ResponseEntity进行下载

项目实例：

    @GetMapping("getPermitSignFile")@ApiOperation(value = "获取许可证签名文件")public ResponseEntity<Resource> getPermitSignFile(@ApiParam(name = "permitId", value = "许可证ID") String permitId) throws UnsupportedEncodingException {//判断所要下载的文件ID是否存在！！！//专门有个存图的表在其中查 fileId ，存在才可以下载！！！String fileId = this.service.getPermitSignFileId(permitId);if (!StringUtils.isEmpty(fileId)) {Map<String, Object> file = this.documentService.loadAsResource(fileId);//这种方式返回body 内容！！！ResponseEntity.BodyBuilder ok = ResponseEntity.ok().header("Content-Disposition", new String[]{"attachment; filename= \"" + URLEncoder.encode((String) file.get("fileName"), "UTF-8") + "\""})).body((Resource) file.get("resource"));return ok;}return null;}

解释上文：
ResponseEntity概念是可以添加HttpStatus状态码的HttpEntity的扩展类；那么不难推测出这个OK状态其实就是HttpStatus状态码

//无参ok
public static ResponseEntity.BodyBuilder ok() {return status(HttpStatus.OK);}

HttpStatus状态码中代表OK的是200

BodyBuilder又是什么鬼：

通过ResponseEntity的结构，我们知道BodyBuilder是ResponseEntity中的接口
直译：
定义一个可以添加body到response entity的builder
简单粗暴理解：
ResponseEntity可以通过这个builder返回任意类型的body内容。
BodyBuilder源码：

public interface BodyBuilder extends ResponseEntity.HeadersBuilder<ResponseEntity.BodyBuilder> {ResponseEntity.BodyBuilder contentLength(long var1);ResponseEntity.BodyBuilder contentType(MediaType var1);<T> ResponseEntity<T> body(@Nullable T var1);}

通过BodyBuilder源码，不难发现

BodyBuilder接口中的body方法的参数可以为空值（有@Nullable标签名字推测其允许空值）

loadAsResource 接口(直接用)：


public Map<String, Object> loadAsResource(String fileId) {Map<String, Object> result = new HashedMap();FileInfo fileInfo = (FileInfo)this.fileInfoRepository.findOne(fileId);if (fileInfo != null) {String fileName = fileInfo.getFileOriginalName();try {Resource resource = new InputStreamResource(MinioUtil.getInstance().getObjectStream(fileInfo.getFileStorageId()));if (!resource.exists() && !resource.isReadable()) {throw new StorageFileNotFoundException("读取文件失败: " + fileName);} else {result.put("fileName", fileName);result.put("resource", resource);return result;}} catch (MalformedURLException var6) {throw new StorageFileNotFoundException("读取文件失败: " + fileName, var6);} catch (Exception var7) {var7.printStackTrace();throw new StorageFileNotFoundException("读取文件失败: " + fileName, var7);}} else {throw new StorageFileNotFoundException("读取文件失败: " + fileId);}}

Resource(应该可以直接用):

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package org.springframework.core.io;import java.io.File;
import java.io.IOException;
import java.net.URI;
import java.net.URL;public interface Resource extends InputStreamSource {boolean exists();boolean isReadable();boolean isOpen();URL getURL() throws IOException;URI getURI() throws IOException;File getFile() throws IOException;long contentLength() throws IOException;long lastModified() throws IOException;Resource createRelative(String var1) throws IOException;String getFilename();String getDescription();
}

MinioUtil:

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//package com.richfit.ip.document.minio;import com.richfit.ip.utils.StringUtil;
import com.richfit.ip.webmvc.SpringContextHelper;
import io.minio.MinioClient;
import io.minio.Result;
import io.minio.errors.ErrorResponseException;
import io.minio.errors.InsufficientDataException;
import io.minio.errors.InternalException;
import io.minio.errors.InvalidArgumentException;
import io.minio.errors.InvalidBucketNameException;
import io.minio.errors.NoResponseException;
import io.minio.messages.Item;
import java.io.IOException;
import java.io.InputStream;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import org.apache.commons.lang3.StringUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.xmlpull.v1.XmlPullParserException;public class MinioUtil {private static final Logger log = LoggerFactory.getLogger(MinioUtil.class);private static MinioUtil minioUtil;private MinioProperty minioProperty = (MinioProperty)SpringContextHelper.getBean(MinioProperty.class);private MinioClient minioClient;private static int RETRY_NUM = 3;public static MinioUtil getInstance() {if (null != minioUtil) {return minioUtil;} else {Class var0 = MinioUtil.class;synchronized(MinioUtil.class) {if (null == minioUtil) {minioUtil = new MinioUtil();}}return minioUtil;}}private MinioUtil() {if (null == this.minioProperty) {this.minioProperty = new MinioProperty();}this.init();}private void init() {try {if (StringUtils.isNotEmpty(this.minioProperty.getUrl()) && StringUtils.isNotEmpty(this.minioProperty.getAccessKey()) && StringUtils.isNotEmpty(this.minioProperty.getSecretKey())) {this.minioClient = new MinioClient(this.minioProperty.getUrl(), this.minioProperty.getAccessKey(), this.minioProperty.getSecretKey(), false);if (!StringUtil.isNullOrEmpty(this.minioProperty.getDefaultBucketName())) {this.createBucket(this.minioProperty.getDefaultBucketName());}}} catch (Exception var2) {log.error("初始化minio客户端失败：", var2);}}public MinioClient getMinioClient() {return this.minioClient;}public boolean createBucket(String bucketName) {boolean isCreated;try {if (!this.minioClient.bucketExists(bucketName)) {this.minioClient.makeBucket(bucketName);}isCreated = true;} catch (Exception var4) {isCreated = false;log.error("创建Bucket失败", var4);var4.printStackTrace();}return isCreated;}public String uploadStream(String bucketName, String minioFilePath, InputStream inputStream, String mediaType) {if (StringUtils.isBlank(mediaType)) {mediaType = "application/octet-stream";}try {this.putObjectWithRetry(bucketName, minioFilePath, inputStream, mediaType);return this.cleanUrlByRemoveIp(this.minioClient.getObjectUrl(bucketName, minioFilePath));} catch (Exception var6) {log.error("上传文件流发生错误:", var6);throw new RuntimeException(var6);}}public String uploadStream(String minioFilePath, InputStream inputStream, String mediaType) {return this.uploadStream(this.minioProperty.getDefaultBucketName(), minioFilePath, inputStream, mediaType);}public String uploadFile(String minioFilePath, String localFile, String mediaType) {return this.uploadFile(this.minioProperty.getDefaultBucketName(), minioFilePath, localFile, mediaType);}public String uploadFile(String bucketName, String minioFilePath, String localFile, String mediaType) {if (StringUtils.isBlank(mediaType)) {mediaType = "application/octet-stream";}try {this.putObjectWithRetry(bucketName, minioFilePath, localFile, mediaType);return this.cleanUrlByRemoveIp(this.minioClient.getObjectUrl(bucketName, minioFilePath));} catch (Exception var6) {log.error("上传文件发生错误:", var6);throw new RuntimeException(var6);}}public List<MinioFile> listFilesSwap(String bucketName, String prefix, boolean recursive) {return this.swapResultToEntityList(this.minioClient.listObjects(bucketName, prefix, recursive));}public Iterable<Result<Item>> listFiles(String bucketName, String prefix, boolean recursive) {return this.minioClient.listObjects(bucketName, prefix, recursive);}public List<MinioFile> listFilesByBucketNameSwap(String bucketName) {return this.swapResultToEntityList(this.minioClient.listObjects(bucketName, (String)null, true));}public Iterable<Result<Item>> listFilesByBucketName(String bucketName) {return this.minioClient.listObjects(bucketName, (String)null, true);}public Iterable<Result<Item>> listFilesByBucketAndPrefix(String bucketName, String prefix) {return this.minioClient.listObjects(bucketName, prefix, true);}public List<MinioFile> listFilesByBucketAndPrefixSwap(String bucketName, String prefix) {return this.swapResultToEntityList(this.minioClient.listObjects(bucketName, prefix, true));}private MinioFile swapResultToEntity(Result<Item> result) {MinioFile entity = new MinioFile();try {if (result.get() != null) {Item item = (Item)result.get();entity.setObjectName(this.cleanUrlByRemoveIp(item.objectName()));entity.setIsDir(item.isDir());entity.setEtag(item.etag());entity.setLastModified(item.lastModified());entity.setObjectSize(item.objectSize());entity.setStorageClass(item.storageClass());}} catch (Exception var4) {log.error("获取文件信息出错, e={}", var4.getMessage());}return entity;}private String cleanUrlByRemoveIp(String s) {return s;}private List<MinioFile> swapResultToEntityList(Iterable<Result<Item>> results) {List<MinioFile> files = new ArrayList();Iterator var3 = results.iterator();while(var3.hasNext()) {Result<Item> result = (Result)var3.next();files.add(this.swapResultToEntity(result));}return files;}public void putObjectWithRetry(String bucketName, String objectName, InputStream stream, String contentType) throws IOException, InvalidKeyException, NoSuchAlgorithmException, InsufficientDataException, InvalidArgumentException, NoResponseException, InvalidBucketNameException, XmlPullParserException, InternalException {int current = 0;boolean isSuccess = false;while(!isSuccess && current < RETRY_NUM) {try {this.minioClient.putObject(bucketName, objectName, stream, contentType);stream.close();isSuccess = true;} catch (ErrorResponseException var8) {log.warn("[minio] putObject stream, ErrorResponseException occur for time =" + current, var8);++current;}}if (current == RETRY_NUM) {log.error("[minio] putObject, backetName={}, objectName={}, failed finally!");}}public String getObjectUrl(String objectName) throws Exception {return this.getObjectUrl(this.minioProperty.getDefaultBucketName(), objectName, 86400);}public void removeObject(String objectName) throws Exception {this.minioClient.removeObject(this.minioProperty.getDefaultBucketName(), objectName);}public void removeObject(String bucketName, String objectName) throws Exception {this.minioClient.removeObject(bucketName, objectName);}public void removeObjects(String bucketName, List<String> objectNames) throws Exception {this.minioClient.removeObject(bucketName, objectNames);}public void removeObjects(List<String> objectNames) throws Exception {this.minioClient.removeObject(this.minioProperty.getDefaultBucketName(), objectNames);}public String getObjectUrl(String bucketName, String objectName) throws Exception {return this.getObjectUrl(bucketName, objectName, 86400);}public InputStream getObjectStream(String bucketName, String objectName) throws Exception {return this.minioClient.getObject(bucketName, objectName);}public InputStream getObjectStream(String objectName) throws Exception {return this.getObjectStream(this.minioProperty.getDefaultBucketName(), objectName);}public String getObjectUrl(String bucketName, String objectName, Integer expires) throws Exception {return this.minioClient.presignedGetObject(bucketName, objectName, expires);}public void putObjectWithRetry(String bucketName, String objectName, String fileName, String contentType) throws InvalidBucketNameException, NoSuchAlgorithmException, InsufficientDataException, IOException, InvalidKeyException, NoResponseException, XmlPullParserException, ErrorResponseException, InternalException, InvalidArgumentException, InsufficientDataException {int current = 0;boolean isSuccess = false;while(!isSuccess && current < RETRY_NUM) {try {this.minioClient.putObject(bucketName, objectName, fileName, contentType);isSuccess = true;} catch (ErrorResponseException var8) {++current;log.debug("[minio] putObject file, ErrorResponseException occur!");}}if (current == RETRY_NUM) {log.error("[minio] putObject, backetName={}, objectName={}, failed finally!");}}public static void main(String[] args) throws Exception {List<MinioFile> files = getInstance().listFilesByBucketNameSwap("image");String url = getInstance().getObjectUrl("image", ((MinioFile)files.get(0)).getObjectName());}
}

    @RequestMapping("/testResponseEntity")public ResponseEntity<byte[]> testResponseEntity(HttpSession session) throws IOException{byte [] body = null;ServletContext servletContext = session.getServletContext();InputStream in = servletContext.getResourceAsStream("/files/abc.txt");body = new byte[in.available()];in.read(body);HttpHeaders headers = new HttpHeaders();headers.add("Content-Disposition", "attachment;filename=abc.txt");HttpStatus statusCode = HttpStatus.OK;ResponseEntity<byte[]> response = new ResponseEntity<byte[]>(body, headers, statusCode);return response;}

其中对Content-Disposition 响应头进行解析：
在页面内打开代码：

    File file = new File("rfc1806.txt");String filename = file.getName();response.setHeader("Content-Type","text/plain");response.addHeader("Content-Disposition","inline;filename=" + new String(filename.getBytes(),"utf-8"));response.addHeader("Content-Length","" + file.length());

弹出保存框代码：

    File file = new File("rfc1806.txt");String filename = file.getName();response.setHeader("Content-Type","text/plain");response.addHeader("Content-Disposition","attachment;filename=" + new String(filename.getBytes(),"utf-8"));response.addHeader("Content-Length","" + file.length());

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