com.devonfw.cobigen.tempeng.freemarker.FreeMarkerTemplateEngine Maven / Gradle / Ivy

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package com.devonfw.cobigen.tempeng.freemarker;

import java.io.Writer;
import java.nio.file.Path;
import java.util.Map;

import com.devonfw.cobigen.api.annotation.Name;
import com.devonfw.cobigen.api.exception.CobiGenRuntimeException;
import com.devonfw.cobigen.api.extension.TextTemplate;
import com.devonfw.cobigen.api.extension.TextTemplateEngine;
import com.devonfw.cobigen.tempeng.freemarker.constant.FreemarkerMetadata;

import freemarker.cache.NullCacheStorage;
import freemarker.core.Environment;
import freemarker.core.ParseException;
import freemarker.template.Configuration;
import freemarker.template.DefaultObjectWrapperBuilder;
import freemarker.template.Template;
import freemarker.template.TemplateException;

/**
 * {@link TextTemplateEngine} implementation for Apache FreeMarker.
 */
@Name("FreeMarker")
public class FreeMarkerTemplateEngine implements TextTemplateEngine {

    /** The file extension of the template files. */
    private static final String TEMPLATE_EXTENSION = ".ftl";

    /** The commonly used FreeMarker engine configuration */
    private Configuration freeMarkerConfig;

    /**
     * Constructor, which initializes the commonly used FreeMarker configuration.
     */
    public FreeMarkerTemplateEngine() {
        freeMarkerConfig = new Configuration(Configuration.VERSION_2_3_23);
        freeMarkerConfig.setObjectWrapper(new DefaultObjectWrapperBuilder(Configuration.VERSION_2_3_23).build());
        freeMarkerConfig.clearEncodingMap();
        freeMarkerConfig.setDefaultEncoding("UTF-8");
        freeMarkerConfig.setLocalizedLookup(false);
        freeMarkerConfig.setTemplateLoader(new NioFileSystemTemplateLoader());
        freeMarkerConfig.setCacheStorage(new NullCacheStorage());
    }

    @Override
    public String getTemplateFileEnding() {
        return TEMPLATE_EXTENSION;
    }

    @Override
    public void process(TextTemplate template, Map model, Writer out, String outputEncoding) {
        Template fmTemplate = null;
        try {
            fmTemplate = freeMarkerConfig.getTemplate(template.getRelativeTemplatePath());
        } catch (ParseException e) {
            throw new CobiGenRuntimeException(
                "Could not parse FreeMarker template: " + template.getAbsoluteTemplatePath() + ". (FreeMarker v"
                    + FreemarkerMetadata.VERSION + " )\n" + e.getMessage(),
                e);
        } catch (Throwable e) {
            throw new CobiGenRuntimeException(
                "An error occured while retrieving the FreeMarker template: " + template.getAbsoluteTemplatePath()
                    + " from the FreeMarker configuration. (FreeMarker v" + FreemarkerMetadata.VERSION + " )",
                e);
        }

        if (fmTemplate != null) {
            try {
                Environment env = fmTemplate.createProcessingEnvironment(model, out);
                env.setOutputEncoding(outputEncoding);
                env.process();
            } catch (TemplateException e) {
                throw new CobiGenRuntimeException(
                    "An error occurred while generating the template: " + template.getAbsoluteTemplatePath()
                        + " (FreeMarker v" + FreemarkerMetadata.VERSION + ")" + "\n" + e.getMessage(),
                    e);
            } catch (Throwable e) {
                throw new CobiGenRuntimeException("An unkonwn error occurred while generating the template: "
                    + template.getAbsoluteTemplatePath() + " (FreeMarker v" + FreemarkerMetadata.VERSION + ")", e);
            }
        }
    }

    @Override
    public void setTemplateFolder(Path templateFolderPath) {
        ((NioFileSystemTemplateLoader) freeMarkerConfig.getTemplateLoader()).setTemplateRoot(templateFolderPath);
    }

}