BAEL-4840: Read Flux<DataBuffer> into a single InputStream (#12500)
Co-authored-by: Tapan Avasthi <tavasthi@Tapans-MacBook-Air.local>
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package com.baeldung.databuffer;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.core.io.buffer.DataBuffer;
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import org.springframework.core.io.buffer.DataBufferUtils;
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import org.springframework.web.reactive.function.BodyExtractors;
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import org.springframework.web.reactive.function.client.WebClient;
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import reactor.core.publisher.Flux;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.PipedInputStream;
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import java.io.PipedOutputStream;
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public class DataBufferToInputStream {
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private static final Logger logger = LoggerFactory.getLogger(DataBufferToInputStream.class);
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private static final String REQUEST_ENDPOINT = "https://gorest.co.in/public/v2/users";
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private static WebClient getWebClient() {
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WebClient.Builder webClientBuilder = WebClient.builder();
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return webClientBuilder.build();
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}
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public static InputStream getResponseAsInputStream(WebClient client, String url) throws IOException, InterruptedException {
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PipedOutputStream pipedOutputStream = new PipedOutputStream();
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PipedInputStream pipedInputStream = new PipedInputStream(1024 * 10);
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pipedInputStream.connect(pipedOutputStream);
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Flux<DataBuffer> body = client.get()
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.uri(url)
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.exchangeToFlux(clientResponse -> {
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return clientResponse.body(BodyExtractors.toDataBuffers());
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})
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.doOnError(error -> {
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logger.error("error occurred while reading body", error);
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})
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.doFinally(s -> {
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try {
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pipedOutputStream.close();
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} catch (IOException e) {
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throw new RuntimeException(e);
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}
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})
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.doOnCancel(() -> {
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logger.error("Get request is cancelled");
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});
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DataBufferUtils.write(body, pipedOutputStream)
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.log("Writing to output buffer")
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.subscribe();
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return pipedInputStream;
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}
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private static String readContentFromPipedInputStream(PipedInputStream stream) throws IOException {
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StringBuffer contentStringBuffer = new StringBuffer();
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try {
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Thread pipeReader = new Thread(() -> {
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try {
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contentStringBuffer.append(readContent(stream));
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} catch (IOException e) {
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throw new RuntimeException(e);
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}
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});
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pipeReader.start();
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pipeReader.join();
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} catch (InterruptedException e) {
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throw new RuntimeException(e);
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} finally {
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stream.close();
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}
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return String.valueOf(contentStringBuffer);
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}
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private static String readContent(InputStream stream) throws IOException {
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StringBuffer contentStringBuffer = new StringBuffer();
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byte[] tmp = new byte[stream.available()];
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int byteCount = stream.read(tmp, 0, tmp.length);
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logger.info(String.format("read %d bytes from the stream\n", byteCount));
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contentStringBuffer.append(new String(tmp));
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return String.valueOf(contentStringBuffer);
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}
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public static void main(String[] args) throws IOException, InterruptedException {
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WebClient webClient = getWebClient();
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InputStream inputStream = getResponseAsInputStream(webClient, REQUEST_ENDPOINT);
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Thread.sleep(3000);
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String content = readContentFromPipedInputStream((PipedInputStream) inputStream);
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logger.info("response content: \n{}", content.replace("}", "}\n"));
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}
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}
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@ -0,0 +1,77 @@
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package databuffer;
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import com.baeldung.databuffer.DataBufferToInputStream;
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import io.restassured.internal.util.IOUtils;
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import org.junit.jupiter.api.Test;
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import org.mockito.Mockito;
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import org.springframework.http.HttpStatus;
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import org.springframework.web.reactive.function.client.ClientResponse;
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import org.springframework.web.reactive.function.client.ExchangeFunction;
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import org.springframework.web.reactive.function.client.WebClient;
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import reactor.core.publisher.Mono;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.io.InputStream;
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import java.io.InputStreamReader;
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import java.util.stream.Collectors;
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import static org.junit.jupiter.api.Assertions.assertArrayEquals;
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class DataBufferToInputStreamUnitTest {
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private String getResponseStub() throws IOException {
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InputStream inputStream = null;
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BufferedReader reader = null;
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String content = null;
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try {
