java 实现 PDF 文件下载到服务器

目前负责的项目遇到下载 pdf 文件到本地的需求，有 http 请求和 https 请求发个帖记录一下！

1.http 请求 pdf 文件地址并下载到本地，别的不太会说，直接粘代码了

package cn.com.test;

import java.io.DataInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;

import javax.net.ssl.HttpsURLConnection;

/**
 * 
 * @ClassName: HttpDownloaderPDF
 * @Description: 下载pdf文件到本地
 * @author Stone
 * @date 2016年12月1日
 * 
 */
public class HttpDownloaderPDF {
	
	String remoteFileUrl = "";//pdf文件请求地址
	String localFilePath = "";//本地存放pdf文件路径

	public void httpDownloader(String remoteFileUrl, String localFilePath) {
		try {
			URL url = new URL(remoteFileUrl);

			HttpURLConnection httpURLConnection = (HttpsURLConnection) url.openConnection();
			httpURLConnection.setConnectTimeout(5 * 1000); // 5000 自定义连接超时毫秒数
			httpURLConnection.connect(); // 连接
			System.out.println("connect URL success!");

			int fileLenght = httpURLConnection.getContentLength();
			System.out.println("file size：" + (fileLenght / 1024.0) + " KB");

			System.out.println("start the download...");
			try (DataInputStream dis = new DataInputStream(
					httpURLConnection.getInputStream());
					FileOutputStream fos = new FileOutputStream(localFilePath)) {
				byte[] buf = new byte[10240]; // 根据实际情况自定义 buf 大小
				for (int readSize; (readSize = dis.read(buf)) > 0;) {
					fos.write(buf, 0, readSize);
				}
				System.out.println("download is complete!");
			} catch (IOException ex) {
				System.out.println("download is error");
			}

			httpURLConnection.disconnect();
		} catch (IOException ex) {
			ex.printStackTrace();
			System.out.println("URL Does not exist or connection timeout!");
		}
	}

}

class PDFTest {
	public static void main(String[] args) {
		HttpDownloaderPDF hdl = new HttpDownloaderPDF();
		hdl.httpDownloader("requestURL", "/home/Stone/Downloader/file.pdf");
	}
	
}

2.有 http 请求就应该考虑 https 请求，还是简单粗暴直接粘代码

package cn.com.test;

import java.io.DataInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.cert.X509Certificate;

import javax.net.ssl.HostnameVerifier;
import javax.net.ssl.HttpsURLConnection;
import javax.net.ssl.SSLContext;
import javax.net.ssl.SSLSession;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;

/**
 * 
 * @ClassName: HttpDownloaderPDF
 * @Description: 下载pdf文件到本地
 * @author Stone
 * @date 2016年12月1日
 * 
 */
public class HttpDownloaderPDF {

	/**
	 * 验证证书
	 */
	final static HostnameVerifier DO_NOT_VERIFY = new HostnameVerifier() {
		public boolean verify(String hostname, SSLSession session) {
			return true;
		}
	};

	private static void trustAllHosts() {
		// 创建信任管理器跃过证书校验
		TrustManager[] trustAllCerts = new TrustManager[] { new X509TrustManager() {
			public java.security.cert.X509Certificate[] getAcceptedIssuers() {
				return new java.security.cert.X509Certificate[] {};
			}
			public void checkClientTrusted(X509Certificate[] chain, String authType) {
				
			}
			public void checkServerTrusted(X509Certificate[] chain, String authType) {
				
			}
		} };

		// 安装 all-trusting 信托管理
		try {
			SSLContext sc = SSLContext.getInstance("TLS");
			sc.init(null, trustAllCerts, new java.security.SecureRandom());
			HttpsURLConnection.setDefaultSSLSocketFactory(sc.getSocketFactory());
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	public void httpDownloader(String remoteFileUrl, String localFilePath) {
		try {
			trustAllHosts();
			URL url = new URL(remoteFileUrl);

			HttpsURLConnection https = (HttpsURLConnection) url.openConnection();
			https.setHostnameVerifier(DO_NOT_VERIFY);

			HttpURLConnection httpURLConnection = https;
			httpURLConnection.setConnectTimeout(5 * 1000); // 5000 自定义连接超时毫秒数
			httpURLConnection.connect(); // 连接
			System.out.println("connect URL success!");

			int fileLenght = httpURLConnection.getContentLength();
			System.out.println("file size：" + (fileLenght / 1024.0) + " KB");

			System.out.println("start the download...");
			try (DataInputStream dis = new DataInputStream(
					httpURLConnection.getInputStream());
					FileOutputStream fos = new FileOutputStream(localFilePath)) {
				byte[] buf = new byte[10240]; // 根据实际情况自定义 buf 大小
				for (int readSize; (readSize = dis.read(buf)) > 0;) {
					fos.write(buf, 0, readSize);
				}
				System.out.println("download is complete!");
			} catch (IOException ex) {
				System.out.println("download is error");
			}

			httpURLConnection.disconnect();
		} catch (IOException ex) {
			ex.printStackTrace();
			System.out.println("URL Does not exist or connection timeout!");
		}
	}

}

class PDFTest {
	public static void main(String[] args) {
		HttpDownloaderPDF hdl = new HttpDownloaderPDF();
		hdl.httpDownloader("requestURL", "/home/Stone/Downloader/file.pdf");
	}
	
}

注意：记得在服务器自定义目录下（不要在需要权限的目录下创建，很麻烦还要授权）创建你存文件的文件夹，不然的话程序顺利执行完，但是你要的文件不一定能下载成功！就好比你告诉我，石头哥哥晚上我请你吃饭记得来我家哈！说的挺好听，你不告诉我你家地址和门牌号，我怎么知道去哪里找你，所以啊写程序也得多点儿真诚少点儿套路 0.0

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