Replacing many if statements

I recently was asked by a colleague how to get rid of a staggering amount of if statements.

They all seem to have remarkable similarities, as is obvious from the code below.

	public List<ValidationMessage> verifyAddress(Address address)
	{
	List<ValidationMessage> messages = new ArrayList<>();
	if (address.getHousenumber() == null)
	{
	messages.add(new ValidationMessage(AddressPart.HOUSENUMBER, "Housenumber is missing"));
	}
	if (address.getHousenumber() != null && (address.getHousenumber() < 0 || address.getHousenumber() > 50000))
	{
	messages.add(new ValidationMessage(AddressPart.HOUSENUMBER, "Housenumber should be between 0 and 50000"));
	}
	if (address.getCity() == null)
	{
	messages.add(new ValidationMessage(AddressPart.CITY, "City is missing"));
	}
	if (address.getStreetName() == null)
	{
	messages.add(new ValidationMessage(AddressPart.STREETNAME, "Streetname is missing"));
	}
	if (address.getState() == null)
	{
	messages.add(new ValidationMessage(AddressPart.STATE, "State is missing"));
	} else if (address.getState().length() != 2)
	{
	messages.add(new ValidationMessage(AddressPart.STATE, "Expecting State to be a 2-letter abbreviation"));
	}
	if (address.getSuffix() != null && address.getSuffix().length() != 1)
	{
	messages.add(new ValidationMessage(AddressPart.SUFFIX, "Suffix to a house number should be just one letter"));
	}
	return messages;
	}

view raw AddressVerifier.java hosted with ❤ by GitHub

So I initially thought about changing it to:

	public List<ValidationMessage> verifyAddress3(Address address)
	{
	Map<Boolean, ValidationMessage> map = new HashMap<>();
	map.put(address.getHousenumber() == null, new ValidationMessage(AddressPart.HOUSENUMBER, "Housenumber is missing"));
	map.put(address.getHousenumber() != null && (address.getHousenumber() < 0 || address.getHousenumber() > 50000),
	new ValidationMessage(AddressPart.HOUSENUMBER, "Housenumber should be between 0 and 50000"));
	map.put(address.getCity() == null, new ValidationMessage(AddressPart.CITY, "City is missing"));
	map.put(address.getStreetName() == null, new ValidationMessage(AddressPart.STREETNAME, "Streetname is missing"));
	map.put(address.getState() == null, new ValidationMessage(AddressPart.STATE, "State is missing"));
	map.put(address.getState() != null && address.getState().length() != 2, new ValidationMessage(AddressPart.STATE, "Expecting State to be a 2-letter abbreviation"));
	map.put(address.getSuffix() != null && address.getSuffix().length() != 1, new ValidationMessage(AddressPart.SUFFIX, "Suffix to a house number should be just one letter"));
	return map.entrySet().stream()
	.filter(Map.Entry::getKey)
	.map(Map.Entry::getValue)
	.collect(Collectors.toList());
	}

view raw AddressVerifier.java hosted with ❤ by GitHub

Of course it is also possible to create a static Map, that contains Functions. That way, the ValidationMessage instances are only created once. It depends on your needs, really.

	private static final Map<Function<Address, Boolean>, ValidationMessage> map = new HashMap<>();
	static
	{
	map.put(address -> address.getHousenumber() == null, new ValidationMessage(AddressPart.HOUSENUMBER, "Housenumber is missing"));
	map.put(address -> address.getHousenumber() != null && (address.getHousenumber() < 0 || address.getHousenumber() > 50000),
	new ValidationMessage(AddressPart.HOUSENUMBER, "Housenumber should be between 0 and 50000"));
	map.put(address -> address.getCity() == null, new ValidationMessage(AddressPart.CITY, "City is missing"));
	map.put(address -> address.getStreetName() == null, new ValidationMessage(AddressPart.STREETNAME, "Streetname is missing"));
	map.put(address -> address.getState() == null, new ValidationMessage(AddressPart.STATE, "State is missing"));
	map.put(address -> address.getState() != null && address.getState().length() != 2, new ValidationMessage(AddressPart.STATE, "Expecting State to be a 2-letter abbreviation"));
	map.put(address -> address.getSuffix() != null && address.getSuffix().length() != 1, new ValidationMessage(AddressPart.SUFFIX, "Suffix to a house number should be just one letter"));
	}
	public List<ValidationMessage> verifyAddress(Address address)
	{
	return map.entrySet().stream()
	.filter((x) -> x.getKey().apply(address))
	.map(Map.Entry::getValue)
	.collect(Collectors.toList());
	}

view raw AddressVerifier.java hosted with ❤ by GitHub

In the end, I don't know if the improvement is really that huge.

