[REST] New API for conversion between file format and JSON

Related to #4585

This PR supports conversion of things and items.
It supports DSL and YAML file formats.

A first new API (POST /file-format/create) allows to create a file format (DSL or YAML) from a JSON object.
A second new API (POST /file-format/parse) allows to parse a file format (DSL or YAML) to a JSON object.

These 2 APIs should help Main UI displaying DSL and YAML file formats for things.

Signed-off-by: Laurent Garnier <[email protected]>

Author: lolodomo

bundles/org.openhab.core.io.rest.core/src/main/java/org/openhab/core/io/rest/core/fileformat/ExtendedFileFormatDTO.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright (c) 2010-2025 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.core.io.rest.core.fileformat;
+
+import java.util.List;
+
+/**
+ * This is a data transfer object to serialize the different components that can be contained
+ * in a file format (items, things, ...) including an optional list of warnings.
+ *
+ * @author Laurent Garnier - Initial contribution
+ */
+public class ExtendedFileFormatDTO extends FileFormatDTO {
+
+    public List<String> warnings;
+}

bundles/org.openhab.core.io.rest.core/src/main/java/org/openhab/core/io/rest/core/fileformat/FileFormatChannelLinkDTO.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright (c) 2010-2025 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.core.io.rest.core.fileformat;
+
+import java.util.Map;
+
+/**
+ * This is a data transfer object to serialize a channel link for an item contained in a file format.
+ *
+ * @author Laurent Garnier - Initial contribution
+ */
+public class FileFormatChannelLinkDTO {
+
+    public String channelUID;
+    public Map<String, Object> configuration;
+
+    public FileFormatChannelLinkDTO(String channelUID, Map<String, Object> configuration) {
+        this.channelUID = channelUID;
+        this.configuration = configuration;
+    }
+}

bundles/org.openhab.core.io.rest.core/src/main/java/org/openhab/core/io/rest/core/fileformat/FileFormatDTO.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright (c) 2010-2025 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.core.io.rest.core.fileformat;
+
+import java.util.List;
+
+import org.openhab.core.thing.dto.ThingDTO;
+
+/**
+ * This is a data transfer object to serialize the different components that can be contained
+ * in a file format (items, things, ...).
+ *
+ * @author Laurent Garnier - Initial contribution
+ */
+public class FileFormatDTO {
+
+    public List<FileFormatItemDTO> items;
+    public List<ThingDTO> things;
+}

bundles/org.openhab.core.io.rest.core/src/main/java/org/openhab/core/io/rest/core/fileformat/FileFormatItemDTO.java

@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2010-2025 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.core.io.rest.core.fileformat;
+
+import java.util.List;
+import java.util.Map;
+
+import org.openhab.core.items.dto.GroupFunctionDTO;
+import org.openhab.core.items.dto.GroupItemDTO;
+import org.openhab.core.items.dto.ItemDTO;
+import org.openhab.core.items.dto.MetadataDTO;
+
+/**
+ * This is a data transfer object to serialize an item contained in a file format.
+ *
+ * @author Laurent Garnier - Initial contribution
+ */
+public class FileFormatItemDTO extends ItemDTO {
+
+    public String groupType;
+    public GroupFunctionDTO function;
+    public Map<String, MetadataDTO> metadata;
+    public List<FileFormatChannelLinkDTO> channelLinks;
+
+    public FileFormatItemDTO(ItemDTO itemDTO, boolean isGroup) {
+        this.type = itemDTO.type;
+        this.name = itemDTO.name;
+        this.label = itemDTO.label;
+        this.category = itemDTO.category;
+        this.tags = itemDTO.tags;
+        this.groupNames = itemDTO.groupNames;
+        if (isGroup) {
+            this.groupType = ((GroupItemDTO) itemDTO).groupType;
+            this.function = ((GroupItemDTO) itemDTO).function;
+        }
+    }
+}

bundles/org.openhab.core.io.rest.core/src/main/java/org/openhab/core/io/rest/core/fileformat/FileFormatItemDTOMapper.java

