diff --git a/spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java b/spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java index 6212a210ea8..d6581241a30 100644 --- a/spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java +++ b/spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java @@ -29,6 +29,7 @@ import java.util.List; import java.util.Map; import java.util.Random; +import org.springframework.lang.Nullable; import org.springframework.util.MimeType.SpecificityComparator; /** @@ -46,8 +47,6 @@ public abstract class MimeTypeUtils { 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z'}; - private static final Random RND = new SecureRandom(); - /** * Comparator used by {@link #sortBySpecificity(List)}. */ @@ -153,6 +152,9 @@ public abstract class MimeTypeUtils { */ public static final String TEXT_XML_VALUE = "text/xml"; + @Nullable + private static volatile Random random; + static { ALL = MimeType.valueOf(ALL_VALUE); @@ -314,15 +316,31 @@ public abstract class MimeTypeUtils { } - + /** + * Lazily initialize the {@link SecureRandom} for {@link #generateMultipartBoundary()}. + */ + private static Random initRandom() { + Random randomToUse = random; + if (randomToUse == null) { + synchronized (MimeTypeUtils.class) { + randomToUse = random; + if (randomToUse == null) { + randomToUse = new SecureRandom(); + random = randomToUse; + } + } + } + return randomToUse; + } /** * Generate a random MIME boundary as bytes, often used in multipart mime types. */ public static byte[] generateMultipartBoundary() { - byte[] boundary = new byte[RND.nextInt(11) + 30]; + Random randomToUse = initRandom(); + byte[] boundary = new byte[randomToUse.nextInt(11) + 30]; for (int i = 0; i < boundary.length; i++) { - boundary[i] = BOUNDARY_CHARS[RND.nextInt(BOUNDARY_CHARS.length)]; + boundary[i] = BOUNDARY_CHARS[randomToUse.nextInt(BOUNDARY_CHARS.length)]; } return boundary; }