It's closer together at least, but I feel it could be improved.

Running Mariadb on the Raspberry Pi

This is going to be a small blurb, on what I did to get this working.

Nothing out of the ordinary, really.

$ apt-get install mariadb-server
$ cd /etc/mysql/mariadb.conf.d
$ joe 50-server.cnf
# started vi and replaced 127.0.0.1 with 0.0.0.0
$ service mysql restart

And of course allow the user accounts to access mariadb remotely over the network.

Attention! I'm only doing this locally on a testing server! It's not a great idea to run mariadb connections remotely if you do not have to.

GRANT ALL PRIVILEGES ON *.* TO 'root'@'192.168.100.%' IDENTIFIED BY 'my-new-password' WITH GRANT OPTION;

LetsEncrypt with Webroot

All righty then, time to get working with LetsEncrypt. Again.

So there are several different ways to have LetsEncrypt verify that the domain you wish to have a certificate for is actually yours.

I usually use the webroot version.

But in the past, I found it irksome that I had to let certbot spin up a http server to verify my domain.

What was easier was to have my application server have a part on the filesystem mapped to the Webpages¹.

Then certbot could simply use that webroot directory. Which is option 2.

So let's try that.

~]# certbot certonly
Saving debug log to /var/log/letsencrypt/letsencrypt.log

How would you like to authenticate with the ACME CA?
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
1: Spin up a temporary webserver (standalone)
2: Place files in webroot directory (webroot)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Select the appropriate number [1-2] then [enter] (press 'c' to cancel): 2
Plugins selected: Authenticator webroot, Installer None
Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org
Please enter in your domain name(s) (comma and/or space separated) (Enter 'c'
to cancel): www.mrbear.org
Cert is due for renewal, auto-renewing...
Renewing an existing certificate for www.mrbear.org
Performing the following challenges:
http-01 challenge for www.mrbear.org
Input the webroot for www.mrbear.org: (Enter 'c' to cancel): /home/jelastic/media
Waiting for verification...
Cleaning up challenges

IMPORTANT NOTES:
- Congratulations! Your certificate and chain have been saved at:
/etc/letsencrypt/live/www.mrbear.org/fullchain.pem
Your key file has been saved at:
/etc/letsencrypt/live/www.mrbear.org/privkey.pem
Your certificate will expire on 2021-11-10. To obtain a new or
tweaked version of this certificate in the future, simply run
certbot again. To non-interactively renew *all* of your
certificates, run "certbot renew"
- If you like Certbot, please consider supporting our work by:

Donating to ISRG / Let's Encrypt: https://letsencrypt.org/donate
Donating to EFF: https://eff.org/donate-le

It will put stuff in /home/jelastic/media/.well-known. Usually in the acme-challenge directory. It'll put some random file in there, for example 366_oWEFaizWeQqOts4KhuTBQcCsFH5dBgG7-jNX32k with a similar string inside, but usually a lot longer.

This file is accessed by the LetsEncrypt server, and if that works, the domain is yours and you get your certificate.

"certbot renew" is preferably easier, as it takes into account the previous configuration settings. Nice for cron jobs.

	]# certbot renew
	Saving debug log to /var/log/letsencrypt/letsencrypt.log
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	Processing /etc/letsencrypt/renewal/www.mrbear.org.conf
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	Cert is due for renewal, auto-renewing...
	Plugins selected: Authenticator webroot, Installer None
	Starting new HTTPS connection (1): acme-v02.api.letsencrypt.org
	Renewing an existing certificate for www.mrbear.org
	Performing the following challenges:
	http-01 challenge for www.mrbear.org
	Waiting for verification...
	Cleaning up challenges
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	new certificate deployed without reload, fullchain is
	/etc/letsencrypt/live/www.mrbear.org/fullchain.pem
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
	Congratulations, all renewals succeeded:
	/etc/letsencrypt/live/www.mrbear.org/fullchain.pem (success)
	- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

view raw letsencrypt_renew.txt hosted with ❤ by GitHub

Also, I found this great script for importing the ssl certificates on the Forums of LetsEncrypt² for my Java Application Server!

