[java] Spring RestTemplate - how to enable full debugging/logging of requests/responses?

The trick of configuring your RestTemplate with a BufferingClientHttpRequestFactory doesn't work if you are using any ClientHttpRequestInterceptor, which you will if you are trying to log via interceptors. This is due to the way that InterceptingHttpAccessor (which RestTemplate subclasses) works.

Long story short... just use this class in place of RestTemplate (note this uses the SLF4J logging API, edit as needed):

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Map;

import javax.annotation.PostConstruct;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpRequest;
import org.springframework.http.HttpStatus;
import org.springframework.http.client.ClientHttpRequestExecution;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.http.client.ClientHttpResponse;
import org.springframework.web.client.RestTemplate;

/**
 * A {@link RestTemplate} that logs every request and response.
 */
public class LoggingRestTemplate extends RestTemplate {

    // Bleh, this class is not public
    private static final String RESPONSE_WRAPPER_CLASS = "org.springframework.http.client.BufferingClientHttpResponseWrapper";

    private Logger log = LoggerFactory.getLogger(this.getClass());

    private boolean hideAuthorizationHeaders = true;
    private Class<?> wrapperClass;
    private Constructor<?> wrapperConstructor;

    /**
     * Configure the logger to log requests and responses to.
     *
     * @param log log destination, or null to disable
     */
    public void setLogger(Logger log) {
        this.log = log;
    }

    /**
     * Configure the logger to log requests and responses to by name.
     *
     * @param name name of the log destination, or null to disable
     */
    public void setLoggerName(String name) {
        this.setLogger(name != null ? LoggerFactory.getLogger(name) : null);
    }

    /**
     * Configure whether to hide the contents of {@code Authorization} headers.
     *
     * <p>
     * Default true.
     *
     * @param hideAuthorizationHeaders true to hide, otherwise false
     */
    public void setHideAuthorizationHeaders(boolean hideAuthorizationHeaders) {
        this.hideAuthorizationHeaders = hideAuthorizationHeaders;
    }

    /**
     * Log a request.
     */
    protected void traceRequest(HttpRequest request, byte[] body) {
        this.log.debug("xmit: {} {}\n{}{}", request.getMethod(), request.getURI(), this.toString(request.getHeaders()),
          body != null && body.length > 0 ? "\n\n" + new String(body, StandardCharsets.UTF_8) : "");
    }

    /**
     * Log a response.
     */
    protected void traceResponse(ClientHttpResponse response) {
        final ByteArrayOutputStream bodyBuf = new ByteArrayOutputStream();
        HttpStatus statusCode = null;
        try {
            statusCode = response.getStatusCode();
        } catch (IOException e) {
            // ignore
        }
        String statusText = null;
        try {
            statusText = response.getStatusText();
        } catch (IOException e) {
            // ignore
        }
        try (final InputStream input = response.getBody()) {
            byte[] b = new byte[1024];
            int r;
            while ((r = input.read(b)) != -1)
                bodyBuf.write(b, 0, r);
        } catch (IOException e) {
            // ignore
        }
        this.log.debug("recv: {} {}\n{}{}", statusCode, statusText, this.toString(response.getHeaders()),
          bodyBuf.size() > 0 ? "\n\n" + new String(bodyBuf.toByteArray(), StandardCharsets.UTF_8) : "");
    }

    @PostConstruct
    private void addLoggingInterceptor() {
        this.getInterceptors().add(new ClientHttpRequestInterceptor() {
            @Override
            public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution)
              throws IOException {

                // Log request
                if (LoggingRestTemplate.this.log != null && LoggingRestTemplate.this.log.isDebugEnabled())
                    LoggingRestTemplate.this.traceRequest(request, body);

                // Perform request
                ClientHttpResponse response = execution.execute(request, body);

                // Log response
                if (LoggingRestTemplate.this.log != null && LoggingRestTemplate.this.log.isDebugEnabled()) {
                    final ClientHttpResponse bufferedResponse = LoggingRestTemplate.this.ensureBuffered(response);
                    if (bufferedResponse != null) {
                        LoggingRestTemplate.this.traceResponse(bufferedResponse);
                        response = bufferedResponse;
                    }
                }

                // Done
                return response;
            }
        });
    }

    private ClientHttpResponse ensureBuffered(ClientHttpResponse response) {
        try {
            if (this.wrapperClass == null)
                this.wrapperClass = Class.forName(RESPONSE_WRAPPER_CLASS, false, ClientHttpResponse.class.getClassLoader());
            if (!this.wrapperClass.isInstance(response)) {
                if (this.wrapperConstructor == null) {
                    this.wrapperConstructor = this.wrapperClass.getDeclaredConstructor(ClientHttpResponse.class);
                    this.wrapperConstructor.setAccessible(true);
                }
                response = (ClientHttpResponse)this.wrapperConstructor.newInstance(response);
            }
            return response;
        } catch (Exception e) {
            this.log.error("error creating {} instance: {}", RESPONSE_WRAPPER_CLASS, e);
            return null;
        }
    }

    private String toString(HttpHeaders headers) {
        final StringBuilder headerBuf = new StringBuilder();
        for (Map.Entry<String, List<String>> entry : headers.entrySet()) {
            if (headerBuf.length() > 0)
                headerBuf.append('\n');
            final String name = entry.getKey();
            for (String value : entry.getValue()) {
                if (this.hideAuthorizationHeaders && name.equalsIgnoreCase(HttpHeaders.AUTHORIZATION))
                    value = "[omitted]";
                headerBuf.append(name).append(": ").append(value);
            }
        }
        return headerBuf.toString();
    }
}

I agree it's silly that it takes this much work just to do this.