@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2010-2025 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.core.io.rest.core.fileformat;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.eclipse.jdt.annotation.Nullable;
+import org.openhab.core.items.GroupItem;
+import org.openhab.core.items.Item;
+import org.openhab.core.items.ItemBuilderFactory;
+import org.openhab.core.items.Metadata;
+import org.openhab.core.items.MetadataKey;
+import org.openhab.core.items.dto.GroupItemDTO;
+import org.openhab.core.items.dto.ItemDTO;
+import org.openhab.core.items.dto.ItemDTOMapper;
+import org.openhab.core.items.dto.MetadataDTO;
+import org.openhab.core.thing.link.ItemChannelLink;
+
+/**
+ * The {@link FileFormatItemDTOMapper} is a utility class to map items into file format item data transfer objects
+ * (DTOs).
+ *
+ * @author Laurent Garnier - Initial contribution
+ */
+@NonNullByDefault
+public class FileFormatItemDTOMapper {
+
+    /**
+     * Maps item into file format item DTO object.
+     *
+     * @param item the item
+     * @param metadata some metadata
+     * @param channelLinks some items channel links
+     * @return file format item DTO object
+     */
+    public static FileFormatItemDTO map(Item item, Collection<Metadata> metadata,
+            Collection<ItemChannelLink> channelLinks) {
+        ItemDTO itemDto = ItemDTOMapper.map(item);
+        FileFormatItemDTO dto = new FileFormatItemDTO(itemDto, itemDto instanceof GroupItemDTO);
+
+        Map<String, MetadataDTO> metadataDTO = new LinkedHashMap<>();
+        metadata.forEach(md -> {
+            if (item.getName().equals(md.getUID().getItemName())) {
+                MetadataDTO mdDTO = new MetadataDTO();
+                mdDTO.value = md.getValue();
+                mdDTO.config = md.getConfiguration().isEmpty() ? null : md.getConfiguration();
+                metadataDTO.put(md.getUID().getNamespace(), mdDTO);
+            }
+        });
+        if (!metadataDTO.isEmpty()) {
+            dto.metadata = metadataDTO;
+        }
+
+        List<FileFormatChannelLinkDTO> hannelLinksDTO = new ArrayList<>();
+        channelLinks.forEach(link -> {
+            if (item.getName().equals(link.getItemName())) {
+                hannelLinksDTO.add(new FileFormatChannelLinkDTO(link.getLinkedUID().getAsString(),
+                        link.getConfiguration().getProperties().isEmpty() ? null
+                                : link.getConfiguration().getProperties()));
+            }
+        });
+        if (!hannelLinksDTO.isEmpty()) {
+            dto.channelLinks = hannelLinksDTO;
+        }
+
+        return dto;
+    }
+
+    /**
+     * Maps file format item DTO object into item.
+     *
+     * @param dto the file format item DTO object
+     * @param itemBuilderFactory the item builder factory
+     * @return item
+     */
+    public static @Nullable Item map(FileFormatItemDTO dto, ItemBuilderFactory itemBuilderFactory) {
+        if (GroupItem.TYPE.equals(dto.type)) {
+            GroupItemDTO groupDto = new GroupItemDTO();
+            groupDto.type = dto.type;
+            groupDto.name = dto.name;
+            groupDto.label = dto.label;
+            groupDto.category = dto.category;
+            groupDto.tags = dto.tags;
+            groupDto.groupNames = dto.groupNames;
+            groupDto.groupType = dto.groupType;
+            groupDto.function = dto.function;
+            return ItemDTOMapper.map(groupDto, itemBuilderFactory);
+        }
+        return ItemDTOMapper.map(dto, itemBuilderFactory);
+    }
+
+    /**
+     * Maps file format item DTO object into a collection of metadata including channels links
+     * provided through the "channel" namespace.
+     *
+     * @param dto the file format item DTO object
+     * @return the collection of metadata
+     */
+    public static Collection<Metadata> mapMetadata(FileFormatItemDTO dto) {
+        String name = dto.name;
+        Collection<Metadata> metadata = new ArrayList<>();
+        if (dto.channelLinks != null) {
+            for (FileFormatChannelLinkDTO link : dto.channelLinks) {
+                MetadataKey key = new MetadataKey("channel", name);
+                metadata.add(new Metadata(key, link.channelUID, link.configuration));
+            }
+        }
+        if (dto.metadata != null) {
+            for (Map.Entry<String, MetadataDTO> md : dto.metadata.entrySet()) {
+                MetadataKey key = new MetadataKey(md.getKey(), name);
+                metadata.add(new Metadata(key, Objects.requireNonNull(md.getValue().value), md.getValue().config));
+            }
+        }
+        return metadata;
+    }
+}