JMustacheRenderer.java

package com.vtence.molecule.templating;

import com.samskivert.mustache.Mustache;
import com.samskivert.mustache.Template;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.Writer;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;

public class JMustacheRenderer implements RenderingEngine {

    private Mustache.Compiler mustache;
    private File path = new File(".");
    private Charset encoding = StandardCharsets.UTF_8;
    private String extension = "mustache";

    public JMustacheRenderer() {
        this(Mustache.compiler());
    }

    public JMustacheRenderer(Mustache.Compiler compiler) {
        this.mustache = compiler.withLoader(this::loadTemplate);
    }

    public JMustacheRenderer fromDir(File dir) {
        this.path = dir;
        return this;
    }

    public JMustacheRenderer extension(String ext) {
        this.extension = ext;
        return this;
    }

    public JMustacheRenderer defaultValue(String defaultValue) {
        mustache = mustache.defaultValue(defaultValue);
        return this;
    }

    public JMustacheRenderer nullValue(String nullValue) {
        mustache = mustache.nullValue(nullValue);
        return this;
    }

    public JMustacheRenderer encoding(String charsetName) {
        encoding(Charset.forName(charsetName));
        return this;
    }

    public JMustacheRenderer encoding(Charset charset) {
        this.encoding = charset;
        return this;
    }

    public void render(Writer out, String templateName, Object context) throws IOException {
        try (Reader source = loadTemplate(templateName)) {
            Template template = mustache.compile(source);
            template.execute(context, out);
        }
    }

    private Reader loadTemplate(String name) throws IOException {
        return new InputStreamReader(new FileInputStream(templateFile(name)), encoding);
    }

    private File templateFile(String name) {
        return new File(path, name + "." + extension);
    }
}