Java中如何使用HttpURLConnection下载文件呢?

实现思路:
   1.定义URL对象
   2.使用url对象中的openConnection()方法,返回HttpURLConnection对象
   3.使用httpurlConnection对象的getInputStream()方法即可获取相应的文件流
   4.将文件流转换为相应的文件,并存储到硬盘上

package com.java265;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.URL;
 
public class TestClass {
	public static void main(String[] args) {
		HttpURLConnection conn = null;
		try {
			URL url = new URL("http://localhost:8080/test.jpg");//获得服务器的下载地址
			conn = (HttpURLConnection) url.openConnection();//打开连接
			conn.setRequestProperty("Content-Type", "application/json; charset=UTF-8");//设置字符集,格式
			conn.setRequestProperty("Connection", "close");//设置连接状态
			conn.setRequestMethod("GET");//设置请求方式
			conn.setDoOutput(true);//如果要使用URL连接进行输出，则标记为true
			conn.setRequestProperty("Authorization","token");//设置请求的token
			byte[] getData = readInputStream(conn.getInputStream());//把文件流放进字节数组里
			File file = new File("d:\\test.jpg");//新建文件
			FileOutputStream fos = new FileOutputStream(file);//放人文件
			fos.write(getData);//把字节数组写进文件流中
		} catch (Exception ex) {
			ex.printStackTrace();
			String aa = ex.getMessage();
		} finally {
			if (conn != null) {
				conn.disconnect();
			}
		}
 
	}
	public static  byte[] readInputStream(InputStream inputStream) throws IOException {
		byte[] buffer = new byte[1024];
		int len = 0;
		ByteArrayOutputStream bos = new ByteArrayOutputStream();
		while((len = inputStream.read(buffer)) != -1) {
			bos.write(buffer, 0, len);
		}
		bos.close();
		return bos.toByteArray();
	}
 
}