Spring Resource tutorial

last modified October 18, 2023

Spring Resource tutorial shows how to use Resource to work with various resources in a Spring application.

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

Spring Resource

Resource abstracts from the actual type of an underlying resource, such as a file or class path resource. It can be used to identify local or remote resources.

Spring ApplicationContext contains the getResource method, which returns a resource handle for the specified resource type. It can be a classpath, file, or URL resource.

Spring Resource example

The application uses Spring’s Resource to read a local file and a remote web page.

pom.xml src ├───main │ ├───java │ │ └───com │ │ └───zetcode │ │ │ Application.java │ │ └───service │ │ MyService.java │ └───resources │ logback.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>resourceex</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, 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/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} %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.

resources/words.txt

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The words.txt file contains a couple of words.

com/zetcode/MyService.java

package com.zetcode.service;

import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.ApplicationContext; import org.springframework.stereotype.Service;

import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader;

@Service public class MyService {

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

@Autowired
private ApplicationContext ctx;

public void readWebPage() {

    var res = ctx.getResource("http://webcode.me");

    try (var is = new InputStreamReader(res.getInputStream());
            var bis = new BufferedReader(is)) {

        bis.lines().forEach(System.out::println);

    } catch (IOException ex) {
        logger.warn("{}", ex);
    }
}

public void readFile() {

    // var res = ctx.getResource("file:C:/Users/Jano/Documents/words.txt");
    var res = ctx.getResource("classpath:words.txt");

    try (var is = new InputStreamReader(res.getInputStream());
            var bis = new BufferedReader(is)) {

        bis.lines().forEach(System.out::println);

    } catch (IOException ex) {
        logger.warn("{}", ex);
    }
}

}

The MyService has two methods that read a web page and a local text file.

@Autowired private ApplicationContext ctx;

We inject the ApplicationContext. We use its getResource method to get resource handlers.

var res = ctx.getResource(“http://webcode.me”);

We get a Resource from a web page.

// var res = ctx.getResource(“file:C:/Users/Jano/Documents/words.txt”); var res = ctx.getResource(“classpath:words.txt”);

We can get a Resource from an absoute file path or a classpath.

com/zetcode/Application.java

package com.zetcode;

import com.zetcode.service.MyService; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.AnnotationConfigApplicationContext; import org.springframework.context.annotation.ComponentScan;

@ComponentScan(basePackages = “com.zetcode”) public class Application {

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

@Autowired
private MyService myService;

public static void main(String[] args) {

    var ctx = new AnnotationConfigApplicationContext(Application.class);
    var app = ctx.getBean(Application.class);

    app.run();
    ctx.close();
}

public void run() {

    myService.readWebPage();
    myService.readFile();
}

}

This is the main application class.

@Autowired private MyService myService;

A service bean is injected into the class with @Autowired.

myService.readWebPage(); myService.readFile();

We call the myService methods.

In this article we have shown how to use Resource to read a local text file and a web page.

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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