Avoid reader on empty content to be shared by multiple requests

This commit avoids several instances of MockHttpServletRequest to
have a common reader for empty content as closing it will have an
unwanted side effect on the others.

Closes gh-32848

spring-test/src/main/java/org/springframework/mock/web/MockHttpServletRequest.java

@@ -100,9 +100,6 @@ public class MockHttpServletRequest implements HttpServletRequest {
 
  private static final TimeZone GMT = TimeZone.getTimeZone("GMT");
 
- private static final BufferedReader EMPTY_BUFFERED_READER =
- new BufferedReader(new StringReader(""));
-
  /**
  * Date formats as specified in the HTTP RFC.
  * @see <a href="https://tools.ietf.org/html/rfc7231#section-7.1.1.1">Section 7.1.1.1 of RFC 7231</a>
@@ -736,7 +733,7 @@ else if (this.inputStream != null) {
  this.reader = new BufferedReader(sourceReader);
  }
  else {
- this.reader = EMPTY_BUFFERED_READER;
+ this.reader = new BufferedReader(new StringReader(""));
  }
  return this.reader;
  }

spring-test/src/test/java/org/springframework/mock/web/MockHttpServletRequestTests.java

@@ -93,6 +93,17 @@ void readEmptyInputStreamWorksAcrossRequests() throws IOException {
  secondRequest.getInputStream().close();
  }
 
+ @Test // gh-32820
+ void readEmptyReaderWorksAcrossRequests() throws IOException {
+ MockHttpServletRequest firstRequest = new MockHttpServletRequest();
+ firstRequest.getReader().read(new char[256]);
+ firstRequest.getReader().close();
+
+ MockHttpServletRequest secondRequest = new MockHttpServletRequest();
+ secondRequest.getReader().read(new char[256]);
+ secondRequest.getReader().close();
+ }
+
  @Test
  void setContentAndGetReader() throws IOException {
  byte[] bytes = "body".getBytes(Charset.defaultCharset());