在jar文件中加载速度模板

Question

我有一个项目,我想加载一个速度模板来完成它与参数.整个应用程序打包为jar文件.我最初想到的是这样的:

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();

当我在eclipse中运行时,这很好用.但是,一旦我打包程序并尝试使用命令行运行它,我得到一个错误,因为找不到该文件.

我想问题就在这一行:

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

因为在jar中绝对文件不存在,因为它在zip中,但我还没有找到更好的方法来做到这一点.

有人有什么想法吗？

Answer 1

如果要使用类路径中的资源,则应使用资源加载器进行类路径:

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

Answer 2

最终代码,使用上述两个答案中提出的想法开发:

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();

Answer 3

除非JAR爆炸,否则您无法将JAR中的资源作为文件读取.使用输入流.

请参阅以下代码段,

    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)) 
                ......