我有一个类调用 Rest Web 服务来从服务器接收文件。在传输字节时,我创建了一个异步任务,它检查与服务器的连接是否正常,以便在出现错误时允许停止连接。
这个异步任务有一个我必须停止的循环:
@Component
public class ConnectionTest {
@Async
//Check connection with the server, if for three attemp it failes, throw exception
public void checkServerConnection(String serverIp) throws Exception{
int count=0;
for(;;Thread.sleep(7000)){
try{
System.out.println("TEST");
URL url = new URL(serverIp);
HttpURLConnection con = (HttpURLConnection) url
.openConnection();
con.connect();
if (con.getResponseCode() == 200){
System.out.println("Connection established!!");
}
if (count>0) count=0;
}catch(Exception e){
count++;
if (count==3)
throw new Exception("Connection error");
}
}
}
}
但我怎样才能阻止调用者使用这个方法呢?
@Autowired
private ConnectionTest connectionTest;
@Override
public Response getFile(String username, String password, String serverIp, String toStorePath, String filePath){
ResponseEntity<byte[]> responseEntity = null;
try{
//it is used to check if connection of the client with the server goes down
connectionTest.checkServerConnection();
RestClient restClient = new RestClient(username, password);
// SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
// requestFactory.setBufferRequestBody(false);
// restClient.setRequestFactory(requestFactory);
// RestTemplate restClient = new RestTemplate();
responseEntity = restClient.getForEntity(serverIp + "client/file/?filePath={filePath}", byte[].class, filePath);
//TODO kill async task and return false
UPDATE:正如@Thomas建议我在ConnectionTest中使用了布尔变量,我将循环更改为while (!stop)
在网络服务调用之后我设置了ConnectionTest.setStop(true)
.
注意在循环之前设置 stop=false (而不是作为实例字段),否则只有第一个请求具有此值并进入 while 内。
UPDATE 2这是我的最后一个代码,它似乎有效,也许我应该用 wait-notify 更改 while 循环:
public Response getFile(String username, String password, String serverIp, String toStorePath, String filePath){
try{
//it is used to check if connection of the client with the server goes down
Future<Boolean> isConnect = connectionTest.checkServerConnection(serverIp);
Future<ResponseEntity<byte[]>> downloadResult = downloadAsync.makeRequest(username, password, serverIp, filePath);
while(!isConnect.isDone() && !downloadResult.isDone()){
}
if (isConnect.isDone()){
downloadResult.cancel(true);
return new Response(false, false, "Error with server connection!", null);
}else{
connectionTest.setStop(true);
ResponseEntity<byte[]> responseEntity = downloadResult.get();
if (MediaType.TEXT_PLAIN.toString().equals(responseEntity.getHeaders().getContentType().toString())){
ErrorResponse errorResponse= ErrorResponseBuilder.buildErrorResponse(new FileException("Error with file transfert!"));
return new Response(false, false, new String(Base64.decodeBase64(responseEntity.getBody()),Charset.forName("UTF-8")), errorResponse);
}else{
Path p = Paths.get(filePath);
String fileName = p.getFileName().toString();
FileOutputStream fos = new FileOutputStream(toStorePath+"\\"+ fileName);
fos.write(responseEntity.getBody());
fos.close();
return new Response(true, true, "Your file has been downloaded!", null);
}
}
}catch(Exception e){
ErrorResponse errorResponse= ErrorResponseBuilder.buildErrorResponse(e);
return new Response(false, false, "Error on the client side!" , errorResponse);
}
}
连接检查异步:
@Component
public class ConnectionTest {
private boolean stop;
@Async
//Check connection with the server, if for three attemp it failes, throw exception
/**
*
* @param serverIp
* @throws IOException
*/
public Future<Boolean> checkServerConnection(String serverIp) throws IOException {
int count=0;
stop = false;
while (!stop){
try{
Thread.sleep(7000);
System.out.println("TEST");
//java.net.InetAddress.getByName(SERVER_ADDRESSS);
URL url = new URL(serverIp);
HttpURLConnection con = (HttpURLConnection) url
.openConnection();
con.connect();
if (count>0) count=0;
}catch(Exception e){
count++;
System.out.println(count);
if (count==3)
return new AsyncResult<Boolean>(stop);
}
}
return new AsyncResult<Boolean>(stop);
}
/**
* @return the stop
*/
public boolean isStop() {
return stop;
}
/**
* @param stop the stop to set
*/
public void setStop(boolean stop) {
this.stop = stop;
}
}
下载异步:
@Component
public class DownloadAsync {
@Async
public Future<ResponseEntity<byte[]>> makeRequest(String username, String password, String serverIp, String filePath){
RestClient restClient = new RestClient(username, password);
ResponseEntity<byte[]> response= restClient.getForEntity(serverIp + "client/file/?filePath={filePath}", byte[].class, filePath);
return new AsyncResult<ResponseEntity<byte[]>>(response);
}
}