如何在 log4j2 中为自定义记录器编写单元测试

我创建了几个自定义记录器，其某些级别覆盖了 Log4J2 中的自定义记录器。我已按照指南进行操作http://logging.apache.org/log4j/2.x/manual/customloglevels.html.

我需要创建一些单元测试来验证事件是否在正确的自定义级别和配置上注册。

我很感激任何有关如何开始的提示。多谢。

您可以看到我在其中一项 JUnit 测试中所做的事情。

1- 创建一个自定义附加程序，在内存中保存消息列表。

package com.example.appender;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import lombok.Getter;
import org.apache.logging.log4j.core.Filter;
import org.apache.logging.log4j.core.Layout;
import org.apache.logging.log4j.core.LogEvent;
import org.apache.logging.log4j.core.appender.AbstractAppender;
import org.apache.logging.log4j.core.config.Property;
import org.apache.logging.log4j.core.config.plugins.Plugin;
import org.apache.logging.log4j.core.config.plugins.PluginAttribute;
import org.apache.logging.log4j.core.config.plugins.PluginElement;
import org.apache.logging.log4j.core.config.plugins.PluginFactory;
import org.apache.logging.log4j.core.layout.PatternLayout;

/**
 * @author carrad
 * 
 */
@Plugin(name = "TestAppender", category = "Core", elementType = "appender", printObject = true)
public class TestAppender extends AbstractAppender {

    @Getter
    private final List<LogEvent> messages = new ArrayList<>();

    protected TestAppender(String name, Filter filter, Layout<? extends Serializable> layout) {
        super(name, filter, layout, true, Property.EMPTY_ARRAY);
    }

    @Override
    public void append(LogEvent event) {
        messages.add(event);
    }

    @PluginFactory
    public static TestAppender createAppender(
            @PluginAttribute("name") String name,
            @PluginElement("Layout") Layout<? extends Serializable> layout,
            @PluginElement("Filter") final Filter filter,
            @PluginAttribute("otherAttribute") String otherAttribute
    ) {
        if (name == null) {
            LOGGER.error("No name provided for TestAppender");
            return null;
        }
        if (layout == null) {
            layout = PatternLayout.createDefaultLayout();
        }
        return new TestAppender(name, filter, layout);
    }
}

2-将附加器添加到log4j2-test.xml

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN" packages="com.example.appender">
    <Appenders>
        <Console name="Console" target="SYSTEM_OUT">
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </Console>
        <TestAppender name="TestAppender" >
            <PatternLayout pattern="%d{HH:mm:ss.SSS} [%t] %-5level %logger{36} - %msg%n" />
        </TestAppender> 
    </Appenders>
    <Loggers>
        <Logger name="com.example" level="All" />
        <Root>
            <AppenderRef ref="Console" level="All" />
            <AppenderRef ref="TestAppender" level="All" /> 
        </Root>
    </Loggers>
</Configuration>

3- 在 Junit 测试中获取对附加器的引用。

public class LoggingInterceptorTest {

    @Autowired  // Whatever component you want to test
    private InterceptedComponent helperComponent;

    private TestAppender appender;

    @Before
    public void setUp() {
        final LoggerContext ctx = (LoggerContext) LogManager.getContext(false);
        final Configuration config = ctx.getConfiguration();
        appender = (TestAppender) config.getAppenders().get("TestAppender");
    }

    @Test
    public void test_wrapping() {
        helperComponent.doStuff("437");
        Assert.assertEquals(appender.getMessages().size(), 2);
    }
}

在您的测试用例中，您可以检查写入的消息数或包含所需消息的列表，包括级别等元信息。