DefaultStateGenerator->Base64StringKeyGenerator

Rename and move DefaultStateGenerator since it is more generic than just
OAuth.

Fixes gh-4645

crypto/src/test/java/org/springframework/security/crypto/keygen/Base64StringKeyGeneratorTests.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright 2002-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.security.crypto.keygen;
+
+import org.junit.Test;
+
+import java.util.Base64;
+
+import static org.assertj.core.api.Assertions.*;
+
+/**
+ * @author Rob Winch
+ * @since 5.0
+ */
+public class Base64StringKeyGeneratorTests {
+	@Test(expected = IllegalArgumentException.class)
+	public void constructorIntWhenLessThan32ThenIllegalArgumentException() {
+		new Base64StringKeyGenerator(31);
+	}
+
+	@Test(expected = IllegalArgumentException.class)
+	public void constructorEncoderWhenEncoderNullThenThrowsIllegalArgumentException() {
+		Base64.Encoder encoder = null;
+		new Base64StringKeyGenerator(null);
+	}
+
+	@Test
+	public void generateKeyWhenDefaultConstructorThen32Bytes() {
+		String result = new Base64StringKeyGenerator().generateKey();
+		assertThat(Base64.getDecoder().decode(result.getBytes())).hasSize(32);
+	}
+
+	@Test
+	public void generateKeyWhenCustomKeySizeThen32Bytes() {
+		int size = 40;
+		String result = new Base64StringKeyGenerator(size).generateKey();
+		assertThat(Base64.getDecoder().decode(result.getBytes())).hasSize(size);
+	}
+
+	@Test
+	public void generateKeyWhenBase64Then32Bytes() {
+		String result = new Base64StringKeyGenerator(Base64.getUrlEncoder()).generateKey();
+		assertThat(Base64.getUrlDecoder().decode(result.getBytes())).hasSize(32);
+	}
+
+	@Test
+	public void generateKeyWhenBase64AndCustomKeySizeThen32Bytes() {
+		int size = 40;
+		String result = new Base64StringKeyGenerator(Base64.getUrlEncoder(), size).generateKey();
+		assertThat(Base64.getUrlDecoder().decode(result.getBytes())).hasSize(size);
+	}
+}