Enhance ContentResponseHandler to be fault-tolerant

This commit enhances the `ContentResponseHandler` class to be more fault-tolerant by handling responses with null or empty bodies without throwing exceptions. If the response was successful (a 2xx status code), the `Content` object is returned. If no response body exists, `Content.NO_CONTENT` is returned.

The implementation extends `ContentResponseHandler` and overrides its methods to handle the response entity and transform it into the actual response object. This is designed to be efficient and use minimal memory.

httpclient5-fluent/src/main/java/org/apache/hc/client5/http/fluent/ContentResponseHandler.java

@@ -28,7 +28,9 @@ package org.apache.hc.client5.http.fluent;
 
 import java.io.IOException;
 
+import org.apache.hc.client5.http.HttpResponseException;
 import org.apache.hc.client5.http.impl.classic.AbstractHttpClientResponseHandler;
+import org.apache.hc.core5.http.ClassicHttpResponse;
 import org.apache.hc.core5.http.ContentType;
 import org.apache.hc.core5.http.HttpEntity;
 import org.apache.hc.core5.http.io.entity.EntityUtils;
@@ -39,11 +41,16 @@ import org.apache.hc.core5.http.io.entity.EntityUtils;
  * to {@link Content} instances.
  *
  * @see Content
- *
  * @since 4.4
  */
 public class ContentResponseHandler extends AbstractHttpClientResponseHandler<Content> {
 
+
+    /**
+     * The maximum length of the exception message, to avoid excessive memory usage.
+     */
+    private static final int MAX_MESSAGE_LENGTH = 256;
+
     @Override
     public Content handleEntity(final HttpEntity entity) throws IOException {
         return entity != null ?
@@ -51,4 +58,26 @@ public class ContentResponseHandler extends AbstractHttpClientResponseHandler<Co
                 Content.NO_CONTENT;
     }
 
+    /**
+     * Handles a successful response (2xx status code) and returns the response entity as a {@link Content} object.
+     * If no response entity exists, {@link Content#NO_CONTENT} is returned.
+     *
+     * @param response the HTTP response.
+     * @return a {@link Content} object that encapsulates the response body, or {@link Content#NO_CONTENT} if the
+     * response body is {@code null} or has zero length.
+     * @throws HttpResponseException if the response was unsuccessful (a >= 300 status code).
+     * @throws IOException           if an I/O error occurs.
+     */
+    @Override
+    public Content handleResponse(final ClassicHttpResponse response) throws IOException {
+        final int statusCode = response.getCode();
+        final HttpEntity entity = response.getEntity();
+        final byte[] contentBytes = (entity != null) ? EntityUtils.toByteArray(entity, MAX_MESSAGE_LENGTH) : new byte[0];
+        final ContentType contentType = (entity != null && entity.getContentType() != null) ? ContentType.parse(entity.getContentType()) : ContentType.DEFAULT_BINARY;
+        final Content content = new Content(contentBytes, contentType);
+        if (statusCode >= 300) {
+            throw new HttpResponseException(statusCode, response.getReasonPhrase(), contentBytes, contentType);
+        }
+        return content;
+    }
 }

httpclient5/src/main/java/org/apache/hc/client5/http/HttpResponseException.java

@@ -26,6 +26,7 @@
  */
 package org.apache.hc.client5.http;
 
+import org.apache.hc.core5.http.ContentType;
 import org.apache.hc.core5.util.TextUtils;
 
 /**
@@ -39,14 +40,45 @@ public class HttpResponseException extends ClientProtocolException {
 
     private final int statusCode;
     private final String reasonPhrase;
+    private final byte[] contentBytes;
+    private final ContentType contentType;
 
+    /**
+     * Constructs a new instance of {@code HttpResponseException} with the given
+     * status code and reason phrase, and no content bytes or content type.
+     *
+     * @param statusCode   the HTTP status code
+     * @param reasonPhrase the reason phrase associated with the HTTP status code
+     */
     public HttpResponseException(final int statusCode, final String reasonPhrase) {
+        this(statusCode, reasonPhrase, null, null);
+    }
+
+    /**
+     * Constructs a new instance of {@code HttpResponseException} with the given
+     * status code, reason phrase, content bytes, and content type.
+     *
+     * @param statusCode   the HTTP status code
+     * @param reasonPhrase the reason phrase associated with the HTTP status code
+     * @param contentBytes the content bytes of the HTTP response
+     * @param contentType  the content type of the HTTP response
+     */
+    public HttpResponseException(final int statusCode, final String reasonPhrase, final byte[] contentBytes, final ContentType contentType) {
         super(String.format("status code: %d" +
-                (TextUtils.isBlank(reasonPhrase) ? "" : ", reason phrase: %s"), statusCode, reasonPhrase));
+                        (TextUtils.isBlank(reasonPhrase) ? "" : ", reason phrase: %s") +
+                        (contentBytes == null ? "" : ", content: %s"),
+                statusCode, reasonPhrase,
+                contentBytes == null || contentType == null || contentType.getCharset() == null ?
+                        null :
+                        new String(contentBytes, contentType.getCharset())));
+
         this.statusCode = statusCode;
         this.reasonPhrase = reasonPhrase;
+        this.contentBytes = contentBytes;
+        this.contentType = contentType;
     }
 
+
     public int getStatusCode() {
         return this.statusCode;
     }
@@ -55,4 +87,11 @@ public class HttpResponseException extends ClientProtocolException {
         return this.reasonPhrase;
     }
 
+    public byte[] getContentBytes() {
+        return contentBytes;
+    }
+
+    public ContentType getContentType() {
+        return contentType;
+    }
 }