A simple and easy-to-use validation utility library.

By Tom Ansill

I got tired of manually including null checks, empty array checks, and various kinds of checks against bad input parameters. So I decided to build a library to make things a bit easier for me.

Objects.requireNonNull(T) will throw NullPointerException and I disagree with this choice of exception because NullPointerException is supposed to be thrown in event of null object being de-referenced. Like:

StringBuilder sb = null; sb.append("something"); // <-- This will throw NullPointerException because you are trying to de-reference a null object 

So, hence the name NullPointerException, you get the exception because you are attempting to de-reference a null value and it blows up on you. I don't believe this is the case here where I want to ensure that parameters that are passed in is not null. I'm not necessarily trying to dereference it. I think IllegalArgumentException is more appropriate exception to best describe the problem.

• Java 8 or better

The library is availble for download on Sonatype public Maven repository (https://oss.sonatype.org/#nexus):

<dependency> <groupId>com.ansill.validation</groupId> <artifactId>validation</artifactId> <version>0.2.2</version> </dependency>

Maven (or other similar build tools) is needed to build and install JavaValidation.

$ git clone https://github.com/tomansill/javavalidation $ cd javavalidation $ mvn install

Then include the dependency in your project's pom.xml:

<dependency> <groupId>com.ansill.validation</groupId> <artifactId>validation</artifactId> <version>0.2.2</version> </dependency>

Use Validation.assertNonnull(Object) to assert that object is not null:

import com.ansill.validation.Validation; public class Application{ public static void main(String[] args){ String message = null; Application application = new Application(); application.print(message); } public void print(String message){ System.out.println(Validation.assertNonnull(message)); } }

When you run the code, it will yield this message:

Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to be non-null but is found to be null	at Application.print(Application.java:9)	at Application.main(Application.java:7) 

Use Validation.assertNaturalNumber(long) to assert that number is a natural number (no negative number or zero):

import com.ansill.validation.Validation; public class Application{ public static void main(String[] args){ Application application = new Application(); application.setPort(0); } private int port = 80; public void setPort(int port){ this.port = Validation.assertNaturalNumber(port, "port"); } }

When you run the code, it will yield this message:

Exception in thread "main" java.lang.IllegalArgumentException: Value in variable 'port' is expected to be a natural number (1, 2, ..., N-1, N) but it is actually not a natural number	at Application.setPort(Application.java:9)	at Application.main(Application.java:6) 

Use Validation.assertNonnegative(long) to assert that number is a positive number:

import com.ansill.validation.Validation; public class Application{ public static void main(String[] args){ Application application = new Application(); application.add((short) 0, -1); } public void add(short one, long two){ Validation.assertNonnegative(one); Validation.assertNonnegative(two); System.out.println(one + two); } }

When you run the code, it will yield this message:

Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to be non-negative but value is actually a negative number	at Application.add(Application.java:10)	at Application.main(Application.java:6) 

Use Validation.assertNonemptyString(String) to assert that String is non-empty:

import com.ansill.validation.Validation; public class Application{ public static void main(String[] args){ Application application = new Application(""); } public final String name; public Application(String name){ Validation.assertNonemptyString(name, "name"); this.name = name; } }

When you run the code, it will yield this message:

Exception in thread "main" java.lang.IllegalArgumentException: Value in variable 'name' is expected to be non-empty but value is actually a empty string	at Application.<init>(Application.java:9)	at Application.main(Application.java:5) 

Use Validation.assertNonempty(Object[]) or Validation.assertNonempty(Collection) to assert that Array/Collection is non-empty:

import com.ansill.validation.Validation; import java.util.*; public class Application{ public static void main(String[] args){ Application application = new Application(Collections.emptyList()); } public final Collection hostnames; public Application(Collection hostnames){ Validation.assertNonempty(hostnames); this.hostnames = hostnames; } }

When you run the code, it will yield this message:

Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to be non-empty but value is actually empty	at Application.<init>(Application.java:11)	at Application.main(Application.java:7) 

Use Validation.assertNonnullElements(Object[]) or Validation.assertNonnullElements(Collection) to assert that Array/Collection does not have null elements:

import com.ansill.validation.Validation; import java.util.*; public class Application{ public static void main(String[] args){ Application application = new Application(Arrays.asList("google.com", null, "github.com", null, null, "reddit.com")); } public final Collection hostnames; public Application(Collection hostnames){ Validation.assertNonnullElements(hostnames, false); this.hostnames = hostnames; } }

When you run the code, it will yield this message:

Exception in thread "main" java.lang.IllegalArgumentException: Value is expected to have all of its list members to be non-null but the list contains null members. Invalid members are located at indices [1, 3, 4]	at Application.<init>(Application.java:11)	at Application.main(Application.java:7)