Add JSON Patch processor

Signed-off-by: Francis Galiegue <[email protected]>

Author: fge

pom.xml

@@ -115,6 +115,11 @@
             <artifactId>json-schema-avro</artifactId>
             <version>0.1.2</version>
         </dependency>
+        <dependency>
+            <groupId>com.github.fge</groupId>
+            <artifactId>json-patch</artifactId>
+            <version>1.0</version>
+        </dependency>
         <dependency>
             <groupId>org.testng</groupId>
             <artifactId>testng</artifactId>

src/main/java/com/github/fge/jsonpatch/JsonPatchInput.java

@@ -0,0 +1,34 @@
+package com.github.fge.jsonpatch;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.github.fge.jsonschema.report.MessageProvider;
+import com.github.fge.jsonschema.report.ProcessingMessage;
+
+public final class JsonPatchInput
+    implements MessageProvider
+{
+    private final JsonNode rawPatch;
+    private final JsonNode node;
+
+    public JsonPatchInput(final JsonNode rawPatch, final JsonNode node)
+    {
+        this.rawPatch = rawPatch;
+        this.node = node;
+    }
+
+    public JsonNode getRawPatch()
+    {
+        return rawPatch;
+    }
+
+    public JsonNode getNode()
+    {
+        return node;
+    }
+
+    @Override
+    public ProcessingMessage newMessage()
+    {
+        return new ProcessingMessage().put("patch", rawPatch).put("node", node);
+    }
+}

src/main/java/com/github/fge/jsonpatch/JsonPatchProcessor.java

@@ -0,0 +1,55 @@
+package com.github.fge.jsonpatch;
+
+import com.fasterxml.jackson.databind.JsonNode;
+import com.github.fge.jackson.JsonLoader;
+import com.github.fge.jsonschema.exceptions.ProcessingException;
+import com.github.fge.jsonschema.main.JsonSchema;
+import com.github.fge.jsonschema.main.JsonSchemaFactory;
+import com.github.fge.jsonschema.processing.Processor;
+import com.github.fge.jsonschema.report.ProcessingReport;
+import com.github.fge.jsonschema.util.ValueHolder;
+
+import java.io.IOException;
+
+public final class JsonPatchProcessor
+    implements Processor<JsonPatchInput, ValueHolder<JsonNode>>
+{
+    private static final JsonSchema SCHEMA;
+
+    static {
+        final JsonSchemaFactory factory = JsonSchemaFactory.byDefault();
+        try {
+            final JsonNode node = JsonLoader.fromResource("/json-patch.json");
+            SCHEMA = factory.getJsonSchema(node);
+        } catch (ProcessingException e) {
+            throw new ExceptionInInitializerError(e);
+        } catch (IOException e) {
+            throw new ExceptionInInitializerError(e);
+        }
+    }
+
+    @Override
+    public ValueHolder<JsonNode> process(final ProcessingReport report,
+        final JsonPatchInput input)
+        throws ProcessingException
+    {
+        final JsonNode rawPatch = input.getRawPatch();
+        report.mergeWith(SCHEMA.validate(rawPatch));
+        if (!report.isSuccess())
+            throw new ProcessingException(input.newMessage()
+                .message("illegal JSON patch"));
+
+        try {
+            final JsonPatch patch = JsonPatch.fromJson(rawPatch);
+            final JsonNode ret = patch.apply(input.getNode());
+            return ValueHolder.hold("result", ret);
+        } catch (JsonPatchException e) {
+            throw new ProcessingException(input.newMessage()
+                .message("failed to apply patch"), e);
+        } catch (IOException e) {
+            throw new ProcessingException(input.newMessage()
+                .message("patch considered invalid but schema validated it"),
+                e);
+        }
+    }
+}

src/main/resources/json-patch.json

@@ -0,0 +1,74 @@
+{
+    "title": "JSON Patch",
+    "description": "A JSON Schema describing a JSON Patch",
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "notes": [
+        "Only required members are accounted for, other members are ignored"
+    ],
+    "type": "array",
+    "items": {
+        "description": "one JSON Patch operation",
+        "allOf": [
+            {
+                "description": "Members common to all operations",
+                "type": "object",
+                "required": [ "op", "path" ],
+                "properties": {
+                    "path": { "$ref": "#/definitions/jsonPointer" }
+                }
+            },
+            { "$ref": "#/definitions/oneOperation" }
+        ]
+    },
+    "definitions": {
+        "jsonPointer": {
+            "type": "string",
+            "pattern": "^(/[^/~]*(~[01][^/~]*)*)*$"
+        },
+        "add": {
+            "description": "add operation. Value can be any JSON value.",
+            "properties": { "op": { "enum": [ "add" ] } },
+            "required": [ "value" ]
+        },
+        "remove": {
+            "description": "remove operation. Only a path is specified.",
+            "properties": { "op": { "enum": [ "remove" ] } }
+        },
+        "replace": {
+            "description": "replace operation. Value can be any JSON value.",
+            "properties": { "op": { "enum": [ "replace" ] } },
+            "required": [ "value" ]
+        },
+        "move": {
+            "description": "move operation. \"from\" is a JSON Pointer.",
+            "properties": {
+                "op": { "enum": [ "move" ] },
+                "from": { "$ref": "#/definitions/jsonPointer" }
+            },
+            "required": [ "from" ]
+        },
+        "copy": {
+            "description": "copy operation. \"from\" is a JSON Pointer.",
+            "properties": {
+                "op": { "enum": [ "copy" ] },
+                "from": { "$ref": "#/definitions/jsonPointer" }
+            },
+            "required": [ "from" ]
+        },
+        "test": {
+            "description": "test operation. Value can be any JSON value.",
+            "properties": { "op": { "enum": [ "test" ] } },
+            "required": [ "value" ]
+        },
+        "oneOperation": {
+            "oneOf": [
+                { "$ref": "#/definitions/add" },
+                { "$ref": "#/definitions/remove" },
+                { "$ref": "#/definitions/replace" },
+                { "$ref": "#/definitions/move" },
+                { "$ref": "#/definitions/copy" },
+                { "$ref": "#/definitions/test" }
+            ]
+        }
+    }
+}