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KarstenSchnitterKarstenSchnitter
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Add Correlation Id Filter
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‎cf-java-logging-support-servlet/src/main/java/com/sap/hcp/cf/logging/servlet/filter/CorrelationIdFilter.java‎

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package com.sap.hcp.cf.logging.servlet.filter;
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import java.util.UUID;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import com.sap.hcp.cf.logging.common.Defaults;
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import com.sap.hcp.cf.logging.common.LogContext;
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import com.sap.hcp.cf.logging.common.request.HttpHeader;
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import com.sap.hcp.cf.logging.common.request.HttpHeaders;
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/**
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* The {@link CorrelationIdFilter} extracts a correlation id according to
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* {@link HttpHeaders#CORRELATION_ID}. It will generate a random uuid, if no
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* correlation id is found in the headers. In any case the correlation id is set
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* as a response header, if possible
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*/
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public class CorrelationIdFilter extends AbstractLoggingFilter {
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private static final Logger LOG = LoggerFactory.getLogger(CorrelationIdFilter.class);
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private HttpHeader correlationHeader;
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public CorrelationIdFilter() {
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this(HttpHeaders.CORRELATION_ID);
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}
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public CorrelationIdFilter(HttpHeader correlationHeader) {
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this.correlationHeader = correlationHeader;
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}
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@Override
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protected void preProcess(HttpServletRequest request, HttpServletResponse response) {
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String correlationId = determineCorrelationId(request);
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LogContext.add(correlationHeader.getField(), correlationId);
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addCorrelationIdHeader(response, correlationId);
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}
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private String determineCorrelationId(HttpServletRequest request) {
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String correlationId = HttpHeaderUtilities.getHeaderValue(request, correlationHeader);
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if (correlationId == null || correlationId.isEmpty() || correlationId.equals(Defaults.UNKNOWN)) {
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correlationId = String.valueOf(UUID.randomUUID());
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LOG.debug("Generated new correlation-id <{}>", correlationId);
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}
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return correlationId;
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}
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private void addCorrelationIdHeader(HttpServletResponse response, String correlationId) {
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if (!response.isCommitted() && response.getHeader(correlationHeader.getName()) == null) {
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response.setHeader(correlationHeader.getName(), correlationId);
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}
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}
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@Override
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protected void postProcess(HttpServletRequest request, HttpServletResponse response) {
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LogContext.remove(correlationHeader.getField());
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}
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}

‎cf-java-logging-support-servlet/src/test/java/com/sap/hcp/cf/logging/servlet/filter/CorrelationIdFilterTest.java‎

