This blog post is part 2 of a series of blogs on how to develop full-stack To-Do application in SAP Web IDE Full-Stack.

Prerequisites

Before reading this blog please make sure that you have read, understood and implemented part 0 and part 1 of this series.

Create your Java Module

The Java module is responsible for:

In our app we will use it for the OData provisioning.

To create the Java module, follow these steps:

In SAP Web IDE, select the todo project folder Right-click it and select New -> Java Module Select OData V4 Service Using SAP Cloud Platform SDK template and then click on Next. Enter service as the module name and click Next. Enter Group ID, artifact ID and package or just use the default values. Make sure that Enable SAP HANA Database support checkbox is checked! It’s needed to allow connectivity from the Java service to the HANA database module. Finally, click Finish. SAP Web IDE creates a new service folder under your todo project folder. In addition, the mta.yaml file is updated and now contains the service java module in addition to the db module. Specifically notice the ‘provides’ and ‘requires’ sections in the mta.yaml file. The db and java modules both require HANA and provides a service_api which will be used by the UI module (that we will create in part 3 of this series). Next, select the service folder which is located under service > src > main > java > {your_package_path} > service Right-click it and select New > Java Class to create a new Java class Enter ToDoService in the Name field, click Next and Finish SAP Web IDE creates the ToDoService.java file in the service folder Open the ToDoService.java file in the code editor Copy the code below and paste it under the first line in the file (under the package {your_package_name} ) import java.sql.Connection; import java.util.List; import javax.naming.Context; import javax.naming.InitialContext; import javax.sql.DataSource; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import com.sap.cloud.sdk.hana.connectivity.cds.CDSQuery; import com.sap.cloud.sdk.hana.connectivity.cds.CDSSelectQueryBuilder; import com.sap.cloud.sdk.hana.connectivity.cds.CDSSelectQueryResult; import com.sap.cloud.sdk.hana.connectivity.handler.CDSDataSourceHandler; import com.sap.cloud.sdk.hana.connectivity.handler.DataSourceHandlerFactory; import com.sap.cloud.sdk.service.prov.api.EntityData; import com.sap.cloud.sdk.service.prov.api.operations.Query; import com.sap.cloud.sdk.service.prov.api.operations.Read; import com.sap.cloud.sdk.service.prov.api.request.QueryRequest; import com.sap.cloud.sdk.service.prov.api.request.ReadRequest; import com.sap.cloud.sdk.service.prov.api.response.QueryResponse; import com.sap.cloud.sdk.service.prov.api.response.ReadResponse; /** * * @author I059508 */ public class ToDoService { private static Logger logger = LoggerFactory.getLogger(ToDoService.class); @Query(entity = "Task", serviceName = "todo") public QueryResponse findTasks(QueryRequest request) { try { QueryResponse res = QueryResponse.setSuccess().setEntityData(getEntitySet(request)).response(); return res; } catch (Exception e) { return null; } } @Read(entity = "Task", serviceName = "todo") public ReadResponse getProposedBooks(ReadRequest readRequest){ try { ReadResponse readResponse = ReadResponse.setSuccess().setData(readEntity(readRequest)).response(); return readResponse; } catch (Exception e) { return null; } } private List getEntitySet(QueryRequest queryRequest) { String fullQualifiedName = queryRequest.getEntityMetadata().getNamespace() + "." + queryRequest.getEntityMetadata().getName(); CDSDataSourceHandler dsHandler = DataSourceHandlerFactory.getInstance().getCDSHandler(getConnection(), queryRequest.getEntityMetadata().getNamespace()); try { CDSQuery cdsQuery = new CDSSelectQueryBuilder(fullQualifiedName).build(); CDSSelectQueryResult cdsSelectQueryResult = dsHandler.executeQuery(cdsQuery); return cdsSelectQueryResult.getResult(); } catch (Exception e) { logger.error("==> Eexception while fetching query data from CDS: " + e.getMessage()); e.printStackTrace(); } return null; } private EntityData readEntity(ReadRequest readRequest) throws Exception { CDSDataSourceHandler dsHandler = DataSourceHandlerFactory.getInstance().getCDSHandler(getConnection(), readRequest.getEntityMetadata().getNamespace()); EntityData ed = dsHandler.executeRead(readRequest.getEntityMetadata().getName(), readRequest.getKeys(), readRequest.getEntityMetadata().getElementNames()); return ed; } private static Connection getConnection(){ Connection conn = null; Context ctx; try { ctx = new InitialContext(); conn = ((DataSource) ctx.lookup("java:comp/env/jdbc/java-hdi-container")).getConnection(); System.out.println("conn = " + conn); } catch (Exception e) { e.printStackTrace(); } return conn; } }​   The java code that you just added is doing the following: Connects to the SAP HANA database – see the getConnection() method Uses the @Read and @Query annotations to expose a task and a list of tasks in OData. This is done using the SAP Cloud Java SDK which is added automatically by SAP Web IDE as a Maven dependency in the module (to understand more, review the pom.xml). Notice: This java code handles only the Task entity’s ‘query’ and ‘read’ operations. Handling the SubTask entity or any other CUD (create, update, delete) operations can be done in the same way (using the same SDK with similar code).