使用freemarker模板生成html的最简单java代码可以是：config.setapibuiltinenabled（true）；线路可能是你要找的。

import freemarker.cache.ClassTemplateLoader;
import freemarker.core.Environment;
import freemarker.template.Configuration;
import freemarker.template.Template;
// ... other imports

private byte[] createHtmlContent() throws Exception {
    Map<String, Object> data = new HashMap<String, Object>();
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    Writer w = new OutputStreamWriter(baos, StandardCharsets.UTF_8);

    Configuration config = new Configuration();
    config.setAPIBuiltinEnabled(true);

    config.setTemplateLoader(new ClassTemplateLoader(getClass(), "/META-INF/resources/ftl/"));
    Template template = config.getTemplate("template.ftl");

    Environment env = template.createProcessingEnvironment(data, w);
    env.setOutputEncoding("UTF-8");
    env.process();

    return baos.toByteArray();
}