Debug logging of RestTemplate/RestOperations on Spring Framework [Kotlin/Java]

This article shows debug logging of RestTemplate/RestOperations.

🐠 Set DEBUG to log level for RestTemplate

Set DEBUG to log level for RestTemplate with src/main/resources/application.yml.

logging:
  level:
    org.springframework.web.client.RestTemplate: DEBUG

🎳 Add logging process to Request/Response

This is a sample code for adding logging process to Request/Response by ClientHttpRequestInterceptor.

Implement ClientHttpRequestInterceptor Interface

This is a sample code of implemented ClientHttpRequestInterceptor interface. Please create app/util/RestTemplateLoggingInterceptor.kt and add the following code.

import org.slf4j.LoggerFactory
import org.springframework.http.HttpHeaders
import org.springframework.http.HttpRequest
import org.springframework.http.HttpStatus
import org.springframework.http.client.*
import org.springframework.lang.Nullable
import org.springframework.util.StreamUtils
import java.io.*
import java.io.ByteArrayInputStream
import java.io.IOException

class RestTemplateLoggingInterceptor : ClientHttpRequestInterceptor {
    private val log = LoggerFactory.getLogger(HelpDeskController::class.java)

    @Throws(IOException::class)
    override fun intercept(request: HttpRequest, body: ByteArray, execution: ClientHttpRequestExecution): ClientHttpResponse {
        // Show request object
        log.info("RestTemplate Request: URI={}, Headers={}, Body={}",
                request.uri,
                request.headers,
                String(body))

        // Fetch response
        val response = BufferingClientHttpResponseWrapper(execution.execute(request, body))

        // load response object
        val inputStringBuilder = StringBuilder()
        val bufferedReader = BufferedReader(InputStreamReader(response.body, "UTF-8"))
        var line: String? = bufferedReader.readLine()
        while (line != null) {
            inputStringBuilder.append(line)
            inputStringBuilder.append('\n')
            line = bufferedReader.readLine()
        }

        // Show response object
        log.info("RestTemplate Response: StatusCode={} {}, Headers={}, Body={}",
                response.statusCode,
                response.statusText,
                response.headers,
                inputStringBuilder.toString()
        )

        return response
    }

    private class BufferingClientHttpResponseWrapper internal constructor(private val response: ClientHttpResponse) : ClientHttpResponse {
        override fun getHeaders(): HttpHeaders {
            return this.response.headers
        }

        override fun getStatusCode(): HttpStatus {
            return this.response.statusCode
        }

        override fun getRawStatusCode(): Int {
            return this.response.rawStatusCode
        }

        override fun close() {
            this.response.close()
        }

        override fun getStatusText(): String {
            return this.response.statusText
        }

        override fun getBody(): InputStream {
            if (this.body == null) {
                this.body = StreamUtils.copyToByteArray(this.response.body)
            }

            return ByteArrayInputStream(this.body)
        }

        @Nullable
        private var body: ByteArray? = null
    }
}

Load the above Interceptor

Load the Interceptor created earlier.

import app.util.RestTemplateLoggingInterceptor
import org.springframework.context.annotation.Configuration
import org.springframework.boot.web.client.RestTemplateBuilder
import org.springframework.context.annotation.Bean
import org.springframework.web.client.RestOperations

@Configuration
class RestOperationsConfig {
    @Bean
    fun restOperations(): RestOperations {
        return RestTemplateBuilder().additionalInterceptors(RestTemplateLoggingInterceptor()).build()
    }
}

Logging sample

After then you can see request/response information in your log.

level:INFO  RestTemplate Request: URI=https://example.com, Headers={Accept=[text/plain, application/json, application/*+json, */*], Content-Length=[0]}, Body=
level:INFO  RestTemplate Response: StatusCode=200 OK, Headers={Accept-Ranges=[bytes], Cache-Control=[max-age=604800], Content-Type=[text/html], Date=[Wed, 09 May 2018 08:23:02 GMT], Expires=[Wed, 16 May 2018 08:23:02 GMT], Last-Modified=[Fri, 09 Aug 2013 23:54:35 GMT], Body=\n\n\n

🍮 References

• https://qiita.com/shotana/items/14972c681e5fc315deec

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