Add file output parameters to Maven plugin

README.md

@@ -145,6 +145,12 @@ Add openapi-diff to your POM to show diffs when you test your Maven project. You
         <failOnIncompatible>true</failOnIncompatible>
         <!-- Fail if API changed (default: false) -->
         <failOnChanged>true</failOnChanged>
+        <!-- Supply file path for console output to file if desired. -->
+        <consoleOutputFileName>${project.basedir}/../maven/target/diff.txt</consoleOutputFileName>
+        <!-- Supply file path for json output to file if desired. -->
+        <jsonOutputFileName>${project.basedir}/../maven/target/diff.json</jsonOutputFileName>
+        <!-- Supply file path for markdown output to file if desired. -->
+        <markdownOutputFileName>${project.basedir}/../maven/target/diff.md</markdownOutputFileName>
       </configuration>
     </execution>
   </executions>
@@ -167,6 +173,7 @@ public class Main {
 ```
 
 ### Render difference
+
 ---
 #### HTML
 
@@ -176,11 +183,9 @@ String html = new HtmlRender("Changelog",
                 .render(diff);
 
 try {
-    FileWriter fw = new FileWriter(
-            "testNewApi.html");
+    FileWriter fw = new FileWriter("testNewApi.html");
     fw.write(html);
     fw.close();
-
 } catch (IOException e) {
     e.printStackTrace();
 }
@@ -191,11 +196,9 @@ try {
 ```java
 String render = new MarkdownRender().render(diff);
 try {
-    FileWriter fw = new FileWriter(
-            "testDiff.md");
+    FileWriter fw = new FileWriter("testDiff.md");
     fw.write(render);
     fw.close();
-
 } catch (IOException e) {
     e.printStackTrace();
 }
@@ -207,11 +210,9 @@ try {
 ```java
 String render = new JsonRender().render(diff);
 try {
-    FileWriter fw = new FileWriter(
-            "testDiff.json");
+    FileWriter fw = new FileWriter("testDiff.json");
     fw.write(render);
     fw.close();
-
 } catch (IOException e) {
     e.printStackTrace();
 }

core/src/main/java/org/openapitools/openapidiff/core/utils/ChangedUtils.java

@@ -5,7 +5,9 @@
 
 public class ChangedUtils {
 
-  private ChangedUtils() {}
+  private ChangedUtils() {
+    throw new UnsupportedOperationException("Utility class. Do not instantiate");
+  }
 
   public static boolean isUnchanged(Changed changed) {
     return changed == null || changed.isUnchanged();

core/src/main/java/org/openapitools/openapidiff/core/utils/Copy.java

@@ -5,7 +5,9 @@
 
 public class Copy {
 
-  private Copy() {}
+  private Copy() {
+    throw new UnsupportedOperationException("Utility class. Do not instantiate");
+  }
 
   public static <K, V> Map<K, V> copyMap(Map<K, V> map) {
     if (map == null) {

core/src/main/java/org/openapitools/openapidiff/core/utils/EndpointUtils.java

@@ -10,7 +10,9 @@
 
 public class EndpointUtils {
 
-  private EndpointUtils() {}
+  private EndpointUtils() {
+    throw new UnsupportedOperationException("Utility class. Do not instantiate");
+  }
 
   public static Collection<Endpoint> convert2Endpoints(
       String pathUrl, Map<PathItem.HttpMethod, Operation> map) {

core/src/main/java/org/openapitools/openapidiff/core/utils/FileUtils.java

@@ -0,0 +1,48 @@
+package org.openapitools.openapidiff.core.utils;
+
+import java.io.FileOutputStream;
+import java.io.IOException;
+import java.io.OutputStreamWriter;
+import java.nio.file.Files;
+import java.nio.file.InvalidPathException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import org.apache.commons.lang3.StringUtils;
+import org.openapitools.openapidiff.core.model.ChangedOpenApi;
+import org.openapitools.openapidiff.core.output.Render;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+public final class FileUtils {
+  private static final Logger logger = LoggerFactory.getLogger(FileUtils.class);
+
+  private FileUtils() {
+    throw new UnsupportedOperationException("Utility class. Do not instantiate");
+  }
+
+  public static void writeToFile(
