在ERROR级别日志事件上使Logback抛出异常

Question

运行单元测试时,我想在记录ERROR级别消息的任何测试中失败.使用SLF4J/Logback实现此目的的最简单方法是什么？我想避免编写自己的ILoggerFactory实现.

我尝试编写自定义Appender,但我不能通过调用Appender的代码传播异常,Appender的所有异常都会被捕获.

Answer 1

关键是编写自定义附加程序。您没有说要使用哪个单元测试框架，但是对于JUnit，我需要做类似的事情（它比所有错误都要复杂一点，但基本上是相同的概念），并创建了一个JUnit @Rule，添加了我的appender ，追加程序将根据需要使测试失败。

我将此答案的代码放置在公共领域：

import ch.qos.logback.classic.Level;
import ch.qos.logback.classic.Logger;
import ch.qos.logback.classic.LoggerContext;
import ch.qos.logback.classic.spi.ILoggingEvent;
import ch.qos.logback.core.AppenderBase;
import org.junit.rules.ExternalResource;
import org.slf4j.LoggerFactory;
import static org.junit.Assert.fail;

/**
 * A JUnit {@link org.junit.Rule} which attaches itself to Logback, and fails the test if an error is logged.
 * Designed for use in some tests, as if the system would log an error, that indicates that something
 * went wrong, even though the error was correctly caught and logged.
 */
public class FailOnErrorLogged extends ExternalResource {

    private FailOnErrorAppender appender;

    @Override
    protected void before() throws Throwable {
        super.before();
        final LoggerContext loggerContext = (LoggerContext)(LoggerFactory.getILoggerFactory());
        final Logger rootLogger = (Logger)(LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME));
        appender = new FailOnErrorAppender();
        appender.setContext(loggerContext);
        appender.start();
        rootLogger.addAppender(appender);
    }

    @Override
    protected void after() {
        appender.stop();
        final Logger rootLogger = (Logger)(LoggerFactory.getLogger(Logger.ROOT_LOGGER_NAME));
        rootLogger.detachAppender(appender);
        super.after();
    }

    private static class FailOnErrorAppender extends AppenderBase<ILoggingEvent> {
        @Override
        protected void append(final ILoggingEvent eventObject) {
            if (eventObject.getLevel().isGreaterOrEqual(Level.ERROR)) {
                fail("Error logged: " + eventObject.getFormattedMessage());
            }
        }
    }
}

用法示例：

import org.junit.Rule;
import org.junit.Test;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class ExampleTest {
    private static final Logger log = LoggerFactory.getLogger(ExampleTest.class);

    @Rule
    public FailOnErrorLogged failOnErrorLogged = new FailOnErrorLogged();

    @Test
    public void testError() {
        log.error("Test Error");
    }

    @Test
    public void testInfo() {
        log.info("Test Info");
    }
}

testError方法失败，并且testInfo方法通过。如果测试调用的真实被测类也记录了错误，则其工作原理相同。