運用HttpClient完成文件的上傳下載辦法。本站提示廣大學習愛好者：（運用HttpClient完成文件的上傳下載辦法）文章只能為提供參考，不一定能成為您想要的結果。以下是運用HttpClient完成文件的上傳下載辦法正文
1 HTTP
HTTP 協議能夠是如今 Internet 上運用得最多、最重要的協議了，越來越多的 Java 使用順序需求直接經過 HTTP 協議來訪問網絡資源。
雖然在 JDK 的 java.net 包中曾經提供了訪問 HTTP 協議的根本功用，但是關於大局部使用順序來說，JDK 庫自身提供的功用還不夠豐厚和靈敏。HttpClient 用來提供高效的、最新的、功用豐厚的支持 HTTP 協議的客戶端編程工具包，並且它支持 HTTP 協議最新的版本和建議。
普通的狀況下我們都是運用Chrome或許其他閱讀器來訪問一個WEB服務器，用來閱讀頁面檢查信息或許提交一些數據、文件上傳下載等等。所訪問的這些頁面有的僅僅是一些普通的頁面，有的需求用戶登錄前方可運用，或許需求認證以及是一些經過加密方式傳輸，例如HTTPS。目前我們運用的閱讀器處置這些狀況都不會構成問題。但是一旦我們有需求不經過閱讀器來訪問服務器的資源呢？那該怎樣辦呢？
上面以本地客戶端發起文件的上傳、下載為例做個小Demo。HttpClient有兩種方式，一種是org.apache.http下的，一種是org.apache.commons.httpclient.HttpClient。
2 文件上傳
文件上傳可以運用兩種方式完成，一種是PostMethod方式，一種是HttpPost方式。兩者的處置迥然不同。PostMethod是運用FileBody將文件包裝流包裝起來，HttpPost是運用FilePart將文件流包裝起來。在傳遞文件流給服務端的時分，都可以同時傳遞其他的參數。
2.1 客戶端處置
2.1.1 PostMethod方式
將文件封裝到FilePart中，放入Part數組，同時，其他參數可以放入StringPart中，這裡沒有寫，只是單純的將參數以setParameter的方式停止設置。此處的HttpClient是org.apache.commons.httpclient.HttpClient。
public void upload(String localFile){
File file = new File(localFile);
PostMethod filePost = new PostMethod(URL_STR);
HttpClient client = new HttpClient();
try {
// 經過以下辦法可以模仿頁面參數提交
filePost.setParameter("userName", userName);
filePost.setParameter("passwd", passwd);
Part[] parts = { new FilePart(file.getName(), file) };
filePost.setRequestEntity(new MultipartRequestEntity(parts, filePost.getParams()));
client.getHttpConnectionManager().getParams().setConnectionTimeout(5000);
int status = client.executeMethod(filePost);
if (status == HttpStatus.SC_OK) {
System.out.println("上傳成功");
} else {
System.out.println("上傳失敗");
}
} catch (Exception ex) {
ex.printStackTrace();
} finally {
filePost.releaseConnection();
}
}
記得搞完之後，要經過releaseConnection釋放銜接。
2.1.2 HttpPost方式
這種方式，與下面相似，只不過變成了FileBody。下面的Part數組在這裡對應HttpEntity。此處的HttpClient是org.apache.http.client.methods下的。
public void upload(String localFile){
CloseableHttpClient httpClient = null;
CloseableHttpResponse response = null;
try {
httpClient = HttpClients.createDefault();
// 把一個普通參數和文件上傳給上面這個地址 是一個servlet
HttpPost httpPost = new HttpPost(URL_STR);
// 把文件轉換成流對象FileBody
FileBody bin = new FileBody(new File(localFile));
StringBody userName = new StringBody("Scott", ContentType.create(
"text/plain", Consts.UTF_8));
StringBody password = new StringBody("123456", ContentType.create(
"text/plain", Consts.UTF_8));
HttpEntity reqEntity = MultipartEntityBuilder.create()
// 相當於<input type="file" name="file"/>
.addPart("file", bin)
// 相當於<input type="text" name="userName" value=userName>
.addPart("userName", userName)
.addPart("pass", password)
.build();
httpPost.setEntity(reqEntity);
// 發起懇求 並前往懇求的呼應
response = httpClient.execute(httpPost);
System.out.println("The response value of token:" + response.getFirstHeader("token"));
// 獲取呼應對象
HttpEntity resEntity = response.getEntity();
if (resEntity != null) {
// 打印呼應長度
System.out.println("Response content length: " + resEntity.getContentLength());
// 打印呼應內容
System.out.println(EntityUtils.toString(resEntity, Charset.forName("UTF-8")));
}
// 銷毀
EntityUtils.consume(resEntity);
}catch (Exception e){
e.printStackTrace();
}finally {
try {
if(response != null){
response.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if(httpClient != null){
httpClient.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
2.2 服務端處置
無論客戶端是哪種上傳方式，服務端的處置都是一樣的。在經過HttpServletRequest取得參數之後，把失掉的Item停止分類，分為普通的表單和File表單。
經過ServletFileUpload 可以設置上傳文件的大小及編碼格式等。
總之，服務端的處置是把失掉的參數當做HTML表單停止處置的。
public void processUpload(HttpServletRequest request, HttpServletResponse response){
File uploadFile = new File(uploadPath);
if (!uploadFile.exists()) {
uploadFile.mkdirs();
}
System.out.println("Come on, baby .......");
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
//檢測是不是存在上傳文件
