#BAEL-2461 (#7116)

Implement methods to download a large file through Spring RestTemplate

spring-resttemplate/src/test/java/org/baeldung/resttemplate/LargeFileDownloadIntegrationTest.java

@@ -0,0 +1,109 @@
+package org.baeldung.resttemplate;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.core.io.FileSystemResource;
+import org.springframework.http.HttpHeaders;
+import org.springframework.http.HttpMethod;
+import org.springframework.http.converter.HttpMessageConverter;
+import org.springframework.util.StreamUtils;
+import org.springframework.web.client.RestTemplate;
+
+import java.io.File;
+import java.io.FileOutputStream;
+import java.util.ArrayList;
+import java.util.List;
+
+public class LargeFileDownloadIntegrationTest {
+
+    static String FILE_URL = "http://ovh.net/files/1Mio.dat";
+
+    RestTemplate restTemplate;
+
+    @Before
+    public void setUp() {
+        restTemplate = new RestTemplate();
+    }
+
+    @Test
+    public void givenResumableUrl_whenUrlCalledByHeadOption_thenExpectHeadersAvailable() {
+        HttpHeaders headers = restTemplate.headForHeaders(FILE_URL);
+        Assertions
+          .assertThat(headers.get("Accept-Ranges"))
+          .contains("bytes");
+        Assertions
+          .assertThat(headers.getContentLength())
+          .isGreaterThan(0);
+    }
+
+    @Test
+    public void givenResumableUrl_whenDownloadCompletely_thenExpectCorrectFileSize() {
+        HttpHeaders headers = restTemplate.headForHeaders(FILE_URL);
+        long contentLength = headers.getContentLength();
+        File file = restTemplate.execute(FILE_URL, HttpMethod.GET, null, clientHttpResponse -> {
+            File ret = File.createTempFile("download", "tmp");
+            StreamUtils.copy(clientHttpResponse.getBody(), new FileOutputStream(ret));
+            return ret;
+        });
+
+        Assert.assertNotNull(file);
+        Assertions
+          .assertThat(file.length())
+          .isEqualTo(contentLength);
+    }
+
+    @Test
+    public void givenResumableUrl_whenDownloadRange_thenExpectFileSizeEqualOrLessThanRange() {
+        int range = 10;
+        File file = restTemplate.execute(FILE_URL, HttpMethod.GET, clientHttpRequest -> clientHttpRequest
+          .getHeaders()
+          .set("Range", String.format("bytes=0-%d", range - 1)), clientHttpResponse -> {
+            File ret = File.createTempFile("download", "tmp");
+            StreamUtils.copy(clientHttpResponse.getBody(), new FileOutputStream(ret));
+            return ret;
+        });
+
+        Assert.assertNotNull(file);
+        Assertions
+          .assertThat(file.length())
+          .isLessThanOrEqualTo(range);
+    }
+
+    @Test
+    public void givenResumableUrl_whenPauseDownloadAndResume_thenExpectCorrectFileSize() {
+
+        int range = 10;
+
+        HttpHeaders headers = restTemplate.headForHeaders(FILE_URL);
+        long contentLength = headers.getContentLength();
+
+        File file = restTemplate.execute(FILE_URL, HttpMethod.GET, clientHttpRequest -> clientHttpRequest
+          .getHeaders()
+          .set("Range", String.format("bytes=0-%d", range - 1)), clientHttpResponse -> {
+            File ret = File.createTempFile("download", "tmp");
+            StreamUtils.copy(clientHttpResponse.getBody(), new FileOutputStream(ret));
+            return ret;
+        });
+
+        Assert.assertNotNull(file);
+
+        Assertions
+          .assertThat(file.length())
+          .isLessThanOrEqualTo(range);
+
+        restTemplate.execute(FILE_URL, HttpMethod.GET, clientHttpRequest -> clientHttpRequest
+          .getHeaders()
+          .set("Range", String.format("bytes=%d-%d", file.length(), contentLength)), clientHttpResponse -> {
+            StreamUtils.copy(clientHttpResponse.getBody(), new FileOutputStream(file, true));
+            return file;
+        });
+
+        Assertions
+          .assertThat(file.length())
+          .isEqualTo(contentLength);
+
+    }
+
+}