作为 jar 运行时找不到类路径资源

Question

在 Spring Boot 1.1.5 和 1.1.6 中都有这个问题 - 我正在使用 @Value 注释加载类路径资源，当我从 STS（3.6.0，Windows）中运行应用程序时，它工作得很好.但是，当我运行 mvn 包然后尝试运行 jar 时，我得到 FileNotFound 异常。

资源 message.txt 位于 src/main/resources 中。我检查了 jar 并验证它在顶层（与 application.properties 相同的级别）包含文件“message.txt”。

这是应用程序：

@Configuration
@ComponentScan
@EnableAutoConfiguration
public class Application implements CommandLineRunner {

    private static final Logger logger = Logger.getLogger(Application.class);

    @Value("${message.file}")
    private Resource messageResource;

    public static void main(String[] args) {
        SpringApplication.run(Application.class, args);
    }

    @Override
    public void run(String... arg0) throws Exception {
        // both of these work when running as Spring boot app from STS, but
        // fail after mvn package, and then running as java -jar
        testResource(new ClassPathResource("message.txt"));
        testResource(this.messageResource);
    }

    private void testResource(Resource resource) {
        try {
            resource.getFile();
            logger.debug("Found the resource " + resource.getFilename());
        } catch (IOException ex) {
            logger.error(ex.toString());
        }
    }
}

例外：

c:\Users\glyoder\Documents\workspace-sts-3.5.1.RELEASE\classpath-resource-proble
m\target>java -jar demo-0.0.1-SNAPSHOT.jar

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v1.1.5.RELEASE)

2014-09-16 08:46:34.635  INFO 5976 --- [           main] demo.Application
                  : Starting Application on 8W59XV1 with PID 5976 (C:\Users\glyo
der\Documents\workspace-sts-3.5.1.RELEASE\classpath-resource-problem\target\demo
-0.0.1-SNAPSHOT.jar started by glyoder in c:\Users\glyoder\Documents\workspace-s
ts-3.5.1.RELEASE\classpath-resource-problem\target)
2014-09-16 08:46:34.640 DEBUG 5976 --- [           main] demo.Application
                  : Running with Spring Boot v1.1.5.RELEASE, Spring v4.0.6.RELEA
SE
2014-09-16 08:46:34.681  INFO 5976 --- [           main] s.c.a.AnnotationConfigA
pplicationContext : Refreshing org.springframework.context.annotation.Annotation
ConfigApplicationContext@1c77b086: startup date [Tue Sep 16 08:46:34 EDT 2014];
root of context hierarchy
2014-09-16 08:46:35.196  INFO 5976 --- [           main] o.s.j.e.a.AnnotationMBe
anExporter        : Registering beans for JMX exposure on startup
2014-09-16 08:46:35.210 ERROR 5976 --- [           main] demo.Application
                  : java.io.FileNotFoundException: class path resource [message.
txt] cannot be resolved to absolute file path because it does not reside in the
file system: jar:file:/C:/Users/glyoder/Documents/workspace-sts-3.5.1.RELEASE/cl
asspath-resource-problem/target/demo-0.0.1-SNAPSHOT.jar!/message.txt
2014-09-16 08:46:35.211 ERROR 5976 --- [           main] demo.Application
                  : java.io.FileNotFoundException: class path resource [message.
txt] cannot be resolved to absolute file path because it does not reside in the
file system: jar:file:/C:/Users/glyoder/Documents/workspace-sts-3.5.1.RELEASE/cl
asspath-resource-problem/target/demo-0.0.1-SNAPSHOT.jar!/message.txt
2014-09-16 08:46:35.215  INFO 5976 --- [           main] demo.Application
                  : Started Application in 0.965 seconds (JVM running for 1.435)

2014-09-16 08:46:35.217  INFO 5976 --- [       Thread-2] s.c.a.AnnotationConfigA
pplicationContext : Closing org.springframework.context.annotation.AnnotationCon
figApplicationContext@1c77b086: startup date [Tue Sep 16 08:46:34 EDT 2014]; roo
t of context hierarchy
2014-09-16 08:46:35.218  INFO 5976 --- [       Thread-2] o.s.j.e.a.AnnotationMBe
anExporter        : Unregistering JMX-exposed beans on shutdown

Answer 1

resource.getFile() 期望资源本身在文件系统上可用，即它不能嵌套在 jar 文件中。这就是为什么当您在 STS（Spring Tool Suite）中运行您的应用程序时它可以工作，但一旦您构建了应用程序并从可执行 jar 运行它就不能工作。我建议不要使用getFile() 来访问资源的内容，而是使用getInputStream()。这将允许您阅读资源的内容，无论它位于何处。

Answer 2

如果您使用的是 Spring 框架，那么使用 Spring framework's FileCopyUtils 将 ClassPathResource 读入 String 非常简单：

String data = "";
ClassPathResource cpr = new ClassPathResource("static/file.txt");
try {
    byte[] bdata = FileCopyUtils.copyToByteArray(cpr.getInputStream());
    data = new String(bdata, StandardCharsets.UTF_8);
} catch (IOException e) {
    LOG.warn("IOException", e);
}

Answer 3

如果要使用文件：

ClassPathResource classPathResource = new ClassPathResource("static/something.txt");