boolean isMultipart = ServletFileUpload.isMultipartContent(request);
if(isMultipart){
DiskFileItemFactory factory = new DiskFileItemFactory();
//指定在內存中緩存數據大小,單位為byte,這裡設為1Mb
factory.setSizeThreshold(1024*1024);
//設置一旦文件大小超越getSizeThreshold()的值時數據寄存在硬盤的目錄
factory.setRepository(new File("D:\\temp"));
// Create a new file upload handler
ServletFileUpload upload = new ServletFileUpload(factory);
// 指定單個上傳文件的最大尺寸,單位:字節，這裡設為50Mb
upload.setFileSizeMax(50 * 1024 * 1024);
//指定一次上傳多個文件的總尺寸,單位:字節，這裡設為50Mb
upload.setSizeMax(50 * 1024 * 1024);
upload.setHeaderEncoding("UTF-8");
List<FileItem> items = null;
try {
// 解析request懇求
items = upload.parseRequest(request);
} catch (FileUploadException e) {
e.printStackTrace();
}
if(items!=null){
//解析表單項目
Iterator<FileItem> iter = items.iterator();
while (iter.hasNext()) {
FileItem item = iter.next();
//假如是普通表單屬性
if (item.isFormField()) {
//相當於input的name屬性 <input type="text" name="content">
String name = item.getFieldName();
//input的value屬性
String value = item.getString();
System.out.println("屬性:" + name + " 屬性值:" + value);
}
//假如是上傳文件
else {
//屬性名
String fieldName = item.getFieldName();
//上傳文件途徑
String fileName = item.getName();
fileName = fileName.substring(fileName.lastIndexOf("/") + 1);// 取得上傳文件的文件名
try {
item.write(new File(uploadPath, fileName));
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
}
response.addHeader("token", "hello");
}
服務端在處置之後，可以在Header中設置前往給客戶端的復雜信息。假如前往客戶端是一個流的話，流的大小必需提早設置！
response.setContentLength((int) file.length());
3 文件下載
文件的下載可以運用HttpClient的GetMethod完成，還可以運用HttpGet方式、原始的HttpURLConnection方式。
3.1 客戶端處置
3.1.1 GetMethod方式
此處的HttpClient是org.apache.commons.httpclient.HttpClient。
public void downLoad(String remoteFileName, String localFileName) {
HttpClient client = new HttpClient();
GetMethod get = null;
FileOutputStream output = null;
try {
get = new GetMethod(URL_STR);
get.setRequestHeader("userName", userName);
get.setRequestHeader("passwd", passwd);
get.setRequestHeader("fileName", remoteFileName);
int i = client.executeMethod(get);
if (SUCCESS == i) {
System.out.println("The response value of token:" + get.getResponseHeader("token"));
File storeFile = new File(localFileName);
output = new FileOutputStream(storeFile);
// 失掉網絡資源的字節數組,並寫入文件
output.write(get.getResponseBody());
} else {
System.out.println("DownLoad file occurs exception, the error code is :" + i);
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if(output != null){
output.close();
}
} catch (IOException e) {
e.printStackTrace();
}
get.releaseConnection();
client.getHttpConnectionManager().closeIdleConnections(0);
}
}
3.1.2 HttpGet方式
此處的HttpClient是org.apache.http.client.methods下的。
public void downLoad(String remoteFileName, String localFileName) {
DefaultHttpClient httpClient = new DefaultHttpClient();
OutputStream out = null;
InputStream in = null;
try {
HttpGet httpGet = new HttpGet(URL_STR);
httpGet.addHeader("userName", userName);
httpGet.addHeader("passwd", passwd);
httpGet.addHeader("fileName", remoteFileName);
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity entity = httpResponse.getEntity();
in = entity.getContent();
long length = entity.getContentLength();
if (length <= 0) {
System.out.println("下載文件不存在！");
return;
}
System.out.println("The response value of token:" + httpResponse.getFirstHeader("token"));
File file = new File(localFileName);
if(!file.exists()){
file.createNewFile();
}
out = new FileOutputStream(file);
byte[] buffer = new byte[4096];
int readLength = 0;
while ((readLength=in.read(buffer)) > 0) {
byte[] bytes = new byte[readLength];
System.arraycopy(buffer, 0, bytes, 0, readLength);
out.write(bytes);
}
out.flush();
} catch (IOException e) {
e.printStackTrace();
} catch (Exception e) {
e.printStackTrace();
}finally{
try {
if(in != null){
