How to work with Command in the new MDM Java API Vijendra Singh Bhanot

How to work with Command in the new MDM Java API
Vijendra Singh Bhanot


I am new to the MDM Java API. For one of the existing project I was asked to explore the new MDM Java API. I do not have any experience with the earlier MDM4J but still I was able to understand and explore the new MDM Java API. I think this API is excellent and I am almost fallen in love with it. The best part I like about this API is the Commands. Initially it took me time to understand the concept but very soon it was all clear. With this blog I would like to share my knowledge about how to work with Commands. Also in this blog you will see an example of Validation Command.




Why you need a Command? What is a Command?


I command the MDM Java API to get me the list of Validations …..

Well, that’s what the idea is.


Command is a special class that instructs MDM Java API to perform some action. All actions like managing repository content, searching records, managing repository schema and etc, have dedicated commands.


All these commands are logically organized in packages. You can always refer Java Doc to identify which Command you need to use. (https://help.sap.com/javadocs/MDM/current/index.html)

How to Use a Command?



All Command’s are used in the following way:



1 RetrieveValidationsCommand objRetrieveValidationsCommand = new RetrieveValidationsCommand();

2 objRetrieveValidationsCommand.setSession();

3 objRetrieveValidationsCommand.setTableId(<>); // Required

try {

4 objRetrieveValidationsCommand.execute();
} catch (CommandException e) {
e.printStackTrace();
return;
}



(1) You create a new instance of a particular command by passing it the ConnectionAccessor object.

(2) The very second step is mostly the setSession(). Here it is important that you use the right type of session (Server Session, Repository Session or User Session). For Example, you may not be able to get list of validations if you use a Repository Session instead of User Session.

As I already mentioned that setSession() is not always the second step. Actually the commands responsible for creation of session are the ones that do not require a session. Thus these commands (CreateServerSessionCommand, CreateRepositorySessionCommand and CreateUserSessionCommand) do not require setSession().

(3) Some commands require specific setter method to be set before it is used. These setter methods are marked as “Required” in the Java Dock. There are few which are marked optional.

(4) Inside a try block you execute the command. If there is an error then CommandException is thrown.


Here is a sample of RetrieveValidationsCommand in action…

/*
* Created on Feb 7, 2008
*
* To change the template for this generated file go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
package demo.validation;

import com.sap.mdm.commands.AuthenticateUserSessionCommand;
import com.sap.mdm.commands.CommandException;
import com.sap.mdm.commands.CreateUserSessionCommand;
import com.sap.mdm.commands.GetRepositoryRegionListCommand;
import com.sap.mdm.data.RegionProperties;
import com.sap.mdm.ids.TableId;
import com.sap.mdm.net.ConnectionException;
import com.sap.mdm.net.ConnectionPool;
import com.sap.mdm.net.ConnectionPoolFactory;
import com.sap.mdm.server.DBMSType;
import com.sap.mdm.server.RepositoryIdentifier;
import com.sap.mdm.validation.ValidationProperties;
import com.sap.mdm.validation.ValidationPropertiesResult;
import com.sap.mdm.validation.commands.RetrieveValidationsCommand;

/**
*
*
* To change the template for this generated type comment go to
* Window>Preferences>Java>Code Generation>Code and Comments
*/
public class GetListOfValidations {

public static void main(String[] args) {
// create connection pool to a MDM server
String serverName = "LOCALHOST";
ConnectionPool connections = null;
try {
connections = ConnectionPoolFactory.getInstance(serverName);
} catch (ConnectionException e) {
e.printStackTrace();
return;
}

// specify the repository to use
// alternatively, a repository identifier can be obtain from the GetMountedRepositoryListCommand
String repositoryName = "INQDemo";
String dbmsName = "localhost";
RepositoryIdentifier reposId =
new RepositoryIdentifier(repositoryName, dbmsName, DBMSType.ORACLE);

// get list of available regions for the repository
GetRepositoryRegionListCommand regionListCommand =
new GetRepositoryRegionListCommand(connections);
regionListCommand.setRepositoryIdentifier(reposId);
try {
regionListCommand.execute();
} catch (CommandException e) {
e.printStackTrace();
return;
}
RegionProperties[] regions = regionListCommand.getRegions();

// create a user session
CreateUserSessionCommand sessionCommand =
new CreateUserSessionCommand(connections);
sessionCommand.setRepositoryIdentifier(reposId);
sessionCommand.setDataRegion(regions[0]); // use the first region
try {
sessionCommand.execute();
} catch (CommandException e) {
e.printStackTrace();
return;
}
String sessionId = sessionCommand.getUserSession();

// authenticate the user session
String userName = "admin";
String userPassword = "admin";
AuthenticateUserSessionCommand authCommand =
new AuthenticateUserSessionCommand(connections);
authCommand.setSession(sessionId);
authCommand.setUserName(userName);
authCommand.setUserPassword(userPassword);
try {
authCommand.execute();
} catch (CommandException e) {
e.printStackTrace();
return;
}

// the main table, hard-coded
TableId mainTableId = new TableId(1);

// Get the list of validations

RetrieveValidationsCommand objRtvVldCmd =
new RetrieveValidationsCommand(connections);
// set the user session
objRtvVldCmd.setSession(sessionId);
// get validation for the following tables.
objRtvVldCmd.setTableId(mainTableId);

try {
objRtvVldCmd.execute();

} catch (CommandException e) {
e.printStackTrace();
return;
}

ValidationPropertiesResult objVldPropRslt =
objRtvVldCmd.getValidationPropertiesResult();

ValidationProperties[] validations = objVldPropRslt.getValidations();


//disply --> Validation ID | error/warning message | Validation Name
for (int i = 0; i < validations.length; i++) {

System.out.println(
validations[i].getId()
+ " | "
+ validations[i].getMessage()
+ " | "
+ validations[i].getName());
}

}
}

Vijendra Singh Bhanot is a certified XI Consultant