//To following code creates a metadata connection
import com.sforce.soap.metadata.*;
import com.sforce.soap.partner.LoginResult;
import com.sforce.soap.partner.PartnerConnection;
import com.sforce.ws.ConnectionException;
import com.sforce.ws.ConnectorConfig;
/**
* Login utility.
*/
public class MetadataLoginUtil {
public static MetadataConnection login() throws ConnectionException {
final String USERNAME = "username@gmail.com";
// This is only a sample. Hard coding passwords in source files is a bad practice.
final String PASSWORD = "Password+SecurityToken";
final String URL = "https://login.salesforce.com/services/Soap/u/31.0";

//Quick Start Step 3: Walk through the Java Sample Code
final LoginResult loginResult = loginToSalesforce(USERNAME, PASSWORD, URL);
//System.out.println(loginResult);
return createMetadataConnection(loginResult);
}
private static MetadataConnection createMetadataConnection(
final LoginResult loginResult) throws ConnectionException {
final ConnectorConfig config = new ConnectorConfig();
config.setServiceEndpoint(loginResult.getMetadataServerUrl());
config.setSessionId(loginResult.getSessionId());
return new MetadataConnection(config);
}
private static LoginResult loginToSalesforce(
final String username,
final String password,
final String loginUrl) throws ConnectionException {
final ConnectorConfig config = new ConnectorConfig();
config.setAuthEndpoint(loginUrl);
config.setServiceEndpoint(loginUrl);
config.setManualLogin(true);
return (new PartnerConnection(config)).login(username, password);
}

}

//The following code creates a custom field using metadata conncetion and createMetadata() method.

import java.util.ArrayList;
import java.util.concurrent.ForkJoinPool.ManagedBlocker;
import com.sforce.async.Error;
import com.sforce.soap.metadata.*;
import com.sforce.soap.metadata.FieldType;
import com.sforce.soap.metadata.Package;
import com.sforce.soap.metadata.SaveResult;
import com.sforce.soap.partner.*;
import com.sforce.ws.ConnectionException;
import com.sforce.ws.ConnectorConfig;
import com.sforce.ws.wsdl.SfdcApiType;
/**
* Login utility.
*/
public class PartnerLoginUtil {

public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
try {
PartnerLoginUtil p= new PartnerLoginUtil( );
p.createCustomExtField("CustomObjectName");

} catch (ConnectionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

private void createCustomExtField(String name) {
// TODO Auto-generated method stub
CustomField cs = new CustomField();
cs.setFullName(name+".CustExtField__c");
cs.setLabel("CustExtField");
cs.setType(FieldType.Number);
cs.setExternalId(true);
cs.setPrecision(10);
cs.setScale(8);
try {
MetadataConnection metadataConnection = MetadataLoginUtil.login();
SaveResult[] results = metadataConnection
.updateMetadata(new Metadata[] {cs});

for (SaveResult r : results) {
if (r.isSuccess()) {
System.out.println("Created component: " + r.getFullName());
} else {
System.out
.println("Errors were encountered while creating "
+ r.getFullName());
for (com.sforce.soap.metadata.Error e : r.getErrors()) {
System.out.println("Error message: " + e.getMessage());
System.out.println("Status code: " + e.getStatusCode());
}
}
}
} catch (ConnectionException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

}

}