+      final Render render, final ChangedOpenApi diff, final String fileName) {
+    if (StringUtils.isEmpty(fileName)) {
+      logger.debug("File name cannot be null or empty.");
+      return;
+    }
+
+    final Path filePath;
+    try {
+      filePath = Paths.get(fileName);
+      if (Files.exists(filePath)) {
+        logger.warn("File {} already exists. Skip writing to file.", fileName);
+        return;
+      }
+    } catch (final InvalidPathException invalidPathException) {
+      throw new IllegalArgumentException("File name is an invalid path.");
+    }
+
+    try (final FileOutputStream outputStream = new FileOutputStream(filePath.toFile());
+        final OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream)) {
+      render.render(diff, outputStreamWriter);
+    } catch (final IOException ioException) {
+      logger.error("Exception while writing to file {}", fileName);
+    }
+  }
+}

core/src/main/resources/logback.xml

@@ -0,0 +1,11 @@
+<configuration>
+  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
+    <encoder>
+      <pattern>[%thread] %-5level %logger{36} - %msg%n</pattern>
+    </encoder>
+  </appender>
+
+  <root level="debug">
+    <appender-ref ref="STDOUT"/>
+  </root>
+</configuration>

core/src/test/java/org/openapitools/openapidiff/core/utils/FileUtilsTest.java

@@ -0,0 +1,72 @@
+package org.openapitools.openapidiff.core.utils;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+
+import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Collections;
+import org.apache.commons.lang3.StringUtils;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.io.TempDir;
+import org.openapitools.openapidiff.core.model.ChangedOpenApi;
+import org.openapitools.openapidiff.core.output.ConsoleRender;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+class FileUtilsTest {
+
+  private static final Logger logger = LoggerFactory.getLogger(FileUtilsTest.class);
+
+  private ChangedOpenApi changedOpenApi;
+
+  @BeforeEach
+  void setup() {
+    changedOpenApi = new ChangedOpenApi();
+    changedOpenApi.setChangedSchemas(Collections.emptyList());
+    changedOpenApi.setChangedOperations(Collections.emptyList());
+    changedOpenApi.setNewEndpoints(Collections.emptyList());
+    changedOpenApi.setMissingEndpoints(Collections.emptyList());
+  }
+
+  @Test
+  void writeToFile_contentIsNull_doesNothing(@TempDir Path tempDir) throws IOException {
+    Path path = tempDir.resolve("output.txt");
+    Files.write(path, "Test".getBytes(StandardCharsets.UTF_8));
+
+    assertDoesNotThrow(() -> FileUtils.writeToFile(null, changedOpenApi, path.toString()));
+    assertThat(path).exists().content().isEqualTo("Test");
+  }
+
+  @Test
+  void writeToFile_filenameIsNull_doesNothing() {
+    assertDoesNotThrow(() -> FileUtils.writeToFile(new ConsoleRender(), changedOpenApi, null));
+  }
+
+  @Test
+  void writeToFile_filenameIsEmpty_doesNothing() {
+    assertDoesNotThrow(
+        () -> FileUtils.writeToFile(new ConsoleRender(), changedOpenApi, StringUtils.EMPTY));
+  }
+
+  @Test
+  void writeToFile_fileExists_doesNothing(@TempDir Path tempDir) throws IOException {
+    final Path path = tempDir.resolve("output.txt");
+    Files.write(path, "Test".getBytes(StandardCharsets.UTF_8));
+
+    assertDoesNotThrow(
+        () -> FileUtils.writeToFile(new ConsoleRender(), changedOpenApi, path.toString()));
+    assertThat(path).exists().content().isEqualTo("Test");
+  }
+
+  @Test
+  void writeToFile_fileDoesNotExist_createsFile(@TempDir Path tempDir) {
+    final Path path = tempDir.resolve("output.txt");
+    assertDoesNotThrow(
+        () -> FileUtils.writeToFile(new ConsoleRender(), changedOpenApi, path.toString()));
+    assertThat(path).exists();
+  }
+}

maven-example/pom.xml

@@ -33,6 +33,9 @@
                             <oldSpec>${project.basedir}/../maven/src/test/resources/oldspec.yaml</oldSpec>
