Validation

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

By Tom Ansill

Motivation

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.

Why not use Objects.requireNonNull(T)?

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.

Prerequisites

• Java 8 or better

Download

Package Repository

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>

Build

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>

How to use

Null Checks

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)

Natural Number Checks

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)

Non-Negative Checks

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)

Non-Empty String Checks

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)

Non-Empty Array/Collection

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)

Array/Collection Member Null Check

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)