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Fix Slf4jLogger and JavaLogger returning unbuffered response when logging disabled #3172

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9f29c17
Fix Slf4jLogger and JavaLogger returning unbuffered response when log…
loadkrnis Jan 14, 2026
2dddbdc
Merge branch 'master' into issue/1336
loadkrnis Jan 16, 2026
916deff
Merge branch 'master' into issue/1336
loadkrnis Jan 19, 2026
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5 changes: 1 addition & 4 deletions core/src/main/java/feign/Logger.java
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Original file line number Diff line number Diff line change
Expand Up @@ -230,10 +230,7 @@ protected void logRequest(String configKey, Level logLevel, Request request) {
@Override
protected Response logAndRebufferResponse(
String configKey, Level logLevel, Response response, long elapsedTime) throws IOException {
if (logger.isLoggable(java.util.logging.Level.FINE)) {
return super.logAndRebufferResponse(configKey, logLevel, response, elapsedTime);
}
return response;
return super.logAndRebufferResponse(configKey, logLevel, response, elapsedTime);
}

@Override
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117 changes: 117 additions & 0 deletions core/src/test/java/feign/JavaLoggerTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,117 @@
/*
* Copyright © 2012 The Feign Authors (feign@commonhaus.dev)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package feign;

import feign.Logger.JavaLogger;
import feign.Request.HttpMethod;
import java.util.Collection;
import java.util.Collections;
import java.util.logging.Level;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

public class JavaLoggerTest {

private static final String CONFIG_KEY = "TestApi#testMethod()";
private java.util.logging.Logger julLogger;
private JavaLogger logger;

@BeforeEach
void setUp() {
julLogger = java.util.logging.Logger.getLogger(JavaLoggerTest.class.getName());
logger = new JavaLogger(JavaLoggerTest.class);
}

@Test
void rebuffersResponseBodyWhenJulLevelIsInfo() throws Exception {
// given
julLogger.setLevel(Level.INFO);
Response responseWithBody =
Response.builder()
.status(200)
.reason("OK")
.request(
Request.create(HttpMethod.GET, "/api", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body("{\"error\":\"test\"}", Util.UTF_8)
.build();

// when
Response result =
logger.logAndRebufferResponse(
CONFIG_KEY, feign.Logger.Level.HEADERS, responseWithBody, 273);

// then
String body1 = Util.toString(result.body().asReader(Util.UTF_8));
String body2 = Util.toString(result.body().asReader(Util.UTF_8));
assert body1.equals("{\"error\":\"test\"}") : "First read should return body content";
assert body2.equals("{\"error\":\"test\"}") : "Second read should return same body content";
}

@Test
void rebuffersResponseBodyWhenJulLevelIsWarning() throws Exception {
// given
julLogger.setLevel(Level.WARNING);
Response responseWithBody =
Response.builder()
.status(500)
.reason("Internal Server Error")
.request(
Request.create(HttpMethod.GET, "/api", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body("{\"message\":\"error details\"}", Util.UTF_8)
.build();

// when
Response result =
logger.logAndRebufferResponse(CONFIG_KEY, feign.Logger.Level.FULL, responseWithBody, 100);

// then
byte[] bodyBytes = Util.toByteArray(result.body().asInputStream());
assert new String(bodyBytes, Util.UTF_8).equals("{\"message\":\"error details\"}")
: "Body should be readable after rebuffering";
}

@Test
void responseBodyReadableMultipleTimesForErrorDecoder() throws Exception {
// given
julLogger.setLevel(Level.SEVERE);
String originalBody = "{\"errorCode\":\"E001\",\"message\":\"Validation failed\"}";
Response responseWithBody =
Response.builder()
.status(400)
.reason("Bad Request")
.request(
Request.create(
HttpMethod.POST, "/api/submit", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body(originalBody, Util.UTF_8)
.build();

// when
Response result =
logger.logAndRebufferResponse(
CONFIG_KEY, feign.Logger.Level.HEADERS, responseWithBody, 150);

// then
String read1 = Util.toString(result.body().asReader(Util.UTF_8));
String read2 = Util.toString(result.body().asReader(Util.UTF_8));
String read3 = Util.toString(result.body().asReader(Util.UTF_8));
assert read1.equals(originalBody) : "First read should match original body";
assert read2.equals(originalBody) : "Second read should match original body";
assert read3.equals(originalBody) : "Third read should match original body";
}
}
207 changes: 207 additions & 0 deletions core/src/test/java/feign/LoggerRebufferTest.java
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Original file line number Diff line number Diff line change
@@ -0,0 +1,207 @@
/*
* Copyright © 2012 The Feign Authors (feign@commonhaus.dev)
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package feign;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertNull;

import feign.Request.HttpMethod;
import java.util.Collection;
import java.util.Collections;
import org.junit.jupiter.api.Test;

public class LoggerRebufferTest {

private static final String CONFIG_KEY = "TestApi#testMethod()";

private static class TestLogger extends Logger {
@Override
protected void log(String configKey, String format, Object... args) {}
}

