如何使用HTTPClient的HEAD方法获取所有标头

Question

我必须使用 HttpClient 的 HEAD 方法来获取标头字段并检查服务器文件的“上次修改”日期。
我无法得到这一点，如果您知道如何获取标题字段，请回复。 如何将“last-modified”标头获取到 String 对象中进行比较。

这是我的代码：

HttpClient client = new DefaultHttpClient();
//HttpGet get = new HttpGet(url);
HttpHead method = new HttpHead(url);
HttpResponse response= client.execute(method);

Header[] s = response.getAllHeaders();

System.out.println("THe header from the httpclient:");
for(int i=0; i < s.length; i++){
    Header hd = s[i];
    System.out.println("Header Name: "+hd.getName()
                        +"       "+" Header Value: "+ hd.getValue());
}

Answer 1

在 httpClient 4.5 上您将使用：

final HttpHead headMethod = new HttpHead(fileUri);
final Header header = headMethod.getFirstHeader("last-modified");
final String lastModified = header.getValue();

Answer 2

从 HttpClient 文档

HeadMethod head = new HeadMethod("http://jakarta.apache.org");

// Excecute the method here with your HttpClient

Header[] headers = head.getResponseHeaders();
String lastModified = head.getResponseHeader("last-modified").getValue();

您需要添加自己的错误处理。

Answer 3

最好使用这样的东西：

CloseableHttpClient client = HttpClientBuilder.create().build();
HttpHead head = new HttpHead(url);
String lastModified;
try {
    CloseableHttpResponse response = client.execute(head);
    int statusCode = response.getStatusLine().getStatusCode();
    if (statusCode == 200) {
        Header header = headMethod.getFirstHeader("last-modified");
        lastModified = header.getValue();
    }
} catch (IOException ignored) {
}