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Java JSR 303 bean validation: a simple example 

Fang
Joined:
08/13/2009
Posts:
164

March 05, 2012 20:32:37    Last update: March 05, 2012 20:32:37
In this simple example, I create a simple validating bean and create a JUnit test to test the validation.
  1. The bean (src/main/java/com/example/Person.java): 
    package com.example;

import javax.validation.constraints.NotNull;

public class Person {
    @NotNull
    private String name;

    public Person(String name) {
	this.name = name;
    }

    public String getName() {
	return this.name;
    }

    public void setName(String name) {
	this.name = name;
    }
}

  2. The test (src/test/java/com/example/TestPerson.java): 
    package com.example;

import java.util.Set;
import javax.validation.ConstraintViolation;
import javax.validation.Validation;
import javax.validation.Validator;
import javax.validation.ValidatorFactory;

import static org.junit.Assert.*;
import org.junit.Before;
import org.junit.Test;

public class TestPerson {
    private Validator validator;

    @Before
    public void setUp() {
	ValidatorFactory f = Validation.buildDefaultValidatorFactory();
	validator = f.getValidator();
    }

    @Test
    public void testNameNull() {
	Person p = new Person(null);
	Set<ConstraintViolation<Person>> violations = validator.validate(p);
	assertEquals(1, violations.size());
    }

    @Test
    public void testNameEmpty() {
	Person p = new Person("  ");
	Set<ConstraintViolation<Person>> violations = validator.validate(p);
	assertEquals(1, violations.size());
    }
}

  3. Run the test: 
    mvn clean test

    You'll notice that one test passed and the other failed.
  4. The tests require that a person must have a name and the name cannot be empty, so @NotNull is not the right rule to use here. To make sure that the name is not empty, we need to use @Pattern. But since a null String matches any pattern, @NotNull is also needed: 
    package com.example;

import javax.validation.constraints.NotNull;
import javax.validation.constraints.Pattern;

public class Person {
    @NotNull
    @Pattern(regexp="\\w.*")
    private String name;

    public Person(String name) {
	this.name = name;
    }

    public String getName() {
	return this.name;
    }

    public void setName(String name) {
	this.name = name;
    }
}

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