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怎么在JAVA中利用HttpURLConnection实现一个文件上传下载功能？很多新手对此不是很清楚，为了帮助大家解决这个难题，下面小编将为大家详细讲解，有这方面需求的人可以来学习下，希望你能有所收获。
HttpURLConnection文件上传
HttpURLConnection采用模拟浏览器上传的数据格式，上传给服务器
上传代码如下：
package com.util;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Iterator;
import java.util.Map;
/**
* Java原生的API可用于发送HTTP请求，即java.net.URL、java.net.URLConnection，这些API很好用、很常用，
* 但不够简便；
*
* 1.通过统一资源定位器（java.net.URL）获取连接器（java.net.URLConnection） 2.设置请求的参数 3.发送请求
* 4.以输入流的形式获取返回内容 5.关闭输入流
*
* @author H__D
*
*/
public class HttpConnectionUtil {
/**
* 多文件上传的方法
*
* @param actionUrl：上传的路径
* @param uploadFilePaths：需要上传的文件路径，数组
* @return
*/
@SuppressWarnings("finally")
public static String uploadFile(String actionUrl, String[] uploadFilePaths) {
String end = "\r\n";
String twoHyphens = "--";
String boundary = "*****";
DataOutputStream ds = null;
InputStream inputStream = null;
InputStreamReader inputStreamReader = null;
BufferedReader reader = null;
StringBuffer resultBuffer = new StringBuffer();
String tempLine = null;
try {
// 统一资源
URL url = new URL(actionUrl);
// 连接类的父类，抽象类
URLConnection urlConnection = url.openConnection();
// http的连接类
HttpURLConnection httpURLConnection = (HttpURLConnection) urlConnection;
// 设置是否从httpUrlConnection读入，默认情况下是true;
httpURLConnection.setDoInput(true);
// 设置是否向httpUrlConnection输出
httpURLConnection.setDoOutput(true);
// Post 请求不能使用缓存
httpURLConnection.setUseCaches(false);
// 设定请求的方法，默认是GET
httpURLConnection.setRequestMethod("POST");
// 设置字符编码连接参数
httpURLConnection.setRequestProperty("Connection", "Keep-Alive");
// 设置字符编码
httpURLConnection.setRequestProperty("Charset", "UTF-8");
// 设置请求内容类型
httpURLConnection.setRequestProperty("Content-Type", "multipart/form-data;boundary=" + boundary);
// 设置DataOutputStream
ds = new DataOutputStream(httpURLConnection.getOutputStream());
for (int i = 0; i < uploadFilePaths.length; i++) {
String uploadFile = uploadFilePaths[i];
String filename = uploadFile.substring(uploadFile.lastIndexOf("//") + 1);
ds.writeBytes(twoHyphens + boundary + end);
ds.writeBytes("Content-Disposition: form-data; " + "name=\"file" + i + "\";filename=\"" + filename
+ "\"" + end);
ds.writeBytes(end);
FileInputStream fStream = new FileInputStream(uploadFile);
int bufferSize = 1024;
byte[] buffer = new byte[bufferSize];
int length = -1;
while ((length = fStream.read(buffer)) != -1) {
ds.write(buffer, 0, length);
}
ds.writeBytes(end);
/* close streams */
fStream.close();
}
ds.writeBytes(twoHyphens + boundary + twoHyphens + end);
/* close streams */
ds.flush();
if (httpURLConnection.getResponseCode() >= 300) {
throw new Exception(
"HTTP Request is not success, Response code is " + httpURLConnection.getResponseCode());
}
if (httpURLConnection.getResponseCode() == HttpURLConnection.HTTP_OK) {
inputStream = httpURLConnection.getInputStream();
inputStreamReader = new InputStreamReader(inputStream);
reader = new BufferedReader(inputStreamReader);
tempLine = null;
resultBuffer = new StringBuffer();
while ((tempLine = reader.readLine()) != null) {
resultBuffer.append(tempLine);
resultBuffer.append("\n");
}
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (ds != null) {
try {
ds.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (reader != null) {
try {
reader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (inputStreamReader != null) {
try {
inputStreamReader.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return resultBuffer.toString();
}
}
public static void main(String[] args) {
// 上传文件测试
String str = uploadFile("http://127.0.0.1:8080/image/image.do",new String[] { "/Users//H__D/Desktop//1.png","//Users/H__D/Desktop/2.png" });
System.out.println(str);
}
}HttpURLConnection文件下载
下载代码如下：
package com.util;
import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.OutputStreamWriter;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import java.util.Iterator;
import java.util.Map;
/**
* Java原生的API可用于发送HTTP请求，即java.net.URL、java.net.URLConnection，这些API很好用、很常用，
* 但不够简便；
*
* 1.通过统一资源定位器（java.net.URL）获取连接器（java.net.URLConnection） 2.设置请求的参数 3.发送请求
* 4.以输入流的形式获取返回内容 5.关闭输入流
*
* @author H__D
*
*/
public class HttpConnectionUtil {
/**
*
* @param urlPath
* 下载路径
* @param downloadDir
* 下载存放目录
* @return 返回下载文件
*/
public static File downloadFile(String urlPath, String downloadDir) {
File file = null;
try {
// 统一资源
URL url = new URL(urlPath);
// 连接类的父类，抽象类
URLConnection urlConnection = url.openConnection();
// http的连接类
HttpURLConnection httpURLConnection = (HttpURLConnection) urlConnection;
// 设定请求的方法，默认是GET
httpURLConnection.setRequestMethod("POST");
// 设置字符编码
httpURLConnection.setRequestProperty("Charset", "UTF-8");
// 打开到此 URL 引用的资源的通信链接（如果尚未建立这样的连接）。
httpURLConnection.connect();
// 文件大小
int fileLength = httpURLConnection.getContentLength();
// 文件名
String filePathUrl = httpURLConnection.getURL().getFile();
String fileFullName = filePathUrl.substring(filePathUrl.lastIndexOf(File.separatorChar) + 1);
System.out.println("file length---->" + fileLength);
URLConnection con = url.openConnection();
BufferedInputStream bin = new BufferedInputStream(httpURLConnection.getInputStream());
String path = downloadDir + File.separatorChar + fileFullName;
file = new File(path);
if (!file.getParentFile().exists()) {
file.getParentFile().mkdirs();
}
OutputStream out = new FileOutputStream(file);
int size = 0;
int len = 0;
byte[] buf = new byte[1024];
while ((size = bin.read(buf)) != -1) {
len += size;
out.write(buf, 0, size);
// 打印下载百分比
// System.out.println("下载了-------> " + len * 100 / fileLength +
// "%\n");
}
bin.close();
out.close();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
return file;
}
}
public static void main(String[] args) {
// 下载文件测试
downloadFile("http://localhost:8080/images/1467523487190.png", "/Users/H__D/Desktop");
}
}看完上述内容是否对您有帮助呢？如果还想对相关知识有进一步的了解或阅读更多相关文章，请关注亿速云行业资讯频道，感谢您对亿速云的支持。
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