java – 对某些异常重新尝试方法

发布时间：2020-12-15 02:15:29 所属栏目：Java 来源：网络整理

导读：我有以下方法使用代理从服务器检索信息.有时由于代理错误,我得到SocketException,SSLException,SSLHandshakeException或ConnectException 正如你在我的方法中看到的,我已经在使用catch(IOException ioe)我需要这样做,以便在服务器返回除代码200之外的任何内

我有以下方法使用代理从服务器检索信息.有时由于代理错误,我得到SocketException,SSLException,SSLHandshakeException或ConnectException

正如你在我的方法中看到的,我已经在使用catch(IOException ioe)我需要这样做,以便在服务器返回除代码200之外的任何内容时获取服务器响应的内容.

如果出现上述异常,如何重置方法？

public String getMeta() throws IOException
{

    HttpsURLConnection con = null;
    InputStream is = null;
    StringWriter writer = new StringWriter();
    try
    {
        String url = "https://api.myapp.com/meta";
        URL urlObj = new URL(url);

        if (useProxy && fullProxy)
        {
            myapp.Proxy proxyCustom = getRandomProxy();
            Proxy proxy = new Proxy(Proxy.Type.HTTP,new InetSocketAddress(proxyCustom.getProxyIp(),proxyCustom.getProxyPort()));
            con = (HttpsURLConnection) urlObj.openConnection(proxy);
        }
        else
        {
            con = (HttpsURLConnection) urlObj.openConnection();
        }

        con.setRequestMethod("GET");
        con.setRequestProperty("User-Agent",USER_AGENT);
        con.setRequestProperty("Content-Type","application/json; charset=utf-8");
        con.setRequestProperty("host",urlObj.getHost());
        con.setRequestProperty("Connection","Keep-Alive");

        int responseCode = 0;

        responseCode = con.getResponseCode();

        is = con.getInputStream();
        writer = new StringWriter();
        IOUtils.copy(is,writer,"UTF-8");
    }
    catch (IOException ioe)
    {
        if (con instanceof HttpsURLConnection)
        {
            HttpsURLConnection httpConn = (HttpsURLConnection) con;
            int statusCode = httpConn.getResponseCode();
            if (statusCode != 200)
            {
                is = httpConn.getErrorStream();
                writer = new StringWriter();
                IOUtils.copy(is,"UTF-8");
            }
        }
    }
    catch (Exception e)
    {
        e.printStackTrace();
    }

    return writer.toString();
}

解决方法

How can I make the method retry in case of the above exceptions?

下面显示的一种方法是让getMeta方法实际抛出IOException.然后,由于任何捕获的异常,您可以使用调用方法递归调用自身.

I hope there is an simple way of setting how times it should retry

为了能够多次调用该方法,传递次数作为参数并相应地处理停止标准逻辑.例如：

public String caller(int total) throws IOException{
    return callerImpl(1,total);
}

public String callerImpl(int current,int total) throws IOException{
    try{
        return getMeta();
    }catch(IOException e){
        current++;
        if ( current > total ){
            throw e;//or return null or empty string,depending upon upstream requirements
        }
        return callerImpl(current,total);
    }

    return null;
}

在getMeta中：

try{
    ....
}catch(IOException io){
    //log or handle io
    throw io;
}

注意,上面没有涉及抛出异常的日志/逻辑,您可能希望以某种方式处理它们.

（编辑：李大同）

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