Add support for inline JSON in SPRING_APPLICATION_JSON

User can supply inline JSON as an env var (SPRING_APPLICATION_JSON)
or System property (spring.application.json).

Fixes gh-4239

spring-boot-docs/src/main/asciidoc/spring-boot-features.adoc

@@ -291,6 +291,7 @@ Spring Boot uses a very particular `PropertySource` order that is designed to al
 sensible overriding of values, properties are considered in the following order:
 
 . Command line arguments.
+. Properties from `SPRING_APPLICATION_JSON` (inline JSON embedded in an environment variable or system property)
 . JNDI attributes from `java:comp/env`.
 . Java System properties (`System.getProperties()`).
 . OS environment variables.
@@ -333,6 +334,33 @@ default `name`. When running in production, an `application.properties` can be p
 outside of your jar that overrides `name`; and for one-off testing, you can launch with
 a specific command line switch (e.g. `java -jar app.jar --name="Spring"`).
 
+[TIP]
+====
+
+The `SPRING_APPLICATION_JSON` properties can be supplied on the
+command line with an environment variable. For example in a
+UN{asterisk}X shell:
+
+----
+$ SPRING_APPLICATION_JSON='{"foo":{"bar":"spam"}}' java -jar myapp.jar
+----
+
+In this example you will end up with `foo.bar=spam` in the Spring
+`Environment`. You can also supply the JSON as
+`spring.application.json` in a System variable:
+
+----
+$ java -Dspring.application.json='{"foo":"bar"}' -jar myapp.jar
+----
+
+or command line argument:
+
+----
+$ java -jar myapp.jar --spring.application.json='{"foo":"bar"}'
+----
+
+or as a JNDI variable `java:comp/env/spring.application.json`.
+====
 
 
 [[boot-features-external-config-random-values]]

spring-boot/src/main/java/org/springframework/boot/env/SpringApplicationJsonEnvironmentPostProcessor.java

@@ -0,0 +1,140 @@
+/*
+ * Copyright 2012-2015 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
+ *
+ *      http://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.env;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.json.JsonParser;
+import org.springframework.boot.json.JsonParserFactory;
+import org.springframework.core.Ordered;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.Environment;
+import org.springframework.core.env.MapPropertySource;
+import org.springframework.core.env.MutablePropertySources;
+import org.springframework.core.env.StandardEnvironment;
+import org.springframework.util.ClassUtils;
+import org.springframework.util.StringUtils;
+import org.springframework.web.context.support.StandardServletEnvironment;
+
+/**
+ * An {@link EnvironmentPostProcessor} that parses JSON from
+ * <code>spring.application.json</code> or equivalently
+ * {@link SpringApplicationJsonEnvironmentPostProcessor} and adds it as a map property
+ * source to the {@link Environment}. The new properties are added with higher priority
+ * than the system properties.
+ *
+ * @author Dave Syer
+ */
+public class SpringApplicationJsonEnvironmentPostProcessor
+		implements EnvironmentPostProcessor, Ordered {
+
+	private static final Log logger = LogFactory
+			.getLog(SpringApplicationJsonEnvironmentPostProcessor.class);
+
+	/**
+	 * The default order for the processor.
+	 */
+	public static final int DEFAULT_ORDER = Ordered.HIGHEST_PRECEDENCE + 20;
+
+	private int order = DEFAULT_ORDER;
+
+	@Override
+	public int getOrder() {
+		return this.order;
+	}
+
+	public void setOrder(int order) {
+		this.order = order;
+	}
+
+	@Override
+	public void postProcessEnvironment(ConfigurableEnvironment environment,
+			SpringApplication application) {
+		String json = environment.resolvePlaceholders(
+				"${spring.application.json:${SPRING_APPLICATION_JSON:}}");
+		if (StringUtils.hasText(json)) {
+			try {
+				JsonParser parser = JsonParserFactory.getJsonParser();
+				Map<String, Object> map = parser.parseMap(json);
+				if (!map.isEmpty()) {
+					MapPropertySource source = new MapPropertySource(
+							"spring.application.json", flatten(map));
+					MutablePropertySources sources = environment.getPropertySources();
+					String name = findPropertySource(sources);
+					if (sources.contains(name)) {
+						sources.addBefore(name, source);
+					}
+					else {
+						sources.addFirst(source);
+					}
+				}
+			}
+			catch (Exception e) {
+				logger.warn("Cannot parse JSON for spring.application.json: " + json, e);
+			}
+		}
+	}
+
+	/**
+	 * Flatten the map keys using period separator.
+	 */
+	private Map<String, Object> flatten(Map<String, Object> map) {
+		Map<String, Object> result = new LinkedHashMap<String, Object>();
+		flatten(null, result, map);
+		return result;
+	}
+
+	private void flatten(String prefix, Map<String, Object> result,
+			Map<String, Object> map) {
+		if (prefix == null) {
+			prefix = "";
+		}
+		else {
+			prefix = prefix + ".";
+		}
+		for (String key : map.keySet()) {
+			String name = prefix + key;
+			Object value = map.get(key);
+			if (value instanceof Map) {
+				@SuppressWarnings("unchecked")
+				Map<String, Object> nested = (Map<String, Object>) value;
+				flatten(name, result, nested);
+			}
+			else {
+				result.put(name, value);
+			}
+		}
+	}
+
+	private String findPropertySource(MutablePropertySources sources) {
+		if (ClassUtils.isPresent(
+				"org.springframework.web.context.support.StandardServletEnvironment",
+				null)
+				&& sources
+						.contains(StandardServletEnvironment.JNDI_PROPERTY_SOURCE_NAME)) {
+			return StandardServletEnvironment.JNDI_PROPERTY_SOURCE_NAME;
+
+		}
+		return StandardEnvironment.SYSTEM_PROPERTIES_PROPERTY_SOURCE_NAME;
+	}
+
+}

