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API / Apache Velocity Interview questions

What is the role of the ResourceManager and ResourceLoader in Velocity?

ResourceLoader is the pluggable interface responsible for actually locating and reading a template's raw source, whether from the file system, the classpath, a JAR, a database, or a custom source you implement yourself. ResourceManager sits above it, coordinating one or more configured loaders and applying the caching policy so a resource isn't re-read and re-parsed unnecessarily.

Properties p = new Properties();
p.setProperty("resource.loader", "file, classpath");
p.setProperty("file.resource.loader.path", "/opt/app/templates");
p.setProperty("file.resource.loader.cache", "true");
p.setProperty("classpath.resource.loader.class",
  "org.apache.velocity.runtime.resource.loader.ClasspathResourceLoader");

VelocityEngine engine = new VelocityEngine(p);
engine.init();

Multiple loaders can be chained, as shown above, so the engine tries the file system first and falls back to the classpath. When a requested template isn't found by any configured loader, getTemplate() throws a ResourceNotFoundException.

What is the ResourceLoader responsible for?
What role does ResourceManager play relative to ResourceLoader?

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