任意读取json数据到javafx treeview，只显示其中任意数组的第一个元素

Question

我需要在 javafx 树视图上显示一个 json 文件，json 的结构是未知的。像网站一样： json 查看器站点 我显示树供用户选择值的路径（如 xml 的 xpath），所以如果json太大了，我只需要显示json中任何数组的第一个元素。

例如，原始数据为：

{
    name:"tom",
    schools:[
        {
            name:"school1",
            tags:["maths","english"]
        },
        {
            name:"school2",
            tags:["english","biological"]
        },
    ]
}

我想展示：

再次：json的结构未知，仅举一例。

Answer 1

除了递归处理 json 并TreeItem根据元素信息创建结构外，别无选择。

（可能有更好的添加符号的方法，但我没有找到合适的图标。）

private static final String INPUT = "{\n"
        + "    name:\"tom\",\n"
        + "    schools:[\n"
        + "        {\n"
        + "            name:\"school1\",\n"
        + "            tags:[\"maths\",\"english\"]\n"
        + "        },\n"
        + "        {\n"
        + "            name:\"school2\",\n"
        + "            tags:[\"english\",\"biological\"]\n"
        + "        },\n"
        + "    ]\n"
        + "}";

private static final Image JSON_IMAGE = new Image("https://i.stack.imgur.com/1slrh.png");

private static void prependString(TreeItem<Value> item, String string) {
    String val = item.getValue().text;
    item.getValue().text = (val == null
            ? string
            : string + " : " + val);
}

private enum Type {
    OBJECT(new Rectangle2D(45, 52, 16, 18)),
    ARRAY(new Rectangle2D(61, 88, 16, 18)),
    PROPERTY(new Rectangle2D(31, 13, 16, 18));

    private final Rectangle2D viewport;

    private Type(Rectangle2D viewport) {
        this.viewport = viewport;
    }

}

private static final class Value {

    private String text;
    private final Type type;

    public Value(Type type) {
        this.type = type;
    }

    public Value(String text, Type type) {
        this.text = text;
        this.type = type;
    }

}

private static TreeItem<Value> createTree(JsonElement element) {
    if (element.isJsonNull()) {
        return new TreeItem<>(new Value("null", Type.PROPERTY));
    } else if (element.isJsonPrimitive()) {
        JsonPrimitive primitive = element.getAsJsonPrimitive();
        return new TreeItem<>(new Value(primitive.isString()
                ? '"' + primitive.getAsString() + '"'
                : primitive.getAsString(), Type.PROPERTY));
    } else if (element.isJsonArray()) {
        JsonArray array = element.getAsJsonArray();
        TreeItem<Value> item = new TreeItem<>(new Value(Type.ARRAY));
       // for (int i = 0, max = Math.min(1, array.size()); i < max; i++) {
        for (int i = 0, max = array.size(); i < max; i++) {
            TreeItem<Value> child = createTree(array.get(i));
            prependString(child, Integer.toString(i));
            item.getChildren().add(child);
        }
        return item;
    } else {
        JsonObject object = element.getAsJsonObject();
        TreeItem<Value> item = new TreeItem<>(new Value(Type.OBJECT));
        for (Map.Entry<String, JsonElement> property : object.entrySet()) {
            TreeItem<Value> child = createTree(property.getValue());
            prependString(child, property.getKey());
            item.getChildren().add(child);
        }
        return item;
    }
}

@Override
public void start(Stage primaryStage) {
    JsonParser parser = new JsonParser();
    JsonElement root = parser.parse(INPUT);

    TreeItem<Value> treeRoot = createTree(root);
    TreeView<Value> treeView = new TreeView<>(treeRoot);
    treeView.setCellFactory(tv -> new TreeCell<Value>() {
        private final ImageView imageView;

        {
            imageView = new ImageView(JSON_IMAGE);
            imageView.setFitHeight(18);
            imageView.setFitWidth(16);
            imageView.setPreserveRatio(true);
            setGraphic(imageView);
        }

        @Override
        protected void updateItem(Value item, boolean empty) {
            super.updateItem(item, empty);

            if (empty || item == null) {
                setText("");
                imageView.setVisible(false);
            } else {
                setText(item.text);
                imageView.setVisible(true);
                imageView.setViewport(item.type.viewport);
            }
        }


    });

    final Scene scene = new Scene(treeView);

    primaryStage.setScene(scene);
    primaryStage.show();
}