当对 XML 以外的树使用 #recurse 时，我需要数据模型的 Freemarker 文档

Question

我正在尝试在 Freemarker 中处理树结构，并想使用 #recurse、#visit 指令，但我找不到任何关于如何设置数据模型的好文档。我能看到的唯一示例是为 XML 结构创建数据模型的示例。我不需要这么详细。我的树很简单。

为了测试我需要的功能，我构建了一个单元测试，但是当我运行它时，我得到

FreeMarker template error:
For "." left-hand operand: Expected a hash, but this has evaluated to a node

这里是源代码：

public class FreemarkerXmlTests {

    static class Element implements TemplateNodeModel {
        private final String name;
        private final String text;
        private Element parent;
        private final List<Element> elements = new ArrayList<>();

        public Element(String name) {
            this(name, null);
        }

        public Element(String name, String text) {
            this.name = name;
            this.text = text;
        }

        public void add(Element element) {
            element.parent = this;
            this.elements.add(element);
        }

        public List<Element> getElements() {
            return this.elements;
        }

        public String getName() {
            return this.name;
        }

        public String getText() {
            return this.text;
        }

        public String getTitle() {
            return this.name;
        }

        public TemplateModel get(String key) {
            return null;
        }

        @Override
        public TemplateNodeModel getParentNode() throws TemplateModelException {
            return this.parent;
        }

        @Override
        public TemplateSequenceModel getChildNodes() throws TemplateModelException {
            // TODO Auto-generated method stub
            return new SimpleSequence(this.elements, cfg.getObjectWrapper());
        }

        @Override
        public String getNodeName() throws TemplateModelException {
            return this.name;
        }

        @Override
        public String getNodeType() throws TemplateModelException {
            return this.name;
        }

        @Override
        public String getNodeNamespace() throws TemplateModelException {
            return null;
        }
    }

    private static Configuration cfg;
    private static final String myTestTemplate = "<#recurse doc>\r\n" +
            "\r\n" +
            "<#macro book>\r\n" +
            "  Book element with title ${.node.title} \r\n" +
            "    <#recurse>\r\n" +
            "  End book\r\n" +
            "</#macro>\r\n" +
            "\r\n" +
            "<#macro title>\r\n" +
            "  Title element\r\n" +
            "</#macro>\r\n" +
            "\r\n" +
            "<#macro chapter>\r\n" +
            "  Chapter element with title: ${.node.title}\r\n" +
            "</#macro>";

    @BeforeClass
    public static void classInit() throws IOException {

        StringTemplateLoader stringTemplateLoader = new StringTemplateLoader();
        stringTemplateLoader.putTemplate("myTestTemplate", myTestTemplate);

        cfg = new Configuration(Configuration.VERSION_2_3_29);
        cfg.setTemplateLoader(stringTemplateLoader);
        cfg.setDefaultEncoding("UTF-8");
        cfg.setTemplateExceptionHandler(TemplateExceptionHandler.RETHROW_HANDLER);
        cfg.setLogTemplateExceptions(false);
        cfg.setWrapUncheckedExceptions(true);
        cfg.setFallbackOnNullLoopVariable(false);
    }

    @Test
    public void basicXmlTest() throws TemplateException, IOException {

        Element doc = new Element("doc");

        Element book = new Element("book");
        book.add(new Element("title", "Test Book"));
        doc.add(book);

        Element chapter1 = new Element("chapter");
        chapter1.add(new Element("title", "Ch1"));
        chapter1.add(new Element("para", "p1.1"));
        chapter1.add(new Element("para", "p1.2"));
        chapter1.add(new Element("para", "p1.3"));
        book.add(chapter1);

        Element chapter2 = new Element("chapter");
        chapter2.add(new Element("title", "Ch2"));
        chapter2.add(new Element("para", "p2.1"));
        chapter2.add(new Element("para", "p2.2"));
        chapter2.add(new Element("para", "p2.3"));
        book.add(chapter2);

        Map<String, Object> root = new HashMap<>();
        // Put string "user" into the root
        root.put("doc", doc);

        Template temp = cfg.getTemplate("myTestTemplate");

        Writer out = new OutputStreamWriter(System.out);
        temp.process(root, out);

    }

有什么想法吗？

Answer 1

看看 freemarker.template.TemplateNodeModel interface. Your objects have to implement that, or they have to be wrapped (via the ObjectWrapper) into a TemplateModel 的实现。然后 #recurse/#visit/?parent/?children/等等。将与他们合作。

下面是一个实现的例子TemplateNodeModel for traversing JSON: https://github.com/freemarker/fmpp/blob/master/src/main/java/fmpp/models/JSONNode.java

上面使用的一些模板： https://github.com/freemarker/fmpp/tree/master/src/test/resources/tests/dl_json/src

从 . 运算符开始，您需要实现 TemplateHashModel（或其子接口，如 TemplateHashModelEx2）。

Answer 2

借助 ddekany 发布的示例，我添加了以下内容：

为元素实现 TemplateHashModel class

    static class Element implements TemplateNodeModel, TemplateHashModel {

元素的方法 class 并且单元测试有效：

        @Override
        public TemplateModel get(String key) throws TemplateModelException {

            switch (key) {
            case "title":
            case "name":
                return cfg.getObjectWrapper().wrap(this.name);

            default:
                throw new TemplateModelException("unknown hash get: " + key);
            }
        }

当对 XML 以外的树使用 #recurse 时，我需要数据模型的 Freemarker 文档

I need Freemarker documentation for data model when using #recurse with trees other than XML

java

freemarker