项目在本地可以获取到classpath下的文件，但是打包发布到服务器(Linux)上后，就会报错cannot be resolved to absolute file path because it does not reside in the file system: jar:file:/srv/project.jar!/BOOT-INF/classes!/static/json/14.json

代码如下

import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import lombok.extern.slf4j.Slf4j;
import org.springframework.context.ApplicationListener;
import org.springframework.context.event.ContextRefreshedEvent;
import org.springframework.core.io.Resource;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;
import org.springframework.core.io.support.ResourcePatternResolver;
import org.springframework.stereotype.Service;

import java.nio.charset.StandardCharsets;

/**
 * 等待spring容器都加载完再执行
 */
@Service
@Slf4j
public class LoadFileHandler implements ApplicationListener<ContextRefreshedEvent> {

    public static final String JSON_FILE_SIZE = "json_file_size";
    private static final String JSON_FILE_PATH = "classpath:static/json/*.json";

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {
        loadJsonFIleToCache();
    }

    /**
     * 读取json文件到缓存
     */
    public void loadJsonFIleToCache() {
        ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
        try {
            Resource[] resources = resolver.getResources(JSON_FILE_PATH);
            for (Resource resource : resources) {
                if (resource.isFile()) {
                    String filename = resource.getFilename();
                    JSONObject json = JSONUtil.readJSONObject(resource.getFile(), StandardCharsets.UTF_8);
                    CacheUtils.put(filename,json);
                }
            }
            //缓存中存入文件数量，方便遍历
            CacheUtils.put(JSON_FILE_SIZE,resources.length);
        } catch (Exception e) {
            log.info("LoadJson文件失败:{}",e.getMessage());
        }

    }
}

resource.getFile()在本地上测试是没问题的，因为是直接运行的SpringBoot项目，但是打成jar包之后就会报错cannot be resolved to absolute file path...。跟到源码org.springframework.util.ResourceUtils#getFile(java.net.URL, java.lang.String)中之后，代码如下

/** URL protocol for a file in the file system: "file". */
public static final String URL_PROTOCOL_FILE = "file";

public static File getFile(URL resourceUrl, String description) throws FileNotFoundException {
   Assert.notNull(resourceUrl, "Resource URL must not be null");
   if (!URL_PROTOCOL_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);
   }
   try {
      return new File(toURI(resourceUrl).getSchemeSpecificPart());
   }
   catch (URISyntaxException ex) {
      // Fallback for URLs that are not valid URIs (should hardly ever happen).
      return new File(resourceUrl.getFile());
   }
}

resourceUrl.getProtocol()返回的是jar,不是上面定义的file，所以会报错

解决方法

public void loadJsonFIleToCache() {
    ResourcePatternResolver resolver = new PathMatchingResourcePatternResolver();
    try {
        Resource[] resources = resolver.getResources(JSON_FILE_PATH);
        log.info("加载json文件数量：{}",resources.length);
        for (Resource resource : resources) {
            byte[] bytes = FileCopyUtils.copyToByteArray(resource.getInputStream());
            String filename = resource.getFilename();
            String jsonString = new String(bytes, StandardCharsets.UTF_8);
            JSONObject json = JSONUtil.parseObj(jsonString);
            CacheUtils.put(filename,json);
            log.info("加载json文件{}到缓存中",filename);
        }
        //缓存中存入文件数量，方便遍历
        CacheUtils.put(JSON_FILE_SIZE,resources.length);
    } catch (Exception e) {
        log.info("LoadJson文件失败:{}",e.getMessage());
    }

}

通过resource.getInputStream()是可以获取到jar下的文件流，通过转成byte[] -> String后，再转成JSONObject存到缓存中