在springboot项目中,resource下创建data目录,然后把test.txt文件放进去,通过下面代码是可以读取其中内容的:
private static List<Integer> test(String filePath) {
try {
ClassPathResource classpathResource = new ClassPathResource(filePath);
File file = classpathResource.getFile();
List<Integer> readLines = Files.readLines(file, Charsets.UTF_8, new LineProcessor<List<Integer>>() {
List<Integer> sorts = new ArrayList<>();
@Override
public List<Integer> getResult() {
return sorts;
}
@Override
public boolean processLine(String s) throws IOException {
sorts.add(Integer.parseInt(s));
return true;
}
});
return readLines;
} catch (Exception e) {
logger.error("load sort file error...",e);
throw new RuntimeException(e);
}
}
public static void main(String... s) {
String fp = "data/test.txt";
List<Integer> list = test(fp);
}
通过mvn打成jar包:
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
用命令行执行,会报如下错误:
Caused by: java.io.FileNotFoundException: class path resource [application.yml] cannot be resolved to absolute file path because it does not reside in the file system: jar:file:/D:/sunmnet/JetBrains/workspace/bigdata-parse-table/target/bigdata-parse-table-1.0-SNAPSHOT.jar!/BOOT-INF/classes!/application.yml
at org.springframework.util.ResourceUtils.getFile(ResourceUtils.java:215) ~[spring-core-4.3.12.RELEASE.jar!/:4.3.12.RELEASE]
at org.springframework.core.io.AbstractFileResolvingResource.getFile(AbstractFileResolvingResource.java:53) ~[spring-core-4.3.12.RELEASE.jar!/:4.3.12.RELEASE]
at hello.whz.Application.lambda$lookup$0(Application.java:30) [classes!/:1.0-SNAPSHOT]
at org.springframework.boot.SpringApplication.callRunner(SpringApplication.java:732) [spring-boot-1.5.8.RELEASE.jar!/:1.5.8.RELEASE]
... 14 common frames omitted
这是因为:在jar文件中,不能直接通过文件资源路径拿到文件,但是可以在jar包中拿到文件流。(一定要用流,不要尝试去拿到绝对路径,否则报错!)
原因分析:
Resource resource = new ClassPathResource("data/test/txt");
String path = resource.getFile().getPath());
上述代码的getFile()方法,在本地可以运行成功,但是打包成jar后会报错。主要原因是在jar里,返回的是一个Jar协议地址:jar:file:/xxx/xx.jar!/xxxx
而getFile方法如下:
public static File getFile(URL resourceUrl, String description) throws FileNotFoundException {
Assert.notNull(resourceUrl, "Resource URL must not be null");
if (!"file".equals(resourceUrl.getProtocol())) {
throw new FileNotFoundException(description + " cannot be resolved to absolute file path because it does not reside in the file system: " + resourceUrl);
} else {
try {
return new File(toURI(resourceUrl).getSchemeSpecificPart());
} catch (URISyntaxException var3) {
return new File(resourceUrl.getFile());
}
}
}
参考:
https://smarterco.de/java-load-file-from-classpath-in-spring-boot/