                             <newSpec>${project.basedir}/../maven/src/test/resources/newspec.yaml</newSpec>
                             <failOnIncompatible>true</failOnIncompatible>
+                            <consoleOutputFileName>${project.basedir}/../maven/target/diff.txt</consoleOutputFileName>
+                            <jsonOutputFileName>${project.basedir}/../maven/target/diff.json</jsonOutputFileName>
+                            <markdownOutputFileName>${project.basedir}/../maven/target/diff.md</markdownOutputFileName>
                         </configuration>
                     </execution>
                 </executions>

maven/src/main/java/org/openapitools/openapidiff/maven/OpenApiDiffMojo.java

@@ -1,7 +1,11 @@
 package org.openapitools.openapidiff.maven;
 
+import static org.openapitools.openapidiff.core.utils.FileUtils.writeToFile;
+
 import java.io.ByteArrayOutputStream;
+import java.io.IOException;
 import java.io.OutputStreamWriter;
+import java.io.UncheckedIOException;
 import org.apache.maven.plugin.AbstractMojo;
 import org.apache.maven.plugin.MojoExecutionException;
 import org.apache.maven.plugin.MojoFailureException;
@@ -11,10 +15,13 @@
 import org.openapitools.openapidiff.core.OpenApiCompare;
 import org.openapitools.openapidiff.core.model.ChangedOpenApi;
 import org.openapitools.openapidiff.core.output.ConsoleRender;
+import org.openapitools.openapidiff.core.output.JsonRender;
+import org.openapitools.openapidiff.core.output.MarkdownRender;
 
 /** A Maven Mojo that diffs two OpenAPI specifications and reports on differences. */
 @Mojo(name = "diff", defaultPhase = LifecyclePhase.TEST)
 public class OpenApiDiffMojo extends AbstractMojo {
+
   @Parameter(property = "oldSpec")
   String oldSpec;
 
@@ -30,6 +37,15 @@ public class OpenApiDiffMojo extends AbstractMojo {
   @Parameter(property = "skip", defaultValue = "false")
   Boolean skip = false;
 
+  @Parameter(property = "consoleOutputFileName")
+  String consoleOutputFileName;
+
+  @Parameter(property = "jsonOutputFileName")
+  String jsonOutputFileName;
+
+  @Parameter(property = "markdownOutputFileName")
+  String markdownOutputFileName;
+
   @Override
   public void execute() throws MojoExecutionException, MojoFailureException {
     if (Boolean.TRUE.equals(skip)) {
@@ -39,10 +55,18 @@ public void execute() throws MojoExecutionException, MojoFailureException {
 
     try {
       final ChangedOpenApi diff = OpenApiCompare.fromLocations(oldSpec, newSpec);
-      ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
-      OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream);
-      new ConsoleRender().render(diff, outputStreamWriter);
-      getLog().info(outputStream.toString());
+
+      try (ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
+          OutputStreamWriter outputStreamWriter = new OutputStreamWriter(outputStream)) {
+        new ConsoleRender().render(diff, outputStreamWriter);
+        getLog().info(outputStream.toString());
+      } catch (IOException e) {
+        throw new UncheckedIOException(e);
+      }
+
+      writeDiffAsTextToFile(diff);
+      writeDiffAsJsonToFile(diff);
+      writeDiffAsMarkdownToFile(diff);
 
       if (failOnIncompatible && diff.isIncompatible()) {
         throw new BackwardIncompatibilityException("The API changes broke backward compatibility");
@@ -55,4 +79,16 @@ public void execute() throws MojoExecutionException, MojoFailureException {
       throw new MojoExecutionException("Unexpected error", e);
     }
   }
+
+  private void writeDiffAsTextToFile(final ChangedOpenApi diff) {
+    writeToFile(new ConsoleRender(), diff, consoleOutputFileName);
+  }
+
+  private void writeDiffAsJsonToFile(final ChangedOpenApi diff) {
+    writeToFile(new JsonRender(), diff, jsonOutputFileName);
+  }
+
+  private void writeDiffAsMarkdownToFile(final ChangedOpenApi diff) {
+    writeToFile(new MarkdownRender(), diff, markdownOutputFileName);
+  }
 }