深入解析Java -jar运行JAR包时报org.yaml.snakeyaml.error.YAMLException异常

深入解析Java -jar运行JAR包时报org.yaml.snakeyaml.error.YAMLException异常

在日常的Java开发中，我们经常会打包我们的应用程序为JAR文件，然后通过命令行使用java -jar命令来运行它。然而，有时候我们会遇到一些异常，比如org.yaml.snakeyaml.error.YAMLException。今天我们就来深入解析这个异常，并提供一些解决方案。

什么是YAMLException？

YAMLException是由SnakeYAML库抛出的异常。SnakeYAML是一个用于解析和生成YAML格式数据的Java库。YAML（YAML Ain't Markup Language）是一种简洁而强大的数据序列化格式，广泛应用于配置文件中。

当我们在Java应用中使用YAML配置文件时，如果YAML文件格式不正确，或者在解析过程中出现问题，就会抛出YAMLException。

典型场景

假设我们有一个Spring Boot应用程序，使用了YAML格式的配置文件application.yml。我们将应用程序打包为JAR文件，并尝试通过命令行运行它：

java -jar myapp.jar

结果却抛出了如下异常：

Exception in thread "main" org.yaml.snakeyaml.error.YAMLException: java.nio.charset.MalformedInputException: Input length = 1
    at org.yaml.snakeyaml.reader.StreamReader.update(StreamReader.java:218)
    at org.yaml.snakeyaml.reader.StreamReader.ensureEnoughData(StreamReader.java:176)
    at org.yaml.snakeyaml.reader.StreamReader.ensureEnoughData(StreamReader.java:171)
    at org.yaml.snakeyaml.reader.StreamReader.peek(StreamReader.java:126)
    at org.yaml.snakeyaml.scanner.ScannerImpl.scanToNextToken(ScannerImpl.java:1177)
    at org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:287)
    at org.yaml.snakeyaml.scanner.ScannerImpl.checkToken(ScannerImpl.java:227)
    at org.yaml.snakeyaml.parser.ParserImpl$ParseImplicitDocumentStart.produce(ParserImpl.java:195)
    at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:158)
    at org.yaml.snakeyaml.parser.ParserImpl.getEvent(ParserImpl.java:168)
    at org.yaml.snakeyaml.composer.Composer.getSingleNode(Composer.java:144)
    at org.yaml.snakeyaml.constructor.BaseConstructor.getSingleData(BaseConstructor.java:141)
    at org.yaml.snakeyaml.Yaml.loadFromReader(Yaml.java:525)
    at org.yaml.snakeyaml.Yaml.load(Yaml.java:438)
    at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:200)
    at org.springframework.beans.factory.config.YamlProcessor.process(YamlProcessor.java:164)
    at org.springframework.beans.factory.config.YamlMapFactoryBean.createMap(YamlMapFactoryBean.java:183)
    at org.springframework.beans.factory.config.YamlMapFactoryBean.createInstance(YamlMapFactoryBean.java:145)
    at org.springframework.beans.factory.config.YamlMapFactoryBean.createInstance(YamlMapFactoryBean.java:37)
    at org.springframework.beans.factory.config.AbstractFactoryBean.afterPropertiesSet(AbstractFactoryBean.java:141)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1845)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1782)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.config.DependencyDescriptor.resolveCandidate(DependencyDescriptor.java:276)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1307)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1227)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.resolveFieldValue(AutowiredAnnotationBeanPostProcessor.java:722)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:692)
    at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:119)
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessProperties(AutowiredAnnotationBeanPostProcessor.java:399)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.populateBean(AbstractAutowireCapableBeanFactory.java:1420)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:594)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:516)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:324)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:322)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1109)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:869)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:144)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:730)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:302)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1290)
    at com.example.demo.DemoApplication.main(DemoApplication.java:10)
Caused by: java.nio.charset.MalformedInputException: Input length = 1
    at java.base/java.nio.charset.CoderResult.throwException(CoderResult.java:274)
    at java.base/sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:355)
    at java.base/sun.nio.cs.StreamDecoder.read(StreamDecoder.java:188)
    at java.base/java.io.InputStreamReader.read(InputStreamReader.java:181)
    at org.yaml.snakeyaml.reader.UnicodeReader.read(UnicodeReader.java:125)
    at org.yaml.snakeyaml.reader.StreamReader.update(StreamReader.java:196)
    ... 54 more

分析异常

从异常堆栈中，我们可以看到YAMLException是由于java.nio.charset.MalformedInputException引起的。这通常意味着我们的YAML文件中包含了非法的字符，或者文件编码不正确。

解决方案

1. 检查YAML文件格式

   首先，我们需要确保我们的YAML文件格式正确。YAML文件应该使用空格缩进，而不是Tab键。确保每一行的缩进级别一致。

   server:
     port: 8080
   spring:
     datasource:
       url: jdbc:mysql://localhost:3306/mydb
       username: root
       password: password
   

2. 检查文件编码

   确保我们的YAML文件使用UTF-8编码保存。有时候，文件可能会被错误地保存为其他编码格式，导致解析错误。

   在IDE中，我们可以右键点击文件，选择“File Encoding”并确保选择UTF-8。

3. 使用正确的YAML解析器

   确保我们在项目中使用的是最新版本的SnakeYAML库。可以在pom.xml中添加或更新依赖：

   <dependency>
       <groupId>org.yaml</groupId>
       <artifactId>snakeyaml</artifactId>
       <version>1.30</version>
   </dependency>
   

4. 调试和日志

   如果以上方法都无法解决问题，可以在代码中添加一些调试和日志信息，帮助我们定位问题。例如：

   import org.yaml.snakeyaml.Yaml;
   import java.io.InputStream;
   import java.nio.charset.StandardCharsets;
   import java.nio.file.Files;
   import java.nio.file.Paths;
   
   public class YamlLoader {
       public static void main(String[] args) {
           try {
               InputStream inputStream = Files.newInputStream(Paths.get("application.yml"));
               Yaml yaml = new Yaml();
               Object data = yaml.load(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
               System.out.println(data);
           } catch (Exception e) {
               e.printStackTrace();
           }
       }
   }
   

   通过这种方式，我们可以更清晰地看到YAML文件的加载过程，并捕获具体的异常信息。

总结

org.yaml.snakeyaml.error.YAMLException异常通常是由于YAML文件格式不正确或文件编码问题引起的。通过检查文件格式、确保文件编码为UTF-8、使用最新版本的SnakeYAML库以及添加调试和日志信息，我们可以有效地解决这个问题。

希望这篇文章能帮助你更好地理解和解决YAMLException异常。如果你有任何问题或建议，欢迎在评论区留言。Happy coding!

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