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MimeTypeUtils lazily initializes SecureRandom for multipart boundary 

Issue: SPR-16974
This commit is contained in:
Juergen Hoeller 2018-06-25 18:12:43 +02:00
parent 2a15962d7f
commit 847202c8f8
1 changed files with 23 additions and 5 deletions
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28
spring-core/src/main/java/org/springframework/util/MimeTypeUtils.java
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@ -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;
}