java中怎么利用oss實現下載功能

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首先，導入依賴包

<dependency>  <groupId>com.aliyun.oss</groupId>  <artifactId>aliyun-sdk-oss</artifactId>  <version>3.6.0</version> </dependency>

參數類

public class OssParams {  public static final String endpoint = "oss-cn-hangzhou.aliyuncs.com";  public static final String accessKeyId = ""; public static final String accessKeySecret = "";  public static final String bucketName = "";  public static final String rootName = "";//根目錄}

工具類

import com.aliyun.oss.ClientException;import com.aliyun.oss.OSS;import com.aliyun.oss.OSSClientBuilder;import com.aliyun.oss.OSSException;import com.aliyun.oss.model.AppendObjectRequest;import com.aliyun.oss.model.ObjectMetadata;import org.joda.time.DateTime;import org.slf4j.Logger;import org.slf4j.LoggerFactory; import java.io.ByteArrayInputStream;import java.net.URL;import java.util.Date;import java.util.concurrent.atomic.AtomicLong; import static OssParams.bucketName; /** * 先做單例對象調用，防止多線程并發(fā)bug * 后期加入線程鎖控制后，做成公共utils */public class WriteLeadsOssUtils { private static Logger LOG = LoggerFactory.getLogger(WriteLeadsOssUtils.class.getName());  private static final String fileSub = ".csv";  private AtomicLong atomicLong = new AtomicLong(0L);  private WriteLeadsOssUtils() { }  private static class BuildWriteOSS {  private static final WriteLeadsOssUtils instance = new WriteLeadsOssUtils(); }  public static WriteLeadsOssUtils getInstance() {  return BuildWriteOSS.instance; }  private OSS getOssClient() {  return new OSSClientBuilder().build(OssParams.endpoint, OssParams.accessKeyId, OssParams.accessKeySecret); }  public URL writeJSONObjectFile(String content,String fileName) {  // 創(chuàng)建OSSClient實例。  OSS ossClient = getOssClient();  try {   DateTime currentTime = new DateTime(System.currentTimeMillis());//   String objectName = OssParams.rootName + currentTime.toString("yyyy-MM-dd-HH") + fileSub;   String objectName = OssParams.rootName + fileName;//   AppendObjectRequest appendObjectRequest = null;   String data = content;    ossClient.putObject(bucketName, objectName, new ByteArrayInputStream(content.getBytes()));    Date expiration = new Date(System.currentTimeMillis() + 3600L * 1000 * 24 * 180);   URL url = ossClient.generatePresignedUrl(bucketName, objectName, expiration);    LOG.info("{} saved to OSS, url={}", objectName,url.toString());//   for (IngestLeadingRequest param : params) {//    String jsonStr = JSONObject.toJSONString(param);//    JSONObject object = JSONObject.parseObject(jsonStr);//    data += object.toJSONString() + "\n";//   }   //文件不存在//   if (!ossClient.doesObjectExist(OssParams.bucketName, objectName)) {//    atomicLong.set(0L);//    appendObjectRequest = getAppendObjectRequest(data, true, objectName);//    appendObjectRequest.setPosition(0L);//   } else {//    appendObjectRequest = getAppendObjectRequest(data, false, objectName);//   }//   AppendObjectResult appendObjectResult = ossClient.appendObject(appendObjectRequest);//   atomicLong.set(appendObjectResult.getNextPosition());//   System.gc();   return url;  } catch (OSSException e) {   e.printStackTrace();   return null;  } catch (ClientException e) {   e.printStackTrace();   return null;  } finally {   ossClient.shutdown();  } }   /**  * flag標志位，true為新文件，false為追加文件  *  * @param data  * @param flag  * @param objectName  * @return  */ private AppendObjectRequest getAppendObjectRequest(String data, Boolean flag, String objectName) {  ObjectMetadata meta = new ObjectMetadata();  // 指定上傳的內容類型。  meta.setContentType("text/plain;charset=utf-8");  if (flag == true) {   return new AppendObjectRequest(bucketName, objectName,     new ByteArrayInputStream(data.getBytes()), meta);  } else {   return new AppendObjectRequest(bucketName, objectName,     new ByteArrayInputStream(data.getBytes()), meta).withPosition(atomicLong.get());  } }}

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