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package com.sap.hcp.cf.logging.servlet.filter;
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import static org.hamcrest.MatcherAssert.assertThat;
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import static org.hamcrest.Matchers.equalTo;
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import static org.hamcrest.Matchers.is;
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import static org.hamcrest.Matchers.not;
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import static org.hamcrest.Matchers.nullValue;
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import static org.mockito.Mockito.doAnswer;
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import static org.mockito.Mockito.verify;
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import static org.mockito.Mockito.verifyNoMoreInteractions;
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import static org.mockito.Mockito.when;
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import java.util.Collections;
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import java.util.List;
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import java.util.UUID;
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import javax.servlet.FilterChain;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import org.junit.Before;
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import org.junit.Test;
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import org.junit.runner.RunWith;
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import org.mockito.Mock;
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import org.mockito.invocation.InvocationOnMock;
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import org.mockito.runners.MockitoJUnitRunner;
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import org.mockito.stubbing.Answer;
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import org.slf4j.MDC;
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import com.sap.hcp.cf.logging.common.request.HttpHeader;
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import com.sap.hcp.cf.logging.common.request.HttpHeaders;
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@RunWith(MockitoJUnitRunner.class)
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public class CorrelationIdFilterTest {
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private static String KNOWN_CORRELATION_ID = UUID.randomUUID().toString();
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@Mock
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private HttpServletRequest request;
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@Mock
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private HttpServletResponse response;
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@Mock
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private FilterChain chain;
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private CorrelationIdFromMDCExtractor mdcExtractor;
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@Before
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public void setUp() throws Exception {
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mdcExtractor = new CorrelationIdFromMDCExtractor(HttpHeaders.CORRELATION_ID.getField());
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doAnswer(mdcExtractor).when(chain).doFilter(request, response);
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}
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@Test
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public void addsKnownCorrelationIdToMDC() throws Exception {
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when(request.getHeader(HttpHeaders.CORRELATION_ID.getName())).thenReturn(KNOWN_CORRELATION_ID);
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new CorrelationIdFilter().doFilter(request, response, chain);
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assertThat(mdcExtractor.getCorrelationId(), is(equalTo(KNOWN_CORRELATION_ID)));
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}
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@Test
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public void addsGeneratedCorrelationIdToMDC() throws Exception {
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new CorrelationIdFilter().doFilter(request, response, chain);
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assertThat(mdcExtractor.getCorrelationId(), is(not(nullValue())));
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assertThat(mdcExtractor.getCorrelationId(), is(not(equalTo(KNOWN_CORRELATION_ID))));
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}
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@Test
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public void removesCorrelationIdAfterFiltering() throws Exception {
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new CorrelationIdFilter().doFilter(request, response, chain);
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assertThat(MDC.get(HttpHeaders.CORRELATION_ID.getField()), is(nullValue()));
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}
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@Test
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public void addsKnownCorrelationIdAsResponseHeader() throws Exception {
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when(request.getHeader(HttpHeaders.CORRELATION_ID.getName())).thenReturn(KNOWN_CORRELATION_ID);
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new CorrelationIdFilter().doFilter(request, response, chain);
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verify(response).setHeader(HttpHeaders.CORRELATION_ID.getName(), KNOWN_CORRELATION_ID);
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}
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@Test
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public void doesNotAddCorrelationIdToCommittedResponse() throws Exception {
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when(response.isCommitted()).thenReturn(true);
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new CorrelationIdFilter().doFilter(request, response, chain);
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verify(response).isCommitted();
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verifyNoMoreInteractions(response);
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}
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@Test
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public void doesNotOverwriteCorrelationIdInResponse() throws Exception {
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when(response.isCommitted()).thenReturn(false);
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when(response.getHeader(HttpHeaders.CORRELATION_ID.getName())).thenReturn("preexisting-correlation-id");
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new CorrelationIdFilter().doFilter(request, response, chain);
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verify(response).isCommitted();
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verify(response).getHeader(HttpHeaders.CORRELATION_ID.getName());
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verifyNoMoreInteractions(response);
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}
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@Test
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public void usesCustomHeader() throws Exception {
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HttpHeader myHeader = new HttpHeader() {
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@Override
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public boolean isPropagated() {
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return true;
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}
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@Override
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public String getName() {
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return "my-header";
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}
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@Override
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public String getFieldValue() {
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return null;
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}
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@Override
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public String getField() {
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return "my-field";
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}
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@Override
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public List<HttpHeader> getAliases() {
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return Collections.emptyList();
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}
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};
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when(request.getHeader("my-header")).thenReturn(KNOWN_CORRELATION_ID);
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CorrelationIdFromMDCExtractor myMdcExtractor = new CorrelationIdFromMDCExtractor("my-field");
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doAnswer(myMdcExtractor).when(chain).doFilter(request, response);
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new CorrelationIdFilter(myHeader).doFilter(request, response, chain);
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assertThat(myMdcExtractor.getCorrelationId(), is(equalTo(KNOWN_CORRELATION_ID)));
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verify(response).setHeader("my-header", KNOWN_CORRELATION_ID);
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}
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private static class CorrelationIdFromMDCExtractor implements Answer<Void> {
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private String correlationId;
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private String field;
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private CorrelationIdFromMDCExtractor(String field) {
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this.field = field;
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}
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public String getCorrelationId() {
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return correlationId;
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}
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@Override
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public Void answer(InvocationOnMock invocation) throws Throwable {
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correlationId = MDC.get(field);
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return null;
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}
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}
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}

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