Spring Boot Read File from resources using ClassPathResource

Introduction

In this Spring Boot tutorial, we learn how to read files located in the resources folder in a Spring Boot application using ClassPathResource class.

Create New Spring Boot Project

Open Spring Tool Suite IDE, select menu File > New > Spring Starter Project.

On the New Spring Starter Project popup input new project information as below and click Next.

Name: spring-boot-classpathresource
Group: dev.simplesolution
Artifact: spring-boot-classpathresource
Version: 1.0.0
Description: Spring Boot Read File from resources
Package: dev.simplesolution

Spring Boot Read File from resources using ClassPathResource

On the New Spring Starter Project Dependencies popup click Finish.

Spring Boot Read File from resources using ClassPathResource

You can also creating new Spring Boot project using Spring initializr online tool at start.spring.io

Create Sample File in resources folder for Testing

Add a new text file to the resources folder named data.json with content as below for testing purposes.

/src/main/resources/data.json

{
	"firstName": "Simple",
	"lastName": "Solution"
}

How to use ClassPathResource class to read file from resources folder

Create a new class named TestReadFile and use ClassPathResource class to read data.json file then print the log message file content as following code.

TestReadFile.java

package dev.simplesolution;

import java.io.InputStream;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.boot.CommandLineRunner;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
import org.springframework.stereotype.Component;
import org.springframework.util.FileCopyUtils;

@Component
public class TestReadFile implements CommandLineRunner {
	
	private Logger logger = LoggerFactory.getLogger(SpringBootClasspathresourceApplication.class);
	
	@Override
	public void run(String... args) throws Exception {
		// Read file from resources folder
		Resource resource = new ClassPathResource("data.json");
		InputStream inputStream = resource.getInputStream();
		byte[] fileData = FileCopyUtils.copyToByteArray(inputStream);
		String outputString = new String(fileData);
		
		logger.info("File content:");
		logger.info(outputString);
	}
	
}

Run the application, we can see the log messages showing the file content.

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::                (v2.4.3)

2021-03-03 00:25:21.108  INFO 12092 --- [           main] s.SpringBootClasspathresourceApplication : Starting SpringBootClasspathresourceApplication using Java 1.8.0_231 on SS with PID 12092 (D:\SimpleSolution\spring-boot-classpathresource\bin\main started by SS in D:\SimpleSolution\spring-boot-classpathresource)
2021-03-03 00:25:21.110  INFO 12092 --- [           main] s.SpringBootClasspathresourceApplication : No active profile set, falling back to default profiles: default
2021-03-03 00:25:21.387  INFO 12092 --- [           main] s.SpringBootClasspathresourceApplication : Started SpringBootClasspathresourceApplication in 0.481 seconds (JVM running for 1.364)
2021-03-03 00:25:21.389  INFO 12092 --- [           main] s.SpringBootClasspathresourceApplication : File content:
2021-03-03 00:25:21.389  INFO 12092 --- [           main] s.SpringBootClasspathresourceApplication : {
	"firstName": "Simple",
	"lastName": "Solution"
}

Final Application Source Code

At this step we have the complete Spring Boot project with code structure as below.

Spring Boot Read File from resources using ClassPathResource

Download Source Code

The source code in this article can be found at: github.com/simplesolutiondev/spring-boot-classpathresource

or clone at:

git clone https://github.com/simplesolutiondev/spring-boot-classpathresource.git

or download at:

Download Source Code

Happy Coding 😊