Using EWS Java API to set custom headers on a draft email

EmailTweaker.java

import java.net.URI;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

//You'll need: https://github.com/OfficeDev/ews-java-api/

import microsoft.exchange.webservices.data.core.ExchangeService;
import microsoft.exchange.webservices.data.core.PropertySet;
import microsoft.exchange.webservices.data.core.service.folder.Folder;
import microsoft.exchange.webservices.data.core.service.item.Item;
import microsoft.exchange.webservices.data.core.service.schema.EmailMessageSchema;
import microsoft.exchange.webservices.data.core.service.schema.ItemSchema;
import microsoft.exchange.webservices.data.credential.WebCredentials;
import microsoft.exchange.webservices.data.enumeration.ComparisonMode;
import microsoft.exchange.webservices.data.enumeration.ConflictResolutionMode;
import microsoft.exchange.webservices.data.enumeration.ContainmentMode;
import microsoft.exchange.webservices.data.enumeration.DefaultExtendedPropertySet;
import microsoft.exchange.webservices.data.enumeration.ExchangeVersion;
import microsoft.exchange.webservices.data.enumeration.MapiPropertyType;
import microsoft.exchange.webservices.data.enumeration.SortDirection;
import microsoft.exchange.webservices.data.enumeration.WellKnownFolderName;
import microsoft.exchange.webservices.data.property.complex.MessageBody;
import microsoft.exchange.webservices.data.property.definition.ExtendedPropertyDefinition;
import microsoft.exchange.webservices.data.search.FindItemsResults;
import microsoft.exchange.webservices.data.search.ItemView;
import microsoft.exchange.webservices.data.search.filter.SearchFilter;

public class EmailTweaker {
	private static final ExchangeVersion EV = ExchangeVersion.Exchange2010_SP2;
	private static final URI EWS_URI = URI.create("https://email.example.com/EWS/Exchange.asmx");
	private static final String DOMAIN = "EXAMPLE_DOMAIN";
	
	public static void main(String... args) throws Exception {
		if (args.length != 2) {
			System.err.println("Supply only username and password as arguments please");
			System.exit(1);
		}
		
		String username = args[0];
		String password = args[1];

		try (ExchangeService service = new ExchangeService(EV)) {
			service.setUrl(EWS_URI);
			service.setCredentials(new WebCredentials(username, password, DOMAIN));
			new EmailTweaker(service).run();
		}
	}

	private final ExchangeService service;

	private EmailTweaker(ExchangeService service) {
		this.service = service;
	}

	private final int PAGE_SIZE = 100;
	
	private static final Pattern HEADERS=Pattern.compile("(?<=(?:>|^))SetHeader:\\s*([!-9;-~]+):\\s*(.+?)(?=(?:<|$))");
	
	private static final SearchFilter FILTER = new SearchFilter.ContainsSubstring(ItemSchema.Subject, "HEADERS ", ContainmentMode.Prefixed, ComparisonMode.Exact);
	
	private void run() throws Exception {
		Folder folder = Folder.bind(service, WellKnownFolderName.Drafts);
		ItemView view = new ItemView(PAGE_SIZE);
		view.setPropertySet(PropertySet.getIdOnly());
		view.getOrderBy().add(EmailMessageSchema.DateTimeSent,
				SortDirection.Ascending);
				
		FindItemsResults<Item> results;
		do {

			results = folder.findItems(FILTER, view);
			
			for (Item item : results) {
				// Sadly, the view won't let us just load all of these.
				item.load(new PropertySet(ItemSchema.Body,ItemSchema.Subject));
				
				MessageBody body = item.getBody();
				String bodyString = body.toString();
				Matcher bodyMatcher = HEADERS.matcher(bodyString);
				
				StringBuffer sb = new StringBuffer(bodyString.length());
				
				while(bodyMatcher.find()) {
					String key = bodyMatcher.group(1);
					String value = bodyMatcher.group(2);
					System.out.printf("Setting %s:%s\n",key,value);
					ExtendedPropertyDefinition header = new ExtendedPropertyDefinition(DefaultExtendedPropertySet.InternetHeaders,
                            key,
                            MapiPropertyType.String);
					item.setExtendedProperty(header, value);
					bodyMatcher.appendReplacement(sb, "");
				}
				bodyMatcher.appendTail(sb);
				
				String newBodyString = sb.toString();
				
				//Dealing with HTML bodies, sometimes Outlook / OWA sucks and splits lines. 
				//When this happens, it helps to see the raw message body so you can edit and try again.
				if(!newBodyString.equals(bodyString)) {
					//Even if you get here, not all of the custom headers may be put in place.
					item.setSubject(item.getSubject().substring(8));
					body.setText(sb.toString());
					item.update(ConflictResolutionMode.AlwaysOverwrite);
					System.out.println(item.getId());
				} else {
					System.err.printf("Subject: %s ,Id: %s\n\t%s\n\n",item.getSubject(),item.getId(),newBodyString);
				}
			}
			
		} while (results.isMoreAvailable());
	}
}