从Java服务器到客户端接收字符串

我有一个java客户端，它将JSON对象发送到服务器（REST服务）。 代码工作得很完美。我当前的服务器返回“RESPONSE”，但我想修改我的代码，将字符串从服务器返回到客户端（类似于“transfer was OK”）——除了将对象从客户端发送到服务器之外。 这是我的密码

服务器：

@Path("/w")
public class JSONRESTService {
@POST
@Path("/JSONService")
@Consumes(MediaType.APPLICATION_JSON)
public Response JSONREST(InputStream incomingData) {
    StringBuilder JSONBuilder = new StringBuilder();
    try {
        BufferedReader in = new BufferedReader(new InputStreamReader(incomingData));
        String line = null;
        while ((line = in.readLine()) != null) {
            JSONBuilder.append(line);
        }
    } catch (Exception e) {
        System.out.println("Error Parsing: - ");
    }
    System.out.println("Data Received: " + JSONBuilder.toString());

    // return HTTP response 200 in case of success
    return Response.status(200).entity(JSONBuilder.toString()).build();
}
}

客户：

public class JSONRESTServiceClient {
public static void main(String[] args) {
    String string = "";
    try {

        JSONObject jsonObject = new JSONObject("string");

        // Step2: Now pass JSON File Data to REST Service
        try {
            URL url = new URL("http://localhost:8080/w/JSONService");
            URLConnection connection = url.openConnection();
            connection.setDoOutput(true);
            connection.setRequestProperty("Content-Type", "application/json");
            connection.setConnectTimeout(5000);
            connection.setReadTimeout(5000);
            OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream());
            out.write(jsonObject.toString());
            out.close();

            BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));

            while (in.readLine() != null) {
            }
            System.out.println("\nJSON REST Service Invoked Successfully..");
            in.close();
        } catch (Exception e) {
            System.out.println("\nError while calling JSON REST Service");
            System.out.println(e);
        }

        br.close();
    } catch (Exception e) {
        e.printStackTrace();
    }
}
}

因此，为了将字符串从服务器返回到客户端-我首先修改了服务器中的方法以返回字符串， 我将此添加到我的客户：

 BufferedReader in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
 StringBuffer sb = new StringBuffer("");
 String line="";
 while (in.readLine() != null) {
                sb.append(line);
                break;
            }
  System.out.println("message from server: " + sb.toString());
  in.close();

但是我的字符串是空的。 我做错了什么？我应该如何修改我的服务器/客户机以接收一个简单的字符串，甚至一个对象？ 谢谢。

您的代码（示例）：

---

上一个清单中的“连接”是什么？它与我在客户端上打开的连接相同（我刚刚将此部分添加到客户端）。嘿，感谢这个示例，它看起来与我所做的类似，但不起作用。我还需要我的客户端上的输入和输出流。所以还不清楚我是否需要一个新的连接？（一个用于outputstream，一个用于inputstream？）@SHAI替换了该示例。我想你需要一个连接。我希望它能起作用。谢谢！我发现了我的问题，而您的代码确实有所帮助-这是我的客户端中的while循环-while（in.readLine（）！=null）。我需要写-while（line=in.readLine（）！=null）。我只需要更换这条线路，是的，一个连接。

package com.javacodegeeks.enterprise.rest.javaneturlclient;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;

public class JavaNetURLRESTFulClient {

    private static final String targetURL = "http://localhost:8080/w/JSONService";

    public static void main(String[] args) {

        try {

            URL targetUrl = new URL(targetURL);

            HttpURLConnection httpConnection = (HttpURLConnection) targetUrl.openConnection();
            httpConnection.setDoOutput(true);
            httpConnection.setRequestMethod("POST");
            httpConnection.setRequestProperty("Content-Type", "application/json");

            String input = "{\"id\":1,\"firstName\":\"Liam\",\"age\":22,\"lastName\":\"Marco\"}";

            OutputStream outputStream = httpConnection.getOutputStream();
            outputStream.write(input.getBytes());
            outputStream.flush();

            if (httpConnection.getResponseCode() != 200) {
                throw new RuntimeException("Failed : HTTP error code : "
                    + httpConnection.getResponseCode());
            }

            BufferedReader responseBuffer = new BufferedReader(new InputStreamReader(
                    (httpConnection.getInputStream())));

            String output;
            System.out.println("Output from Server:\n");
            while ((output = responseBuffer.readLine()) != null) {
                System.out.println(output);
            }

            httpConnection.disconnect();

          } catch (MalformedURLException e) {

            e.printStackTrace();

          } catch (IOException e) {

            e.printStackTrace();

         }

        }    
    }