對於類型為StringUtils的方法isNullOrEmpty（String）未定義

Question

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import org.apache.log4j.MDC;
import java.util.UUID;

import org.springframework.util.StringUtils;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

/**
 * A webflow request interceptor injecting correlation id to the request context.
 */
public class TestController extends HandlerInterceptorAdapter {

    private static final String CORRELATION_ID_HEADER_NAME = "X-Correlation-Id";
    private static final String CORRELATION_ID_LOG_VAR_NAME = "correlationId";

    @Override
    public boolean preHandle(final HttpServletRequest request, final HttpServletResponse response,
                             final Object handler) throws Exception {
        final String correlationId = getCorrelationIdFromHeader(request);
        MDC.put(CORRELATION_ID_LOG_VAR_NAME, correlationId);
        return true;
    }

    @Override
    public void afterCompletion(final HttpServletRequest request, final HttpServletResponse response,
                             final Object handler, final Exception ex) throws Exception {
        MDC.remove(CORRELATION_ID_LOG_VAR_NAME);
    }

    private String getCorrelationIdFromHeader(final HttpServletRequest request) {
        String correlationId = request.getHeader(CORRELATION_ID_HEADER_NAME);
        ***if (StringUtils.isNullOrEmpty(correlationId)) {***
            correlationId = generateUniqueCorrelationId();
        }
        return correlationId;
    }

    private String generateUniqueCorrelationId() {
        return UUID.randomUUID().toString();
    }
}

我試圖運行此程序，但出現錯誤您能幫我嗎？ 我在記錄日志時正在學習相關ID，但找不到正確和良好的來源，然后我發現顯示此代碼的網站可以有人幫助：）

PS錯誤是方法isNullOrEmpty（String）對於類型StringUtils ..未定義，我在上面的代碼中給***的行

Answer 1

您正在使用org.springframework.util.StringUtils ，它具有isEmpty(value)方法。 但是，您可能需要Apache的Commons Lang ，它具有更完整的StringUtils。