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.

<?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.

<?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.

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The words.txt file contains a couple of words.

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.

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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