spring-boot/src/main/resources/META-INF/spring.factories

@@ -27,4 +27,5 @@ org.springframework.boot.logging.LoggingApplicationListener
 
 # Environment Post Processors
 org.springframework.boot.env.EnvironmentPostProcessor=\
-org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor
+org.springframework.boot.cloud.CloudFoundryVcapEnvironmentPostProcessor,\
+org.springframework.boot.env.SpringApplicationJsonEnvironmentPostProcessor

spring-boot/src/test/java/org/springframework/boot/env/SpringApplicationJsonEnvironmentPostProcessorTests.java

@@ -0,0 +1,98 @@
+/*
+ * Copyright 2012-2015 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
+ *
+ *      http://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.env;
+
+import org.junit.Test;
+
+import org.springframework.boot.test.EnvironmentTestUtils;
+import org.springframework.core.env.ConfigurableEnvironment;
+import org.springframework.core.env.StandardEnvironment;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * @author Dave Syer
+ */
+public class SpringApplicationJsonEnvironmentPostProcessorTests {
+
+	private SpringApplicationJsonEnvironmentPostProcessor processor = new SpringApplicationJsonEnvironmentPostProcessor();
+
+	private ConfigurableEnvironment environment = new StandardEnvironment();
+
+	@Test
+	public void error() {
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+		EnvironmentTestUtils.addEnvironment(this.environment,
+				"spring.application.json=foo:bar");
+		this.processor.postProcessEnvironment(this.environment, null);
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+	}
+
+	@Test
+	public void missing() {
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+		this.processor.postProcessEnvironment(this.environment, null);
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+	}
+
+	@Test
+	public void empty() {
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+		EnvironmentTestUtils.addEnvironment(this.environment,
+				"spring.application.json={}");
+		this.processor.postProcessEnvironment(this.environment, null);
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+	}
+
+	@Test
+	public void periodSeparated() {
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+		EnvironmentTestUtils.addEnvironment(this.environment,
+				"spring.application.json={\"foo\":\"bar\"}");
+		this.processor.postProcessEnvironment(this.environment, null);
+		assertEquals("bar", this.environment.resolvePlaceholders("${foo:}"));
+	}
+
+	@Test
+	public void envVar() {
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+		EnvironmentTestUtils.addEnvironment(this.environment,
+				"SPRING_APPLICATION_JSON={\"foo\":\"bar\"}");
+		this.processor.postProcessEnvironment(this.environment, null);
+		assertEquals("bar", this.environment.resolvePlaceholders("${foo:}"));
+	}
+
+	@Test
+	public void nested() {
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+		EnvironmentTestUtils.addEnvironment(this.environment,
+				"SPRING_APPLICATION_JSON={\"foo\":{\"bar\":\"spam\",\"rab\":\"maps\"}}");
+		this.processor.postProcessEnvironment(this.environment, null);
+		assertEquals("spam", this.environment.resolvePlaceholders("${foo.bar:}"));
+		assertEquals("maps", this.environment.resolvePlaceholders("${foo.rab:}"));
+	}
+
+	@Test
+	public void prefixed() {
+		assertEquals("", this.environment.resolvePlaceholders("${foo:}"));
+		EnvironmentTestUtils.addEnvironment(this.environment,
+				"SPRING_APPLICATION_JSON={\"foo.bar\":\"spam\"}");
+		this.processor.postProcessEnvironment(this.environment, null);
+		assertEquals("spam", this.environment.resolvePlaceholders("${foo.bar:}"));
+	}
+
+}