Polish constructor assertions

Previously the JSON modules didn't use Spring's Assert.

This commit changes the assertions to use Spring's Assert and does
some minor restructuring.

Issue gh-3736

core/src/main/java/org/springframework/security/authentication/AnonymousAuthenticationToken.java

@@ -20,6 +20,7 @@ import java.io.Serializable;
 import java.util.Collection;
 
 import org.springframework.security.core.GrantedAuthority;
+import org.springframework.util.Assert;
 
 /**
  * Represents an anonymous <code>Authentication</code>.
@@ -48,7 +49,7 @@ public class AnonymousAuthenticationToken extends AbstractAuthenticationToken im
 	 */
 	public AnonymousAuthenticationToken(String key, Object principal,
 										Collection<? extends GrantedAuthority> authorities) {
-		this(extractKeyHash(key), nullSafeValue(principal), authorities);
+		this(extractKeyHash(key), principal, authorities);
 	}
 
 	/**
@@ -63,9 +64,10 @@ public class AnonymousAuthenticationToken extends AbstractAuthenticationToken im
 										Collection<? extends GrantedAuthority> authorities) {
 		super(authorities);
 
-		if (authorities == null || authorities.isEmpty()) {
-			throw new IllegalArgumentException("Cannot pass null or empty values to constructor");
+		if (principal == null || "".equals(principal)) {
+			throw new IllegalArgumentException("principal cannot be null or empty");
 		}
+		Assert.notEmpty(authorities, "authorities cannot be null or empty");
 
 		this.keyHash = keyHash;
 		this.principal = principal;
@@ -76,15 +78,8 @@ public class AnonymousAuthenticationToken extends AbstractAuthenticationToken im
 	// ========================================================================================================
 
 	private static Integer extractKeyHash(String key) {
-		Object value = nullSafeValue(key);
-		return value.hashCode();
-	}
-
-	private static Object nullSafeValue(Object value) {
-		if (value == null || "".equals(value)) {
-			throw new IllegalArgumentException("Cannot pass null or empty values to constructor");
-		}
-		return value;
+		Assert.hasLength(key, "key cannot be empty or null");
+		return key.hashCode();
 	}
 
 	public boolean equals(Object obj) {

core/src/test/java/org/springframework/security/authentication/anonymous/AnonymousAuthenticationTokenTests.java

@@ -19,6 +19,7 @@ package org.springframework.security.authentication.anonymous;
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
 
+import java.util.Collections;
 import java.util.List;
 
 import org.junit.Test;
@@ -146,4 +147,19 @@ public class AnonymousAuthenticationTokenTests {
 		token.setAuthenticated(false);
 		assertThat(!token.isAuthenticated()).isTrue();
 	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void constructorWhenNullAuthoritiesThenThrowIllegalArgumentException() throws Exception {
+		new AnonymousAuthenticationToken("key", "principal", null);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void constructorWhenEmptyAuthoritiesThenThrowIllegalArgumentException() throws Exception {
+		new AnonymousAuthenticationToken("key", "principal", Collections.<GrantedAuthority>emptyList());
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void constructorWhenPrincipalIsEmptyStringThenThrowIllegalArgumentException() throws Exception {
+		new AnonymousAuthenticationToken("key", "", ROLES_12);
+	}
 }

core/src/test/java/org/springframework/security/jackson2/AnonymousAuthenticationTokenMixinTests.java

@@ -16,19 +16,18 @@
 
 package org.springframework.security.jackson2;
 
+import java.io.IOException;
+
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.JsonMappingException;
 import org.json.JSONException;
 import org.junit.Test;
 import org.skyscreamer.jsonassert.JSONAssert;
+
 import org.springframework.security.authentication.AnonymousAuthenticationToken;
-import org.springframework.security.core.GrantedAuthority;
 import org.springframework.security.core.authority.SimpleGrantedAuthority;
 import org.springframework.security.core.userdetails.User;
 
-import java.io.IOException;
-import java.util.Collections;
-
 import static org.assertj.core.api.Assertions.assertThat;
 
 /**
@@ -45,15 +44,6 @@ public class AnonymousAuthenticationTokenMixinTests extends AbstractMixinTests {
 			"[{\"@class\": \"org.springframework.security.core.authority.SimpleGrantedAuthority\", \"role\": \"ROLE_USER\"}]]}, \"authenticated\": true, \"keyHash\": " + hashKey.hashCode() + "," +
 			"\"authorities\": [\"java.util.ArrayList\", [{\"@class\": \"org.springframework.security.core.authority.SimpleGrantedAuthority\", \"role\": \"ROLE_USER\"}]]}";
 
-	@Test(expected = IllegalArgumentException.class)
-	public void testWithNullAuthorities() throws JsonProcessingException, JSONException {
-		new AnonymousAuthenticationToken("key", "principal", null);
-	}
-
-	@Test(expected = IllegalArgumentException.class)
-	public void testWithEmptyAuthorities() throws JsonProcessingException, JSONException {
-		new AnonymousAuthenticationToken("key", "principal", Collections.<GrantedAuthority>emptyList());
-	}
 
 	@Test
 	public void serializeAnonymousAuthenticationTokenTest() throws JsonProcessingException, JSONException {