Http请求超时的一种处理方法[通俗易懂]

全栈程序员-站长 • 2022年8月2日下午4:46 • 未分类 • 阅读 8

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URLConnection类常见的超时处理就是调用其setConnectTimeout和setReadTimeout方法：

setConnectTimeout：设置连接主机超时（单位：毫秒）
setReadTimeout：设置从主机读取数据超时（单位：毫秒）

还有一种比较另类的就是利用java Object对象的wait()和notify()、notifyAll()方法，利用线程的等待和通知机制处理urlConnection的超时，下面直接贴代码：

public class HttpConnProcessThread implements Runnable {

    public boolean isStop = false;

    public boolean readOK = false;

    private HttpURLConnection reqConnection = null;
    
    public Thread readingThread;

    private int readLen;

    private String msg = null;
        
    private String reqMethod;

    private byte[] data;
    
    /**
     * ReadThread constructor comment.
     */
    public HttpConnProcessThread(HttpURLConnection reqConnection, String msg, String reqMethod ) {
        super();
        this.reqConnection = reqConnection;
        this.msg = msg;
        this.reqMethod = reqMethod;
    }

    public void run() {

        InputStream input = null;
        OutputStream output = null;

        try{
            //reqConnection.connect();
            output = reqConnection.getOutputStream();
            if ("post".equalsIgnoreCase(reqMethod) && msg != null && msg.length() >0) 
            {
                output.write(msg.getBytes());
                output.close();
                output = null;
            }

            // 处理HTTP响应的返回状态信息
            int responseCode = reqConnection.getResponseCode();// 响应的代码if( responseCode != 200 )
                System.out.println("connect failed! responseCode = " + responseCode + " msg=" + reqConnection.getResponseMessage());
            
            input = reqConnection.getInputStream();

            int len;
            byte[] buf = new byte[2048];
            readLen = 0;
            ByteArrayOutputStream outStream = new ByteArrayOutputStream();  
　　　　　　　// 读取inputStream
            while (!isStop) 
            {
                len = input.read(buf);
                if (len <= 0) 
                {
                    this.readOK = true;
                    input.close();
                    data=outStream.toByteArray();
                    break;
                }
                outStream.write(buf, 0, len);  
                readLen += len;
            }
        }
        catch( IOException ie)
        {}
        catch(Exception e)
        {}
        finally
        {
            try{
                reqConnection.disconnect();
                if( input != null )
                    input.close();
                if( output != null )
                    output.close();
                
                //唤醒线程，跳出等待
                wakeUp();
            }catch(Exception e)
            {
                
            }
        }
    }

    public String getMessage(){
        if (!readOK) //超时
        {
            return "";
        }
        
        if (readLen <= 0) {
            return "";
        }
        return new String(data, 0, readLen);
    }

    public void startUp() {
        this.readingThread = new Thread(this);
        readingThread.start();
    }


    //唤醒线程，不再等待
    private synchronized void wakeUp() {
        notifyAll();
    }

    public synchronized void waitForData(int timeout) 
    {
        try {
            //指定超时时间，等待connection响应
            wait(timeout);
        } 
        catch (Exception e) 
        {
        }
            
        if (!readOK)
        {
            isStop = true;
            try{
                //中断线程
                if( readingThread.isAlive() )
                    readingThread.interrupt();
            }catch(Exception e)
            {
                
            }
        }
    }

    public static main(String[] args){
        String msg="";
        URL reqUrl = new URL("http://127.0.0.1:8080/");

        // 建立URLConnection连接
        reqConnection = (HttpURLConnection) reqUrl.openConnection();
        HttpConnProcessThread rec = new HttpConnProcessThread(reqConnection, msg, "post" );
        rec.startUp();
　　     // 如果顺利连接到并读完数据，则跳出等待，否则等待超时
        rec.waitForData(2000);
        
        String retMessage = rec.getMessage();
    }
}