HttpConnection下载文件

import java.io.Closeable;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.HttpURLConnection;
import java.net.URL;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.Assert;

import com.odianyun.cc.client.exception.OccClientRequestException;
import com.odianyun.cc.model.dto.OccConfigDownloadDTO;

public class OccRequestUtils {

    private final static Logger logger = LoggerFactory.getLogger(OccRequestUtils.class);

    private static int BUFFER_SIZE = 4096;//缓冲区大小



    /**
     * 向指定 URL 发送POST方法的请求
     *
     * @param url
     *            发送请求的 URL
     * @param param
     *            请求参数，参数为JSON格式。
     * @param dir
     *            下载文件存储目录
     * @return 所代表远程资源的响应结果
     */
    public static OccConfigDownloadDTO sendPost(String url, String param,String dir) {
        InputStreamReader isr = null;
        FileWriter fw = null;
        char[] buf = new char[BUFFER_SIZE];
        int size = 0;
        String groupPath = null;
        String fileName = null;
        String fileVersion = null;
        File proFile = null;
        try {
            //发送请求
            HttpURLConnection connection = sendParam(url,param);
            //读取Properties文件流
            isr = new InputStreamReader(connection.getInputStream(),"UTF-8");
            //从头中拿到文件相关属性
            groupPath = connection.getHeaderField("groupPath");
            Assert.notNull(groupPath,"Failed to obtain parameters from OCC-Server,groupPath is required; maybe record not found.");
            fileName = connection.getHeaderField("fileName");
            Assert.notNull(fileName,"Failed to obtain parameters from OCC-Server,fileName is required; maybe record not found.");
            fileVersion = connection.getHeaderField("fileVersion");
            Assert.notNull(fileName,"Failed to obtain parameters from OCC-Server,fileVersion is required; maybe record not found.");
            proFile = new File(System.getProperty("global.config.path") + File.separator + dir + File.separator + groupPath , fileName);
            if (proFile.exists()){
                proFile.delete();
            }else{
                proFile.getParentFile().mkdirs();
            }
            fw = new FileWriter(proFile);
            while ((size = isr.read(buf)) != -1){
                fw.write(buf,0,size);
            }
            fw.flush();
        } catch (Exception e) {
            throw new OccClientRequestException(e.getMessage(),e);
        }
        //使用finally块来关闭输出流、输入流
        finally{
            close(isr,fw);
        }
        return new OccConfigDownloadDTO(proFile,groupPath, fileName, fileVersion);
    }

    private static HttpURLConnection sendParam(String url,String param) throws IOException {
        URL realUrl = new URL(url);
        // 打开和URL之间的连接
        HttpURLConnection connection = (HttpURLConnection)realUrl.openConnection();
        // 设置通用的请求属性
        connection.setDoOutput(true);
        connection.setDoInput(true);
        connection.setRequestMethod("POST");
        connection.setUseCaches(false);
        connection.setInstanceFollowRedirects(true);
        connection.setRequestProperty("Content-Type","application/json;charset=utf-8");
        connection.connect();
        PrintWriter out = null;
        try {
            // 获取URLConnection对象对应的输出流
            out = new PrintWriter(connection.getOutputStream());
            // 发送请求参数
            out.print(param);
            // flush输出流的缓冲
            out.flush();
        }finally {
            if (out != null){
                out.close();
            }
        }
        return connection;
    }

    private static void close(Closeable... closeAbles){
        if (closeAbles == null || closeAbles.length <= 0) {
            return;
        }
        for (Closeable closeAble : closeAbles) {
            if (closeAble != null) {
                try {
                    closeAble.close();
                } catch (IOException e) {
                    logger.error(e.getMessage(), e);
                }
            }
        }
    }


}