From ffd1e32dc6ba0c8731d5c09f5f9944c6eadb44e4 Mon Sep 17 00:00:00 2001
From: kssumin <201566@jnu.ac.kr>
Date: Thu, 3 Apr 2025 18:56:18 +0900
Subject: [PATCH] Fix inconsistent query parameter conversion for String param

Signed-off-by: kssumin <201566@jnu.ac.kr>
---
 .../bind/support/WebRequestDataBinder.java    | 35 +++++++++++++++++--
 .../support/WebRequestDataBinderTests.java    | 13 +++++++
 2 files changed, 46 insertions(+), 2 deletions(-)

diff --git a/spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.java b/spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.java
index 1e393922f304..590a89dc937c 100644
--- a/spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.java
+++ b/spring-web/src/main/java/org/springframework/web/bind/support/WebRequestDataBinder.java
@@ -21,7 +21,7 @@
 import jakarta.servlet.http.Part;
 import org.jspecify.annotations.Nullable;
 
-import org.springframework.beans.MutablePropertyValues;
+import org.springframework.beans.*;
 import org.springframework.core.MethodParameter;
 import org.springframework.http.HttpHeaders;
 import org.springframework.http.HttpMethod;
@@ -36,6 +36,10 @@
 import org.springframework.web.multipart.MultipartRequest;
 import org.springframework.web.multipart.support.StandardServletPartUtils;
 
+import java.beans.PropertyDescriptor;
+
+import static org.springframework.beans.BeanUtils.getPropertyDescriptor;
+
 /**
  * Special {@link org.springframework.validation.DataBinder} to perform data binding
  * from web request parameters to JavaBeans, including support for multipart files.
@@ -167,6 +171,34 @@ else if (StringUtils.startsWithIgnoreCase(
 		doBind(mpvs);
 	}
 
+	@Override
+	protected void doBind(MutablePropertyValues mpvs) {
+		Object target = getTarget();
+		if (target == null) {
+			super.doBind(mpvs);
+			return;
+		}
+
+		ConfigurablePropertyAccessor accessor = getPropertyAccessor();
+
+		for (PropertyValue pv : mpvs.getPropertyValues()) {
+			String name = pv.getName();
+			Object value = pv.getValue();
+			if (!name.endsWith("[]") && value instanceof String[] array && array.length > 0) {
+				try {
+					Class<?> propertyType = accessor.getPropertyType(name);
+					if (propertyType == null || !propertyType.isArray()) {
+						mpvs.add(name, new String[] { array[0] });
+					}
+				}
+				catch (InvalidPropertyException ex) {
+					mpvs.add(name, new String[] { array[0] });
+				}
+			}
+		}
+		super.doBind(mpvs);
+	}
+
 	/**
 	 * Treats errors as fatal.
 	 * <p>Use this method only if it's an error if the input isn't valid.
@@ -178,5 +210,4 @@ public void closeNoCatch() throws BindException {
 			throw new BindException(getBindingResult());
 		}
 	}
-
 }
diff --git a/spring-web/src/test/java/org/springframework/web/bind/support/WebRequestDataBinderTests.java b/spring-web/src/test/java/org/springframework/web/bind/support/WebRequestDataBinderTests.java
index cc89017f3624..466eda8a2ac1 100644
--- a/spring-web/src/test/java/org/springframework/web/bind/support/WebRequestDataBinderTests.java
+++ b/spring-web/src/test/java/org/springframework/web/bind/support/WebRequestDataBinderTests.java
@@ -40,6 +40,7 @@
 
 /**
  * @author Juergen Hoeller
+ * @author Sumin Kim
  */
 class WebRequestDataBinderTests {
 
@@ -124,6 +125,18 @@ public void testFieldWithEmptyArrayIndex() {
 		assertThat(target.getStringArray()).containsExactly("ONE", "TWO");
 	}
 
+	@Test
+	public void testFieldWithEmptyArrayIndex1() {
+		TestBean target = new TestBean();
+		WebRequestDataBinder binder = new WebRequestDataBinder(target);
+
+		MockHttpServletRequest request = new MockHttpServletRequest();
+		request.addParameter("touchy", "ONE");
+		request.addParameter("touchy", "TWO");
+		binder.bind(new ServletWebRequest(request));
+		assertThat(target.getTouchy()).isEqualTo("ONE");
+	}
+
 	@Test
 	void testFieldDefault() {
 		TestBean target = new TestBean();