feat: project course lesson 1 (ydb-platform#47)

* feat: lesson 1

* feat: lesson 1

Author: KirillKurdyukov

pom.xml

@@ -29,6 +29,7 @@
         <module>ydb-cookbook</module>
         <module>url-shortener-demo</module>
         <module>jdbc</module>
+        <module>project-course</module>
     </modules>
 
     <dependencyManagement>

project-course/pom.xml

@@ -0,0 +1,40 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+    <parent>
+        <groupId>tech.ydb.examples</groupId>
+        <artifactId>ydb-sdk-examples</artifactId>
+        <version>1.1.0-SNAPSHOT</version>
+    </parent>
+
+    <groupId>tech.ydb.app</groupId>
+    <artifactId>project-course</artifactId>
+    <packaging>jar</packaging>
+
+    <name>project-course</name>
+    <url>http://maven.apache.org</url>
+
+    <properties>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>tech.ydb</groupId>
+            <artifactId>ydb-sdk-query</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.codehaus.mojo</groupId>
+                <artifactId>exec-maven-plugin</artifactId>
+                <version>3.5.0</version>
+                <configuration>
+                    <mainClass>tech.ydb.app.App</mainClass>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

project-course/src/main/java/tech/ydb/app/App.java

@@ -0,0 +1,13 @@
+package tech.ydb.app;
+
+import tech.ydb.app.repository.YdbRepository;
+
+public class App {
+    public static void main(String[] args) {
+        if (args.length != 1) {
+            throw new UnsupportedOperationException("Expected 1 parameter connectionString");
+        }
+
+        new YdbRepository(args[0]).TestDatabase();
+    }
+}

project-course/src/main/java/tech/ydb/app/repository/YdbRepository.java

@@ -0,0 +1,33 @@
+package tech.ydb.app.repository;
+
+import tech.ydb.common.transaction.TxMode;
+import tech.ydb.core.grpc.GrpcTransport;
+import tech.ydb.query.QueryClient;
+import tech.ydb.query.tools.QueryReader;
+import tech.ydb.query.tools.SessionRetryContext;
+import tech.ydb.table.result.ResultSetReader;
+
+/**
+ * @author Kirill Kurdyukov
+ */
+public class YdbRepository {
+    private final SessionRetryContext retryCtx;
+
+    public YdbRepository(String connectionString) {
+        GrpcTransport transport = GrpcTransport.forConnectionString(connectionString).build();
+        QueryClient queryClient = QueryClient.newClient(transport).build();
+        this.retryCtx = SessionRetryContext.create(queryClient).build();
+    }
+
+    public void TestDatabase() {
+        QueryReader resultSet = retryCtx.supplyResult(session ->
+                QueryReader.readFrom(session.createQuery("SELECT 1;", TxMode.NONE))
+        ).join().getValue();
+
+        ResultSetReader resultSetReader = resultSet.getResultSet(0);
+
+        if (resultSetReader.next()) {
+            System.out.println("Database is available!");
+        }
+    }
+}