Add JsonRender and --json command line option

README.md

@@ -21,7 +21,7 @@ Compare two OpenAPI specifications (3.x) and render the difference to HTML plain
 * Depth comparison of parameters, responses, endpoint, http method (GET,POST,PUT,DELETE...)
 * Supports swagger api Authorization
 * Render difference of property with Expression Language
-* HTML & Markdown render
+* HTML, Markdown & JSON render
 
 # Maven
 
@@ -52,6 +52,7 @@ usage: openapi-diff <old> <new>
     --header <property=value>   use given header for authorisation
     --html <file>               export diff as html in given file
     --info                      Print additional information
+    --json <file>               export diff as json in given file
  -l,--log <level>               use given level for log (TRACE, DEBUG,
                                 INFO, WARN, ERROR, OFF). Default: ERROR
     --markdown <file>           export diff as markdown in given file
@@ -104,6 +105,7 @@ usage: openapi-diff <old> <new>
     --header <property=value>   use given header for authorisation
     --html <file>               export diff as html in given file
     --info                      Print additional information
+    --json <file>               export diff as json in given file
  -l,--log <level>               use given level for log (TRACE, DEBUG,
                                 INFO, WARN, ERROR, OFF). Default: ERROR
     --markdown <file>           export diff as markdown in given file
@@ -168,6 +170,22 @@ try {
 }
 ```
 
+
+#### JSON
+
+```java
+String render = new JsonRender().render(diff);
+try {
+    FileWriter fw = new FileWriter(
+            "testDiff.json");
+    fw.write(render);
+    fw.close();
+
+} catch (IOException e) {
+    e.printStackTrace();
+}
+```
+
 ### Extensions
 
 This project uses Java Service Provider Inteface (SPI) so additional extensions can be added. 
@@ -350,6 +368,71 @@ Then, including your library with the `openapi-diff` module will cause it to be
         Changed response : [200] //successful operation
 ```
 
+### JSON
+
+```json
+{
+    "changedElements": [...],
+    "changedExtensions": null,
+    "changedOperations": [...],
+    "compatible": false,
+    "deprecatedEndpoints": [...],
+    "different": true,
+    "incompatible": true,
+    "missingEndpoints": [...],
+    "newEndpoints": [
+        {
+            "method": "GET",
+            "operation": {
+                "callbacks": null,
+                "deprecated": null,
+                "description": "Returns a single pet",
+                "extensions": null,
+                "externalDocs": null,
+                "operationId": "getPetById",
+                "parameters": [
+                    {
+                        "$ref": null,
+                        "allowEmptyValue": null,
+                        "allowReserved": null,
+                        "content": null,
+                        "deprecated": null,
+                        "description": "ID of pet to return",
+                        "example": null,
+                        "examples": null,
+                        "explode": false,
+                        "extensions": null,
+                        "in": "path",
+                        "name": "petId",
+                        "required": true,
+                        "schema": {...},
+                        "style": "SIMPLE"
+                    }
+                ],
+                "requestBody": null,
+                "responses": {...},
+                "security": [
+                    {
+                        "api_key": []
+                    }
+                ],
+                "servers": null,
+                "summary": "Find pet by ID",
+                "tags": [
+                    "pet"
+                ]
+            },
+            "path": null,
+            "pathUrl": "/pet/{petId}",
+            "summary": "Find pet by ID"
+        }
+    ],
+    "newSpecOpenApi": {...},
+    "oldSpecOpenApi": {...},
+    "unchanged": false
+}
+```
+
 # License
 
 openapi-diff is released under the Apache License 2.0.

cli/src/main/java/org/openapitools/openapidiff/cli/Main.java

@@ -24,6 +24,7 @@
 import org.openapitools.openapidiff.core.model.ChangedOpenApi;
 import org.openapitools.openapidiff.core.output.ConsoleRender;
 import org.openapitools.openapidiff.core.output.HtmlRender;
+import org.openapitools.openapidiff.core.output.JsonRender;
 import org.openapitools.openapidiff.core.output.MarkdownRender;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -106,6 +107,13 @@ public static void main(String... args) {
             .argName("file")
             .desc("export diff as text in given file")
             .build());
+    options.addOption(
+        Option.builder()
+            .longOpt("json")
+            .hasArg()
+            .argName("file")
+            .desc("export diff as json in given file")
+            .build());
 
     // create the parser
     CommandLineParser parser = new DefaultParser();
@@ -188,6 +196,12 @@ public static void main(String... args) {
         String outputFile = line.getOptionValue("text");
         writeOutput(output, outputFile);
       }
+      if (line.hasOption("json")) {
+        JsonRender jsonRender = new JsonRender();
+        String output = jsonRender.render(result);
+        String outputFile = line.getOptionValue("json");
+        writeOutput(output, outputFile);
+      }
       if (line.hasOption("state")) {
         System.out.println(result.isChanged().getValue());
         System.exit(0);

core/src/main/java/org/openapitools/openapidiff/core/output/JsonRender.java

@@ -0,0 +1,18 @@
+package org.openapitools.openapidiff.core.output;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.openapitools.openapidiff.core.model.ChangedOpenApi;
+
+public class JsonRender implements Render {
+    private final ObjectMapper objectMapper = new ObjectMapper();
+
+    @Override
+    public String render(ChangedOpenApi diff) {
+        try {
+            return objectMapper.writeValueAsString(diff);
+        } catch (JsonProcessingException e) {
+            throw new RuntimeException("Could not serialize diff as JSON", e);
+        }
+    }
+}

core/src/test/java/org/openapitools/openapidiff/core/JsonRenderTest.java

@@ -0,0 +1,17 @@
+package org.openapitools.openapidiff.core;
+
+import org.junit.jupiter.api.Test;
+import org.openapitools.openapidiff.core.model.ChangedOpenApi;
+import org.openapitools.openapidiff.core.output.JsonRender;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class JsonRenderTest {
+  @Test
+  public void renderDoesNotFailWhenPropertyHasBeenRemoved() {
+    JsonRender render = new JsonRender();
+    ChangedOpenApi diff =
+        OpenApiCompare.fromLocations("missing_property_1.yaml", "missing_property_2.yaml");
+    assertThat(render.render(diff)).isNotBlank();
+  }
+}

core/src/test/java/org/openapitools/openapidiff/core/OpenApiDiffTest.java

@@ -11,6 +11,7 @@
 import org.openapitools.openapidiff.core.model.ChangedOperation;
 import org.openapitools.openapidiff.core.model.Endpoint;
 import org.openapitools.openapidiff.core.output.HtmlRender;
+import org.openapitools.openapidiff.core.output.JsonRender;
 import org.openapitools.openapidiff.core.output.MarkdownRender;
 
 public class OpenApiDiffTest {
@@ -102,4 +103,18 @@ public void testDiffAndMarkdown() {
       e.printStackTrace();
     }
   }
+
+  @Test
+  public void testDiffAndJson() {
+    ChangedOpenApi diff = OpenApiCompare.fromLocations(OPENAPI_DOC1, OPENAPI_DOC2);
+    String render = new JsonRender().render(diff);
+    try {
+      FileWriter fw = new FileWriter("target/testDiff.json");
+      fw.write(render);
+      fw.close();
+
+    } catch (IOException e) {
+      e.printStackTrace();
+    }
+  }
 }