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.
<?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.
<?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.
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.
<?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.
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.
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.
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