修复StrSplitter.splitByRegex使用空参数导致的OOM问题

hutool-core/src/main/java/org/dromara/hutool/core/text/finder/PatternFinder.java

@@ -63,9 +63,16 @@ public class PatternFinder extends TextFinder {
 	@Override
 	public int start(final int from) {
 		if (matcher.find(from)) {
+			final int end = matcher.end();
 			// 只有匹配到的字符串结尾在limit范围内，才算找到
-			if(matcher.end() <= getValidEndIndex()){
+			if(end <= getValidEndIndex()){
-				return matcher.start();
+				final int start = matcher.start();
+				if(start == end){
+					// issue#3421，如果匹配空串，按照未匹配对待，避免死循环
+					return INDEX_NOT_FOUND;
+				}
+
+				return start;
 			}
 		}
 		return INDEX_NOT_FOUND;

hutool-core/src/main/java/org/dromara/hutool/core/text/split/SplitUtil.java

@@ -258,7 +258,12 @@ public class SplitUtil {
 	}
 
 	/**
-	 * 通过正则切分字符串
+	 * 通过正则切分字符串，规则如下：
+	 * <ul>
+	 *     <li>当提供的str为{@code null}时，返回new ArrayList(0)</li>
+	 *     <li>当提供的str为{@code ""}时，返回[""]</li>
+	 *     <li>当提供的separatorRegex为empty(null or "")时，返回[str]，即只有原串一个元素的数组</li>
+	 * </ul>
 	 *
 	 * @param str            字符串
 	 * @param separatorRegex 分隔符正则
@@ -269,19 +274,19 @@ public class SplitUtil {
 	 * @since 3.0.8
 	 */
 	public static List<String> splitByRegex(final CharSequence str, final String separatorRegex, final int limit, final boolean isTrim, final boolean ignoreEmpty) {
-		if (StrUtil.isEmpty(str)) {
+		return splitByRegex(str,
-			return ListUtil.zero();
+			// 给定字符串或正则为empty，就不再需要解析pattern
-		}
+			(StrUtil.isEmpty(str) || StrUtil.isEmpty(separatorRegex)) ? null : PatternPool.get(separatorRegex),
-		if(StrUtil.isEmpty(separatorRegex)){
+			limit, isTrim, ignoreEmpty);
-			return ListUtil.of(str.toString());
-		}
-		final Pattern pattern = PatternPool.get(separatorRegex);
-		return splitByRegex(str, pattern, limit, isTrim, ignoreEmpty);
 	}
 
 	/**
-	 * 通过正则切分字符串<br>
+	 * 通过正则切分字符串，规则如下：
-	 * 如果为空字符串或者null 则返回空集合
+	 * <ul>
+	 *     <li>当提供的str为{@code null}时，返回new ArrayList(0)</li>
+	 *     <li>当提供的str为{@code ""}时，返回[""]</li>
+	 *     <li>当提供的separatorRegex为empty(null or "")时，返回[str]，即只有原串一个元素的数组</li>
+	 * </ul>
 	 *
 	 * @param str              字符串
 	 * @param separatorPattern 分隔符正则{@link Pattern}
@@ -292,11 +297,18 @@ public class SplitUtil {
 	 * @since 3.0.8
 	 */
 	public static List<String> splitByRegex(final CharSequence str, final Pattern separatorPattern, final int limit, final boolean isTrim, final boolean ignoreEmpty) {
-		if (StrUtil.isEmpty(str)) {
+		if (null == str) {
 			return ListUtil.zero();
 		}
+		if(0 == str.length()){
+			return ignoreEmpty ? ListUtil.zero() : ListUtil.of(StrUtil.EMPTY);
+		}
 		if(null == separatorPattern){
-			return ListUtil.of(str.toString());
+			final String result = str.toString();
+			if(StrUtil.isEmpty(result)){
+				return ignoreEmpty ? ListUtil.zero() : ListUtil.of(StrUtil.EMPTY);
+			}
+			return ListUtil.of(result);
 		}
 		final SplitIter splitIter = new SplitIter(str, new PatternFinder(separatorPattern), limit, ignoreEmpty);
 		return splitIter.toList(isTrim);

hutool-core/src/test/java/org/dromara/hutool/core/text/split/SplitUtilTest.java

@@ -14,10 +14,12 @@ package org.dromara.hutool.core.text.split;
 
 import org.dromara.hutool.core.collection.ListUtil;
 import org.dromara.hutool.core.lang.Console;
+import org.dromara.hutool.core.text.finder.PatternFinder;
 import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
 import java.util.List;
+import java.util.regex.Pattern;
 
 /**
  * {@link SplitUtil} 单元测试
@@ -120,9 +122,23 @@ public class SplitUtilTest {
 	@Test
 	void issue3421Test() {
 		List<String> strings = SplitUtil.splitByRegex("", "", 0, false, false);
-		Assertions.assertEquals(ListUtil.empty(), strings);
+		Assertions.assertEquals(ListUtil.of(""), strings);
 
 		strings = SplitUtil.splitByRegex("aaa", "", 0, false, false);
 		Assertions.assertEquals(ListUtil.of("aaa"), strings);
+
+		strings = SplitUtil.splitByRegex("", "aaa", 0, false, false);
+		Assertions.assertEquals(ListUtil.of(""), strings);
+
+		strings = SplitUtil.splitByRegex("", "", 0, false, true);
+		Assertions.assertEquals(ListUtil.of(), strings);
+	}
+
+	@Test
+	void issue3421Test2() {
+		// 测试在无前置判断时，是否死循环
+		final SplitIter splitIter = new SplitIter("", new PatternFinder(Pattern.compile("")), -1, false);
+		final List<String> list = splitIter.toList(false);
+		Assertions.assertEquals(ListUtil.of(""), list);
 	}
 }