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.
clean sky forest blue crystal cloud river
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.
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