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inputStream = this.getClass()
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.getClassLoader()
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.getResourceAsStream("user-response.json");
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if (inputStream != null) {
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reader = new BufferedReader(new InputStreamReader(inputStream));
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content = reader.lines()
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.collect(Collectors.joining(System.lineSeparator()));
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}
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} catch (Exception ex) {
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throw new RuntimeException("exception caught while getting response stub");
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} finally {
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reader.close();
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inputStream.close();
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}
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return content;
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}
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private InputStream getResponseStubAsInputStream() {
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return this.getClass()
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.getClassLoader()
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.getResourceAsStream("user-response.json");
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}
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private WebClient getMockWebClient() throws IOException {
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String content = getResponseStub();
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ClientResponse clientResponse = ClientResponse.create(HttpStatus.OK)
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.header("Content-Type", "application/json")
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.body(content)
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.build();
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ExchangeFunction exchangeFunction = clientRequest -> Mono.just(clientResponse);
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WebClient.Builder webClientBuilder = WebClient.builder()
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.exchangeFunction(exchangeFunction);
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WebClient webClient = webClientBuilder.build();
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return webClient;
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}
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@Test
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public void testResponseAsInputStream() throws IOException, InterruptedException {
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String mockUrl = Mockito.anyString();
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WebClient mockWebClient = getMockWebClient();
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InputStream inputStream = DataBufferToInputStream.getResponseAsInputStream(mockWebClient, mockUrl);
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byte[] expectedBytes = IOUtils.toByteArray(getResponseStubAsInputStream());
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byte[] actualBytes = IOUtils.toByteArray(inputStream);
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assertArrayEquals(expectedBytes, actualBytes);
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}
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}
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@ -0,0 +1,72 @@
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[
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{
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"id": 2683,
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"name": "Maheswar Kocchar",
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"email": "maheswar_kocchar@kihn.info",
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"gender": "male",
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"status": "active"
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},
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{
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"id": 2680,
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"name": "Lakshminath Khan",
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"email": "lakshminath_khan@barrows-cormier.biz",
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"gender": "female",
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"status": "inactive"
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},
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{
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"id": 2679,
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"name": "Tarun Arora",
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"email": "tarun_arora@rolfson.net",
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"gender": "female",
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"status": "inactive"
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},
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{
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"id": 2678,
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"name": "Agnivesh Dubashi",
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"email": "dubashi_agnivesh@senger.name",
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"gender": "male",
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"status": "inactive"
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},
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{
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"id": 2677,
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"name": "Dhanu Gowda",
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"email": "gowda_dhanu@hayes.org",
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"gender": "male",
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"status": "active"
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},
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{
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"id": 2675,
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"name": "Harinakshi Pilla Jr.",
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"email": "pilla_jr_harinakshi@rutherford-monahan.com",
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"gender": "female",
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"status": "inactive"
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},
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{
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"id": 2673,
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"name": "Kalpana Prajapat",
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"email": "prajapat_kalpana@wilkinson-schaefer.net",
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"gender": "female",
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"status": "active"
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},
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{
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"id": 2672,
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"name": "Chakradhar Jha",
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"email": "jha_chakradhar@baumbach.info",
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"gender": "male",
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"status": "active"
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},
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{
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"id": 2670,
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"name": "Divaakar Deshpande Jr.",
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"email": "deshpande_jr_divaakar@mertz.info",
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"gender": "female",
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"status": "inactive"
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},
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{
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"id": 2669,
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"name": "Prasanna Mehra",
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"email": "prasanna_mehra@ruecker-larkin.name",
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"gender": "female",
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"status": "active"
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}
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]
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