JAVA-1246: Removed duplicates from hosts list parameter to ClusterSettings.Builder.hosts(). Also, throw if hosts list is null or empty.

Author: jyemin

src/main/com/mongodb/ClusterSettings.java

@@ -18,7 +18,9 @@
 
 import org.bson.util.annotations.Immutable;
 
+import java.util.ArrayList;
 import java.util.Collections;
+import java.util.LinkedHashSet;
 import java.util.List;
 
 import static org.bson.util.Assertions.isTrueArgument;
@@ -53,14 +55,17 @@ private Builder() {
         // CHECKSTYLE:OFF
 
         /**
-         * Sets the hosts for the cluster.
+         * Sets the hosts for the cluster. And duplicate server addresses are removed from the list.
          *
          * @param hosts the seed list of hosts
          * @return this
          */
         public Builder hosts(final List<ServerAddress> hosts) {
             notNull("hosts", hosts);
-            this.hosts = Collections.unmodifiableList(hosts);
+            if (hosts.isEmpty()) {
+                throw new IllegalArgumentException("hosts list may not be empty");
+            }
+            this.hosts = Collections.unmodifiableList(new ArrayList<ServerAddress>(new LinkedHashSet<ServerAddress>(hosts)));
             return this;
         }
 

src/test/com/mongodb/ClusterSettingsSpecification.groovy

@@ -84,4 +84,30 @@ class ClusterSettingsSpecification extends Specification {
         then:
         thrown(IllegalArgumentException)
     }
+
+    def 'should throws if hosts list is null'() {
+        when:
+         ClusterSettings.builder().hosts(null).build();
+
+        then:
+        thrown(IllegalArgumentException)
+    }
+
+    def 'should throws if hosts list is empty'() {
+        when:
+        ClusterSettings.builder().hosts([]).build();
+
+        then:
+        thrown(IllegalArgumentException)
+    }
+
+    def 'should remove duplicate hosts'() {
+        when:
+        def settings = ClusterSettings.builder().hosts([new ServerAddress('server1'),
+                                                        new ServerAddress('server2'),
+                                                        new ServerAddress('server1')]).build();
+
+        then:
+        settings.getHosts() == [new ServerAddress('server1'), new ServerAddress('server2')]
+    }
 }