將靜態文件下載到服務器本地目錄

package org.x3.cloud.file.util;

import org.apache.commons.lang3.StringUtils;
import org.apache.http.*;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

/**
 * created by Rock-Ayl on 2019-7-15
 * 該工具類就一個作用,將靜態文件下載到服務器本地目錄
 */
public class HttpDownloadUtils {

    protected static Logger logger = LoggerFactory.getLogger(HttpDownloadUtils.class);

    //文件寫入時緩衝區大小
    public static final int cache = 10 * 1024;
    //是否爲windows系統
    public static boolean isWindows = false;
    //默認下載目錄
    public static String dir = "/Users/";

    /**
     * 根據操作系統初始化盤符
     */
    static {
        //系統
        String system = System.getProperty("os.name");
        //判空
        if (StringUtils.isNotEmpty(system)) {
            //判斷是否爲windows
            if (system.toLowerCase().contains("windows")) {
                isWindows = true;
                dir = "C:\\";
            }
        }
    }

    /**
     * 根據url下載文件，保存到filepath中
     *
     * @param url      文件URL
     * @param filePath 文件下載地址,可爲null
     * @return 下載是否成功
     */
    public static boolean download(String url, String filePath) {
        try {
            //創建連接對象
            HttpClient client = new DefaultHttpClient();
            //URL對象
            HttpGet httpget = new HttpGet(url);
            //請求URL,獲取響應
            HttpResponse response = client.execute(httpget);
            //響應實體
            HttpEntity entity = response.getEntity();
            //文件流
            InputStream is = entity.getContent();
            //判空
            if (StringUtils.isEmpty(filePath)) {
                //根據請求生成生成文件地址
                filePath = getFilePath(response);
            }
            //獲取文件對象
            File file = new File(filePath);
            //創建目錄
            file.getParentFile().mkdirs();
            //輸出流對象
            FileOutputStream fileOut = new FileOutputStream(file);
            /**
             * 根據實際運行效果 設置緩衝區大小
             */
            byte[] buffer = new byte[cache];
            int ch;
            while ((ch = is.read(buffer)) != -1) {
                //寫入
                fileOut.write(buffer, 0, ch);
            }
            //清除
            is.close();
            fileOut.flush();
            fileOut.close();
            return true;
        } catch (Exception e) {
            logger.error("下載靜態文件時出錯:{}", e);
            return false;
        }
    }

    /**
     * 獲取response要下載的文件的默認路徑
     *
     * @param response
     * @return
     */
    private static String getFilePath(HttpResponse response) {
        //文件目錄
        String filepath = dir;
        //從響應中獲取文件名
        String filename = getFileNameFromResponse(response);
        //判空
        if (StringUtils.isNotEmpty(filename)) {
            //用請求的
            filepath += filename;
        } else {
            //用隨機的
            filepath += getRandomFileName();
        }
        return filepath;
    }

    /**
     * 從response的header中Content-Disposition中的filename值
     *
     * @param response
     * @return
     */
    private static String getFileNameFromResponse(HttpResponse response) {
        //獲取Content-Disposition
        Header contentHeader = response.getFirstHeader("Content-Disposition");
        //初始化name
        String filename = null;
        //判空
        if (contentHeader != null) {
            HeaderElement[] values = contentHeader.getElements();
            if (values.length == 1) {
                NameValuePair param = values[0].getParameterByName("filename");
                if (param != null) {
                    try {
                        filename = param.getValue();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return filename;
    }

    /**
     * 獲取一個基於當前時間戳的隨機文件名
     *
     * @return
     */
    private static String getRandomFileName() {
        return String.valueOf(System.currentTimeMillis());
    }

}