Stop integer default values from becoming decimals

Fixes gh-25172

buildSrc/build.gradle

@@ -23,7 +23,7 @@ dependencies {
 	implementation("org.gradle:test-retry-gradle-plugin:1.1.9")
 	implementation("org.springframework:spring-core:5.2.2.RELEASE")
 	implementation("org.springframework:spring-web:5.2.2.RELEASE")
-	implementation("com.google.code.gson:gson:2.8.5")
+	implementation("com.fasterxml.jackson.core:jackson-databind:2.11.4")
 	implementation("io.spring.javaformat:spring-javaformat-gradle-plugin:${javaFormatVersion}")
 	testImplementation("org.assertj:assertj-core:3.11.1")
 	testImplementation("org.apache.logging.log4j:log4j-core:2.12.1")

buildSrc/src/main/java/org/springframework/boot/build/context/properties/ConfigurationProperties.java

 /*
- * Copyright 2012-2020 the original author or authors.
+ * Copyright 2012-2021 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -20,17 +20,13 @@ import java.io.File;
 import java.io.FileReader;
 import java.io.IOException;
 import java.io.Reader;
-import java.lang.reflect.Type;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
-import com.google.gson.Gson;
-import com.google.gson.GsonBuilder;
-import com.google.gson.reflect.TypeToken;
-import org.gradle.api.file.FileCollection;
+import com.fasterxml.jackson.databind.ObjectMapper;
 
 /**
  * Configuration properties read from one or more
@@ -40,20 +36,18 @@ import org.gradle.api.file.FileCollection;
  */
 final class ConfigurationProperties {
 
-	private static final Type MAP_TYPE = new MapTypeToken().getType();
-
 	private ConfigurationProperties() {
 
 	}
 
 	@SuppressWarnings("unchecked")
-	static Map<String, ConfigurationProperty> fromFiles(FileCollection files) {
+	static Map<String, ConfigurationProperty> fromFiles(Iterable<File> files) {
 		List<ConfigurationProperty> configurationProperties = new ArrayList<>();
 		try {
-			Gson gson = new GsonBuilder().create();
+			ObjectMapper objectMapper = new ObjectMapper();
 			for (File file : files) {
 				try (Reader reader = new FileReader(file)) {
-					Map<String, Object> json = gson.fromJson(reader, MAP_TYPE);
+					Map<String, Object> json = objectMapper.readValue(file, Map.class);
 					List<Map<String, Object>> properties = (List<Map<String, Object>>) json.get("properties");
 					for (Map<String, Object> property : properties) {
 						String name = (String) property.get("name");
@@ -74,8 +68,4 @@ final class ConfigurationProperties {
 		}
 	}
 
-	private static final class MapTypeToken extends TypeToken<Map<String, Object>> {
-
-	}
-
 }

buildSrc/src/test/java/org/springframework/boot/build/context/properties/ConfigurationPropertiesTests.java

+/*
+ * Copyright 2012-2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.build.context.properties;
+
+import java.io.File;
+import java.util.Arrays;
+import java.util.Map;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Tests for {@link ConfigurationProperties}
+ *
+ * @author Andy Wilkinson
+ */
+class ConfigurationPropertiesTests {
+
+	@Test
+	void whenJsonHasAnIntegerDefaultValueThenItRemainsAnIntegerWhenRead() {
+		Map<String, ConfigurationProperty> properties = ConfigurationProperties
+				.fromFiles(Arrays.asList(new File("src/test/resources/spring-configuration-metadata.json")));
+		assertThat(properties.get("example.counter").getDefaultValue()).isEqualTo(0);
+	}
+
+}

buildSrc/src/test/resources/spring-configuration-metadata.json

+{
+  "properties": [
+    {
+      "name": "example.counter",
+      "type": "java.lang.Integer",
+      "defaultValue": 0
+    }
+  ]
+}