Modifying mongo properties for additional hosts (outdated)

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/MongoProperties.java

@@ -33,6 +33,7 @@
  * @author Nasko Vasilev
  * @author Mark Paluch
  * @author Artsiom Yudovin
+ * @author Safeer Ansari
  * @since 1.0.0
  */
 @ConfigurationProperties(prefix = "spring.data.mongodb")
@@ -105,6 +106,8 @@ public class MongoProperties {
 	 */
 	private Boolean autoIndexCreation;
 
+	private String additionalHosts;
+
 	public String getHost() {
 		return this.host;
 	}
@@ -208,6 +211,14 @@ public void setAutoIndexCreation(Boolean autoIndexCreation) {
 		this.autoIndexCreation = autoIndexCreation;
 	}
 
+	public String getAdditionalHosts() {
+		return additionalHosts;
+	}
+
+	public void setAdditionalHosts(String additionalHosts) {
+		this.additionalHosts = additionalHosts;
+	}
+
 	public static class Gridfs {
 
 		/**

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/MongoPropertiesClientSettingsBuilderCustomizer.java

@@ -16,7 +16,11 @@
 
 package org.springframework.boot.autoconfigure.mongo;
 
-import java.util.Collections;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
 
 import com.mongodb.ConnectionString;
 import com.mongodb.MongoClientSettings;
@@ -30,12 +34,16 @@
  * {@link MongoProperties} to a {@link MongoClientSettings}.
  *
  * @author Scott Frederick
+ * @author Safeer Ansari
  * @since 2.4.0
  */
 public class MongoPropertiesClientSettingsBuilderCustomizer implements MongoClientSettingsBuilderCustomizer, Ordered {
 
 	private final MongoProperties properties;
 
+	private static final Pattern ADDITIONAL_HOSTS_PATTERN = Pattern
+			.compile("^\\[[0-9a-zA-Z]+(.)*(:)*(,[0-9a-zA-Z]+(.)*(:)*)*]$");
+
 	private int order = 0;
 
 	public MongoPropertiesClientSettingsBuilderCustomizer(MongoProperties properties) {
@@ -63,12 +71,28 @@ private void applyHostAndPort(MongoClientSettings.Builder settings) {
 			String host = getOrDefault(this.properties.getHost(), "localhost");
 			int port = getOrDefault(this.properties.getPort(), MongoProperties.DEFAULT_PORT);
 			ServerAddress serverAddress = new ServerAddress(host, port);
-			settings.applyToClusterSettings((cluster) -> cluster.hosts(Collections.singletonList(serverAddress)));
+			List<ServerAddress> serverAddressList = new ArrayList<>(List.of(serverAddress));
+			applyAdditionalHosts(serverAddressList);
+			settings.applyToClusterSettings((cluster) -> cluster.hosts(serverAddressList));
 			return;
 		}
 		settings.applyConnectionString(new ConnectionString(MongoProperties.DEFAULT_URI));
 	}
 
+	private void applyAdditionalHosts(List<ServerAddress> serverAddressList) {
+		if (this.properties.getAdditionalHosts() != null && !this.properties.getAdditionalHosts().isEmpty()) {
+			Matcher matcher = ADDITIONAL_HOSTS_PATTERN.matcher((this.properties.getAdditionalHosts()));
+			if (!matcher.matches()) {
+				return;
+			}
+
+			String[] additionalHosts = this.properties.getAdditionalHosts()
+					.substring(1, this.properties.getAdditionalHosts().length() - 1).split(",");
+			Arrays.stream(additionalHosts)
+					.forEach((additionalHost) -> serverAddressList.add(new ServerAddress(additionalHost)));
+		}
+	}
+
 	private void applyCredentials(MongoClientSettings.Builder builder) {
 		if (this.properties.getUri() == null && this.properties.getUsername() != null
 				&& this.properties.getPassword() != null) {

spring-boot-project/spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoPropertiesClientSettingsBuilderCustomizerTests.java

@@ -53,6 +53,18 @@ void hostCanBeCustomized() {
 		assertServerAddress(allAddresses.get(0), "mongo.example.com", 27017);
 	}
 
+	@Test
+	void additionalHostCanBeAdded() {
+		this.properties.setHost("mongo.example.com");
+		this.properties.setAdditionalHosts("[mongo.example.com:33, mongo.example2.com]");
+		MongoClientSettings settings = customizeSettings();
+		List<ServerAddress> allAddresses = getAllAddresses(settings);
+		assertThat(allAddresses).hasSize(3);
+		assertServerAddress(allAddresses.get(0), "mongo.example.com", 27017);
+		assertServerAddress(allAddresses.get(1), "mongo.example.com", 33);
+		assertServerAddress(allAddresses.get(2), "mongo.example2.com", 27017);
+	}
+
 	@Test
 	void credentialsCanBeCustomized() {
 		this.properties.setUsername("user");