BAEL-1628

Access a File from the Classpath in a Spring Application

spring-core/src/main/java/com/baeldung/resource/AppConfig.java

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+package com.baeldung.resource;
+
+import org.springframework.context.annotation.ComponentScan;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@ComponentScan("com.baeldung.resource")
+public class AppConfig {
+    
+}

spring-core/src/main/java/com/baeldung/resource/ClassPathResourceReader.java

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+package com.baeldung.resource;
+
+import java.io.BufferedReader;
+import java.io.File;
+import java.io.FileNotFoundException;
+import java.io.FileReader;
+import java.io.IOException;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.context.ApplicationContext;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.core.io.Resource;
+import org.springframework.core.io.ResourceLoader;
+import org.springframework.stereotype.Component;
+import org.springframework.util.ResourceUtils;
+
+@Component
+public class ClassPathResourceReader {
+
+    @Autowired
+    ResourceLoader resourceLoader;
+
+    @Autowired
+    ApplicationContext applicationContext;
+
+    @Value("classpath:data/resource-data.txt")
+    Resource resourceFile;
+
+    /**
+     * Constructs Resource object by making use of its built-in implementations.
+     * 
+     * @return Resource
+     */
+    public Resource constructResourceManually() {
+        Resource resource = new ClassPathResource("data/resource-data.txt");
+        return resource;
+    }
+
+    /**
+     * Constructs resource object by making use of ResourceLoader. 
+     * 
+     * @return Resource
+     */
+    public Resource retrieveResourceUsingResourceLoader() {
+        Resource resource = resourceLoader.getResource("classpath:data/resource-data.txt");
+        return resource;
+    }
+
+    /**
+     * Constructs Resource instance by making use of ApplicationContext. 
+     * 
+     * @return Resource
+     */
+    public Resource retrieveResourceUsingApplicationContext() {
+        Resource resource = applicationContext.getResource("classpath:data/resource-data.txt");
+        return resource;
+    }
+
+    /**
+     * ResourceUtils example for getting file data.
+     * 
+     * @return
+     * @throws FileNotFoundException
+     */
+    public File retrieveFileUsingResourceUtils() throws FileNotFoundException {
+        return ResourceUtils.getFile("classpath:data/resource-data.txt");
+    }
+
+    /**
+     * Utility method to list contents ofa file.
+     * 
+     * @param fileResource
+     * @return
+     * @throws IOException
+     */
+    public String listResourceContentsUsingFile(File fileResource) throws IOException {
+        FileReader fileReader = new FileReader(fileResource);
+        BufferedReader bufReader = new BufferedReader(fileReader);
+        String dataLine = bufReader.readLine();
+        StringBuilder fileData = new StringBuilder();
+        while (null != dataLine) {
+            fileData.append(dataLine);
+            dataLine = bufReader.readLine();
+        }
+
+        fileReader.close();
+        return fileData.toString();
+    }
+
+    public Resource getSampleFile() {
+        return resourceFile;
+    }
+
+    public void setSampleFile(Resource sampleFile) {
+        this.resourceFile = sampleFile;
+    }
+}

spring-core/src/main/resources/data/resource-data.txt

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+This is a sample text to demonstrate usage of Spring Resource.

spring-core/src/test/java/com/baeldung/resource/SpringResourceTest.java

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+package com.baeldung.resource;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.core.io.Resource;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.support.AnnotationConfigContextLoader;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@ContextConfiguration(loader = AnnotationConfigContextLoader.class, classes = AppConfig.class)
+public class SpringResourceTest {
+
+    @Autowired
+    private ClassPathResourceReader classPathResourceReader;
+    
+    static final String testData = "This is a sample text to demonstrate usage of Spring Resource.";
+
+    @Test
+    public void whenManualInstance_thenReadSuccessful() throws IOException {
+        Resource resource = classPathResourceReader.constructResourceManually();
+        String fileData = classPathResourceReader.listResourceContentsUsingFile(resource.getFile());
+        assertEquals(testData, fileData);
+    }
+
+    @Test
+    public void whenResourceLoader_thenReadSuccessful() throws IOException {
+        Resource resource = classPathResourceReader.retrieveResourceUsingResourceLoader();
+        String fileData = classPathResourceReader.listResourceContentsUsingFile(resource.getFile());
+        assertEquals(testData, fileData);
+    }
+
+    @Test
+    public void whenApplicationContext_thenReadSuccessful() throws IOException {
+        Resource resource = classPathResourceReader.retrieveResourceUsingApplicationContext();
+        String fileData = classPathResourceReader.listResourceContentsUsingFile(resource.getFile());
+        assertEquals(testData, fileData);
+    }
+
+    @Test
+    public void whenAutowired_thenReadSuccessful() throws IOException {
+        Resource resource = classPathResourceReader.getSampleFile();
+        String fileData = classPathResourceReader.listResourceContentsUsingFile(resource.getFile());
+        assertEquals(testData, fileData);
+    }
+
+    @Test
+    public void whenResourceUtils_thenReadSuccessful() throws IOException {
+        String fileData = classPathResourceReader.listResourceContentsUsingFile(classPathResourceReader.retrieveFileUsingResourceUtils());
+        assertEquals(testData, fileData);
+    }
+}

spring-core/src/test/resources/data/resource-data.txt

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+This is a sample text to demonstrate usage of Spring Resource.