Read file from resources folder in Spring Boot

问题

I'm using Spring Boot and json-schema-validator. I'm trying to read a file called jsonschema.json from the resources folder. I've tried a few different ways but I can't get it to work. This is my code.

ClassLoader classLoader = getClass().getClassLoader();
File file = new File(classLoader.getResource("jsonschema.json").getFile());
JsonNode mySchema = JsonLoader.fromFile(file);

This is the location of the file.

And here I can see the file in the classes folder.

But when I run the code I get the following error.

jsonSchemaValidator error: java.io.FileNotFoundException: /home/user/Dev/Java/Java%20Programs/SystemRoutines/target/classes/jsonschema.json (No such file or directory)

What is it I'm doing wrong in my code?

回答1:

After spending a lot of time trying to resolve this issue, finally found a solution that works. The solution makes use of Spring's ResourceUtils. Should work for json files as well.

Thanks for the well written page by Lokesh Gupta : Blog

package utils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.ResourceUtils;

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Properties;
import java.io.File;


public class Utils {

    private static final Logger LOGGER = LoggerFactory.getLogger(Utils.class.getName());

    public static Properties fetchProperties(){
        Properties properties = new Properties();
        try {
            File file = ResourceUtils.getFile("classpath:application.properties");
            InputStream in = new FileInputStream(file);
            properties.load(in);
        } catch (IOException e) {
            LOGGER.error(e.getMessage());
        }
        return properties;
    }
}

To answer a few concerns on the comments :

Pretty sure I had this running on Amazon EC2 using java -jar target/image-service-slave-1.0-SNAPSHOT.jar Look at my github repo : https://github.com/johnsanthosh/image-service to figure out the right way to run this from a JAR.

回答2:

Very short answer: you are looking for your property in the scope of a particular class loader instead of you target class. This should work:

File file = new File(getClass().getResource("jsonschema.json").getFile());
JsonNode mySchema = JsonLoader.fromFile(file);

Also, see this:

What is the difference between Class.getResource() and ClassLoader.getResource()?
Strange behavior of Class.getResource() and ClassLoader.getResource() in executable jar
Loading resources using getClass().getResource()

P.S. there can be an issue if the project has been compiled on one machine and after that has been launched on another or you run your app in Docker. In this case, paths to your resource folder can be invalid. In this case it would be better to determine paths to your resources at runtime:

ClassPathResource res = new ClassPathResource("jsonschema.json");    
File file = new File(res.getPath());
JsonNode mySchema = JsonLoader.fromFile(file);

回答3:

if you have for example config folder under Resources folder I tried this Class working perfectly hope be useful

File file = ResourceUtils.getFile("classpath:config/sample.txt")

//Read File Content
String content = new String(Files.readAllBytes(file.toPath()));
System.out.println(content);

回答4:

create json folder in resources as subfolder then add json file in folder then you can use this code :

import com.fasterxml.jackson.core.type.TypeReference;

InputStream is = TypeReference.class.getResourceAsStream("/json/fcmgoogletoken.json");

this works in Docker.

回答5:

Here is my solution. May help someone;

It returns InputStream, but i assume you can read from it too.

InputStream is = Thread.currentThread().getContextClassLoader().getResourceAsStream("jsonschema.json");

回答6:

See my answer here: https://stackoverflow.com/a/56854431/4453282

import org.springframework.core.io.Resource;
import org.springframework.core.io.ResourceLoader;

Use these 2 imports.

Declare

@Autowired
ResourceLoader resourceLoader;

Use this in some function

Resource resource=resourceLoader.getResource("classpath:preferences.json");

In your case, as you need the file you may use following

File file = resource.getFile()

Reference:http://frugalisminds.com/spring/load-file-classpath-spring-boot/ As already mentioned in previous answers don't use ResourceUtils it doesn't work after deployment of JAR, this will work in IDE as well as after deployment

回答7:

stuck in the same issue this helps me

URL resource = getClass().getClassLoader().getResource("jsonschema.json");
JsonNode jsonNode = JsonLoader.fromURL(resource);

来源：https://stackoverflow.com/questions/44399422/read-file-from-resources-folder-in-spring-boot

标签

java

Spring

spring-boot

json-schema-validator