in.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if(out != null){
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
3.1.3 HttpURLConnection方式
public void download3(String remoteFileName, String localFileName) {
FileOutputStream out = null;
InputStream in = null;
try{
URL url = new URL(URL_STR);
URLConnection urlConnection = url.openConnection();
HttpURLConnection httpURLConnection = (HttpURLConnection) urlConnection;
// true -- will setting parameters
httpURLConnection.setDoOutput(true);
// true--will allow read in from
httpURLConnection.setDoInput(true);
// will not use caches
httpURLConnection.setUseCaches(false);
// setting serialized
httpURLConnection.setRequestProperty("Content-type", "application/x-java-serialized-object");
// default is GET
httpURLConnection.setRequestMethod("POST");
httpURLConnection.setRequestProperty("connection", "Keep-Alive");
httpURLConnection.setRequestProperty("Charsert", "UTF-8");
// 1 min
httpURLConnection.setConnectTimeout(60000);
// 1 min
httpURLConnection.setReadTimeout(60000);
httpURLConnection.addRequestProperty("userName", userName);
httpURLConnection.addRequestProperty("passwd", passwd);
httpURLConnection.addRequestProperty("fileName", remoteFileName);
// connect to server (tcp)
httpURLConnection.connect();
in = httpURLConnection.getInputStream();// send request to
// server
File file = new File(localFileName);
if(!file.exists()){
file.createNewFile();
}
out = new FileOutputStream(file);
byte[] buffer = new byte[4096];
int readLength = 0;
while ((readLength=in.read(buffer)) > 0) {
byte[] bytes = new byte[readLength];
System.arraycopy(buffer, 0, bytes, 0, readLength);
out.write(bytes);
}
out.flush();
}catch(Exception e){
e.printStackTrace();
}finally{
try {
if(in != null){
in.close();
}
} catch (IOException e) {
e.printStackTrace();
}
try {
if(out != null){
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
3.2 服務端處置
雖然客戶端的處置方式不同，但是服務端是一樣的。
public void processDownload(HttpServletRequest request, HttpServletResponse response){
int BUFFER_SIZE = 4096;
InputStream in = null;
OutputStream out = null;
System.out.println("Come on, baby .......");
try{
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
response.setContentType("application/octet-stream");
String userName = request.getHeader("userName");
String passwd = request.getHeader("passwd");
String fileName = request.getHeader("fileName");
System.out.println("userName:" + userName);
System.out.println("passwd:" + passwd);
System.out.println("fileName:" + fileName);
//可以依據傳遞來的userName和passwd做進一步處置，比方驗證懇求能否合法等
File file = new File(downloadPath + "\\" + fileName);
response.setContentLength((int) file.length());
response.setHeader("Accept-Ranges", "bytes");
int readLength = 0;
in = new BufferedInputStream(new FileInputStream(file), BUFFER_SIZE);
out = new BufferedOutputStream(response.getOutputStream());
byte[] buffer = new byte[BUFFER_SIZE];
while ((readLength=in.read(buffer)) > 0) {
byte[] bytes = new byte[readLength];
System.arraycopy(buffer, 0, bytes, 0, readLength);
out.write(bytes);
}
out.flush();
response.addHeader("token", "hello 1");
}catch(Exception e){
e.printStackTrace();
response.addHeader("token", "hello 2");
}finally {
if (in != null) {
try {
in.close();
} catch (IOException e) {
}
}
if (out != null) {
try {
out.close();
} catch (IOException e) {
}
}
}
}
4 小結
HttpClient最根本的功用就是執行Http辦法。一個Http辦法的執行觸及到一個或許多個Http懇求/Http呼應的交互，通常這個進程都會自動被HttpClient處置，對用戶通明。用戶只需求提供Http懇求對象，HttpClient就會將http懇求發送給目的服務器，並且接納服務器的呼應，假如http懇求執行不成功，httpclient就會拋出異常。所以在寫代碼的時分留意finally的處置。
一切的Http懇求都有一個懇求列（request line），包括辦法名、懇求的URI和Http版本號。HttpClient支持HTTP/1.1這個版本定義的一切Http辦法：GET,HEAD,POST,PUT,DELETE,TRACE和OPTIONS。下面的上傳用到了Post，下載是Get。
目前來說，運用org.apache.commons.httpclient.HttpClient多一些。看自己了~
以上就是為大家帶來的運用HttpClient完成文件的上傳下載辦法全部內容了，希望大家多多支持~