InputStream inputStream = classPathResource.getInputStream();
File somethingFile = File.createTempFile("test", ".txt");
try {
    FileUtils.copyInputStreamToFile(inputStream, somethingFile);
} finally {
    IOUtils.closeQuietly(inputStream);
}

Answer 4

当spring boot项目作为jar运行并且需要读取classpath中的一些文件时，我通过下面的代码实现它

Resource resource = new ClassPathResource("data.sql");
BufferedReader reader = new BufferedReader(new InputStreamReader(resource.getInputStream()));
reader.lines().forEach(System.out::println);

Answer 5

我以 java 8 的方式创建了一个 ClassPathResourceReader 类，以便从类路径轻松读取文件

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.stream.Collectors;

import org.springframework.core.io.ClassPathResource;

public final class ClassPathResourceReader {

    private final String path;

    private String content;

    public ClassPathResourceReader(String path) {
        this.path = path;
    }

    public String getContent() {
        if (content == null) {
            try {
                ClassPathResource resource = new ClassPathResource(path);
                BufferedReader reader = new BufferedReader(new InputStreamReader(resource.getInputStream()));
                content = reader.lines().collect(Collectors.joining("\n"));
                reader.close();
            } catch (IOException ex) {
                throw new RuntimeException(ex);
            }
        }
        return content;
    }
}

利用：

String content = new ClassPathResourceReader("data.sql").getContent();

Answer 6

to get list of data from src/main/resources/data folder --
first of all mention your folder location in properties file as - 
resourceLoader.file.location=data

inside class declare your location. 

@Value("${resourceLoader.file.location}")
    @Setter
    private String location;

    private final ResourceLoader resourceLoader;

public void readallfilesfromresources() {
       Resource[] resources;

        try {
            resources = ResourcePatternUtils.getResourcePatternResolver(resourceLoader).getResources("classpath:" + location + "/*.json");
            for (int i = 0; i < resources.length; i++) {
                try {
                InputStream is = resources[i].getInputStream();
                byte[] encoded = IOUtils.toByteArray(is);
                String content = new String(encoded, Charset.forName("UTF-8"));
                }
            }
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
}

Answer 7

我也遇到了这个限制并创建了这个库来解决这个问题：spring-boot-jar-resources 它基本上允许您使用 Spring Boot 注册一个自定义 ResourceLoader，它可以根据需要透明地从 JAR 中提取类路径资源。

Answer 8

球衣需要解压罐子。

<build>  
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
            <configuration>
                <requiresUnpack>
                    <dependency>
                        <groupId>com.myapp</groupId>
                        <artifactId>rest-api</artifactId>
                    </dependency>
                </requiresUnpack>
            </configuration>
        </plugin>
    </plugins>
</build>  

Answer 9

in spring boot :

1) if your file is ouside jar you can use :        

@Autowired
private ResourceLoader resourceLoader;

**.resource(resourceLoader.getResource("file:/path_to_your_file"))**

2) if your file is inside resources of jar you can `enter code here`use :

**.resource(new ClassPathResource("file_name"))**

Answer 10

基于 Andy 的answer，我使用以下方法获取了资源中一个目录和子目录下所有 YAML 的输入流（注意传递的路径不是以/ 开头）：

private static Stream<InputStream> getInputStreamsFromClasspath(
        String path,
        PathMatchingResourcePatternResolver resolver
) {
    try {
        return Arrays.stream(resolver.getResources("/" + path + "/**/*.yaml"))
                .filter(Resource::exists)
                .map(resource -> {
                    try {
                        return resource.getInputStream();
                    } catch (IOException e) {
                        return null;
                    }
                })
                .filter(Objects::nonNull);
    } catch (IOException e) {
        logger.error("Failed to get definitions from directory {}", path, e);
        return Stream.of();
    }
}

Answer 11

关于原来的错误信息

无法解析为绝对文件路径，因为它不驻留在 文件系统

以下代码可能有助于找到路径问题的解决方案：

Paths.get("message.txt").toAbsolutePath().toString();

有了这个，您可以确定应用程序需要丢失文件的位置。您可以在应用程序的 main 方法中执行此操作。

Answer 12

我注意到的另一件重要的事情是，在运行应用程序时，它会忽略资源文件夹中文件/文件夹中的大写字母，而在作为 jar 运行时它不会忽略它。因此，如果您的文件位于 Testfolder/messages.txt 下的资源文件夹中

@Autowired
ApplicationContext appContext;

// this will work when running the application, but will fail when running as jar
appContext.getResource("classpath:testfolder/message.txt");

因此，不要在资源中使用大写字母，也不要在 ClassPathResource 的构造函数中添加这些大写字母：

appContext.getResource("classpath:Testfolder/message.txt");

Answer 13

我遇到了同样的错误

InputStream inputStream = new ClassPathResource("filename.ext").inputStream();

这应该在运行时解决 FileNotFoundException

Answer 14

这在静态环境中对我有用：

    InputStream inputStream = ClassName.class.getClassLoader().getResourceAsStream("folderName/fileName.xml");
    Reader reader = new InputStreamReader(inputStream);
    String xml = CharStreams.toString(reader);