Spring ClassPathResource tutorial

last modified October 18, 2023

Spring ClassPathResource tutorial shows how to read resources with a ClassPathResource in a Spring application.

Spring is a popular Java application framework for creating enterprise applications.

Spring ClassPathResource

ClassPathResource allows to obtain resources from a Java classpath.

Spring ClassPathResource example

The application reads text data from a file located in the Java classpath.

src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ └───service │ │ ReadWordsService.java │ └───resources │ logback.xml │ my-beans.xml │ words.txt └───test └───java

This is the project structure.

pom.xml

<?xml version=“1.0” encoding=“UTF-8”?> <project xmlns=“http://maven.apache.org/POM/4.0.0" xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=“http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion>

<groupId>com.zetcode</groupId>
<artifactId>classpathres</artifactId>
<version>1.0-SNAPSHOT</version>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <maven.compiler.source>17</maven.compiler.source>
    <maven.compiler.target>17</maven.compiler.target>
    <spring-version>5.3.23</spring-version>

</properties>

<dependencies>

    <dependency>
        <groupId>ch.qos.logback</groupId>
        <artifactId>logback-classic</artifactId>
        <version>1.4.0</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>${spring-version}</version>
    </dependency>

    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>${spring-version}</version>
    </dependency>
    
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>exec-maven-plugin</artifactId>
            <version>3.1.0</version>
            <configuration>
                <mainClass>com.zetcode.Application</mainClass>
            </configuration>
        </plugin>
    </plugins>
</build>

</project>

In the pom.xml file, we have basic Spring dependencies spring-core and spring-context and logging logback-classic dependency.

The exec-maven-plugin is used for executing Spring application from the Maven on the command line.

resources/my-beans.xml

<?xml version=“1.0” encoding=“UTF-8”?> <beans xmlns=“http://www.springframework.org/schema/beans" xmlns:xsi=“http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation=“http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

<bean name="readWordsService" class="com.zetcode.service.ReadWordsService"/>

</beans>

In the my-beans.xml file, we configure the readWordsService bean. It becomes a Spring managed bean.

resources/words.txt

sky blue mountain fresh cloud rock water melon

The resources directory is included in the classpath. The application reads words from the words.txt file.

resources/logback.xml

<?xml version=“1.0” encoding=“UTF-8”?> <configuration> <logger name=“org.springframework” level=“ERROR”/> <logger name=“com.zetcode” level=“INFO”/>

<appender name="consoleAppender" class="ch.qos.logback.core.ConsoleAppender">
    <encoder>
        <Pattern>%d{HH:mm:ss.SSS} [%thread] %blue(%-5level) %magenta(%logger{36}) - %msg %n
        </Pattern>
    </encoder>
</appender>

<root>
    <level value="INFO" />
    <appender-ref ref="consoleAppender" />
</root>

</configuration>

The logback.xml is a configuration file for the Logback logging library.

com/zetcode/service/ReadWordsService.java

package com.zetcode.service;

import org.springframework.core.io.ClassPathResource;

import java.io.IOException; import java.nio.file.Files; import java.util.List;

public class ReadWordsService {

public List<String> readWords() throws IOException {

    var res = new ClassPathResource("words.txt");

    var myFile = res.getFile();
    var lines = Files.readAllLines(myFile.toPath());

    return lines;
}

}

The ReadWordsService reads the words into a list and returns the list to the client.

var res = new ClassPathResource(“words.txt”);

The ClassPathResource is used to locate the text file.

com/zetcode/Application.java

package com.zetcode;

import com.zetcode.service.ReadWordsService; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.context.support.GenericXmlApplicationContext; import java.io.IOException;

public class Application {

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

public static void main(String[] args) throws IOException {

    var ctx = new GenericXmlApplicationContext("my-beans.xml");

    var wordsService = (ReadWordsService) ctx.getBean("readWordsService");
    var words = wordsService.readWords();

    words.forEach(word -> logger.info(word));

    ctx.close();
}

}

This is the main application class.

var wordsService = (ReadWordsService) ctx.getBean(“readWordsService”); var words = wordsService.readWords();

words.forEach(word -> logger.info(word));

We retrieve the readWordsService bean from the container and call its readWords method. The words are printed to the console.

$ mvn -q exec:java 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - sky 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - blue 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - mountain 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - fresh 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - cloud 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - rock 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - water 00:25:49.008 [com.zetcode.Application.main()] INFO com.zetcode.Application - melon

We run the application.

In this article we have worked with Spring’s ClassPathResource.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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