@Test
void headersLevelRebuffersResponseBody() throws Exception {
// given
TestLogger logger = new TestLogger();
String originalBody = "{\"status\":\"error\",\"message\":\"Not found\"}";
Response response =
Response.builder()
.status(404)
.reason("Not Found")
.request(
Request.create(
HttpMethod.GET, "/api/resource", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body(originalBody, Util.UTF_8)
.build();

// when
Response result =
logger.logAndRebufferResponse(CONFIG_KEY, Logger.Level.HEADERS, response, 100);

// then
String read1 = Util.toString(result.body().asReader(Util.UTF_8));
String read2 = Util.toString(result.body().asReader(Util.UTF_8));
assertEquals(originalBody, read1, "First read should return original body");
assertEquals(originalBody, read2, "Second read should return same body (rebuffered)");
}

@Test
void basicLevelDoesNotRebufferResponseBody() throws Exception {
// given
TestLogger logger = new TestLogger();
String originalBody = "{\"status\":\"ok\"}";
Response response =
Response.builder()
.status(200)
.reason("OK")
.request(
Request.create(
HttpMethod.GET, "/api/resource", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body(originalBody, Util.UTF_8)
.build();

// when
Response result = logger.logAndRebufferResponse(CONFIG_KEY, Logger.Level.BASIC, response, 100);

// then
String read1 = Util.toString(result.body().asReader(Util.UTF_8));
assertEquals(originalBody, read1, "First read should return original body");
}

@Test
void fullLevelRebuffersResponseBody() throws Exception {
// given
TestLogger logger = new TestLogger();
String originalBody = "{\"data\":{\"id\":123,\"name\":\"test\"}}";
Response response =
Response.builder()
.status(200)
.reason("OK")
.request(
Request.create(
HttpMethod.POST, "/api/create", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body(originalBody, Util.UTF_8)
.build();

// when
Response result = logger.logAndRebufferResponse(CONFIG_KEY, Logger.Level.FULL, response, 50);

// then
String read1 = Util.toString(result.body().asReader(Util.UTF_8));
String read2 = Util.toString(result.body().asReader(Util.UTF_8));
String read3 = Util.toString(result.body().asReader(Util.UTF_8));
assertEquals(originalBody, read1, "First read should return original body");
assertEquals(originalBody, read2, "Second read should return same body");
assertEquals(originalBody, read3, "Third read should return same body");
}

@Test
void noneLevelDoesNotRebufferResponseBody() throws Exception {
// given
TestLogger logger = new TestLogger();
String originalBody = "{\"result\":\"success\"}";
Response response =
Response.builder()
.status(200)
.reason("OK")
.request(
Request.create(
HttpMethod.GET, "/api/status", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body(originalBody, Util.UTF_8)
.build();

// When
Response result = logger.logAndRebufferResponse(CONFIG_KEY, Logger.Level.NONE, response, 100);

// then
String read1 = Util.toString(result.body().asReader(Util.UTF_8));
assertEquals(originalBody, read1, "Body should be readable");
}

@Test
void http204DoesNotRebufferEvenAtHeadersLevel() throws Exception {
// given
TestLogger logger = new TestLogger();
Response response =
Response.builder()
.status(204)
.reason("No Content")
.request(
Request.create(
HttpMethod.DELETE, "/api/resource/1", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body("should be ignored", Util.UTF_8)
.build();

// when
Response result =
logger.logAndRebufferResponse(CONFIG_KEY, Logger.Level.HEADERS, response, 100);

// then
assertNotNull(result.body(), "Response body object should exist");
}

@Test
void http205DoesNotRebufferEvenAtHeadersLevel() throws Exception {
// given
TestLogger logger = new TestLogger();
Response response =
Response.builder()
.status(205)
.reason("Reset Content")
.request(
Request.create(
HttpMethod.POST, "/api/form", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body("should be ignored", Util.UTF_8)
.build();

// when
Response result =
logger.logAndRebufferResponse(CONFIG_KEY, Logger.Level.HEADERS, response, 100);

// then
assertNotNull(result.body(), "Response body object should exist");
}

@Test
void nullBodyHandledCorrectlyAtHeadersLevel() throws Exception {
// given
TestLogger logger = new TestLogger();
Response response =
Response.builder()
.status(200)
.reason("OK")
.request(
Request.create(
HttpMethod.HEAD, "/api/resource", Collections.emptyMap(), null, Util.UTF_8))
.headers(Collections.<String, Collection<String>>emptyMap())
.body((byte[]) null)
.build();

// when
Response result =
logger.logAndRebufferResponse(CONFIG_KEY, Logger.Level.HEADERS, response, 100);

// then
assertNull(result.body(), "Body should remain null");
}
}
5 changes: 1 addition & 4 deletions slf4j/src/main/java/feign/slf4j/Slf4jLogger.java
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Original file line number Diff line number Diff line change
Expand Up @@ -56,10 +56,7 @@ protected void logRequest(String configKey, Level logLevel, Request request) {
@Override
protected Response logAndRebufferResponse(
String configKey, Level logLevel, Response response, long elapsedTime) throws IOException {
if (logger.isDebugEnabled()) {
return super.logAndRebufferResponse(configKey, logLevel, response, elapsedTime);
}
return response;
return super.logAndRebufferResponse(configKey, logLevel, response, elapsedTime);
}

@Override
Expand Down
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