Java中的可選方法參數

Question

我有這個函數httpGet() ，它調用http() ：

public static int httpGet(String url, StringBuilder response) throws IOException {
    return http(url,(http)->http.setRequestMethod("GET"), response);
}

private static int http(String url, httpMethod method, StringBuilder response) throws IOException {
    HttpURLConnection http = (HttpURLConnection)new URL(url).openConnection();
    http.setConnectTimeout(5000);
    http.setReadTimeout(5000);
    method.doMethod(http);
    int status = 404;
    ......
    ......
    return status;
}

我想為readTimeout添加一個附加參數，該參數必須是可選參數，否則將使用默認值。

在這種情況下，所有調用的readTimeout都設置為5000，但是我希望執行此特定的調用以延長超時時間。

我想我需要這個新參數是可選的，因為我不想更改已調用此http()方法的實現。

這就是我所說的：

Assert.assertEquals(HTTP_OK, httpGet(DEFAULT_BROWSCAP_ENDPOINT, result));

如何為readTimeout實現新的可選參數？

Answer 1

您需要創建2個版本的httpGet方法（一個帶有readTimeout參數，另一個沒有它，它將使用默認值調用第一個版本）：

private static final long DEFAULT_READ_TIMEOUT = 5000;

public static int httpGet(String url, StringBuilder response) throws IOException {
    return httpGet(url, response, DEFAULT_READ_TIMEOUT);
}

public static int httpGet(String url, StringBuilder response, long readTimeout) throws IOException {
    return http(url,(http)->http.setRequestMethod("GET"), response, readTimeout);
}

private static int http(String url, httpMethod method, StringBuilder response, long readTimeout) throws IOException {
    HttpURLConnection http = (HttpURLConnection)new URL(url).openConnection();
    http.setConnectTimeout(5000);
    http.setReadTimeout(readTimeout);
    method.doMethod(http);
    int status = 404;
    ......
    ......
    return status;
}

現在您可以決定提供超時

httpGet(DEFAULT_BROWSCAP_ENDPOINT, result, mytimeout)

或不

httpGet(DEFAULT_BROWSCAP_ENDPOINT, result)

Answer 2

Java沒有默認值，例如Python，C ++，VBA，Delphi和許多語言。 使用替代簽名創建新的構造函數。

public static int httpGet(String url, StringBuilder response) throws IOException {
    return httpGet(URL, response, 5000)
}

public static int httpGet(String url, StringBuilder response, int readTimeout) throws IOException {
    return http(url,(http)->http.setRequestMethod("GET"), response, readTimeout);
}


private static int http(String url, httpMethod method, StringBuilder response) throws IOException {
    return http(url, method, response, 5000);
}

private static int http(String url, httpMethod method, StringBuilder response, int readTimeout) throws IOException {
    HttpURLConnection http = (HttpURLConnection)new URL(url).openConnection();
    http.setConnectTimeout(5000);
    http.setReadTimeout(readTimeout;
    method.doMethod(http);
    int status = 404;
    ......
    ......
    return status;
}

Answer 3

通常，完成此操作的方式是通過提供許多具有不同簽名（假定默認值）的不同功能。 這可以通過將一系列函數“鏈接”在一起來完成，每個函數都指定其默認值並調用更詳細的函數。 例如：

public void myFunctionWithALotOfArguments(int a, int b, int c, int d) {
    // do stuff
}
public void myFunctionWithLessArguments(int a, int b, int c) {
    myFunctionWithALotOfArguments(a, b, c, 50);
}
public void myFunctionWithFewArguments(int a, int b) {
    myFunctionWithLessArguments(a, b, 25);
}
public void mySimplifiedFunction(int a) {
    myFunctionWithFewArguments(a, 9);
}
public void justGuessWhatToDo() {
    mySimplifiedFunction(42);
}