Merge pull request #11105 from gupta-ashu01/master

BAEL-4932-Email Validation in Java

core-java-modules/core-java-string-algorithms-3/pom.xml

@@ -32,6 +32,11 @@
             <artifactId>junit-jupiter</artifactId>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>commons-validator</groupId>
+            <artifactId>commons-validator</artifactId>
+            <version>${validator.version}</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -59,6 +64,7 @@
     <properties>
         <assertj.version>3.6.1</assertj.version>
         <guava.version>28.1-jre</guava.version>
+        <validator.version>1.7</validator.version>
     </properties>
 
-</project>
+</project>

core-java-modules/core-java-string-algorithms-3/src/main/java/com/baeldung/emailvalidation/EmailValidation.java

@@ -0,0 +1,12 @@
+package com.baeldung.emailvalidation;
+
+import java.util.regex.Pattern;
+
+public class EmailValidation {
+
+    public static boolean patternMatches(String emailAddress, String regexPattern) {
+        return Pattern.compile(regexPattern)
+            .matcher(emailAddress)
+            .matches();
+    }
+}

core-java-modules/core-java-string-algorithms-3/src/test/java/com/baeldung/emailvalidation/EmailValidationUnitTest.java

@@ -0,0 +1,79 @@
+package com.baeldung.emailvalidation;
+
+import static org.junit.Assert.assertTrue;
+import org.apache.commons.validator.routines.EmailValidator;
+import org.junit.Test;
+
+public class EmailValidationUnitTest {
+
+    private String emailAddress;
+    private String regexPattern;
+
+    @Test
+    public void testUsingEmailValidator() {
+        emailAddress = "username@domain.com";
+        assertTrue(EmailValidator.getInstance()
+            .isValid(emailAddress));
+    }
+
+    @Test
+    public void testUsingSimpleRegex() {
+        emailAddress = "username@domain.com";
+        regexPattern = "^(.+)@(\\S+)$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+
+    @Test
+    public void testUsingStrictRegex() {
+        emailAddress = "username@domain.com";
+        regexPattern = "^(?=.{1,64}@)[A-Za-z0-9_-]+(\\.[A-Za-z0-9_-]+)*@" 
+            + "[^-][A-Za-z0-9-]+(\\.[A-Za-z0-9-]+)*(\\.[A-Za-z]{2,})$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+
+    @Test
+    public void testUsingUnicodeRegex() {
+        emailAddress = "用户名@领域.电脑";
+        regexPattern = "^(?=.{1,64}@)[\\p{L}0-9_-]+(\\.[\\p{L}0-9_-]+)*@" 
+            + "[^-][\\p{L}0-9-]+(\\.[\\p{L}0-9-]+)*(\\.[\\p{L}]{2,})$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+
+    @Test
+    public void testUsingRFC5322Regex() {
+        emailAddress = "username@domain.com";
+        regexPattern = "^[a-zA-Z0-9_!#$%&'*+/=?`{|}~^.-]+@[a-zA-Z0-9.-]+$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+
+    @Test
+    public void testRestrictDots() {
+        emailAddress = "username@domain.com";
+        regexPattern = "^[a-zA-Z0-9_!#$%&'*+/=?`{|}~^-]+(?:\\.[a-zA-Z0-9_!#$%&'*+/=?`{|}~^-]+)*@" 
+            + "[a-zA-Z0-9-]+(?:\\.[a-zA-Z0-9-]+)*$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+
+    @Test
+    public void testOwaspValidation() {
+        emailAddress = "username@domain.com";
+        regexPattern = "^[a-zA-Z0-9_+&*-]+(?:\\.[a-zA-Z0-9_+&*-]+)*@(?:[a-zA-Z0-9-]+\\.)+[a-zA-Z]{2,7}$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+
+    @Test
+    public void testTopLevelDomain() {
+        emailAddress = "username@domain.com";
+        regexPattern = "^[\\w!#$%&'*+/=?`{|}~^-]+(?:\\.[\\w!#$%&'*+/=?`{|}~^-]+)*" 
+            + "@(?:[a-zA-Z0-9-]+\\.)+[a-zA-Z]{2,6}$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+    
+    @Test
+    public void testGmailSpecialCase() {
+        emailAddress = "username+something@domain.com";
+        regexPattern = "^(?=.{1,64}@)[A-Za-z0-9\\+_-]+(\\.[A-Za-z0-9\\+_-]+)*@" 
+            + "[^-][A-Za-z0-9\\+-]+(\\.[A-Za-z0-9\\+-]+)*(\\.[A-Za-z]{2,})$";
+        assertTrue(EmailValidation.patternMatches(emailAddress, regexPattern));
+    }
+}