org.apache.cayenne.gen.ClassGeneratorResourceLoader Maven / Gradle / Ivy

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package org.apache.cayenne.gen;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.nio.file.Path;
import java.nio.file.Paths;

import org.apache.velocity.exception.ResourceNotFoundException;
import org.apache.velocity.runtime.resource.loader.FileResourceLoader;
import org.apache.velocity.util.ExtProperties;

/**
 * Velocity template resource loader customized for Cayenne use. Supports loading
 * templates from the thread ClassLoader and from relative and absolute paths.
 *
 * @since 1.2
 */
// must be public top-level class as it is instantiated via reflection by Velocity
public class ClassGeneratorResourceLoader extends FileResourceLoader {

    private Path root;

    @Override
    public void init(ExtProperties configuration) {
        root = (Path)configuration.getProperty("root");
    }

    /**
     * Returns resource as InputStream. Searches resource in a following places:
     * 
     *     thread class loader
     *     this class's class loader
     *     tries a path relative to a root path, if set
     *     an absolute path
     * 
     */
    @Override
    public synchronized Reader getResourceReader(String name, String charset) throws ResourceNotFoundException {

        Reader stream;

        stream = loadFromThreadClassLoader(name);
        if (stream != null) {
            return stream;
        }

        stream = loadFromThisClassLoader(name);
        if (stream != null) {
            return stream;
        }

        stream = loadFromRelativePath(name);
        if (stream != null) {
            return stream;
        }

        stream = loadFromAbsPath(name);
        if (stream != null) {
            return stream;
        }
        throw new ResourceNotFoundException("Couldn't find resource '"
                + name
                + "'. Searched filesystem path and classpath");
    }

    protected Reader loadFromRelativePath(String name) {
        if (root != null) {
            Path absolutePath = root.resolve(name).normalize();
            return loadFromAbsPath(absolutePath.toString());
        }
        return null;
    }

    protected Reader loadFromAbsPath(String name) {
        try {
            File file = new File(name);
            return file.canRead()
                    ? new BufferedReader(new FileReader(file.getAbsolutePath()))
                    : null;
        } catch (FileNotFoundException fnfe) {
            return null;
        }
    }

    protected Reader loadFromThreadClassLoader(String name) {
        InputStream stream = Thread.currentThread().getContextClassLoader().getResourceAsStream(name);
        return stream != null ? new InputStreamReader(stream) : null;
    }

    protected Reader loadFromThisClassLoader(String name) {
        InputStream stream = getClass().getClassLoader().getResourceAsStream(name);
        return stream != null ? new InputStreamReader(stream) : null;
    }
}