StreamReader.java

package cn.dreampie.common.util.stream;

import cn.dreampie.common.Constant;
import cn.dreampie.log.Logger;

import java.io.*;

/**
 * Created by ice on 15-1-28.
 */
public class StreamReader {

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

  public static String readString(InputStream is) throws IOException {
    return readString(is, Constant.encoding);
  }

  public static String readString(InputStream is, String encoding) throws IOException {
    String result = null;
    if (is != null) {
      BufferedReader rd = new BufferedReader(new InputStreamReader(is, encoding));

      StringBuilder response = new StringBuilder();
      String line;
      while ((line = rd.readLine()) != null) {
        response.append(line);
      }
      result = response.toString();
      logger.debug("Read stream from inputStream: %s", result);
      rd.close();
    }
    return result;
  }

  public static File readFile(InputStream is, File writeFile) throws IOException {
    return readFile(is, writeFile, null);
  }

  public static File readFile(InputStream is, int contentLength, File writeFile) throws IOException {
    return readFile(is, contentLength, writeFile, null);
  }

  public static File readFile(InputStream is, File writeFile, FileRenamer renamer) throws IOException {
    File file = null;
    if (is != null) {
      if (renamer != null) {
        file = renamer.rename(writeFile);
      } else {
        file = Filer.mkDirs(writeFile);
      }
      //判断文件目录是否存在 如果不存在 创建
      //获取一个写入文件流对象
      OutputStream out = new FileOutputStream(file);
      //创建一个4*1024大小的字节数组，作为循环读取字节流的临时存储空

      byte buffer[] = new byte[4 * 1024];
      int len = -1;
      //循环读取下载的文件到buffer对象数组中
      while ((len = is.read(buffer)) != -1) {
        //把文件流写入到文件
        out.write(buffer, 0, len);
      }
      out.close();
    }
    return file;
  }

  public static File readFile(InputStream is, int contentLength, File writeFile, FileRenamer renamer) throws IOException {
    File file = null;
    if (is != null) {
      //判断文件是否存在
      if (renamer == null && writeFile.exists()) {
        if (contentLength == 0) {
          logger.warn("File download was complete, don't download " + writeFile.getPath());
          return writeFile;
        }
        long start = writeFile.length();
        //必须要使用
        RandomAccessFile out = new RandomAccessFile(writeFile, "rw");
        out.seek(start);
        byte[] buffer = new byte[1024];
        int len = -1;
        while ((len = is.read(buffer)) != -1) {
          out.write(buffer, 0, len);
        }
        out.close();
        file = writeFile;
      } else {
        file = readFile(is, writeFile, renamer);
      }
    }
    return file;
  }

}