	#!/bin/sh
	# this script will remove your cacerts.jks and keystore.jks! And replace them with something completetly new!!
	# Use at your own risk!
	LIVE=##usually /etc/letsencrypt/live/YOURDOMAIN or wherever you store cert.pem and privkey.pem##
	NAME=##ALIASNAME usually s1as when dealing with glassfish/payara
	KEYSTORE=keystore.jks
	TRUSTSTORE=cacerts.jks
	KEYSTOREPW=changeit
	echo Remove keystore.
	rm $KEYSTORE
	echo Import certificate private key into keystore.
	for alias in glassfish-instance s1as
	do
	openssl pkcs12 -export \
	-in $LIVE/cert.pem \
	-inkey $LIVE/privkey.pem \
	-name $alias \
	-password pass:$KEYSTOREPW \
	-out cert.p12
	keytool -importkeystore \
	-srckeystore cert.p12 \
	-srcstoretype PKCS12 \
	-srcstorepass $KEYSTOREPW \
	-destkeystore $KEYSTORE \
	-destkeypass $KEYSTOREPW \
	-deststorepass $KEYSTOREPW \
	-alias $alias
	done
	echo Remove cert.p12.
	rm cert.p12
	echo List keystore.
	keytool -list -keystore $KEYSTORE -storepass $KEYSTOREPW
	echo Remove truststore.
	rm $TRUSTSTORE
	echo Import certificate into trust store.
	keytool -import -noprompt -trustcacerts \
	-alias $NAME \
	-file $LIVE/cert.pem \
	-srcstorepass $KEYSTOREPW \
	-destkeypass $KEYSTOREPW \
	-deststorepass $KEYSTOREPW \
	-keystore $TRUSTSTORE
	echo List truststore.
	keytool -list -keystore $TRUSTSTORE -storepass $KEYSTOREPW

view raw letsencrypt_certificates.sh hosted with ❤ by GitHub

My Payara MicroProfile server uses the following commandline to access the new certificates:

java -server -XX:+UnlockExperimentalVMOptions -javaagent:/java_agent/jelastic-gc-agent.jar=period=300,debug=0 -XX:+UseStringDeduplication -XX:+UseG1GC -Xmaxf0.3 \
-Xminf0.1 -Xmx2048M -Xms32M \
-Djavax.net.ssl.trustStore="/home/jelastic/cacerts.jks" \
-Djavax.net.ssl.keyStore="/home/jelastic/keystore.jks" \
-Djavax.net.ssl.trustStorePassword="changeit" \
-Djavax.net.ssl.keyStorePassword="changeit" \
-jar ./payara-micro-5.2021.1.jar --postbootcommandfile ./postboot --addlibs ../libs/mariadb-java-client-2.5.2.jar --port 8080 --sslport 8743 \
--deploy ../release/mrbear.war \
--deploy ../release/mrbearportal-2.0.9.war \

Please pay special attention to the four "javax.net.ssl.*" properties that take care of the SSL properties.

And that's it!

References

[1] MyBlog - Alternate docroots

http://randomthoughtsonjavaprogramming.blogspot.com/search/label/alternate%20docroot

[2] LetsEncrypt Community Forum - Importing LetsEncrypt into Java and Glassfish

https://community.letsencrypt.org/t/importing-letsencrypt-into-java-and-glassfish/9711/11

Java Keytool Essentials: Working with Java Keystores - Mitchell Anicas

https://www.digitalocean.com/community/tutorials/java-keytool-essentials-working-with-java-keystores

JFall 2021

After all the stuff with Corona and everything, there's finally going to be a genuine JFall in Ede (again) at the Pathe on Thursday, the fourth of November.

It's the first conference where I can go to "in the flesh" so to speak.

The previous one was a virtual conference, which was fun, but I do look forward to having social interaction face-to-face.

References

NLJUG - JFall 2021

http://jfall.nl/