Use an input stream.

See following code snippets,

    InputStream input = classLoader.getResourceAsStream(fileName);
    if (input == null) {
        throw new ConfigurationException("Template file " +
                fileName + " doesn't exist");           
    }

    InputStreamReader reader = new InputStreamReader(input);            
        Writer writer = null;

        try {
            writer = new OutputStreamWriter(output);        

            // Merge template
            if (!engine.evaluate(context, writer, fileName, reader)) 
                ......

score 2 · Answer 4 · answered Sep 26 '12 at 18:50

2

To make Velocity look for the templates in classpath:

VelocityEngine ve = new VelocityEngine();
ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "classpath");
ve.setProperty("classpath.resource.loader.class",ClasspathResourceLoader.class.getName());
ve.init();

answered Sep 26 '12 at 18:50

Mahesh Lavannis

55
1

10

I think you're a bit late to the party. – Samuel Parkinson Sep 26 '12 at 18:58

score 0 · Answer 5 · answered Apr 17 '19 at 00:11

0

Maybe I have an old version, this is the only thing that worked for me

ve.setProperty(RuntimeConstants.RESOURCE_LOADER, "class"); 
ve.setProperty("classpath.resource.loader.class", 
ClasspathResourceLoader.class.getName());

answered Apr 17 '19 at 00:11

Ignacio Tomas Crespo

3,401
1
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Loading velocity template inside a jar file

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