gh-175 Adds schema class exists method

src/main/java/io/weaviate/client/v1/schema/Schema.java

@@ -1,16 +1,17 @@
 package io.weaviate.client.v1.schema;
 
 import io.weaviate.client.base.http.HttpClient;
+import io.weaviate.client.Config;
 import io.weaviate.client.v1.schema.api.ClassCreator;
 import io.weaviate.client.v1.schema.api.ClassDeleter;
+import io.weaviate.client.v1.schema.api.ClassExists;
 import io.weaviate.client.v1.schema.api.ClassGetter;
 import io.weaviate.client.v1.schema.api.PropertyCreator;
 import io.weaviate.client.v1.schema.api.SchemaDeleter;
 import io.weaviate.client.v1.schema.api.SchemaGetter;
 import io.weaviate.client.v1.schema.api.ShardUpdater;
 import io.weaviate.client.v1.schema.api.ShardsGetter;
 import io.weaviate.client.v1.schema.api.ShardsUpdater;
-import io.weaviate.client.Config;
 
 public class Schema {
   private final Config config;
@@ -29,6 +30,10 @@ public ClassGetter classGetter() {
     return new ClassGetter(httpClient, config);
   }
 
+  public ClassExists exists() {
+    return new ClassExists(new ClassGetter(httpClient, config));
+  }
+
   public ClassCreator classCreator() {
     return new ClassCreator(httpClient, config);
   }

src/main/java/io/weaviate/client/v1/schema/api/ClassExists.java

@@ -0,0 +1,44 @@
+package io.weaviate.client.v1.schema.api;
+
+import io.weaviate.client.base.ClientResult;
+import io.weaviate.client.base.Result;
+import io.weaviate.client.base.WeaviateError;
+import io.weaviate.client.base.WeaviateErrorMessage;
+import io.weaviate.client.base.WeaviateErrorResponse;
+import io.weaviate.client.v1.schema.model.WeaviateClass;
+import org.apache.commons.lang3.StringUtils;
+import org.apache.http.HttpStatus;
+
+import java.util.Collections;
+
+public class ClassExists implements ClientResult<Boolean> {
+  private final ClassGetter classGetter;
+  private String className;
+
+  public ClassExists(ClassGetter classGetter) {
+    this.classGetter = classGetter;
+  }
+
+  public ClassExists withClassName(String className) {
+    this.className = className;
+    return this;
+  }
+
+  @Override
+  public Result<Boolean> run() {
+    if (StringUtils.isEmpty(className)) {
+      WeaviateErrorMessage errorMessage = WeaviateErrorMessage.builder()
+        .message("classname cannot be empty").build();
+      WeaviateErrorResponse errors = WeaviateErrorResponse.builder()
+        .error(Collections.singletonList(errorMessage)).build();
+      return new Result<>(HttpStatus.SC_UNPROCESSABLE_ENTITY, null, errors);
+    }
+
+    Result<WeaviateClass> getterClass = classGetter.withClassName(className).run();
+    if (getterClass.hasErrors()) {
+      WeaviateError error = getterClass.getError();
+      return new Result<>(error.getStatusCode(), null, WeaviateErrorResponse.builder().error(error.getMessages()).build());
+    }
+    return new Result<>(HttpStatus.SC_OK, getterClass.getResult() != null, null);
+  }
+}

src/test/java/io/weaviate/integration/client/schema/ClientSchemaTest.java

@@ -39,6 +39,7 @@
 import static org.assertj.core.api.InstanceOfAssertFactories.MAP;
 import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
@@ -760,15 +761,14 @@ public void testSchemaGetShards() {
             .build();
     // when
     Result<Boolean> createStatus = client.schema().classCreator().withClass(clazz).run();
-    Result<WeaviateClass> bandClass = client.schema().classGetter().withClassName(clazz.getClassName()).run();
-
+    Result<Boolean> bandClassStatus = client.schema().exists().withClassName(clazz.getClassName()).run();
+    Result<Boolean> nonExistentClassStatus = client.schema().exists().withClassName("nonExistentClass").run();
     // then
-    assertNotNull(createStatus);
-    assertTrue(createStatus.getResult());
-    assertNotNull(bandClass);
-    assertNotNull(bandClass.getResult());
-    assertNull(bandClass.getError());
-
+    assertResultTrue(createStatus);
+    assertResultTrue(bandClassStatus);
+    assertNotNull(nonExistentClassStatus);
+    assertFalse(nonExistentClassStatus.getResult());
+    assertNull(nonExistentClassStatus.getError());
     Result<Shard[]> shards = client.schema().shardsGetter()
             .withClassName(clazz.getClassName()).run();
     assertNotNull(shards);