Question

我正在尝试从传入的值（使用Bundle）在Android中创建IP地址，如果失败，我将使用硬编码的默认IP地址创建它。如果失败则我退出应用程序。

我想知道的是，如果可以像我在这里做的那样嵌套try / catch，或者是否有更好的方法。

try {
    // serverSettings is the Bundle name that was passed in.
    ipAddress = InetAddress.getByName(serverSettings.getString("serverIp"));
} catch (UnknownHostException e) {
    Log.e("ERROR:", "IOException: Failed to create IP, trying default");
    try {
        // DEFAULT_IP is the hard-coded default fall-back address
        ipAddress = InetAddress.getByName(DEFAULT_IP);
    } catch (UnknownHostException e1) {
        Log.e("ERROR:", "IOException: Total fail, exiting");
        e1.printStackTrace();
        finish();
    }
}

Answer 1

这是合法的Java。它看起来很笨重，我可能会采用不同的方式，但它有效且有效。

我是这样做的：

public InetAddress getServerAddress() {
    for (String address : new String[] {serverSettings.getString("serverIp"), DEFAULT_IP}) {
        try {
            return InetAddress.getByName(address);
        } catch (UnknownHostException e) {
            Log.e("ERROR:", "Cannot resolve " + address);
        }
    }
    Log.e("ERROR:", "Total fail, exiting");
    finish();
    return null;    // not reached
}

Answer 2

我认为哪种方式更好会有争议，但这是另一种选择，有些人可能会认为它更具“表现力”和可读性，尽管它的代码更多：

public InetAddress tryHost(String hostName) {
    InetAddress address = null;
    try {
        address = InetAddress.getByName(hostName);
    } catch (UnknownHostException e) {
        e.printStackTrace();
    }
    return null;
}

然后在您的代码中，执行：

InetAddress address = null;
address = tryHost(serverSettings.getString("serverIp"));
if (address = null)
    address = tryHost(DEFAULT_IP);
if (address = null) {
    // handle error, throw exception
}
finish();

Answer 3

另一种变体是首先设置默认值：

ipAddress = null;
try {
    // serverSettings is the Bundle name that was passed in.
    ipAddress = InetAddress.getByName(DEFAULT_IP); // Set default address
    ipAddress = InetAddress.getByName(serverSettings.getString("serverIp")); // Try passed-in address
} catch (UnknownHostException e) {
    if (ipAddress == null) {
        Log.e("ERROR:", "IOException: Total fail, exiting");
        e1.printStackTrace();
        finish();
    }
}

如果使用Bundle'd值的调用失败，则在修改ipAddress之前抛出异常，因此ipAddress已设置为默认值。当然，如果DEFAULT_IP应该始终可以解析，这只是一个有效的模式。

Answer 4

没关系。您还可以使用在第一个catch中打开的布尔标志，因此如果您的布尔标志已打开，则在catch外部通过IP执行请求。

boolean failed = false;
try {
    // serverSettings is the Bundle name that was passed in.
    ipAddress = InetAddress.getByName(serverSettings.getString("serverIp"));
} catch (UnknownHostException e) {
    failed = true;
    Log.e("ERROR:", "IOException: Failed to create IP, trying default");    
}

if(failed){
    try {
            // DEFAULT_IP is the hard-coded default fall-back address
            ipAddress = InetAddress.getByName(DEFAULT_IP);
        } catch (UnknownHostException e1) {
            Log.e("ERROR:", "IOException: Total fail, exiting");
            e1.printStackTrace();
            finish();
        }
    }
}

Answer 5

我更喜欢这个。它有点清洁，不涉及额外的标志。

InetAddress ipAddress = null;
try {
    // serverSettings is the Bundle name that was passed in.
    ipAddress = InetAddress.getByName(serverSettings.getString("serverIp"));
} catch (UnknownHostException e) {
    Log.e("ERROR:", "IOException: Failed to create IP, trying default");
}
if(ipAddress==null){
    try {
        // DEFAULT_IP is the hard-coded default fall-back address
        ipAddress = InetAddress.getByName(DEFAULT_IP);

    } catch (UnknownHostException e1) {
        Log.e("ERROR:", "IOException: Total fail, exiting");
        e1.printStackTrace();
        finish();
    }
}

Answer 6

在进行更大规模的测试（首先获胜）时，我喜欢的另一种变体：

ipAddress = null;
// serverSettings is the Bundle name that was passed in.
String[] addresses = { DEFAULT_IP,
                       serverSettings.getString("serverIp") };

int i = 0;
do {
    try {
        ipAddress = InetAddress.getByName(addresses[i]);
    } catch (UnknownHostException e) {
        Log.e("ERROR:", "IOException: Failed to create IP, trying next");
    }
} while (ipAddress == null && i < addresses.length);

if (ipAddress == null) {
    Log.e("ERROR:", "IOException: Total fail, exiting");
    e1.printStackTrace();
    finish();
}

这可能更适合我的正常用例（循环使用SimpleDateFormats来匹配第三方日期字符串）

在Java中嵌套try / catch语句是否可以接受？

6 个答案: