java - 对于 StringUtils 类型，方法 isNullOrEmpty(String) 未定义

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();
    }
}

我试图运行这个程序，但错误来了，你能帮我吗？我正在学习有关日志记录的相关 ID，但找不到正确且良好的来源，然后我找到了显示此代码的网站，有人可以帮忙:)

PS 错误是 The method isNullOrEmpty(String) is undefined for the type StringUtils.. 在我在上面的代码中给出 *** 的那一行

Answer 1

您正在使用org.springframework.util.StringUtilswhich has a method isEmpty(value)。但是，您可能想要Apache 的 Commons Lang，它具有更完整的 StringUtils。