Java 使用输入输出流发送与接收HTTP请求数据

由于频繁萃取文件内容，服务器内存被字符串占满，所以使用流的方式处理，因为流一旦被关闭就会释放其占用的资源，而字符串要等着GC回收

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
import java.util.HashMap;
import java.util.Map;
import org.json.simple.JSONObject;

public class TestFile {

  private static final String URL = "http://127.0.0.1/file/getFileContent";

  public static void main(String[] args) throws IOException {
    String get = httpRequest(URL, "GET", new HashMap<>());
    System.err.println(get);
  }

  public static String httpRequest(String requestUrl, String requestMethod, Map requestParameters) throws IOException {
    InputStream inputStream = null;
    InputStreamReader inputStreamReader = null;
    BufferedReader bufferedReader = null;
    try {
      URL url = new URL(requestUrl);
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setDoOutput(true);//需要用到输出流
      conn.setDoInput(true);//需要用到输入流
      conn.setRequestMethod(requestMethod);
      conn.setRequestProperty("content-type", "text/html");//设置内容类型
      // 使用输出流添加数据至请求体
      if (requestParameters.size() != 0) {
        String json = JSONObject.toJSONString(requestParameters);
        OutputStream os = conn.getOutputStream();//获取输出流
        os.write(json.getBytes());//写入
        os.flush();
      }
      conn.connect();
      // 读取服务器端返回的内容
      inputStream = conn.getInputStream();
      inputStreamReader = new InputStreamReader(inputStream, StandardCharsets.UTF_8);
      bufferedReader = new BufferedReader(inputStreamReader);
      StringBuilder buffer = new StringBuilder();
      String line;
      while ((line = bufferedReader.readLine()) != null) {
        buffer.append(line);
      }
      return buffer.toString();
    } catch (Exception e) {
      e.printStackTrace();
      throw e;
    } finally {
      assert inputStream != null;
      inputStream.close();
      assert inputStreamReader != null;
      inputStreamReader.close();
      assert bufferedReader != null;
      bufferedReader.close();
    }
  }
}

package com.demo.controller;

import com.demo.service.FileService;
import com.jfinal.aop.Inject;
import com.jfinal.core.Controller;
import com.jfinal.core.Path;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import javax.servlet.http.HttpServletResponse;



@Path("/file")
public class FileController extends Controller {
  private static final String FILE_PATH = "D:\工作\档案相关文件\电子档案管理系统基本功能规定.pdf";
  @Inject
  FileService fileService;
  public void getFileContent() throws IOException {
    InputStream fileContext = null;
    OutputStream outputStream = null;
    try {
      File file = new File(FILE_PATH);
      fileContext = fileService.getFileContext(file);
      HttpServletResponse response = getResponse();
      response.setContentType("application/octet-stream");
      response.setHeader("Content-disposition", "attachment;filename=" + file.getName());
      outputStream = response.getOutputStream();
      byte[] bis = new byte[1024];
      while (-1 != fileContext.read(bis)) {
        outputStream.write(bis);
      }
      renderNull();
    } catch (Exception e) {
      e.printStackTrace();
    } finally {
      assert fileContext != null;
      fileContext.close();
      assert outputStream != null;
      outputStream.flush();
      outputStream.close();
    }
  }
}