fix: inconsistent behavior when buffer http entity content with org.apache.http.entity.BufferedHttpEntity

Author: QizhengMo

arex-instrumentation/httpclient/arex-httpclient-apache-v4/src/main/java/io/arex/inst/httpclient/apache/common/ApacheHttpClientAdapter.java

@@ -140,7 +140,7 @@ public static void bufferRequestEntity(HttpEntityEnclosingRequest enclosingReque
             return;
         }
         try {
-            enclosingRequest.setEntity(new BufferedHttpEntity(enclosingRequest.getEntity()));
+            enclosingRequest.setEntity(new ArexBufferedHttpEntity(enclosingRequest.getEntity()));
         } catch (Exception ignore) {
             // ignore exception
         }
@@ -151,7 +151,7 @@ public static void bufferResponseEntity(HttpResponse response) {
             return;
         }
         try {
-            EntityUtils.updateEntity(response, new BufferedHttpEntity(response.getEntity()));
+            EntityUtils.updateEntity(response, new ArexBufferedHttpEntity(response.getEntity()));
         } catch (Exception e) {
             // ignore exception
         }

arex-instrumentation/httpclient/arex-httpclient-apache-v4/src/main/java/io/arex/inst/httpclient/apache/common/ArexBufferedHttpEntity.java

@@ -0,0 +1,39 @@
+package io.arex.inst.httpclient.apache.common;
+
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import org.apache.http.HttpEntity;
+import org.apache.http.entity.HttpEntityWrapper;
+
+/**
+ * This class only buffer the original HttpEntity content into a byte array, tt does not modify any
+ * behavior of the original HttpEntity.
+ * This class is known to have performance issues comparing to the original BufferedHttpEntity, but
+ * it provides consistent behavior with the original HttpEntity.
+ * @see org.apache.http.entity.BufferedHttpEntity
+ * @author: QizhengMo
+ * @date: 2025/3/12 15:35
+ */
+public class ArexBufferedHttpEntity extends HttpEntityWrapper {
+  private final byte[] buffer;
+
+  public ArexBufferedHttpEntity(HttpEntity wrappedEntity) throws IOException {
+    super(wrappedEntity);
+    final ByteArrayOutputStream out = new ByteArrayOutputStream();
+
+    // This class is only used in Arex Agent, so we are almost always the first to consume the content.
+    wrappedEntity.writeTo(out);
+    out.flush();
+    this.buffer = out.toByteArray();
+  }
+
+  /**
+   * Return a copy of the original content of the wrapped HttpEntity.
+   */
+  @Override
+  public InputStream getContent() throws IOException {
+    return new ByteArrayInputStream(buffer);
+  }
+}