问题描述

配置内容：

#logging
logging.config=classpath:/logback-lightsword.xml

报错日志：

java.lang.IllegalStateException: java.io.FileNotFoundException: class path resource [/logback-lightsword.xml] cannot be resolved to URL because it does not exist
    at org.springframework.boot.logging.LoggingApplicationListener.initializeSystem(LoggingApplicationListener.java:311)
    at org.springframework.boot.logging.LoggingApplicationListener.initialize(LoggingApplicationListener.java:272)
    at org.springframework.boot.logging.LoggingApplicationListener.onApplicationEnvironmentPreparedEvent(LoggingApplicationListener.java:235)
    at org.springframework.boot.logging.LoggingApplicationListener.onApplicationEvent(LoggingApplicationListener.java:208)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.invokeListener(SimpleApplicationEventMulticaster.java:167)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:139)
    at org.springframework.context.event.SimpleApplicationEventMulticaster.multicastEvent(SimpleApplicationEventMulticaster.java:122)
    at org.springframework.boot.context.event.EventPublishingRunListener.environmentPrepared(EventPublishingRunListener.java:72)
    at org.springframework.boot.SpringApplicationRunListeners.environmentPrepared(SpringApplicationRunListeners.java:54)
    at org.springframework.boot.SpringApplication.prepareEnvironment(SpringApplication.java:338)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:309)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1187)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1176)
    at com.springboot.in.action.LightSwordApplication$.delayedEndpoint$com$springboot$in$action$LightSwordApplication$1(LightSwordApplication.scala:6)
    at com.springboot.in.action.LightSwordApplication$delayedInit$body.apply(LightSwordApplication.scala:5)
    at scala.Function0.apply$mcV$sp(Function0.scala:34)
    at scala.Function0.apply$mcV$sp$(Function0.scala:34)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App.$anonfun$main$1$adapted(App.scala:76)
    at scala.App$$Lambda$5/1451043227.apply(Unknown Source)
    at scala.collection.immutable.List.foreach(List.scala:389)
    at scala.App.main(App.scala:76)
    at scala.App.main$(App.scala:74)
    at com.springboot.in.action.LightSwordApplication$.main(LightSwordApplication.scala:5)
    at com.springboot.in.action.LightSwordApplication.main(LightSwordApplication.scala)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org_scala_tools_maven_executions.MainHelper.runMain(MainHelper.java:161)
    at org_scala_tools_maven_executions.MainWithArgsInFile.main(MainWithArgsInFile.java:26)
Caused by: java.io.FileNotFoundException: class path resource [/logback-lightsword.xml] cannot be resolved to URL because it does not exist
    at org.springframework.util.ResourceUtils.getURL(ResourceUtils.java:135)
    at org.springframework.boot.logging.LoggingApplicationListener.initializeSystem(LoggingApplicationListener.java:303)
    ... 30 common frames omitted

原因分析

涉及报错的源码在org.springframework.util.ResourceUtils

    /**
     * Resolve the given resource location to a {@code java.net.URL}.
     * <p>Does not check whether the URL actually exists; simply returns
     * the URL that the given location would correspond to.
     * @param resourceLocation the resource location to resolve: either a
     * "classpath:" pseudo URL, a "file:" URL, or a plain file path
     * @return a corresponding URL object
     * @throws FileNotFoundException if the resource cannot be resolved to a URL
     */
    public static URL getURL(String resourceLocation) throws FileNotFoundException {
        Assert.notNull(resourceLocation, "Resource location must not be null");
        if (resourceLocation.startsWith(CLASSPATH_URL_PREFIX)) {
            String path = resourceLocation.substring(CLASSPATH_URL_PREFIX.length());
            ClassLoader cl = ClassUtils.getDefaultClassLoader();
            URL url = (cl != null ? cl.getResource(path) : ClassLoader.getSystemResource(path));
            if (url == null) {
                String description = "class path resource [" + path + "]";
                throw new FileNotFoundException(description +
                        " cannot be resolved to URL because it does not exist");
            }
            return url;
        }
        try {
            // try URL
            return new URL(resourceLocation);
        }
        catch (MalformedURLException ex) {
            // no URL -> treat as file path
            try {
                return new File(resourceLocation).toURI().toURL();
            }
            catch (MalformedURLException ex2) {
                throw new FileNotFoundException("Resource location [" + resourceLocation +
                        "] is neither a URL not a well-formed file path");
            }
        }
    }

通过源码，我们可以看出spring配置文件里这个locations是uri表示，也就是说我们写的logback-dev.xml是当前相对路径。

解决方案

spring配置文件里这个locations是相对路径，要访问classpath，要使用相对路径：

logging.config=classpath:logback-dev.xml